原子力規制委員会、NISTの研究炉における2021年の警報に関する特別点検報告書を発表(Nuclear Regulatory Commission Releases Special Inspection Report on 2021 Alert at the NIST Research Reactor)

2022-03-27

2022-03-16 ｱﾒﾘｶ国立標準技術研究所(NIST)

・原子力規制委員会（NRC）は、2021年2月3日に米国国立標準技術研究所（NIST）中性子研究センター（NCNR）で発生した警報に関する特別査察の最終報告書を発表しました。
・報告書では、燃料1本が破損し、原子炉が自動停止した事故中および事故後の公衆の安全が常に確保されていたことが確認されています。
・報告書には7つの違反が含まれており、NRCは今後、どのような強制措置が必要かを決定するため、より詳細に調査する予定です。
・原子炉は、NRCが公衆の安全と健康を守るためのすべての是正措置の有効性を判断し、NISTの再稼働要請を承認するまで停止したままとなる予定です。

NIST’s Center for Neutron Research, in Gaithersburg, Maryland Credit: NIST

＜関連情報＞

NRC、NIST原子炉イベント特別点検の調査結果を発表
NRC Issues Findings from NIST Reactor Event Special Inspection

The Nuclear Regulatory Commission (NRC) March 16, 2022

Nuclear Regulatory Commission staff has released its initial conclusions from its special inspection at the National Institute of Standards and Technology’s non-power reactor in Gaithersburg, Maryland. The NRC launched the inspection in February 2021, a few days after an event during startup of the reactor damaged a reactor fuel element and released radioactive material.
The agency issued an interim inspection report in April 2021.

The inspectors examined independent analyses of the radiation release and concluded that
public health and safety was maintained – any potential dose to the public, while unlikely, would
have been a very small fraction of regulatory limits. The inspectors also concluded that doses to the
reactor facility staff during the event were well below regulatory limits.

During the inspection, NRC inspectors reviewed NIST’s records from the event, the facility
staff’s response, NIST’s root cause analysis, proposed corrective actions and related documentation.
They also interviewed NIST staff and management regarding the event and related matters. The
inspection found seven apparent violations of NRC requirements, including five violations related
to exceeding the fuel temperature safety limit and damaging a fuel element. Other apparent
violations are related to emergency planning and equipment modification.

If finalized at their current level, the findings could result in a civil penalty. After reviewing
the NRC inspection report, NIST can accept the NRC’s findings, provide additional information in
writing or during a regulatory conference, or request alternative dispute resolution. The NRC will
consider all available information before making a final determination and document the decision in
publicly available correspondence. The report notes several items planned for NRC follow-up.
These items will be assessed in supplemental NRC inspections and documented in subsequent
inspection reports.

Since the event violated the fuel temperature safety limit, the NRC must formally approve
any restart of the reactor, which NIST has requested. The NRC will only consider authorizing
restart after the agency has completed reviewing the restart request and has determined that
sufficient corrective actions have been implemented to ensure that the facility will be operated
safely by the licensee. Increased NRC oversight of the NIST facility will continue after any restart
has been authorized.