(February 1, 2002) After the independent radiation monitoring group ACRO showed that Cogema had greatly underestimated radioactive discharges resulting from two incidents last year, Cogema has launched a "program to improve its measuring and filtration systems".
(562.5370) WISE Amsterdam -The two incidents happened on 18 May and 31 October 2001. The May incident happened at the R7 vitrification plant, and was a classic example of how the back-up systems that the nuclear industry is so proud of are not enough to stop things going wrong.
The main ventilation system was faulty, and at first the back-up system did the job. The problem came when Cogema tried to get the main system back online while one of the valves was still blocked. This caused the radioactive gas to go the wrong way through the ventilation system and escape into the environment. It took an hour for the radioactive discharge to be stopped. The incident was classed as level 1 on the 7-level International Nuclear Event Scale (INES).
Exactly how much radioactivity escaped is not known, because the apparatus in the chimney for measuring the discharges was dirty and so gave an abnormally low reading. A reading from inside the plant indicated a maximum release of 4,500 MBq.
The October incident happened in the other vitrification plant, T7, when operators tried to clear a blocked pipe. Again, radioactive ruthenium-106 and its daughter product rhodium-106 escaped into the environment. Cogema claimed that the maximum release was 219 MBq. However, calculations by the independent radiation monitoring group ACRO indicated that the release was actually of the order of 10,000 MBq - 45 times higher than Cogema's value.
Cogema has been under pressure for many years for the inadequacy of its monitoring systems for radioactive discharges at the La Hague reprocessing plant. Back in 1998, Greenpeace flew special kites to collect air samples above the plant. Analysis of these samples revealed levels of the radioactive gas krypton-85 which were up to 90,000 times the background radiation in air. Up until then Cogema had not made any data public about krypton-85 in air.
This time, Cogema has agreed to install new filters and improve the system for measuring gaseous discharges of ruthenium-106. ACRO says that the dramatic underestimate of the ruthenium discharge calls Cogema's other measurements into question; Cogema rejects this. However, a report prepared for the European Parliament's Scientific and Technological Options Assessment Panel (see WISE News Communique 559.5348,"STOA report condemns reprocessing") pointed out that gaseous discharges of some important radionuclides, including chlorine-36, technetium-99 and strontium-90, are not measured at all.
- ASN press releases, 4 July and 7 November 2001
- ACRO press release, 28 January 2002
- Greenpeace press release, 9 September 1998
- Cogema press release, 28 January 2002
- summary of STOA Report (http://www.europarl.eu.int/stoa/publi/pdf/summaries/00-17-01sum_en.pdf)