Fukushima’s lesson: Better real-time monitoring of spent fuel pools is a must

The committee recommended that the U.S. nuclear industry and the U.S. Nuclear Regulatory Commission (USNRC) improve the ability of plant operators to measure real-time conditions in spent fuel pools and maintain adequate cooling of stored spent fuel during severe accidents and terrorist attacks. These improvements should go beyond the current, post-Fukushima response to include hardened and redundant physical surveillance systems such as cameras, radiation monitors, pool temperature and water-level monitors, and means to deliver makeup water or sprays to the pools, even when physical access is limited by facility damage or high radiation levels.

Extreme external events and severe accidents can cause widespread and long-lasting disruptions to security infrastructure, systems, and staffing at nuclear plants, the committee concluded. Such disruptions can create opportunities for malevolent acts and increase the susceptibility of critical plant systems to such acts. Therefore, the committee recommended, nuclear plant operators and their regulators should upgrade and/or protect nuclear plant security infrastructure and systems and train security personnel to cope with extreme external events and severe accidents.  Such upgrades should include redundant and protected power sources dedicated to plant security systems that function independently if safety systems are damaged, as well as diverse and flexible approaches for coping with and reconstituting plant security infrastructure, systems, and staffing during and following extreme external events and severe accidents.

The committee determined that the USNRC has implemented most of the recommendations from previous Academies reports on spent fuel safety and security. However, two recommendations from those reports have not yet been implemented, the committee found. The first was to analyze the vulnerabilities of spent fuel pools to specific terrorist attack scenarios described in the 2004 Academies report, and the second was to carry out an independent examination of surveillance and security measures for protecting stored spent fuel. This independent examination should address the effectiveness of the USNRC’s security and surveillance measures for addressing the insider threat, the committee said. It also recommended that the USNRC and nuclear industry strengthen their capabilities for identifying, evaluating, and managing the risks from terrorist attacks and that the USNRC sponsor a spent fuel storage security risk assessment of sufficient scope and depth to explore the benefits of this methodology for enhancing security at U.S. nuclear plants.

NAS notes that the committee reviewed technical analyses carried out by the USNRC to inform a regulatory decision on whether to expedite the transfer of spent fuel from pools to dry casks to reduce storage risks. Although these analyses are valuable technical contributions to understanding the consequences of spent fuel pool accidents, they are of limited use for assessing spent fuel storage risks because they do not consider sabotage risks, dry cask storage risks, or certain health consequences that would likely result from a severe nuclear accident. It is also difficult to make valid comparisons between pool and dry cask storage risks because of the way the analyses were carried out. The committee recommended that the USNRC perform a spent fuel storage risk assessment that addresses both accident and sabotage risks for both pool and dry cask storage. USNRC staff informed the committee that it is already thinking about how to expand its risk assessment methodologies to include sabotage risks.

— Read more in Lessons Learned From the Fukushima Nuclear Accident for Improving Safety and Security of U.S. Nuclear Plants: Phase 2 (National Academies Press, 2016)