### Leak of uranium from the Hinkley Point nuclear power plant?

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**07 Feb 2011, 01:20**This is the full story related to the blog entry Chris Busby and "The Tall Tale Of Ten Tons Uranium Gone Missing"

Here we give our full investigation of the claims by Chris Busby regarding Hinkley Point. If you have any additional information, please add a comment to the thread.

BACKGROUND

Hinkley Point is a nuclear power plant in Somerset, South West England. At the site there is a decommissioned MAGNOX reactor (http://en.wikipedia.org/wiki/Hinkley_Point_A_nuclear_power_station) that operated during the years 1965-2000, and two Advanced Gas-cooled Reactors (AGR) that were commissioned in 1976 and are still running (http://en.wikipedia.org/wiki/Hinkley_Point_B_nuclear_power_station).

The French company Electricite de France (EDF), who owns the two AGR units, is planning for the construction of new nuclear reactors at the site, this time of the type EPR (European Pressurised Reactor) similar to the one being built in Olkiluoto, Finland (http://en.wikipedia.org/wiki/Hinkley_Point_C_nuclear_power_station).

There are several organisations, for instance Stop Hinkley, that oppose the plans for new installations, and also works for a closure of the existing plants. In support of the campaign is Professor Chris Busby, who we have encountered before, see here. For several years Busby has, mainly through his organization Green Audit claimed an increase of childhood leukaemia, breast cancer (here, here and here) and increased childhood mortality near Hinkley Point and other nuclear power plants. Several of the claims have been opposed by various health authorities and researchers.

In January 2011 Busby and his colleague, Cecily Collingridge, released a study, "Evidence of significant enriched uranium atomic fuel contamination of the Hinkley Point proposed nuclear site in Somerset and its potential implications" (the Green Audit press release is found here, and there is also information at Busby's organization The Low Level Radiation Campaign), where they claim that the ground around the proposed EPR reactors is contaminated with about 10 tonnes of enriched uranium, presumably coming from the older reactors. Is it really so? Let us follow the reasoning of Professor Busby and see if his claims hold any truth this time.

THE MEASURED DATA

EDF has commissioned a company called AMEC to take samples and make measurements of radioactivity, chemicals, etc on the proposed site for the new plant, this is part of the regular Environmental Impact Assessment. The gamma spectroscopy data are presented in the document "AMEC Phase 2 Supplementary Investigation of Potential Radiological Contamination EDF Access Appendix C Soil Sampling Data and Comparison with Background Values- December 2008 AMEC 15011/TR/00091" (an alternative search route is here together with two related reports).

Data are given for about 30 trenches where earth samples have been obtained. The radiological contents of each sample has been identified in a laboratory through standard gamma spectroscopy methods. There are also results from measurements of alpha and beta radiation, but here we focus on the measurements of gamma radiation. The report gives the identified isotopes and the activity measured in Bq/g. Over all the data shows low levels of radioactivity in the area.

Busby has used these data from the AMEC analysis, focusing on the uranium isotopes. In his own words:

"Gamma spectra data can be used (with some caveats, see below) to determine the

activity concentrations of U-235 and U-238.

These are the two isotopes of interest in determining if uranium in a sample is

natural or from a man-made source, namely U-238 and U-235. The natural isotope

activity ratio is 21.3. That is, U-235, the fissile component used in nuclear reactors is

present in natural uranium, from a mine, from the environment with 1/21.3 times the

activity of U-238. The atomic ratio is 137.88, and this is what is measured when

samples are analysed by mass spectrometry. But with gamma spectrometry, the ratio

should be 21.3. If it is less, then there is a proportion of enriched uranium in the

sample, and this has to be man-made. Enriched Uranium (which is more radioactive

than natural uranium) does not exist in nature."

So far so good. Busby expresses the ratio between U-235 and U-238 in the activity ratio, which for natural uranium is 21.3. This ratio is valid provided that one can properly identify certain peaks of gamma radiation, associated with the nuclear de-excitation after the decay, and then correct for the probability that these particular de-excitations will occur, and properly correct for limited detector efficiency. One can consider measuring different peaks, if available, as long as the corrections are properly applied. Most likely the AMEC results are based on some standard procedure. The activity ratio 21.3 corresponds to the 0.7% mass percent of U-235 in natural uranium. For some reason Busby seems to prefer to discuss the matter in terms of the activity ratio rather than in terms of enrichment. We will return to this issue later on.

We should point out that it is difficult to measure how much U-235 there is in environmental uranium samples by using gamma spectroscopy methods. A much more accurate method is to use mass spectroscopy methods, where the fraction of U-235 is measured directly. In the present case, this method has not been used by AMEC.

Busby continues:

"There is, however, a problem in that U-238 is not a gamma emitter, and we

have to rely on the gamma activity of its immediate daughter decay product Thorium-

234 to signal the activity of U-238. Whilst this will give an accurate value for U-238 it

can give an incorrect result for the U238/U235 ratio since Uranium is more soluble

than Thorium, leading to a loss of U-235 relative to Th-234. But such a process would

signal Depleted Uranium as the ratio would be too high, greater than 21.3. So if we

are finding Enriched Uranium from a man-made source, using gamma spectral data, it

is certainly there. And it is."

Really? Here are two statements, both can be questioned.

STATEMENT 1: Any determined enrichment ratio is a lower limit

Busby claims that the solubility of Uranium in water is higher than for Thorium in water. This is probably correct. But we have to consider the life time of the various isotopes in the decay chain. U-238 decays mainly through alpha emission to Th-234. The half life of Th-234 is about 24 days, beta decaying into Pa-234 (Protactinium). Pa-234 has a half life of only 6.7 hours before decaying into U-234, which has a half life of 245 000 years (a chart with the U-238 decay chain is given here). So, for the given case we could, naively, make two alternative assumptions:

(1): If there is only natural uranium in the ground, then we are dealing with changes over geological time scales, where the life times of the three Uranium isotopes (U-234, U-235 and U-238) are very long (245 000 years, 704 million years and 4.5 billion years, respectively). A lower solubility of Thorium-234 then has limited importance because there is only Thorium around for about a month for each decay, to be compared with the hundreds of thousands of years (or much more!) that we have the Uranium, irrespective of which isotope.

(2): The uranium (and Thorium) found on the site origins from the nuclear plant. What is measured then either comes from a continuous release since 1965, or from one or several larger releases after that date up to the year 2008 when the measurements were performed by AMEC. In either case, the released uranium has occurred on the order of one or more years ago, and has remained as Uranium for the vast majority of the time, save for about a month that decaying U-238 is in the Thorium state.

For both cases, the difference in solubility would probably have a very limited role, because the water solubility would affect the amount of U-238 in the same way as for U-235, while the less soluble Thorium isotopes would play a smaller role due to the much shorter time that the decaying nuclide will be in that state.

But, more important, without knowing anything about the local conditions of the ground, with respect to water flows, type of ground, seasonal changes, etc., we are in no position to make any claim whatsoever about the effects of the different solubilities. Neither is Busby.

Thus the claim that the activity ratio U238/U235 will indicate a lower limit must be met with: We don't know, and Busby does not know, he is just speculating.

STATEMENT 2: There is enriched uranium in the samples

Now on to the second statement, i.e. "And it is.", i.e. the uranium has a U-235 content that is higher than from natural uranium.

Busby claims that the uranium is enriched and therefore from a man-made source. Most of the measured activity ratios R=A(Th-234)/A(U-235) are lower than 21.3, indicating enriched uranium. So let us take a look at his calculations.

Below is a figure of part of Busby's table (Table 1 in the report).

The columns are, from left to right: AMEC Sample code number, Mean depth of the sample (m), Mean distance to the sea (m), activity of U-235 (Bq/g), activity of Th-234 (Bq/g), Th-234/U-235 ratio, calculated U-238 activity, and finally notes about if the sample shows natural uranium or any enrichment.

The sample numbers, the mean depth, and the activities of U-235 and Th-234, are from the AMEC report, while the mean distance to the sea, the activity ratio R, and the calculated U-238 activity, are calculated by Busby.

Table 1: Excerpt from Table 1 in Busby's paper, showing measured data from the AMEC report and Busby's calculated data.

In Fig. 1 is Busby's calculation of the activity ratio R=U238/U235 as function of the mean depth (in meters) of where the sample was taken. Shown is also a fitted curve of the form R=k*ln(depth)+m, where k and m are fitted parameters.

Figure 1: Figure 1 in Busby's report, showing the activity ratio as function of depth in the ground.

It looks rather convincing doesn't it? Most of the data is below the 21.3 value that indicates natural uranium. Thus Busby must be right, there has been some kind of leak from the nuclear reactors, and enriched fuel has been spread in the environment. Furthermore, the data points seems to agree pretty well with the curve, don't they? This means that the enrichment is increasing closer to the surface, a further indication that the enriched uranium must have ended up there relatively recently, while the uranium in samples deeper down corresponds to the natural composition.

Now wait a minute. Isn't there something missing in all of this? How about error bars?

For those not used to how measurements (of any kind) are made, it is valuable to know that each measurement has an associated uncertainty, i.e. a value that indicates the quality of the measurement. A good measurement based on a lot of events (i.e. good statistics) is said to have good precision.

So each data point should then have associated error bars, indicating the likely range of uncertainty for each measurement. Small error bars indicate a measurement with good precision, while large error bars indicate that measurement with low statistics. We see no such error bars in Busby's Fig. 1, could there be that AMEC did not give any uncertainties?

We go to the AMEC report, see Table 2 below.

Table 2: Excerpt from table in the AMEC report, showing the identified isotopes from the gamma spectroscopy measurements.

Here we see, from left to right, the reference number of the sample, first from the laboratory (NIRAS) that performed the analysis, and then the reference number from AMEC who did the excavation and ordered the analysis by NIRAS. The next column shows each identified isotope (identified through gamma spectroscopy), followed with the measured activity in Bq/g. Theses are the values given by Busby (he has used the data for U-235 and Th-234). Then there are columns showing the statistical uncertainty of the activity for each measured isotope. First a column with the measured value (the activity), then a column with the statistical uncertainty of the measurement. For example on the second row the activity for K-40 (Potassium-40) is given as 0.670 +- 0.039 Bq/g. For many of the isotopes, for instance I-131 (Iodine-131), there is instead a value given as < 0.0022 Bq/g. This indicates that the measurement was practically below the level of detection (LOD). For I-131 the activity is at the most 0.0022 Bq/g.

Busby seems to have forgotten, or have ignored, to include the error bars in his plot. Maybe it is not so bad to ignore them, the errors for U-235 and Th-234 seem to be very small.

But the measured values themselves are also very small!

Actually, the uncertainties for the measured samples is on average 28% for U-235 and 41% for Th-234. With regular error propagation we get uncertainties for the activity ratio that are on average 51% of the ratio itself. This means that the measured activity may deviate quite a lot from the given value. Let us take a look at Busby's plot again, but now with the error bars included. N.B.: The errors given in the AMEC tables cover two standard deviations instead of one (see page 40 in the Niras part of the AMEC report). For the plots made by us we use error bars corresponding to one standard deviation instead. If the error bars correspond to two standard deviations, then it means that the result from a new measurement has a 95% probability to be somewhere within the limits of the error bars. With error bars corresponding to one standard deviation there is about 67% probability that a new measurement will give results within the error bars, i.e. in about one third of the cases (33%) the new measurement, as well as the true value could very well be outside of the limits of the error bars. For the discussion here our selection of error bars corresponding to one standard deviation may seemingly work in Busby's favour, but it will not change our conclusions as long as we are consistent in the analysis.

Figure 2: Activity ratio as function of depth in the ground, our version. The red line shows the expected value R=21.3 for natural uranium. The black line shows the arithmetic mean value from the measured data, and the dashed black line shows the weighted mean.

The red line shows the expected ratio R=21.3 for natural uranium. The black line is the average value (arithmetic mean) from the measured data, with a value 18.8 (the weighted mean, which takes the size of the error bars into account, is slightly lower, 17.4, and is shown as dashed black line). The blue line is a logarithmic fit to the data, using the trend line function in Open Office spreadsheet. As seen the curve is almost identical to the one in Busby's plot. But all of a sudden the conclusion from Busby that the activity ratio is significantly lower than 21.3 does not look so certain any more. As seen the average value (and the weighted mean) is lower than 21.3, but about two thirds of the data points overlap with the value 21.3. Actually, there are 9 points out of 30 that do not overlap with 21.3, and the data point that do not overlap tend to have a bias towards lower values. But, taking the error bars into account, they do not deviate significantly from a zero hypothesis that the uranium is of natural composition. Busby can draw almost any curve he wants, there are many curves that fit the data with about the same probability. When it comes to the curve selected by Busby, it has an associated R-squared value equal to 0.19. This is a very low value for a curve, indicating that it is not very likely that the blue curve describes the relationship between activity ratio and sample depth. The R-squared value should be closer to 1.0 and at least larger than 0.5, in order to be taken seriously.

So what about the 9 data points whose error bars do not overlap with the value 21.3? Well, that is what to be expected from data with error bars corresponding to one standard deviation; about one third of the data points will not agree. If we had kept the error bars of double size (two standard deviations) then about 5% of the data points will not agree. 5% of 30 data points, that means that one or two data points that would not overlap with 21.3. Anybody in doubt is welcome to plot the data for themselves in this way and count how many data points that do not overlap. The rest of us move on...

In the light of all this, Busby's statement on page 8 of the report, regarding the AMEC report, becomes a bit strange:

"Had the authors of this report bothered, simple division of the U238 activity by the

U235 activity would have yielded the value of 17.4, signalling enriched uranium and

not the natural uranium they claimed was present."

Had Busby bothered, simple inclusion of the statistical uncertainties and error propagation would have yielded error bars to the value (17.4) to be 5.0, i.e. the measured result would be somewhere in the range 12.5 to 22.4. Of course Busby didn't bother, because then it would show that he has nothing to show.

In Busby's table he comments on the enrichment level with terms like "Natural U", "EU" (enriched uranium), "Borderline" and "High EU". The latter is very interesting. Highly enriched uranium, what could it signify. 3%? 5%, or even more? From the given data we can calculate the actual enrichment of each sample, of course we are including the uncertainties into the calculation.

Figure 3: The calculated uranium enrichment level as function of sample depth. For explanation of the lines, see the caption of Fig. 2.

Fig. 3 shows the calculated enrichment of each sample as function of sample depth. In this case the red line shows the 0.72% of U235-content that is expected in natural uranium. The black line is the arithmetic mean, and the dashed black line is the weighted mean. As seen from the data points the highest enrichment level is 1.25%, with the error bars the range is from 0.98% to 1.54%. Thus the comment from Busby's table that it is highly enriched uranium does not seem feasible. If the uranium would have leaked from any of the nearby reactors, then it doesn't fit the picture at all. AGRs use fuel with an enrichment of 2.5-3.5%, so even with some burnup the samples should indicate a higher enrichment. MAGNOX-reactors, on the other hand, use natural uranium, so a leak from that reactor would only show natural uranium. This could be the case (we will return to this issue below), but if so, then why is Busby so keen on saying that there is enriched uranium in the ground? The average value of the enrichment from the samples is 0.84% (black line), but considering the uncertainties on each sample, the zero hypothesis that there is only natural uranium (red line) still holds. And if we would use the AMEC error bars that are twice as large (apologies if this is confusing...) then even the 1.25% data agrees with the hypothesis of natural uranium.

Thus, Busby's statement that there is enriched uranium in the sample have no solid basis. He can not claim any deviation from the zero hypothesis that there is only natural uranium in the ground!

In the figure we have also included a fitted curve (blue), similar to the one used by Busby in Fig. 1. Once again, the R-squared value is lousy, to say the least. But, you may say, in both Fig. 2 and 3, the curve seems to agree very well with the data, at least for the samples deeper than 2 m?!? Well, here we have to look at the distribution of all the data points. There are 25 samples in the depth range 0.5-1.5 m. Those data points are, to put it mildly, all over the place, spanning from 0.6% to 1.25%. Just looking at these data, they look very random, and you can fit just about any line or curve through the blob of data, you will prove nothing.

Now we look at the 5 data points in the depth range 2-4.5 m, don't they prove that there is only natural uranium deep in the ground while the samples closer to the surface include enriched uranium? First, we only have 5 samples in this range, spanning from 0.6% to 0.9%. Thus these data points are not conclusive either, and a few more samples may very well have the same distribution as in the blob, i.e. a completely random distribution. The problem with the fitted curve is that it does not take into account that there are only a few data points here. A proper treatment would be to introduce some kind of weighting factor, reducing the importance of the deeper samples. Busby's fitted curve proves nothing.

HIGHER URANIUM ACTIVITY THAN FROM NATURAL BACKGROUND?

In Table 1 Busby has calculated the activity from U-238 and claims that the levels are up to 4 times higher than the natural background. We ignore any possible errors in how Busby has calculated the activity, and focus on the statement that the activity is higher than what can be expected in the area.

AMEC has a reference level of 330 Bq/kg, which Busby claims is too high, it works as a reference level for the UK on a general scale, but on the local scale Busby refers to a different report (Beresford et al.) and claims that the background level is 18-24 Bq/kg.

Busby writes:

"Data is available for background

Uranium in the UK from the Environment Agency 2007 report (Beresford et al 2007),

as the authors must have known. The range of Uranium activity given in that report

for the area is 1.6 to 2mg/kg or about 18-24Bq/kg. The map of Uranium levels from

Beresford et al 2007 is reproduced in Fig 2. High levels above 100Bq/kg are only

indicated in the granite areas. We conclude (conservatively) that the levels of

Uranium (below 0.4 m depth) in the EDF survey site are up to 40Bq/kg greater than

expected."

Furthermore, in the figure caption for the map, Busby writes:

"Colour over Hinkley Point is pale blue."

Really? Let's take a look. In Fig. 4 is a part of the map from the report. We have marked the approximate location of Hinkley Pont with an open square. To us, the colour over Hinkley Point looks green, not pale blue.

Thus the range 18-24 Bq/kg should be increased to 24-31 Bq/kg. Already by this minor adjustment we have reduced Busby's claim of "up to 4 times higher" to "up to 3 times higher."

The average value is about 58 Bq/kg, or 50 Bq/kg, depending on which approach to use in order to estimate the uranium activity, i.e. less than a factor of 2 from the expected levels (after correcting for the apparent colour blindness of Busby). So, it is still a factor of 2 higher than the expected background? Well, local variations may be quite significant, it may even vary significantly within a few meters. Furthermore, the map Busby refers to is very crude, and is based on geological extrapolation with averages over fairly large grid squares (5 km * 5 km). The British Geological Survey have so far not produced any detailed maps for this part of the UK, but, as the authors must have known (using Busby's exact wording against himself), a look at similar ground types in the better charted areas shows wide variations over small areas.

Figure 4: Excerpt of map (Beresford et al., 2007) with uranium contents. Hinkley Point is marked with an open square.

BUSBY'S INSULT (of the readers' intelligence)

We ignore most of the other figures by Busby. They all give similar conclusions if the statistical uncertainties are taken into account: Busby has nothing to show! We will, however, comment on Fig. 5. The data shows the calculated uranium activity as function of the distance to the sea shore.

Figure 5: Busby's Fig. 5, showing the total uranium activity as function of distance to the sea.

As seen, a quite sophisticated curve has been drawn. According to Busby the figure shows that there is a decreasing uranium activity the further away from the sea you go. This is a theory that he is trying to include in several of his studies, that radioactive particles in the sea gets into the air when the waves hit the shore, then people breathe the particles and get cancer. During the BSRRW tour of 2010 he tried to pull this stunt by separating the counties of Sweden into those facing the Baltic Sea and those who are inland, and then he claimed an increase in breast cancer (due to the Chernobyl accident) in the coastal counties. At that time it was easy to show that Busby was either cheating, or being very careless with how he used public data. Let us see if he has learnt anything and improved his methods since then.

Busby admits that the relation is not statistically significant, but within the first 300 m from the sea he claims that it is significant. To us, the data, with or without error bars, seems to be randomly distributed all over the plot, i.e. indicating that there is no relation at all. A way to check if a set of data is completely random is to try to fit a circle or ellipse to the data. In Fig. 6 below we have drawn an ellipse arbitrarily over the data, but we will not bother to try to fit it and calculate any statistical significance.

Figure 6: Our version of Busby's Fig. 5, with error bars included, and an arbitrary ellipse centered at the coordinate (450,57).

As seen, this arbitrary ellipse overlaps with the error bars for about two thirds of the data points. This is at the same level of agreement, or better, than Busby's sophisticated curve. In other words, we can fit any arbitrary curve through the data, and claim any relation we like. Any claim we make is of the same order of significance as the claim by Busby: zero!

Professor Chris Busby owes us all an apology for the insult of trying to fool the world with that curve.

OTHER STATEMENTS BY BUSBY

On page 3 in the report, Busby draws a number of conclusions. We respond to each conclusion with bold text.

1. The uranium is not natural in most of the samples: it is mostly man-made

enriched uranium, presumably from uranium reactor fuel from the Hinkley

Point reactors.

No, not when taking the measured uncertainties into account!

None of the reactors (MAGNOX or AGR) used fuel that would fit the scenario of enrichment to about 0.8% or slightly more.

2. Samples were taken from different depths. The trend with depth shows that the

surface samples contain significantly more enriched uranium, suggesting that

the contamination is from airborne precipitation.

No, not when taking the measured uncertainties into account!

The few data points a large depths are given too high importance in order to make such conclusions. With proper weighting, many alternative curves could be drawn with similar probability (i.e. none!).

3. The trend with depth also shows that the activity concentration is highest at the

surface, and about double the activity concentration in the deep samples which

appear to be natural uranium.

NO. The reasoning is similar to the point above.

Furthermore: At the upper layers the measured activities vary from 30 to 95 Bq.

At the lower depths the measured activities vary from... 20 to 95 Bq.

Due to the lack of data at lower depths, in comparison with the number of data at the upper layers, no conclusion can be drawn about a correlation. Not by Busby at least.

Points 2 and 3 deserve another comment as well. In point 2 Busby claims that the enrichment level is higher closer to the surface. In point 3 he claims that the activity concentration is higher closer to the surface. Thus, if we plot the enrichment level (or the activity ratio for those who prefer that option) as function of the activity, we should have a clear linear relation. Busby admits that there is about 15% uncertainty in the calculated activity depending on which approach one uses. This is a systematic uncertainty, to be added to the statistical uncertainties. If we plot using the method that Busby used (uranium activity based on the U-235 activity multiplied with 21.3), we may eventually see a weak linear relation, though the statistical significance is very weak. If we plot using the other method (uranium activity based on the Th-234 activity) we once again get a random distribution where we can fit an ellipse or whatever you like. So, doesn't this show that the method used by Busby is better, since it shows at least an indication of a linear relation? No, it just shows that there are, besides the statistical uncertainties (which Busby has ignored to even mention that they exist, and that they are large) some systematic uncertainties that are at least 15% but probably much larger.

4. The trend analysis allows the calculation of the excess man-made uranium to

be approximately 40Bq/kg that, in turn, enables an assessment of the quantity

of enriched uranium contamination in the 2km2 area alone as 10 tonnes.

The excess is rather 20 Bq/kg (average value of about 50 to be compared with the upper range from the map to be 31), and to that we should add local variations that very well could make the claimed excess equal to: zero.

By the way, 20 Bq is the natural radioactivity in a 150 gram banana, just to put Busby's statements into a more reasonable perspective for those who want to believe Busby's claims about cancer clusters in the area.

10 tonnes of uranium spread over 2 square kilometers equals 5 gram per square meter. If we then assume that these 5 grams are evenly distributed in a 1 m deep layer, then we have 5 gram per cubic meter. Assuming a density of about 2000 kg per cubic meter (1600-2500 kg per cubic meter seems to be reasonable for the ground types (sandstone, mudstone, limestone) that are typical in the area. We then get 2.5 mg of excess uranium per kg mud. Busby got that part right, but once again, considering all the uncertainties both with respect to the measurement and the crude estimates of the map, there is no indication whatsoever that this is anything but natural uranium that has been in the ground all the time.

5. There is a non-significant correlation between uranium activity concentration

and distance from the sea suggesting that, at least, part of the contamination is

due to sea-to-land transfer; however, more measurements must be made to

further examine this point.

NON-SIGNIFICANT IS INDEED THE WORD! Busby should apologize for once again trying to force his theory of sea-to-land transfer into the discussion.

THE FINAL ARGUMENT

If you're still not convinced that the whole study is garbage, there is one card left for us to play. The data tables from the AMEC report show values that are above the level of detection only for those isotopes that are part of the U-238 or Th-232 decay chains. The only exception is K-40, which is abundant naturally in many materials (including our bodies). If there would have been a leak from the nuclear reactors of any significance, the data tables would show, besides the uranium isotopes, a number of fission fragments such as Cobolt-60 and Cesium-137. We see no such indication, none at all (some of those isotopes are in the AMEC tables, but the given values are very low, usually below what is considered to be the level of detection). We would also expect to see some plutonium isotopes in the tables.

The only way to get a uranium leak without finding any associated fission fragments, is if the leak would happen before the fuel is put into the nuclear reactor, or before starting a new reactor for the first time. Imagine somebody cutting off pieces from the uranium fuel, milling it into dust, and then let the wind spread it into the surroundings. A likely scenario? It is, in our humble opinion, a more likely scenario that the only pollution of any significance around Hinkley Point is the report itself by Busby and Collingridge.

CONCLUSIONS

Once again we find that Professor Busby is using public data in a selective way, and then draws very wide-reaching conclusions from the data. So, what about all the studies that indicate increased cancer incidence near Hinkley Point? Well, the studies referred to in the report, have all been performed by...Chris Busby. This is the third case where we find serious flaws in Busby's methods. Caution is advised for anybody who wants to take anything that the esteemed Professor says seriously.

Mattias Lantz - member of Nuclear Power Yes Please

Acknowledgements

We would like to thank Martin Solberger and Professor Farid El-Daoushy, both at Uppsala University, for helpful discussions about statistics and environmental gamma spectroscopy methods.

Apologies

In the text above we have almost completely ignored the part of Ms. Cecily Collingridge and only referred to Chris Busby. As co-author of this paper she is equally responsible for it, but we hope that she will find more serious partners for her future efforts.

Other web sources that mention the Hinkley Point study:

http://www.thisissomerset.co.uk/news/Developer-rejects-claims-enriched-uranium-site/article-3101229-detail/article.html

http://cityunslicker.blogspot.com/2011/01/mr-huhne-goes-to-radioactive-hinkley.html

http://bristol.indymedia.org/article/703009

http://bristol.indymedia.org/article/703035

http://stopnuclearpower.blogspot.com/2011/01/campaigners-slam-energy-secretarys.html

http://oneworldcolumn.blogspot.com/2011/02/nuclear-industrys-desperate-last-stand.html

http://www.bsrrw.org/?page_id=11

http://www.bsrrw.org/wp-content/uploads/2011/01/Hinkley-Point-ECRR.pdf,

http://stopnuclearpower.blogspot.com/2011/01/campaigners-slam-energy-secretarys.html

http://sayingnotohinkleycround2.blogspot.com/

http://www.stophinkley.org/NewsPages/new110114.htm

Here we give our full investigation of the claims by Chris Busby regarding Hinkley Point. If you have any additional information, please add a comment to the thread.

BACKGROUND

Hinkley Point is a nuclear power plant in Somerset, South West England. At the site there is a decommissioned MAGNOX reactor (http://en.wikipedia.org/wiki/Hinkley_Point_A_nuclear_power_station) that operated during the years 1965-2000, and two Advanced Gas-cooled Reactors (AGR) that were commissioned in 1976 and are still running (http://en.wikipedia.org/wiki/Hinkley_Point_B_nuclear_power_station).

The French company Electricite de France (EDF), who owns the two AGR units, is planning for the construction of new nuclear reactors at the site, this time of the type EPR (European Pressurised Reactor) similar to the one being built in Olkiluoto, Finland (http://en.wikipedia.org/wiki/Hinkley_Point_C_nuclear_power_station).

There are several organisations, for instance Stop Hinkley, that oppose the plans for new installations, and also works for a closure of the existing plants. In support of the campaign is Professor Chris Busby, who we have encountered before, see here. For several years Busby has, mainly through his organization Green Audit claimed an increase of childhood leukaemia, breast cancer (here, here and here) and increased childhood mortality near Hinkley Point and other nuclear power plants. Several of the claims have been opposed by various health authorities and researchers.

In January 2011 Busby and his colleague, Cecily Collingridge, released a study, "Evidence of significant enriched uranium atomic fuel contamination of the Hinkley Point proposed nuclear site in Somerset and its potential implications" (the Green Audit press release is found here, and there is also information at Busby's organization The Low Level Radiation Campaign), where they claim that the ground around the proposed EPR reactors is contaminated with about 10 tonnes of enriched uranium, presumably coming from the older reactors. Is it really so? Let us follow the reasoning of Professor Busby and see if his claims hold any truth this time.

THE MEASURED DATA

EDF has commissioned a company called AMEC to take samples and make measurements of radioactivity, chemicals, etc on the proposed site for the new plant, this is part of the regular Environmental Impact Assessment. The gamma spectroscopy data are presented in the document "AMEC Phase 2 Supplementary Investigation of Potential Radiological Contamination EDF Access Appendix C Soil Sampling Data and Comparison with Background Values- December 2008 AMEC 15011/TR/00091" (an alternative search route is here together with two related reports).

Data are given for about 30 trenches where earth samples have been obtained. The radiological contents of each sample has been identified in a laboratory through standard gamma spectroscopy methods. There are also results from measurements of alpha and beta radiation, but here we focus on the measurements of gamma radiation. The report gives the identified isotopes and the activity measured in Bq/g. Over all the data shows low levels of radioactivity in the area.

Busby has used these data from the AMEC analysis, focusing on the uranium isotopes. In his own words:

"Gamma spectra data can be used (with some caveats, see below) to determine the

activity concentrations of U-235 and U-238.

These are the two isotopes of interest in determining if uranium in a sample is

natural or from a man-made source, namely U-238 and U-235. The natural isotope

activity ratio is 21.3. That is, U-235, the fissile component used in nuclear reactors is

present in natural uranium, from a mine, from the environment with 1/21.3 times the

activity of U-238. The atomic ratio is 137.88, and this is what is measured when

samples are analysed by mass spectrometry. But with gamma spectrometry, the ratio

should be 21.3. If it is less, then there is a proportion of enriched uranium in the

sample, and this has to be man-made. Enriched Uranium (which is more radioactive

than natural uranium) does not exist in nature."

So far so good. Busby expresses the ratio between U-235 and U-238 in the activity ratio, which for natural uranium is 21.3. This ratio is valid provided that one can properly identify certain peaks of gamma radiation, associated with the nuclear de-excitation after the decay, and then correct for the probability that these particular de-excitations will occur, and properly correct for limited detector efficiency. One can consider measuring different peaks, if available, as long as the corrections are properly applied. Most likely the AMEC results are based on some standard procedure. The activity ratio 21.3 corresponds to the 0.7% mass percent of U-235 in natural uranium. For some reason Busby seems to prefer to discuss the matter in terms of the activity ratio rather than in terms of enrichment. We will return to this issue later on.

We should point out that it is difficult to measure how much U-235 there is in environmental uranium samples by using gamma spectroscopy methods. A much more accurate method is to use mass spectroscopy methods, where the fraction of U-235 is measured directly. In the present case, this method has not been used by AMEC.

Busby continues:

"There is, however, a problem in that U-238 is not a gamma emitter, and we

have to rely on the gamma activity of its immediate daughter decay product Thorium-

234 to signal the activity of U-238. Whilst this will give an accurate value for U-238 it

can give an incorrect result for the U238/U235 ratio since Uranium is more soluble

than Thorium, leading to a loss of U-235 relative to Th-234. But such a process would

signal Depleted Uranium as the ratio would be too high, greater than 21.3. So if we

are finding Enriched Uranium from a man-made source, using gamma spectral data, it

is certainly there. And it is."

Really? Here are two statements, both can be questioned.

STATEMENT 1: Any determined enrichment ratio is a lower limit

Busby claims that the solubility of Uranium in water is higher than for Thorium in water. This is probably correct. But we have to consider the life time of the various isotopes in the decay chain. U-238 decays mainly through alpha emission to Th-234. The half life of Th-234 is about 24 days, beta decaying into Pa-234 (Protactinium). Pa-234 has a half life of only 6.7 hours before decaying into U-234, which has a half life of 245 000 years (a chart with the U-238 decay chain is given here). So, for the given case we could, naively, make two alternative assumptions:

(1): If there is only natural uranium in the ground, then we are dealing with changes over geological time scales, where the life times of the three Uranium isotopes (U-234, U-235 and U-238) are very long (245 000 years, 704 million years and 4.5 billion years, respectively). A lower solubility of Thorium-234 then has limited importance because there is only Thorium around for about a month for each decay, to be compared with the hundreds of thousands of years (or much more!) that we have the Uranium, irrespective of which isotope.

(2): The uranium (and Thorium) found on the site origins from the nuclear plant. What is measured then either comes from a continuous release since 1965, or from one or several larger releases after that date up to the year 2008 when the measurements were performed by AMEC. In either case, the released uranium has occurred on the order of one or more years ago, and has remained as Uranium for the vast majority of the time, save for about a month that decaying U-238 is in the Thorium state.

For both cases, the difference in solubility would probably have a very limited role, because the water solubility would affect the amount of U-238 in the same way as for U-235, while the less soluble Thorium isotopes would play a smaller role due to the much shorter time that the decaying nuclide will be in that state.

But, more important, without knowing anything about the local conditions of the ground, with respect to water flows, type of ground, seasonal changes, etc., we are in no position to make any claim whatsoever about the effects of the different solubilities. Neither is Busby.

Thus the claim that the activity ratio U238/U235 will indicate a lower limit must be met with: We don't know, and Busby does not know, he is just speculating.

STATEMENT 2: There is enriched uranium in the samples

Now on to the second statement, i.e. "And it is.", i.e. the uranium has a U-235 content that is higher than from natural uranium.

Busby claims that the uranium is enriched and therefore from a man-made source. Most of the measured activity ratios R=A(Th-234)/A(U-235) are lower than 21.3, indicating enriched uranium. So let us take a look at his calculations.

Below is a figure of part of Busby's table (Table 1 in the report).

The columns are, from left to right: AMEC Sample code number, Mean depth of the sample (m), Mean distance to the sea (m), activity of U-235 (Bq/g), activity of Th-234 (Bq/g), Th-234/U-235 ratio, calculated U-238 activity, and finally notes about if the sample shows natural uranium or any enrichment.

The sample numbers, the mean depth, and the activities of U-235 and Th-234, are from the AMEC report, while the mean distance to the sea, the activity ratio R, and the calculated U-238 activity, are calculated by Busby.

Table 1: Excerpt from Table 1 in Busby's paper, showing measured data from the AMEC report and Busby's calculated data.

In Fig. 1 is Busby's calculation of the activity ratio R=U238/U235 as function of the mean depth (in meters) of where the sample was taken. Shown is also a fitted curve of the form R=k*ln(depth)+m, where k and m are fitted parameters.

Figure 1: Figure 1 in Busby's report, showing the activity ratio as function of depth in the ground.

It looks rather convincing doesn't it? Most of the data is below the 21.3 value that indicates natural uranium. Thus Busby must be right, there has been some kind of leak from the nuclear reactors, and enriched fuel has been spread in the environment. Furthermore, the data points seems to agree pretty well with the curve, don't they? This means that the enrichment is increasing closer to the surface, a further indication that the enriched uranium must have ended up there relatively recently, while the uranium in samples deeper down corresponds to the natural composition.

Now wait a minute. Isn't there something missing in all of this? How about error bars?

For those not used to how measurements (of any kind) are made, it is valuable to know that each measurement has an associated uncertainty, i.e. a value that indicates the quality of the measurement. A good measurement based on a lot of events (i.e. good statistics) is said to have good precision.

So each data point should then have associated error bars, indicating the likely range of uncertainty for each measurement. Small error bars indicate a measurement with good precision, while large error bars indicate that measurement with low statistics. We see no such error bars in Busby's Fig. 1, could there be that AMEC did not give any uncertainties?

We go to the AMEC report, see Table 2 below.

Table 2: Excerpt from table in the AMEC report, showing the identified isotopes from the gamma spectroscopy measurements.

Here we see, from left to right, the reference number of the sample, first from the laboratory (NIRAS) that performed the analysis, and then the reference number from AMEC who did the excavation and ordered the analysis by NIRAS. The next column shows each identified isotope (identified through gamma spectroscopy), followed with the measured activity in Bq/g. Theses are the values given by Busby (he has used the data for U-235 and Th-234). Then there are columns showing the statistical uncertainty of the activity for each measured isotope. First a column with the measured value (the activity), then a column with the statistical uncertainty of the measurement. For example on the second row the activity for K-40 (Potassium-40) is given as 0.670 +- 0.039 Bq/g. For many of the isotopes, for instance I-131 (Iodine-131), there is instead a value given as < 0.0022 Bq/g. This indicates that the measurement was practically below the level of detection (LOD). For I-131 the activity is at the most 0.0022 Bq/g.

Busby seems to have forgotten, or have ignored, to include the error bars in his plot. Maybe it is not so bad to ignore them, the errors for U-235 and Th-234 seem to be very small.

But the measured values themselves are also very small!

Actually, the uncertainties for the measured samples is on average 28% for U-235 and 41% for Th-234. With regular error propagation we get uncertainties for the activity ratio that are on average 51% of the ratio itself. This means that the measured activity may deviate quite a lot from the given value. Let us take a look at Busby's plot again, but now with the error bars included. N.B.: The errors given in the AMEC tables cover two standard deviations instead of one (see page 40 in the Niras part of the AMEC report). For the plots made by us we use error bars corresponding to one standard deviation instead. If the error bars correspond to two standard deviations, then it means that the result from a new measurement has a 95% probability to be somewhere within the limits of the error bars. With error bars corresponding to one standard deviation there is about 67% probability that a new measurement will give results within the error bars, i.e. in about one third of the cases (33%) the new measurement, as well as the true value could very well be outside of the limits of the error bars. For the discussion here our selection of error bars corresponding to one standard deviation may seemingly work in Busby's favour, but it will not change our conclusions as long as we are consistent in the analysis.

Figure 2: Activity ratio as function of depth in the ground, our version. The red line shows the expected value R=21.3 for natural uranium. The black line shows the arithmetic mean value from the measured data, and the dashed black line shows the weighted mean.

The red line shows the expected ratio R=21.3 for natural uranium. The black line is the average value (arithmetic mean) from the measured data, with a value 18.8 (the weighted mean, which takes the size of the error bars into account, is slightly lower, 17.4, and is shown as dashed black line). The blue line is a logarithmic fit to the data, using the trend line function in Open Office spreadsheet. As seen the curve is almost identical to the one in Busby's plot. But all of a sudden the conclusion from Busby that the activity ratio is significantly lower than 21.3 does not look so certain any more. As seen the average value (and the weighted mean) is lower than 21.3, but about two thirds of the data points overlap with the value 21.3. Actually, there are 9 points out of 30 that do not overlap with 21.3, and the data point that do not overlap tend to have a bias towards lower values. But, taking the error bars into account, they do not deviate significantly from a zero hypothesis that the uranium is of natural composition. Busby can draw almost any curve he wants, there are many curves that fit the data with about the same probability. When it comes to the curve selected by Busby, it has an associated R-squared value equal to 0.19. This is a very low value for a curve, indicating that it is not very likely that the blue curve describes the relationship between activity ratio and sample depth. The R-squared value should be closer to 1.0 and at least larger than 0.5, in order to be taken seriously.

So what about the 9 data points whose error bars do not overlap with the value 21.3? Well, that is what to be expected from data with error bars corresponding to one standard deviation; about one third of the data points will not agree. If we had kept the error bars of double size (two standard deviations) then about 5% of the data points will not agree. 5% of 30 data points, that means that one or two data points that would not overlap with 21.3. Anybody in doubt is welcome to plot the data for themselves in this way and count how many data points that do not overlap. The rest of us move on...

In the light of all this, Busby's statement on page 8 of the report, regarding the AMEC report, becomes a bit strange:

"Had the authors of this report bothered, simple division of the U238 activity by the

U235 activity would have yielded the value of 17.4, signalling enriched uranium and

not the natural uranium they claimed was present."

Had Busby bothered, simple inclusion of the statistical uncertainties and error propagation would have yielded error bars to the value (17.4) to be 5.0, i.e. the measured result would be somewhere in the range 12.5 to 22.4. Of course Busby didn't bother, because then it would show that he has nothing to show.

In Busby's table he comments on the enrichment level with terms like "Natural U", "EU" (enriched uranium), "Borderline" and "High EU". The latter is very interesting. Highly enriched uranium, what could it signify. 3%? 5%, or even more? From the given data we can calculate the actual enrichment of each sample, of course we are including the uncertainties into the calculation.

Figure 3: The calculated uranium enrichment level as function of sample depth. For explanation of the lines, see the caption of Fig. 2.

Fig. 3 shows the calculated enrichment of each sample as function of sample depth. In this case the red line shows the 0.72% of U235-content that is expected in natural uranium. The black line is the arithmetic mean, and the dashed black line is the weighted mean. As seen from the data points the highest enrichment level is 1.25%, with the error bars the range is from 0.98% to 1.54%. Thus the comment from Busby's table that it is highly enriched uranium does not seem feasible. If the uranium would have leaked from any of the nearby reactors, then it doesn't fit the picture at all. AGRs use fuel with an enrichment of 2.5-3.5%, so even with some burnup the samples should indicate a higher enrichment. MAGNOX-reactors, on the other hand, use natural uranium, so a leak from that reactor would only show natural uranium. This could be the case (we will return to this issue below), but if so, then why is Busby so keen on saying that there is enriched uranium in the ground? The average value of the enrichment from the samples is 0.84% (black line), but considering the uncertainties on each sample, the zero hypothesis that there is only natural uranium (red line) still holds. And if we would use the AMEC error bars that are twice as large (apologies if this is confusing...) then even the 1.25% data agrees with the hypothesis of natural uranium.

Thus, Busby's statement that there is enriched uranium in the sample have no solid basis. He can not claim any deviation from the zero hypothesis that there is only natural uranium in the ground!

In the figure we have also included a fitted curve (blue), similar to the one used by Busby in Fig. 1. Once again, the R-squared value is lousy, to say the least. But, you may say, in both Fig. 2 and 3, the curve seems to agree very well with the data, at least for the samples deeper than 2 m?!? Well, here we have to look at the distribution of all the data points. There are 25 samples in the depth range 0.5-1.5 m. Those data points are, to put it mildly, all over the place, spanning from 0.6% to 1.25%. Just looking at these data, they look very random, and you can fit just about any line or curve through the blob of data, you will prove nothing.

Now we look at the 5 data points in the depth range 2-4.5 m, don't they prove that there is only natural uranium deep in the ground while the samples closer to the surface include enriched uranium? First, we only have 5 samples in this range, spanning from 0.6% to 0.9%. Thus these data points are not conclusive either, and a few more samples may very well have the same distribution as in the blob, i.e. a completely random distribution. The problem with the fitted curve is that it does not take into account that there are only a few data points here. A proper treatment would be to introduce some kind of weighting factor, reducing the importance of the deeper samples. Busby's fitted curve proves nothing.

HIGHER URANIUM ACTIVITY THAN FROM NATURAL BACKGROUND?

In Table 1 Busby has calculated the activity from U-238 and claims that the levels are up to 4 times higher than the natural background. We ignore any possible errors in how Busby has calculated the activity, and focus on the statement that the activity is higher than what can be expected in the area.

AMEC has a reference level of 330 Bq/kg, which Busby claims is too high, it works as a reference level for the UK on a general scale, but on the local scale Busby refers to a different report (Beresford et al.) and claims that the background level is 18-24 Bq/kg.

Busby writes:

"Data is available for background

Uranium in the UK from the Environment Agency 2007 report (Beresford et al 2007),

as the authors must have known. The range of Uranium activity given in that report

for the area is 1.6 to 2mg/kg or about 18-24Bq/kg. The map of Uranium levels from

Beresford et al 2007 is reproduced in Fig 2. High levels above 100Bq/kg are only

indicated in the granite areas. We conclude (conservatively) that the levels of

Uranium (below 0.4 m depth) in the EDF survey site are up to 40Bq/kg greater than

expected."

Furthermore, in the figure caption for the map, Busby writes:

"Colour over Hinkley Point is pale blue."

Really? Let's take a look. In Fig. 4 is a part of the map from the report. We have marked the approximate location of Hinkley Pont with an open square. To us, the colour over Hinkley Point looks green, not pale blue.

Thus the range 18-24 Bq/kg should be increased to 24-31 Bq/kg. Already by this minor adjustment we have reduced Busby's claim of "up to 4 times higher" to "up to 3 times higher."

The average value is about 58 Bq/kg, or 50 Bq/kg, depending on which approach to use in order to estimate the uranium activity, i.e. less than a factor of 2 from the expected levels (after correcting for the apparent colour blindness of Busby). So, it is still a factor of 2 higher than the expected background? Well, local variations may be quite significant, it may even vary significantly within a few meters. Furthermore, the map Busby refers to is very crude, and is based on geological extrapolation with averages over fairly large grid squares (5 km * 5 km). The British Geological Survey have so far not produced any detailed maps for this part of the UK, but, as the authors must have known (using Busby's exact wording against himself), a look at similar ground types in the better charted areas shows wide variations over small areas.

Figure 4: Excerpt of map (Beresford et al., 2007) with uranium contents. Hinkley Point is marked with an open square.

BUSBY'S INSULT (of the readers' intelligence)

We ignore most of the other figures by Busby. They all give similar conclusions if the statistical uncertainties are taken into account: Busby has nothing to show! We will, however, comment on Fig. 5. The data shows the calculated uranium activity as function of the distance to the sea shore.

Figure 5: Busby's Fig. 5, showing the total uranium activity as function of distance to the sea.

As seen, a quite sophisticated curve has been drawn. According to Busby the figure shows that there is a decreasing uranium activity the further away from the sea you go. This is a theory that he is trying to include in several of his studies, that radioactive particles in the sea gets into the air when the waves hit the shore, then people breathe the particles and get cancer. During the BSRRW tour of 2010 he tried to pull this stunt by separating the counties of Sweden into those facing the Baltic Sea and those who are inland, and then he claimed an increase in breast cancer (due to the Chernobyl accident) in the coastal counties. At that time it was easy to show that Busby was either cheating, or being very careless with how he used public data. Let us see if he has learnt anything and improved his methods since then.

Busby admits that the relation is not statistically significant, but within the first 300 m from the sea he claims that it is significant. To us, the data, with or without error bars, seems to be randomly distributed all over the plot, i.e. indicating that there is no relation at all. A way to check if a set of data is completely random is to try to fit a circle or ellipse to the data. In Fig. 6 below we have drawn an ellipse arbitrarily over the data, but we will not bother to try to fit it and calculate any statistical significance.

Figure 6: Our version of Busby's Fig. 5, with error bars included, and an arbitrary ellipse centered at the coordinate (450,57).

As seen, this arbitrary ellipse overlaps with the error bars for about two thirds of the data points. This is at the same level of agreement, or better, than Busby's sophisticated curve. In other words, we can fit any arbitrary curve through the data, and claim any relation we like. Any claim we make is of the same order of significance as the claim by Busby: zero!

Professor Chris Busby owes us all an apology for the insult of trying to fool the world with that curve.

OTHER STATEMENTS BY BUSBY

On page 3 in the report, Busby draws a number of conclusions. We respond to each conclusion with bold text.

1. The uranium is not natural in most of the samples: it is mostly man-made

enriched uranium, presumably from uranium reactor fuel from the Hinkley

Point reactors.

No, not when taking the measured uncertainties into account!

None of the reactors (MAGNOX or AGR) used fuel that would fit the scenario of enrichment to about 0.8% or slightly more.

2. Samples were taken from different depths. The trend with depth shows that the

surface samples contain significantly more enriched uranium, suggesting that

the contamination is from airborne precipitation.

No, not when taking the measured uncertainties into account!

The few data points a large depths are given too high importance in order to make such conclusions. With proper weighting, many alternative curves could be drawn with similar probability (i.e. none!).

3. The trend with depth also shows that the activity concentration is highest at the

surface, and about double the activity concentration in the deep samples which

appear to be natural uranium.

NO. The reasoning is similar to the point above.

Furthermore: At the upper layers the measured activities vary from 30 to 95 Bq.

At the lower depths the measured activities vary from... 20 to 95 Bq.

Due to the lack of data at lower depths, in comparison with the number of data at the upper layers, no conclusion can be drawn about a correlation. Not by Busby at least.

Points 2 and 3 deserve another comment as well. In point 2 Busby claims that the enrichment level is higher closer to the surface. In point 3 he claims that the activity concentration is higher closer to the surface. Thus, if we plot the enrichment level (or the activity ratio for those who prefer that option) as function of the activity, we should have a clear linear relation. Busby admits that there is about 15% uncertainty in the calculated activity depending on which approach one uses. This is a systematic uncertainty, to be added to the statistical uncertainties. If we plot using the method that Busby used (uranium activity based on the U-235 activity multiplied with 21.3), we may eventually see a weak linear relation, though the statistical significance is very weak. If we plot using the other method (uranium activity based on the Th-234 activity) we once again get a random distribution where we can fit an ellipse or whatever you like. So, doesn't this show that the method used by Busby is better, since it shows at least an indication of a linear relation? No, it just shows that there are, besides the statistical uncertainties (which Busby has ignored to even mention that they exist, and that they are large) some systematic uncertainties that are at least 15% but probably much larger.

4. The trend analysis allows the calculation of the excess man-made uranium to

be approximately 40Bq/kg that, in turn, enables an assessment of the quantity

of enriched uranium contamination in the 2km2 area alone as 10 tonnes.

The excess is rather 20 Bq/kg (average value of about 50 to be compared with the upper range from the map to be 31), and to that we should add local variations that very well could make the claimed excess equal to: zero.

By the way, 20 Bq is the natural radioactivity in a 150 gram banana, just to put Busby's statements into a more reasonable perspective for those who want to believe Busby's claims about cancer clusters in the area.

10 tonnes of uranium spread over 2 square kilometers equals 5 gram per square meter. If we then assume that these 5 grams are evenly distributed in a 1 m deep layer, then we have 5 gram per cubic meter. Assuming a density of about 2000 kg per cubic meter (1600-2500 kg per cubic meter seems to be reasonable for the ground types (sandstone, mudstone, limestone) that are typical in the area. We then get 2.5 mg of excess uranium per kg mud. Busby got that part right, but once again, considering all the uncertainties both with respect to the measurement and the crude estimates of the map, there is no indication whatsoever that this is anything but natural uranium that has been in the ground all the time.

5. There is a non-significant correlation between uranium activity concentration

and distance from the sea suggesting that, at least, part of the contamination is

due to sea-to-land transfer; however, more measurements must be made to

further examine this point.

NON-SIGNIFICANT IS INDEED THE WORD! Busby should apologize for once again trying to force his theory of sea-to-land transfer into the discussion.

THE FINAL ARGUMENT

If you're still not convinced that the whole study is garbage, there is one card left for us to play. The data tables from the AMEC report show values that are above the level of detection only for those isotopes that are part of the U-238 or Th-232 decay chains. The only exception is K-40, which is abundant naturally in many materials (including our bodies). If there would have been a leak from the nuclear reactors of any significance, the data tables would show, besides the uranium isotopes, a number of fission fragments such as Cobolt-60 and Cesium-137. We see no such indication, none at all (some of those isotopes are in the AMEC tables, but the given values are very low, usually below what is considered to be the level of detection). We would also expect to see some plutonium isotopes in the tables.

The only way to get a uranium leak without finding any associated fission fragments, is if the leak would happen before the fuel is put into the nuclear reactor, or before starting a new reactor for the first time. Imagine somebody cutting off pieces from the uranium fuel, milling it into dust, and then let the wind spread it into the surroundings. A likely scenario? It is, in our humble opinion, a more likely scenario that the only pollution of any significance around Hinkley Point is the report itself by Busby and Collingridge.

CONCLUSIONS

Once again we find that Professor Busby is using public data in a selective way, and then draws very wide-reaching conclusions from the data. So, what about all the studies that indicate increased cancer incidence near Hinkley Point? Well, the studies referred to in the report, have all been performed by...Chris Busby. This is the third case where we find serious flaws in Busby's methods. Caution is advised for anybody who wants to take anything that the esteemed Professor says seriously.

Mattias Lantz - member of Nuclear Power Yes Please

Acknowledgements

We would like to thank Martin Solberger and Professor Farid El-Daoushy, both at Uppsala University, for helpful discussions about statistics and environmental gamma spectroscopy methods.

Apologies

In the text above we have almost completely ignored the part of Ms. Cecily Collingridge and only referred to Chris Busby. As co-author of this paper she is equally responsible for it, but we hope that she will find more serious partners for her future efforts.

Other web sources that mention the Hinkley Point study:

http://www.thisissomerset.co.uk/news/Developer-rejects-claims-enriched-uranium-site/article-3101229-detail/article.html

http://cityunslicker.blogspot.com/2011/01/mr-huhne-goes-to-radioactive-hinkley.html

http://bristol.indymedia.org/article/703009

http://bristol.indymedia.org/article/703035

http://stopnuclearpower.blogspot.com/2011/01/campaigners-slam-energy-secretarys.html

http://oneworldcolumn.blogspot.com/2011/02/nuclear-industrys-desperate-last-stand.html

http://www.bsrrw.org/?page_id=11

http://www.bsrrw.org/wp-content/uploads/2011/01/Hinkley-Point-ECRR.pdf,

http://stopnuclearpower.blogspot.com/2011/01/campaigners-slam-energy-secretarys.html

http://sayingnotohinkleycround2.blogspot.com/

http://www.stophinkley.org/NewsPages/new110114.htm