Development of a criterion to record the facts of fuel carryover from leaking fuel elements during VVER reactor operation
Operation of nuclear fuel at an NPP involves the potential of a fuel cladding failure. One of the possible and gravest consequences of a fuel failure is the fuel composition being washed out from the leaking fuel element and entering the coolant.
Reliable detection of the fuel carryover in the course of the fuel life is important for the further handling of the failed fuel assembly. The fuel carryover can be detected as part of the fuel cladding integrity inspection during the reactor operation. For this purpose, activity of 134I is traditionally used in VVER reactors. In practice, however, the activity of 134I is capable to increase in the course of the fuel lifetime even in the event when there are no fuel failure and the only source of the fission product escape are fuel deposits in the core.
A criterion has been proposed which makes it possible to distinguish cases when the growth in the activity of short-lived radionuclides is the result of the fission product escape from fuel deposits or the fuel composition carryover from the failed fuel elements during VVER reactor operation. Examples are provided of the developed criterion practical application at effective NPPs.
The reported study was funded by RFBR, Project No. 20-38-90081.
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