Spent Fuel Pool Cooling System

Enhance the availability of the residual heat removal function by requiring alternative cooling methods (i.e. spent fuel pool cooling system). 

Decay-heat calculations wbre undertaken to enBrnre that foe spent-fuel pool cooling System would accommodate... 

The spent fuel pool heat exchangers in the spent fuel pool cooling system. 

The spent fuel pool cooling system consists of two mechanical trains of equipment. Each train includes one spent fuel pool pump, one spent fuel pool heat exchanger, one spent fuel pool demineraliser and one spent fuel pool filter. In addition, the spent fuel pool cooling system includes the piping, valves, and instrumentation necessary for system operation. 

The spent fuel pool cooling system has the following capability to provide the additional defence in depth support during and following fault conditions ... 

The spent fuel pool cooling system maintains the level of water in the spent fuel pool such that adequate protection is provided for the operator against radiation from the spent fuel. 

Spent Fuel Pool Cooling System (SFS) testing ... 

Some systems may require specific modelling for a SLP PSA because they are not considered in the power PSA. An example is the Spent fuel pool cooling system. Some operating modes of the RHR system may be specific to a POS. System recoveries credited in power PSA may not be applicable due to on-going activities or due to limited accessibility, etc. 

Spent Fuel Pool Cooling and Cleanup System... 

Component cooling water system Spent fuel pool cooling and cleanup system Residual heat removal system Essential service water system... 

Other auxiliary systems are the radioactive effluents treatment system, the components intermediate cooling system, the spent-fuel pool cooling and purification system. 

The spent fuel pool and the storage racks are described in CESSAR-DC Section 9.1.2, the spent fuel pool cooling and cleanup system is described in Section 9.1.3, and the fuel handling system (which includes the equipment for handling heavy loads) is described in Section 9.1.4. (A more complete description of how the fuel handling system conforms to acceptance criteria for the handling of heavy loads is provided in the response to USI A-36.)... 

The passive containment cooling system must be able to provide makeup water to the spent fuel pool in case of a prolonged loss of normal spent fuel pool cooling. 

A recent example is described in (Babst et al. 2014). The licensee has recently requested the regulatory body for approving technical plant modification concerning the spent fuel pool cooling. Major differences of the intended plant modifications compared to the original situation are the number of emergency power supply systems available and the systems used for cooling the spent fuel. 

The earthquake caused extensive damage to the structures of the Fukushima—Daiichi power plant and knocked out the pump systems that supply cooling water to the reactors and the spent fuel pools. This is known as a Loss of Coolant Accident (LOCA) takes place. 

The RHR system heat exchangers are also available to supplement the fuel pool cooling heat exchangers. RHR system heat exchangers are not normally required but may be needed if more than the normal number of spent fuel assemblies is stored in the pool. The system pumps and heat exchangers are located in the fuel building below the normal fuel pool water level. Heat exchangers are cooled by essential plant service water. 

Verified that the structures and systems required for containing, cooling, cleaning, level monitoring and makeup of water in the spent fuel pool (SFP) were operable and adequate, consistent with the licensing basis, to preclude high levels of radionuclides in the pool water and adverse effects on stored fuel, SFP, fuel transfer components, and related equipment. 

The risk from the spent fuel pool has been evaluated in Reference 5.18. The fuel damage frequency is 1.59x 10 ° per year. This is dominated by the loss of component cooling/service water system (78%). The second largest contributor is loss of offsite power leading to station blackout (17%). 

A normally isolated, manually-opened flow path is available between the passive contaimnent cooling system water storage tank and flie spent fuel pool. 

The option to incorporate high-density storage racks is substantially cheaper than the option of increasing the size of the spent fuel pool, and the safety function of removing the decay heat can still be achieved without any upgrading of the cooling system. It is thus the ALARP option. 

This subsection should provide relevant information on the heating, ventilation, air conditioning and cooling systems in a format as described in paras 3.65-3.70. It should include the ventilation systems for the control room area, the spent fuel pool area, the auxiliary and radioactive waste area and the turbine building (in boiling water reactors) and the ventilation systems for engineered safety features. 

A. 1002. This section shall describe systems for storing fresh and spent fuel, for cooling and cleaning the spent fuel pool (if applicable), and for handling and, if necessary, cooling the fuel as it moves within the facility. The quantity of fuel to be stored and the means for maintaining a subcritical array, even during adverse seismic conditions, shall be provided. 

It is recognized that there are three major points of lessons learned from the Fukushima-Daiichi accident. The first point is the enhancement of systems that may be needed to decrease the likelihood of a severe accident due to extreme external hazards. Namely, robustness should be enhanced in power supphes [direct current and alternating current (AC), if needed to power an active safety system], cooling functions (core, CV, and spent fuel pools), and the heat transportation system, including the final heat sink. The second point is the enhancement of response measures against severe accidents. The means should be provided to prevent severe mechanical loads on CVs and the instrumentation should be prepared to identify the status of the reactor core and the CV. The third point is the reinforcement of safety infirastructure by ensuring the independency and diversity of safety systems. These points are incorporated into SDC taking the characteristics of SFRs into account (Kamide et al., 2015). 

Better use of all three redundancies of the RHR System (including the RHR train cooling the Spent Fuel Pool) when the core is in the vessel and the decay heat level of the fuel in the Pool is low. 

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