Correlation between potential radiation-induced carcinogenic risks associated with WWER-1000 spent nuclear fuel and BREST-1200 radiation waste in case of annual generation of 1 GW of electricity. Part 2. Radiological migration equivalence

Currently it is acknowledged that the problem of disposal of radioactive waste (RW) from the nuclear reactors largely depends on the use of fast neutron reactors (fast reactors) in nuclear power industry. These reactors are able to burn and transmutate long-lived radionuclides in closed nuclear fuel cycle (NFC). In an open NFC with thermal neutron reactors (thermal reactors), unprocessed spent nuclear fuel (SNF) is buried. In a closed NFC with fast reactors the reprocessed SNF is disposed. In this paper, the feasibility and possibility of closing the NFC in a two-component nuclear power industry with thermal and fast reactors are studied. Potential biological hazard (PBH) to the public from unprocessed SNF from the thermal reactor WWER-1000 and reprocessed SNF from the fast reactor BR-1200, were evaluated with account of relevant radionuclides migration from the deep disposal to the earth surface. PBH values were expressed in terms of committed effective dose and lifetime attributable risk (LAR) of malignant neoplasms, normalized to 1 GW of generated electricity. PBH of RW from BR-1200 is about 100 times lower than risk from unprocessed SNF from WWER-1000. Comparative evaluation of PBH from BR-1200 and unprocessed SNF from WWER-1000 demonstrated that the committed effective doses from the dwell-water used by the public from the time of radionuclides appearance at the earth surface are 0.7 µSv and 80 µSv/year respectively, and LAR values are 6∙10-9 and 7.74∙10-6 respectively. At the same time, PBH of reprocessed SNF from WWER-1000, from the time of radionuclides appearance on the earth’s surface is an order less than PBH of RW from BR-1200. In accordance with the principle of radiological equivalence of RW disposal, it was established that the RW from BR-1200 satisfies the time limit for achievement of the equality with the PBH of the equivalent mass of uranium raw material will be within the range of 300 years. If PBH is expressed in terms of LAR the radiological migration equivalence is achieved even earlier. Thus, when reprocessing SNF from thermal reactors and operating thermal reactors with simultaneous construction and operation of fast reactors (in a two-component nuclear power industry), it is advisable to use a closed NFC and dispose of RW, considering the principle of radiation-migration equivalence.