Governments in the four countries started a joint investigation of incidents of surface contamination of rail containers after French authorities reported found "hot spots" on some containers and alerted their German, Swiss and British counterparts (ENDS Daily 7 May). More incidents quickly came to light and the issue rapidly escalated into a political crisis, particularly in Germany and Switzerland (ENDS Daily 1 July).
Released on Friday by French nuclear safety agency DSIN, the report by the four countries concludes that the reported cases of contamination "did not have any radiological consequence."
In a varying number of cases depending on the country, surface contamination above 4 becquerels per square centimetre (bq/cm2) was detected, rising to above 400 bq/cm2 in a very small number of incidents. The competent authorities stress, however, that the 4 bq/cm2 limit is a goal for "cleanliness" rather safety and that there are substantial safety margins built into it.
They report studies showing that French nuclear rail workers received no more than 20% of the annual radiation dose limit for the industry, while the risk of irradiation for the public at two metres of nuclear transports was calculated to be 3% of the routine regulatory limit. Swiss studies found no radiation doses to rail workers attributable to surface contamination of nuclear transports. "The same conclusions" have emerged from similar German and British studies, the group continues.
Incidents of hot spots on transports are not caused by leakage, the competent authorities say, but through contamination during loading in the spent fuel pools of nuclear power stations and unloading at reprocessing plants. Several detailed causes are possible, the report concludes, but the overall cause of the incidents has been a "lack of rigour in decontamination and monitoring procedures".
Greater rigour in decontamination, more monitoring and greater communication between competent authorities, nuclear power firms and reprocessing plants is recommended by the authorities. A database of spent nuclear fuel movements is to be created, including provisions for annual public reporting and reporting of contamination incidents. An international expert group representing the four countries is to be created to evaluate steps taken by nuclear operators to improve monitoring and decontamination.
DSIN, tel: +33 1 43 19 36 36. References: The full report is posted on the web site of the Swiss nuclear safety authority, HSK.
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