Combustible properties of LLW bitumen packages in a fire test

Most Low Level Wastes derived from Japanese nuclear power stations are classified as LSA-II·III material according to ss6 Sec.131 of the IAEA '85 regulations, while whole packages composed of wastes and packaging are classified as Industrial package according to ss6 Sec.131 of the regulations. Concerning LSA material, the fire test for Type B package is not regulated, because a contained activity is limited by the A2 value itself. According to the regulation of the Fire Defense Agency in Japan, straight asphalt is classified as 'semi-dangerous material' because of its calorific power; bitumen package is classified as normal material because of its lower calorific power. However, among these LLW wastes, test results have indicated that bitumen packages are flammable. A fire test for bitumen packages with some simulated nuclides was performed by CRIEPI in 1988 and 1989 in order to discover whether bitumen packages are combustible and also to determine how many nuclides contained in the packages are released into the environment in the event of a fire accident. 1) When the surface temperature of specimens rises to the 350 - 380degC range in a fire environment, the resolved gas will be generated and ignite automatically. In order to keep on burning, it is necessary to supply both excessive heat and sufficient oxygen. 2) The volatile ratio of Cs, which is a typical volatile nuclide, is greater than other nuclides. However, its value is 1.5 wt% of added sulfate at the maximum. (J.P.N.)