Abstract
Research studies by the Electric Power Research Institute (EPRI) established the technical and operational requirements necessary to enable the onsite cask-to-cask dry transfer of spent nuclear fuel. Use of the dry transfer system has the potential to permit shutdown reactor sites to decommission pools and provide the capability of transferring assemblies from storage casks or small transportation casks to sealed transportable canisters. Following an evaluation by the Department of Energy (DOE) and the National Academy of Sciences, a cooperative program was established between DOE and EPRI, which led to the cost-shared design of a dry transfer system (DTS). EPRI used Transnuclear, Inc., of Hawthorne, New York, to design the DTS in accordance with the technical and quality assurance requirements of the code of Federal Regulations, Title 10, Part 72 (10CFR72). EPRI delivered the final design report to DOE in 1995 and the DTS topical safety analysis report (TSAR) in 1996. DOE submitted the TSAR to the United States Nuclear Regulatory Commission (NRC) for review under 10CFR72 and requested that the NRC staff evaluate the TSAR and issue a Safety Evaluation Report (SER) that could be used and referenced by an applicant seeking a site-specific license for the construction and operation of a DTS. DOE also initiated a cold demonstration of major subsystem prototypes in 1996.
After careful assessment, the NRC agreed that the DTS concept has merit. However, because the TSAR was not site-specific and was lacking some detailed information required for a complete review, the NRC decided to issue an Assessment Report (AR) rather than a SER. This was issued in November 2000. Additional information that must be included in a future site-specific Safety Analysis Report for the DTS is identified in the AR.
The DTS consists of three major sections: a Preparation Area, a Lower Access Area, and a Transfer Confinement Area. The Preparation Area is a sheet metal building where casks are prepared for loading, unloading, or shipment. The Preparation Area adjoins the Lower Access Area and is separated from the Lower Access Area by a large shielded door. The Lower Access Area and Transfer Confinement Area are contained within concrete walls approximately three feet thick. These are the areas where the casks are located and where the fuel is moved during transfer operations. A floor containing two portals separates the Lower Access Area and the Transfer Confinement Area. The casks are located below the floor, and the fuel transfer operation occurs above the floor.
The cold demonstration of the DTS was successfully conducted at the Idaho National Engineering and Environmental Laboratory (INEEL) as a cooperative effort between the DOE and EPRI. The cold demonstration was limited to the fuel handling equipment, the cask lid handling equipment, and the cask interface system. The demonstration included recovery operations associated with loss of power or off-normal events. The demonstration did not include cask receiving and lid handling; cask transport and lifting; vacuum/inerting/leak test; canister welding; decontamination; heating, ventilation, and air conditioning; and radiation monitoring. The demonstration test was designed to deliberately challenge the system and determine whether any specific system operation could adversely impact or jeopardize the operation or safety of any other function or system. All known interlocks were challenged. As in all new systems, there were lessons learned during the operation of the system and a few minor modifications made to ease operations. System modifications were subsequently demonstrated. The demonstration showed that the system operated as expected and provided times for normal fuel transfer operations. The demonstration also showed that recovery could be made from off-normal events.
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