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Japan's N-plants to use flame-retardant cables
Publication Date : 22-01-2013
Japan's new safety rules to take effect in July will require nuclear power plants nationwide to make their main power cables flame-retardant, according to the Nuclear Regulation Authority (NRA).
However, observers said introduction of the new rules maygreatly delay reactivation of idle nuclear reactors.
In at least 13 reactors, whose construction was approved in 1975 or earlier, cables coated with flammable materials are used in critical safety zones. Since the length of such cables could total several thousand kilometres for a single reactor, changing them to cables coated with flame-retardant materials will take years, they said.
The NRA presented the draft outline of the new rules to a panel of experts yesterday.
Guidelines for electric cabling used at nuclear power plants were revised in 1975 following a nuclear power plant accident in the United States, obliging the use of flame-retardant materials.
For cables at reactors built before that time, the application of substances to prevent the spread of fire was deemed acceptable.
Under the new guidelines, however, nuclear plants will be required to undertake safety measures for three purposes: to prevent the outbreak of fire, to detect and extinguish fires, and to reduce fire damage. The application of agents, which are formulated to reduce fire damage, to prevent the outbreak of fire will not satisfy the new standards.
Since the reactors whose cables need to be changed were built earlier, their decommissioning may require study in light of a 40-year cap on the operation of nuclear reactors.
Measures to cope with accidents that are more serious than anticipated at the time of their design, including those related to the installation of the second control room, are also included in the draft. As some renovations could require long periods of time, a designated time frame will be allotted for their completion.
To reactivate boiling water reactors such as those at Tokyo Electric Power Co.'s Fukushima No 1 nuclear power plant, a filtering vent must be installed to prevent damage to reactors due to pressure buildup by relieving internal pressure in case of emergency.
The vent discharges steam from the reactor's containment vessel while preventing the escape of radioactive materials.