The configurations

principles of operation

applications and main features of both type ZTCo121 and type ZTCo122 cobalt SPNDs are described in this paper. Formulations are given for computing thermal neutron sensitivity

the correction of burn-up and the lifetime of these two types of SPNDs

and the values are calculated. The distribution of in-core axial neutron flux was mapped by ZTCo121 detectors. The results were compared with that mapped by copper foil activation procedure

and they were found to be in agreement with each other. Performance testing shows that the thermal neutron sensitivities are 1.6×10

-22

and 2.66×10

-22

A/nV.cm respectively; the measurement accuracies are both less than 3% and the high temperature insulation resistance is both higher than 10

8

Ω

.