The nongovernmental Atomic Energy Society of Japan has compiled a draft protocol, the first of its kind, to gauge the likelihood of major accidents at nuclear power plants caused by giant tsunami.
The nongovernmental Atomic Energy Society of Japan has compiled a draft protocol, the first of its kind, to gauge the likelihood of major accidents at nuclear power plants caused by giant tsunami.
While seismic risk assessment is hardly new, the society decided to create a framework for tsunami following the unprecedented crisis at the Fukushima No. 1 nuclear power plant caused the by March 11 Great East Japan Earthquake.
The society, which is made up of scientists, engineers and researchers, strongly backs the use of nuclear technology.
It called on the government and electric power companies to conduct their own risk assessments in line with the protocol as part of practical safety measures.
Until now, such steps have been based on maximum tsunami heights determined by electric power companies for individual nuclear plants under standards set in 2002 by the Japan Society of Civil Engineers.
On March 11, however, tsunami far exceeding the projected height anticipated by Tokyo Electric Power Co., operator of the stricken Fukushima plant, struck the facility, submerging emergency generators and causing a loss of all functions to cool the nuclear reactors. This resulted in a massive discharge of radioactive substances.
As a result, the Standards Committee of the Atomic Energy Society in May set about drafting a protocol for risk assessment.
In the proposed protocol, the frequency of earthquake occurrence and the height of tsunami are assessed on the basis of seismicity records and the size of active faults in the vicinity of a nuclear plant. The probability of damage to reactor buildings caused by an inundation of seawater and heavy objects smashing into vital machinery and piping is evaluated for different tsunami heights.
The protocol presented a method to calculate frequencies of scenarios, in which individual disruptions and damage patterns combine to cause serious incidents, such as damage to reactor cores.
The protocol is intended to help analyze the type of reinforcement and remodeling needed to effectively lessen the probabilities of serious accidents occurring.
The society, following input from the public, plans to issue a final version of its protocol by the end of this year.