Taking the cue from the Fukushima nuclear power plant (NPP) accident in Japan, leading nuclear scientists from around the world have called for an exhaustive round of safety audit and given some preliminary recommendations so that such incidents are repeated “never again.”
The scientists, including the former Atomic Energy Commission chief, Anil Kakodkar, have pointed out the improvements in nuclear plant safety made following the Three Mile accident in the U.S. and the Chernobyl meltdown in the former Soviet Union, to urge another round of soul searching to remove the flaws that led to the Fukushima incident.
“We express here our deep concern about the future of nuclear power in view of the consequences of the earthquake and tsunami at the Fukushima-Daiichi NPP in Japan,” said the scientists while pointing out that “only nuclear power that avoids being a threat to the health and safety of the population and to the environment is acceptable to society.”
Although a comprehensive analysis of the Japan incident is not feasible due to lack of complete data on the events that occurred, the scientists decided to voice their opinion about severe accidents at civilian nuclear power plants and suggested additional measures to avoid them in the light of experience so far gained at Fukushima.
In making a case for a thorough world-wide appraisal, they pointed out that such initiatives in the past had helped vastly improve nuclear safety. The soul searching after the 1979 accident at Three Mile Island revealed weaknesses in the design of instrumentation, operating procedures and personnel training. Lessons learned from the accident allowed improvements with regard to human factors (how people and NPPs relate), design-specific probabilistic safety assessments, emergency preparedness and safety systems.
It also led the nuclear industry to design new NPPs that include passive safety features not dependent on the availability of electrical or mechanical equipment.
The accident at Chernobyl in 1986 was the largest in history. The nuclear industry created the World Association of Nuclear Operators (WANO) for a continuous review and feedback of nuclear power plant operating experience.
According to the scientists, a detailed analysis based on more data is needed to give a full answer, but some preliminary observations show that measures for accident management should be supported with robust technical capabilities, backup equipment, and procedures for restoration of core heat removal before the onset of fuel melting.
Plant staff should be well trained in flexible management of severe accidents. Renewed attention should be given to general safety requirements for plants built to earlier safety standards in view of the considerable remaining operating time envisaged for many such plants.
In the light of failure of electric power caused by the tsunami at Fukushima, authorities should ask to what extent this failure and other common mode failure vulnerabilities in operating plants might be revealed by current technology.
Future plants
“The safety requirements for future NPPs should be refined to assure that their backup cooling systems are able to operate for a long enough time following a complete loss of on-site and off-site power. These future NPPs should be able to promptly restore or compensate for lost power. Passive systems and advanced technologies for system engineering, materials, information management and communications should be applied to new NPPs. New plants should be sited away from areas of extreme natural and manmade hazards. Risk assessments and risk governance should be used for optimisation of plant design and operation but not substitute for deterministic safety justifications. The next generation NPPs should ensure safety even if operating personnel are not able to provide immediate response in an emergency,” they suggested.
