Volume 3, Issue 6 (June 2006)
Evaluation of Diamond Detectors for Fast Neutron Fluence Measurements in WWER-1000 Surveillance Assemblies
The commonly used method of WWER-1000 surveillance dosimetry is based on the measurement of 54Mn absolute activity in the material of surveillance specimens. Special procedures are necessary for the determination of the spectral index for each specimen, which depends on surveillance assembly orientation in the reactor during the irradiation period, and for fluence extrapolation beyond several 54Mn half-life periods taking into account the detailed local power history in the core periphery. The application of the diamond detectors technique is proposed as an alternative method of fast neutron fluence determination. These detectors are located in the surveillance containers as irradiation temperature monitors. The diamond lattice extends under the influence of neutron irradiation, and it allows the fluence measurements after corresponding calibration. The calibration of diamond detectors was carried out using fluence data for 123 surveillance containers irradiated in different WWER-1000 reactors for different fluences. Some results of fluence measurements carried out by two methods are compared.