The extraordinary and tragic criticality event at Tokai Mura reveals a collapse of safety culture approaching Chernobyl proportions (although with nothing like the scale of injury, damage and offsite consequences of the 1986 event of course). The categorization of the Tokai Mura event as level 5 on the International Atomic Energy Agency’s quasi logarithmic “Richter scale” of nuclear events puts it in the same league, in terms of safety significance, as the 1979 Three Mile Island accident and the 1957 Windscale fire. Chernobyl remains unique, at level 7.
An important feature of the Tokai Mura event, although no excuse for it, was that the place where it happened appears to have been more of a test rig for special fuels than a main stream commercial nuclear facility, and it was only used very occasionally. One visitor has even described it as being run like a “back street workshop”. Only one of the three people involved had previous experience of operating the plant, none of them appears to have received training in criticality and, astonishingly, one of them is even reported not to have known the meaning of the term.
Operating procedures seem to have been changed without proper consultation with the regulator, while the way in which plant safety was regulated – or not regulated – is simply amazing. Significantly, as a nuclear fuel materials facility, the regulatory body is the STA (Science and Technology Agency) rather than MITI, which regulates the commercial nuclear power plants and operates a strict regime, as you would expect.
As a result of the Tokai Mura event the safety regulation of the nuclear industry’s fuel cycle outposts needs to be thoroughly re-examined, both in Japan and elsewhere.
