Césium de Fukushima : qui dit vrai ?
C’est la plus grande confusion dans les médias. Jeudi 24 mai 2012, on pouvait lire ces deux titres contradictoires :
Japon – Les fuites radioactives de Fukushima plus fortes qu’annoncé (Reuters)
Après Fukushima, des niveaux de radiation très faibles au Japon (Le Monde)
Le premier article se base sur la dernière estimation de Tepco, le deuxième sur un rapport préliminaire de l’OMS…
Map of Cesium 137 Contamination Created by Tsukuba University Radioisotope Research Center at Tsukuba University collected 110 soil samples from the end of March to the beginning of May in order to create a map of Cesium 137 concentration. The values here are as of March 29, 2011. They are not perfect data by considering that sample numbers are low; however, this study has much meaning as the first of its kind to show the contamination zones by using actual measurement values. The below is the publicized study results (just relized that the actual online article by Chunichi Shinbun has been erased so I here attach a blog that copied the article) , and I added a map of the areas and Ci/km2 values so that it can be easily compared with the Chernobyl contamination. According to the map, populated Fukushima City and Koriyama City are both included in the severely contaminated zone at the level of the Chernobyl accident where voluntary relocation with compensation was accepted (5-15Ci/km2). Moreover, some areas near the capital is found to be at high level of contamination, which is as serious as Iwaki City in Fukushima Prefecture. This zone is at the same contamination level as a part of Belarus. At the third contamination category (1-5Ci/km2), despite the fact that the Former Soviet and IAEA claimed that the level of contamination does not affect human bodies, it is well known now that the increases of cancer and leukemia have been found in the 20 years after the accident (we wrote about this fact in our past blog). When you look at the map above, you can tell that the publicized WSPEEDI data are pretty good at forecasting the actual contamination. It is clear that some parts of Fukushima City are no longer habitable due to the severe contamination, and the Metropolitan Tokyo area has already reached to the level that will definitely cause major impact on residents' health there if no immediate interventions follow. Cesium 137's half life is 30 years, and it will take over 100 years till its radiation level becomes as little as nothing. (http://onioni2.blogspot.com/)
Depuis 14 mois, c’est la valse des chiffres !
Voici par exemple quelques estimations données au fil du temps pour le césium 137 (données en PBq, c’est-à-dire en millions de milliards de becquerels) :
• 8 juin 2011, estimation de la NISA : 15 PBq
• 9 mars 2012, estimation de l’IRSN : 21 PBq
• 3 avril 2012, estimation d’un groupe de scientifiques étatsuniens et japonais : 63 PBq
• 24 mai 2012, estimation de Tepco : 10 PBq pour le relâchement aérien du 12 au 31 mars 2011 et 3,6 PBq pour le relâchement marin du 26 mars au 30 septembre 2011
• 24 mai 2012, autre source, the Daily Yomiuri : 360 PBq ! erreur de journaliste ?
TEPCO estimate sees more radiation than NISA’s
Tokyo Electric Power Co. has estimated the total amount of radioactive substances discharged from its Fukushima No. 1 nuclear power plant measured 760,000 terabecquerels, 1.6 times the estimate released by the Economy, Trade and Industry Ministry’s Nuclear and Industrial Safety Agency in February.
One terabecquerel is equal to 1 trillion becquerels.
TEPCO will include the estimate in a final report to be compiled by an in-house accident investigation committee in June. The firm has also begun explaining how it arrived at the figure to local governments in Fukushima Prefecture.
There are two ways to estimate the amount of discharged radioactive substances. One way is to base calculations on the degree of damage to the reactor core. The other is to reverse calculate based on the density of radioactive substances found in the atmosphere and seawater. As a result, there will be differences in estimates depending on how the figures were obtained.
NISA released an estimate of 770,000 terabecquerels in June last year, and another estimate of 480,000 terabecquerels in February. The Cabinet Office’s Nuclear Safety Commission released an estimate of 570,000 terabecquerels in August last year.
TEPCO combined the two methods and repeated its calculations under different conditions. It reached a final estimate of 400,000 terabecquerels of iodine-131 and 360,000 terabecquerels of cesium-137.
The amount of radioactive substances discharged in the Chernobyl accident in 1986 was 5.2 million terabecquerels.
« As there wasn’t enough available data immediately after the disaster, estimates can differ substantially if conditions change, even just a little, » said Prof. Hideo Yamazaki at Kinki University, an expert in environmental analysis. « The discharged amount of radioactive substances increased, but the figure is within the assumed margin of error. There will be no problems in continuing decontamination work and other measures. »
The Yomiuri Shimbun, 24 mai 2012
Dans ce cas … ça serait 5 fois plus que le césium relâché par Tchernobyl en 1986 !
En savoir plus sur la désinformation ambiante avec les articles :
de Gen4 : Césium-137 et Fukushima : à la recherche de l’erreur
de l’AIPRI : Plus dure sera la chute
de Russia Today : Cesium-137 contamination: Fukushima amounts to four Chernobyls
Le blog de Fukushima, 25 mai 2012