At around 6:20 PM on July 20, 2012, a TEPCO employee on patrol found a fuel oil (gas oil) leakage from the diesel generator used for the spare nitrogen supply equipment (nitrogen gas separator on the hill) at Fukushima Daiichi Nuclear Power Station. The oil leakage was reported to the fire department at 6:35 PM.
As a result of investigation, it was found that the gas oil was leaking from the rubber hose of the upper part of the diesel generator engine and the rubber hose of the fuel oil filter. At 7:36 PM, the leakage was stopped after implementing an emergency measure. The gas oil leakage amount was approx. 20 liters and there is no possibility of further leakage. We are currently checking other areas for leakage.
Due to this leakage, the spare nitrogen supply equipment has been judged to be disabled. In accordance with the technical specification for the nuclear reactor facility*1, the spare nitrogen supply equipment (including the diesel generator) has been judged to be disabled as well, not satisfying the "operational requirements"*2 stipulated in the technical specification for the nuclear reactor facility at 7:14 PM.
The "required measure"*3 to implement when the operational requirements are not satisfied is to promptly start the recovery work of the spare nitrogen supply equipment (including the diesel generator) to make it available for use as soon as possible.
Since 2 nitrogen supply equipments are currently in parallel operation for the nitrogen injection at Unit 1-3 at Fukushima Daiichi Nuclear Power Station and the sufficient nitrogen amount can be supplied by only one equipment, there will not be a major problem caused by this leakage. There are no significant changes in the reactor parameters, hydrogen concentration and monitoring data at this point in time.
The cause of leakage will be investigated and the required measure will be implemented based on the technical specification for the nuclear reactor facility to have the spare nitrogen supply equipment recovered.
*1 Technical specification for the nuclear reactor facility
Government-approved fundamental rules for nuclear power station operators to follow in order to maintain safe operation and stable condition of nuclear power stations (including operation management, fuel management, radiation management, emergency measures and equipment/facility management based on the "Policy on the Mid-term Security"), which are stipulated by Article 37 Section 1 of the Act on the Regulations of Nuclear Source Material, Nuclear Fuel Material and Reactors.
*2 Operational requirements
In accordance with the technical specification for the nuclear reactor facility, operational requirements are stipulated to ensure safety and stability of power stations (such as the number of available equipments, temperatures and pressures). In the case that an issue arises with equipment subject to the technical specification and the operational requirements cannot be satisfied temporarily, the required measures must be implemented.
*3 Required measures
Article 144 of the technical specification for the nuclear reactor facility requires that one nitrogen gas separator is in operation and the nitrogen gas separator (including the diesel generator) on the hill is operable. In the case that the nitrogen gas separator on the hill is disabled, the recovery work of the equipment must be promptly commenced.
