Radioactive inventory calculation for JPDR to be dismantled

The Japan Atomic Energy Research Institute has been conducting the decommissioning program of the Japan Power Demonstration Reactor (JPDR) since 1981. It is essential for planning the dismantlement of JPDR to estimate the radioactive inventory involved in the reactor accurately. For this purpose, a code system DOIC (Discrete Ordinates Inventory Calculation Code) has been developed and its validity is verified by analyzing measured radioactivities in the reactor pressure vessel, its internals and biological shield of JPDR. The calculation with DOIC is found to predict radioactivity fairly well in the reactor internals and pressure vessel. The calculated value in the biological shield, however, is overestimated as compared with the measured one by a factor of 2 to 3 at the core midplane. The radioactive inventory of JPDR due to neutron activation is estimated to be 1.7 x 10/sup 14/ Bq (4600 Ci) as of March 1986 based on the calculations and measurements