Nuclear Regulatory Commission's Japan Task Force Makes Its Report
On 11th March 2011, northeast Japan was struck by a magnitude 9 earthquake and an ensuing tsunami. The Fukushima nuclear power plant was directly in the path of the tsunami and was also at the epicentre of some aftershocks. The US Nuclear Regulatory Commission established a Japan Task Force which was charged with identifying lessons that the USA should learn from the Fukushima incident.
The task force was led by Charles Miller and it came up with a set of twelve recommendations aimed at improving safety at US nuclear power plants (NPP) and re-evaluating the level of public health protection required to meet needs in the 21st century.
The report stressed the fact that a Fukushima-style event is unlikely in the USA because of the specific chain of events which led up to the explosions and nuclear excursions at the plant and that US NPPs could continue to operate safely. Nevertheless, it noted that "an accident involving core damage and uncontrolled release of radioactivity to the environment, even one without significant health consequences, is inherently unacceptable."
Unsurprisingly, in view of the fact that the Fukushima accident was caused by a loss of cooling water to the reactors and fuel storage ponds, the Task Force has called for improvements covering loss of power; spent fuel ponds; venting of reactors (of volatile gases); flooding; seismic events and in emergency preparedness.
The Task Force noted that regulatory requirements within the nuclear sector were a "patchwork" that had been developed over the years and that there was a need to update them with a "logical, systematic and coherent regulatory framework" which would enhance reactor safety in the USA.
"Our recommendations are grouped into four areas beyond the overarching suggestion to clarify the agency's regulatory framework. We looked at ensuring protection, enhancing accident mitigation, strengthening emergency preparedness and improving the efficiency of NRC programs. The independence given our team was outstanding. Everything was on the table and we felt free to take a holistic approach to these key subjects," Miller explained.
That NPPs re-evaluate and upgrade (if necessary) their design-basis flooding and seismic protection plans at least once every 10 years.
Enhance mitigation capability for new and existing reactors for a station black-out (electrical failure) for design and beyond-design natural events. This would require plans to maintain fuel pond and reactor cooling independently for 72 hours.
Facility emergency plans should be drawn up to deal with extended blackouts and multiple reactor events.
Instrumentation and earthquake protected systems should be available to provide additional cooling to fuel ponds, if needed, at all times.
NPPs would be required to establish reliable hardened vent designs for mark I and ii containment vessels for boiling water reactors.
Integrating and enhancing on-site emergency procedures and damage mitigation guidelines.
Learning lessons about hydrogen control within containment buildings and ponds from the Fukushima incident.
In the longer term:
Evaluating enhancements to mitigate or prevent fires and floods caused by seismic activity.
Developing additional emergency preparedness measures related to multi-reactor and power loss events.
Developing emergency preparedness topics on decision making, public education and radiation monitoring.
Enhancing the regulatory oversight of the daily monitoring of NPPs safety performance giving greater emphasis to defence-in-depth requirements.
The Task Force's report has been given to NRC who is responsible for making decisions on the reports recommendations.
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