JRR-3原子炉施設の事故評価

The Accident evaluation of JRR-3

井口 晋太郎; 堀口 洋徳; 荒木 正明

Iguchi, Shintaro; Horiguchi, Hironori; Araki, Masaaki

原子力規制委員会が定めた原子力災害対策指針では、防護措置の実施を判断する基準として、空間放射線量率や環境試料中の放射性物質の濃度等の原則計測可能な値で表される運用上の介入レベル(OIL)が設定されている。本発表では、JRR-3の設計基準事故のうち、炉心流路閉塞事故について燃料破損割合を保守的に変更した場合の線量評価を実施し、OIL1及びOIL2の防護措置の実施基準との比較を行った。評価事象とした炉心流路閉塞事故は、燃料要素の流路が閉塞した直後に損傷し、放射性物質が燃料から冷却系へ放出され、原子炉プール及び建家への移行を経て非常用排気設備から周辺環境へ放出される事故である。評価では、非常用排気設備の正常に作動した場合と作動せず地上放出をした場合を想定した。線量評価については、原子炉建家から大気中に放出された核種による線量率と原子炉建家内に浮遊する核種による線量率を評価した。評価点はJRR-3から原子力科学研究所敷地境界までの距離329m地点とした。その結果、事故直後においても線量率がOIL1の初期設定値を超えないことを確認した。また、事故後急速に線量率が低下し、6時間経過後にはOIL2の初期設定値を下回ることを確認した。

The intervention level on the practical use by which the principle measurement which are the spatial radiation dose rate and the density of the radioactive materials in the environment sample, etc. as the standard by which implementation of protective measure is judged is expressed in the possible price (OIL) is established by the atomic disaster countermeasures guideline an atomic regulatory committee set. The dose evaluation when changing the fuel damaged percentage conservatively about over the design basic accident of JRR-3 and the reactor core way way blockade accident, was put into effect and OIL1 and OIL2 were compared with the implementation standard of the protective measure by this publication. Just after flow pass of a fuel element was blocked up, radioactive materials are damaged, and are released from fuel to a cooling system, and an evaluation phenomenon and a done reactor core way way blockade accident are the accident released from exhaust equipment for emergency use to ambient surroundings via a shift to a nuclear reactor pool and a building. It didn't operate with the case when exhaust equipment for emergency use normally operated by evaluation, and the occasion which did the ground release was assumed. The dose rate by the nuclide released in the atmosphere from a nuclear reactor building and the dose rate by the nuclide floating in the nuclear reactor building were estimated about dose evaluation. The evaluation point was made a distance 329m spot from JRR-3 to the atomic scientific research place site boundary. It was confirmed that there are also no dose rates beyond the initialization value of OIL1 in the result and just after accident. It was confirmed that the dose rate falls and falls below the initialization value of OIL2 after 6 time course rapidly after an accident.