Measurement methods and instrumentation play a crucially important role in nuclear reactor safety. However, instrumentation indications may be lost or become inaccurate during a severe accident due to significant adverse conditions and, in addition, high radiation levels would limit accessibility to restore it. Based on the lessons learnt from the Three Mile Island, Chernobyl and Fukushima Daiichi nuclear accidents, efforts continue to explore and implement new solutions for providing required information on plant conditions before, during and even after a severe accident.
In this context, the NEA Working Group on Analysis and Management of Accidents (WGAMA) organised the Specialist Workshop on Advanced Measurement Method and Instrumentation for Enhancing Severe Accident Management in a Nuclear Power Plant, Addressing Emergency, Stabilisation and Long-term Recovery Phases (SAMMI-2020). Co-hosted by Japan Atomic Energy Agency (JAEA) Nuclear Safety Research Center (NSRC), the workshop was held virtually on 7-9 December 2020 as part of the Collaborative Laboratories for Advanced Decommissioning Science (CLADS) Fukushima Research Conference (FRC) series.
SAMMI-2020 attracted 111 specialists from 15 countries who reviewed the current status of instrumentation and techniques related to severe accident management and exchanged updates on advances made recently in the field. The workshop featured two plenary lectures, four keynote lectures, 14 sessions and 36 peer reviewed papers addressing the following topics:
- Review of measurement methods and instrumentation for severe accident management
- Severe accident management and innovative instruments under development and testing efforts
- Installed instrumentation used for severe accident management with revised strategies
- Severe accident environment identification and instrumentation qualification
- Long-term management to recognise conditions of severe accident-experienced reactors
- Severe accident management and innovative measurement methods for new reactors
The workshop provided significant insights for nuclear power plant severe accident management. It also shed light on revised severe accident guidance based on instrumentation survivability insights in order to prevent, mitigate and recover from severe accidents in existing and future nuclear power plants. Recent advancements from developmental efforts for new instrumentation and methods were presented, as well as results from required testing under prototypical plant conditions for temperature, pressure, chemical and/or radiation effects. Participants discussed numerical simulations identifying the plant system and local conditions during and after severe accidents that help characterise the conditions that key measurement methods and instrumentation must survive. Presentations also defined revised guidance for nuclear power plant severe accident management and emergency decision making.
Alongside promising developments in many areas, participants concluded that it is beneficial to continue to research in order to develop innovative instrumentation techniques and to improve instrumentation robustness and reliability under challenging severe accident conditions. A first challenge is the need to test systems in more realistic severe accident conditions. Another challenge relates to the use and implementation of systems in the plant environment without introducing adverse effects. There are also concerns about potential regulatory and budgetary constraints for incorporating new solutions into the existing fleet. Although the types of new instrumentation deployed in the operating fleet may be limited, advanced reactors, which are still in the design stage, may offer additional opportunities for deployment of such technologies.
International co-operation is key for ever-enhanced global nuclear safety. SAMMI-2020 provided a unique occasion to update the global nuclear community on instrumentation and methods for improved severe accident management. It is important to continue improving advanced methods and instrumentation for enhancing severe accident management during the emergency, stabilization and long-term recovery phases. In this regard, the NEA continues to advance its scientific and technological knowledge base needed for the prevention, mitigation and management of potential accidents in nuclear power plants, and to facilitate international convergence on safety issues and accident management analyses and strategies.