The Ecologist

A welcoming committee at Christmas Island - site of the UK's Grapple X and Grapple Y bomb tests. But do these children, or their parents, know about the long term legacy of uranium pollution? Photo: Philip via Flickr.
A welcoming committee at Christmas Island - site of the UK's Grapple X and Grapple Y bomb tests. But do these children, or their parents, know about the long term legacy of uranium pollution? Photo: Philip via Flickr.
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The 'forgotten' uranium isotope - secrets of the nuclear bomb tests revealed

Chris Busby

4th November 2014

Papers reluctantly released by the UK Government in the bomb test veterans' legal case for compensation reveal what it has long denied, writes Chris Busby - that bomb fallout is rich in uranium, and that most of its radioactivity is concentrated in the 'forgotten' but highly active isotope U-234, explaining much of the substantial, long term damage to veterans' health.

The highly radioactive isotope U-234 accounts for most of the radioactivity in the Uranium in the bomb fallout. This is shown by direct measurement, and is readily explained by its concentration in Enriched Uranium.

Secret documents released to me as a result of an order by the Judge in the nuclear test veteran pension appeals (the late HH Hugh Stubbs) reveal valuable evidence about uranium in fallout.

The documents show that fallout from atmospheric nuclear testing contains enormous amounts of uranium. This should be no surprise as nuclear bombs contain a lot of uranium, and most of it remains unfissioned after a nuclear explosion.

But what will come as news to a great many people is the importance in the fallout of an isotope of uranium that few of us have even heard of: uranium-234, a highly radioactive alpha emitter which concentrates in the 'enriched uranium' (EU) used in nuclear bombs.

All uranium binds to DNA and causes cancer and genetic effects in the children of those exposed - but U-234 is especially hazardous. A restricted document shows that the matter was raised as early as 1953 at a meeting at Harwell by the late Karl Z Morgan, who was in charge of analyzing health effects of the US Nevada tests.

Morgan characterized U-234 as a major unexpected hazard at the test sites. The UK and USA military have consistently failed to take account of the exposures to these uranium components of the bombs in all the official reports published by their experts.

Indeed, they have tied themselves in knots trying refuse to release data and meanwhile (in the courts) to argue that there is no uranium at all in fallout. The secret documents give the lie to all this. All of the calculations made by official agencies of fallout exposures are thus faulty and should be revisited.

Refusing to believe the impossible

In 2009 I was commissioned by Rosenblatts to act as an expert in the big nuclear Test Veteran High Court case AB and Others vs. Ministry of Defence. I spent time at their offices examining 30 box files of evidence they had obtained.

I was astonished to find that although the MoD defence was that there was no appreciable fallout at the test sites (and therefore the veterans could not have been exposed) there was no solid evidence of this. No measurements, no numbers, no reports. This seemed impossible.

So I wrote to the Atomic Weapons Establishment with a Freedom of Information request for all documents dealing with radiation and radioactivity measurements at the test sites. What I did find in the haystack of paper was a copy of minutes of a meeting at Harwell. I made some notes:

"Other subjects were touched upon and Dr (Karl Z) Morgan (Oak Ridge Tennessee) promised to send details of some of their analytical methods for estimating radioactive substances in the urine. In reply to a question from Dr Butterworth he said that the hazard from enriched uranium would be a radioactive hazard rather than a toxic one and related to the presence of U-234. (Minutes of meeting held AERE Harwell, 8th July 1953.)"

I asked Rosenblatts for photocopies of the few papers I had found which might be useful but in the event, this particular document didn't appear. I asked for it again. It had disappeared.

Three tons of uranium - not worth mentioning?

Meanwhile I had begun to think about enriched uranium. This was a period where I was quite involved in DU and its effects in Iraq and the Balkans.

I had also obtained a small grant to re-examine the fallout of the US tests in the Marshall Islands, where the US government had funded a huge desktop analysis by S L Simon et al of the exposures of the Marshall Islanders from the Bikini tests in 1954.

When the 15 megaton Castle Bravo bomb cut Bikini atoll in half, the islanders had to be rescued and the unfortunately named Japanese fishing boat, Lucky Dragon was covered in rainout 100 miles away. Crew members later died from the exposures.

My report criticising the Simon et al. study was sponsored by the American Anthropological Association and I met the Marshall Islands delegates and presented it at the UN Human Rights Council in Geneva in 2012.

This Marshall Islands fallout also contained uranium, including a new hot isotope, U-237, produced by the very high energy (10MeV +) neutron irradiation of the U-238 tamper, and is thus evidence of nuclear fusion in an H-bomb. But the authors of the US Marshall Islands exposure report omitted all mention of uranium.

Which is odd. Because all these bombs are made of uranium. Enriched uranium for the preliminary fission, and DU or natural uranium for the casing and neutron reflectors. The bombs were very heavy. The accepted authority, Glasstone gives 1 ton of uranium per megaton of yield.

The big British Christmas Island bomb, Grapple Y, which figures in most of the test veterans with cancers and congenital effects in offspring was 3 megatons and we would expect it to contain 3 tons of uranium. As we shall see, the secret documents agree although none of this got into court.

Enriched uranium - rich in U-234, not just U-235

Natural uranium has three isotopes, U238, U235 and U234. The proportions can be characterised as mass or activity (kilograms, Becquerels) and I show the numbers in Table 1 (below) since they are relevant to what comes next.


Table 1: Specific activity and half life of U-238, U-235, U-234. A Becquerel (Bq) represents one atomic disintegration per second. The half-life is the time it takes for half of the material to decay.


Specific activity


Half life




1.2 x 107

4.5 x 109

Natural uranium has a U238/U235 atom ratio of 137.88.


8 x 107

7.04 x 108


2.3 x 1011

2.44 x 105


It is only U-235 which spontaneously fissions. It is present in natural uranium at 0.725% and has to be separated using complicated machinery (centrifuges, diffusion membranes) - a tedious and expensive task.

To make bombs you need highly enriched uranium (as high as 80%) hence the arguments about 'enrichment plants' in Iran, and previously Iraq. All methods of separation rely on the fact that U-235 is lighter than U-238.

But what no one seems to have noticed is that U-234 is even lighter. So U-234 will be separated from the natural uranium along with the U235! How much U-234 is this? In terms of mass, a small amount. But in terms of its radioactivity, a lot.

Because the half life of U234 is very much less than U-238 it will be present in 'secular radioactive equilibrium', Becquerel for Becquerel. That is, 100 Bq of natural U-238 will have 100Bq of U234 mixed in with it.

U-235 is present at .0725%, so if we want one kg of 100% U-235, assuming perfect extraction, we have to process 100/0.725 = 137.88 kg. So for 15 kg of 80% enriched uranium (the Hiroshima Bomb) we need to process at least 137.88 x 15 x 0.8 = 1,655 kg of natural uranium.

From the table we can calculate that the activity of the U-238 in those 1,655 kg amounts to 1.2 x 107 x 1655 = 2 x 1010 Bq - which is also equal to the activity of the U-234. This compares with 1.2 x 109 Bq of U-235 in the 15kg of fissile enriched uranium.

This envelope calculation tells us that there should be about 17 times more U-234 in the fallout than U-235 (measured by activity) - just as Karl Z Morgan warned in 1953.

In fact, it may end up being a more than this. In reality only about two thirds of the U-235 is extracted, and the centrifuge process will tend to refine out the lighter U-234 in preference to the U-235 that is actually desired.

If we therefore assume an approximate figure of 20, we find that this exactly matches a number of the results in Table 2 (below).

Author's Note: I now have actual figures for the U-234 concentrations in actual nuclear material used in the bomb tests. They indicate that the U-234 concentration effect is a powerful one, leading to U-234 activity 36 times greater than the U-235 activity.

Uranium is not directly detectable with Geiger counters

In the thermonuclear bombs, in addition to U-234, there is, of course an awful lot of U-238, since the neutron reflectors needed to compress the fusion fuel in the various stages are generally made of either DU or natural uranium. So here we have the real truth.

The thermonuclear bombs contain three isotopes of uranium. Because of the concentration of U-234 into the enriched uranium primary (and secondary) elements, there is theoretically an enormous amount of U-234.

When the bomb explodes (in the Pacific, Christmas Island, the Marshall Islands) moist tropical air is drawn from sea level into the rapidly rising fireball. As the fireball cools, uranium condenses as sub-micron glassy particles. For low level bursts (Bikini, possibly Grapple Y) also sea water and according to one Christmas Island veteran eyewitness, even fish fell from the sky.

As the temperature falls with altitude, this water condenses on the particles and falls as Black Rain (as set out in my article here). This deposits enormous quantities of uranium, also isotopes of plutonium formed by the neutron irradiation of U-238 in the explosion.

The ground is contaminated - but all three uranium isotopes are alpha emitters and thus mostly invisible to Geiger counters and film badges.

If you don't look for uranium, it's easy not to find

Uranium was not looked for at Christmas Island, or at least not reported. However, U-238 can be found through its beta daughters: I was able to analyse some beta gamma measurements made in 1963 by Aldermaston clean-up chief AE Oldbury on the aircraft runway at Christmas Island, and these showed far too much beta activity (just as Morgan had warned).

The only explanation for this high beta-gamma ratio was the presence of U-238 which has two beta-emitting daughters Th-234 and Pa234m. This analysis became part of a number of successful Test Veteran Pensions cases until my reports were sidelined in 2013.

The standard account of the components of fallout is the series of (non peer-reviewed) papers 1982-84 by Harry Hicks of the Lawrence Livermore Laboratory. All of the dose calculations used to defend governments from cases brought by the victims (veterans, Marshallese, etc) are based on Hicks computer program output.

Hicks's printout specifically states that the concentrations of uranium in fallout from fission bombs (called coyly 'oralloy') is ZERO. For thermonuclear bombs ('tubealloy') it is also ZERO. Was this an error? Was it a cover up, a crime?

The Marshall Islands dose reconstruction of S L Simon et al was based on Hicks and ignored uranium. The US government asked the National Academy of Sciences to do a dose reconstruction for the US veterans (three links - see below). No uranium.

Yet in the case of U-234 we are talking about quite a hot isotope (compared with U-238 and U-235) with a long half life (244,000 years) which will be there long after the Caesiums and Strontiums have decayed away.

Denying the obvious - there's plenty of uranium in nuclear fallout

But was the uranium really in the fallout? My Freedom of Information requests turned up some 60 documents. Missing from the list were documents I already had obtained from veterans in Australia (including AE Oldbury). I asked to see the documents and complained that the list was incomplete.

Letters went back and forth. MoD wrote that they would let me have three, as to photocopy more would exceed the £600 limit for FoI requests. Eventually I lost patience and wrote directly to the judge, HH Hugh Stubbs. He ordered the MoD to release the documents.

But a number of them were still refused: now on the grounds that their release would affect Britain's relationship with a foreign power. I was asked to sign the Official Secrets Act (Yes!). I refused. The judge ordered that a redacted version of the papers be made for me by the MoD expert Mr Johnston.

Later Hogan Lovells new expert Prof Paddy Regan was enlisted to collaborate with Johnston on the redacted version of the secret document. When it arrived it was useless: no numbers, no data. I wrote to Stubbs. He ordered them to produce some numbers.

Eventually I was sent a short report written by Bevis Parker of the MoD. It contained tables of the maximum amounts of uranium and Plutonium in the fallout of all the British tests. The judge asked me if that was sufficient. It was good enough.

I analysed the data. It showed that there was a very large amount of uranium, particularly U-234 in the fallout, measured in the material scooped by the Canberra Sniff aircraft that flew through the mushroom clouds. I wrote a supplementary report.

Unfortunately this evidence was excluded from the court when my reports were suddenly set aside at the last minute in January 2013 by Hogan Lovell - the solicitors who intervened to represent the veterans after solicitors Rosenblatts, who originally commissioned me as an expert witness, suddenly and unexpectedly pulled out.

Sadly we will never know what really happened since the judge, also suddenly and unexpectedly, died shortly after the case was heard in February 2013.

Incidentally my evidence was excluded without asking the veterans themselves, who were all of the belief that I would act as expert in their cases.

Paddy Regan, the new (ex-Harwell|) expert that Hogan Lovell brought in agreed with the MoD expert Mr Johnston (in the hearing) that there was no uranium on Christmas Island and that Busby's obsession to the contrary (which in any case by then wasn't even there) was nonsense.

Some of the data on uranium reduced from the secret documents by Bevis Parker for the MoD is given in Table 2 below.


Table 2. Maximum amounts of uranium isotopes in the UK nuclear tests (from Bevis Parker, DCDS-PERS-PCV-COMP-LEGACY-AHD, reduced from the secret documents by order of the judge, the late HH Hugh Stubbs.

Bq Yield. E+10 means x 1010




Yield Mt

U-238 Bq




Grapple 1

Malden Is


2.3 E+10

1.0 E+10



Grapple 2

Malden Is


3.3 E+10

3.4 E+10



Grapple 3

Malden Is


1.7 E+9

1.1 E+9



Grapple X

CI 2250m


4.8 E+10

8.2 E+9



Grapple Y

CI 2600m?


4.5 E+10

1.3 E+10






869 E+3

17.7 E+6






3.3 E+9

9.4 E+9






8.5 E+9

5.3 E+9






638 E+3

23 E+6




So you can see that the theoretical calculation is correct in its prediction that there is a lot of U-234 in the fallout: it is the main radioactive hazard, just as Karl Z Morgan warned.

In fact, in many cases there is considerably more U-234 than my calculation suggests. This may be because the technology of uranium separation, using multiple cascades of centrifuges, is even more effective at concentrating the U-234 than my simple calculation suggests.

By the way, I have obtained the vanished Morgan document. Don't ask. It states:

"In reply to a question from Dr Butterworth, [Dr Morgan] said that the hazard from enriched uranium would be a radioactive hazard rather than a toxic one and related to the presence of U-234."

It's in the bones

There is one final proof of all this in the bones of the veterans themselves. A team of Japanese scientists visited the Semipalatinsk test site in Russia and measured uranium and plutonium in autopsy bones of those who had lived near the Soviet test site and also sampled the local environment.

Using alpha spectrometry they measured U-238 and also U-234. What they found was that the natural U-238 / U-234 ratio of 1.0 was wildly perturbed with the samples of those living near the tests sites having very high ratios and relative levels of U-234. The authors don't say much about this interesting finding.

This hot isotope of uranium is retained in the bones of the veterans for all their lives, and is there on their chromosomes also, causing the chromosome defects found in the New Zealand study but easier to test for. We can have a look.

So finally, let's sum up why all this matters:

  • The UK government has denied the presence of uranium in nuclear bomb fallout, when it is in fact abundant, and very harmful to those exposed to it.
  • The highly radioactive isotope U-234 accounts for most of the radioactivity in the uranium in the bomb fallout. This is shown by direct measurement, and is readily explained by its concentration in enriched uranium.

These facts ought to be of enormous assistance to the bomb test veterans in making their case for compensation, as they provide a straightforward explanation for the health damage they have suffered.

However it appears that complex and unexplained legal machinations will ensure that the evidence is never presented to the court.



Chris Busby is the Scientific Secretary of the European Committee on Radiation Risk and the author of Uranium and Health - The Health Effects of Exposure to Uranium and Uranium Weapons Fallout (Documents of the ECRR 2010 No 2, Brussels, 2010). For details and current CV see For accounts of his work see, and


  1. Morgan minutes:
  2. Test vets report 4th supplement:
  3. My Marshall Islands paper
  4. Semipalatinsk Uranium in bones
  5. S L Simon et al Marshall Islands report
  6. Busby Presentation of Marshall Islands report at UNHRC Geneva October 2012
  7. Hicks 1984
  8. Uranium content of bombs
  9. Rowlands Wahab New Zealand chromosome study
  10. NAP dose reconstruction of test veterans
  11. Bomb test veterans' grandchildren suffer health impacts.
  12. The ICRP's radiation risk model is bogus science.



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