Development of the Unattended Spent Fuel Flow Monitoring Safeguards System (UFFM) for the High Temperature Engineering Test Reactor (HTTR) (Joint research)

Nakagawa, Shigeaki  ; Umeda, Masayuki; Beddingfield, D. H.*; Menlove, H. O.*; Yamashita, Kiyonobu

As of the safeguards approach in the HTTR facility, an unattended spent fuel flow monitor (UFFM) was applied to carry out an item counting of spent fuel blocks. The UFFM is so designed and fabricated as to be the compact and unique monitor system to verify a movement of spent fuel blocks in "difficult to access" area and reduce inspection efforts. This system consists of two detector packages, electronics and computer. One package consists of two ionization chambers and a He-3 counter. The IAEA acceptance tests were performed and it was confirmed the followings: (1) All the detectors were functioning properly to measure a spent fuel block flow. (2) The time difference between detector signals was sufficient to determine the direction of the spent fuel blocks. (3) The UFFM was useful to carry out the item counting. The UFFM was approved as the IAEA safeguards equipment in the safeguards approach in the HTTR.