Improvement of heat-resistant wide range monitoring neutron detector for HTTR

The wide range monitoring neutron detector is a design product developed to be able to measure the thermal neutron flux appropriately under the high temperature environment unique to HTTR. However, this detector had the experiences of disconnection of internal junction part caused by thermal cycle in the past reactor operations. Based on the knowledge of the disconnection points and break mechanism already obtained, this project devised a structural modification plan to improve the heat resistance performance, determined the modification plan, demonstrated the performance through a mock-up test using a dummy, and thus succeeded in the development of a wide range monitoring neutron detector with improved performance. Furthermore, the fact that the structural change could be completed without changing the basic specifications of the existing detector that is the standard product has resulted in securing rationality from the viewpoint of cost and time required for verification. (A.O.)