http://enenews.com/...
In view of reports of an uncontrolled nuclear fission reactor accident in Japan’s Fukushima Munich Radiation expert warns of Prof. Edmund Lengfelder of the possibility of a nuclear explosion.
It would be “a kind of mini-nuclear bomb in the scale,” said Lengfelder the dpa news agency. “The probability, however I can not estimate at all,” said radiation expert. Because nobody knows how much enriched uranium as coalesced into how the derelict nuclear power plant units. It had been found, the radioisotopes 133 and 135 of the xenon gas.
Because these are products of nuclear fission, which have only a half-life of about five days and nine hours, they could not come from the time of the accident in March , “There is there a spontaneous fission – can happen because everything, even if they say, it is not likely. But what is to be kept of statements about probabilities, we have on 11 March seen, Lengfelder said.
At that time had seriously damaged a strength in this unexpected earthquake and a tsunami and the nuclear power plant caused the meltdown. In a functioning reactor is maintained in the words of experts, the chain reaction by control rods under control. “But it is this control in a meltdown so no longer.”
Lengfelder had after the meltdown at Chernobyl 25 years ago the Society for Radiological Protection and the Munich-based Otto Hug Radiation Institute. He cared for people with thyroid cancer today in the former Soviet disaster area. The radiation expert also criticized the crisis management in Japan. “For me, it is also inhumane, that in such a wealthy country like Japan, people still live in the gyms. That there was not even on the Soviets “The evacuation after Chernobyl have worked much better.”
9:22 PM PT:
http://www.scribd.com/...
The significance of Xenon isotope ratios in the Fukushima catastrophe
Chris Busby PhD5
th
November 2011Recently, measurements were reported for Xenon and other radionuclides in theenvironment of the Fukushima reactors. A copy of the handout of TEPCO pressconference is available here:http://www.tepco.co.jp/... It shows:Kr-85 4.4 x 10E-1 Bq/cm3Xe-131m 6.9 x 10E-4 Bq/cm3Xe-133 1.4 x 10E-5 Bq/cm3Xe-135 1.2 x 10E-5 Bq/cm3Because nuclear fission processes create a range of radioactive products and becausethese nuclides have different half lives, it is possible to employ ratios of certainnuclides to show whether fission is occurring and also whether the fission is from arelatively slow controlled process or from an explosive criticality (a bomb or nuclearexplosion) where the production rates are much higher. The method was employedrecently to show that the Chernobyl reactor accident was caused by a nuclearexplosion and not a hydrogen explosion. There is no doubt about this, the Xenonisotope ratios measured in St Petersburg shortly after the plume arrived there made itclear that there was a nuclear explosion.Similar questions arise in the case of the Fukushima explosions, especially that inReactor 3, and I have already explained elsewhere that I believe that a promptcriticality may have been involved there.Here I will briefly look at the recent TEPCO figures. The ratio here of Xenon 135 toXenon 133 can be employed. Details of these nuclides and their half lives are given inTable 1
Table 1
Xenon isotopes measured in Reactor 2 reported by TEPCO at the end of October
Nuclide Half Life Measured activity/ cc Main gamma line keV
Xe 135 9.2h 1.2E-5 249Xe 133 5.27d 1.4E-5 81Xe 131m 11.8d 6.9E-4 164Details of the activities of Xenon isotopes after their creation are given in Fig 1 wherethe ratios may easily be obtained. The graph in Fig 1 is obtained by plotting activityon the basis of decay half lives and was developed to show that it was possible todistinguish nuclear explosions from reactor releases.
Fig 1 The activity ratios Xe 135/Xe133 for different scenarios (From Zhang Hhttp://belfercenter.ksg.harvard.edu/... )
Conclusions
It is clear from Table1 that Xenon isotopes are fairly easy to measure using gammaspectrometry as they each have significant gamma lines.The activity ratio of 0.85 reported by TEPCO can only result from an enrichedUranium fission having occurred about 50 hours before the samples were measured.or an explosive criticality which occurred 60 hours before the measurements. Whatthese results confirm is that there is on-going fission occurring at the site.The identification of prompt criticality is straightforward in samples obtained ormeasured within a few hours of the event.In view of the importance of establishing the nature of the initial explosions it wouldbe of great interest to obtain from TEPCO or any one the Xenon isotope ratiosmeasured immediately after the catastrophe.