Dealing with spent fuel in Idaho29 June 2001
Spent nuclear fuel from power and research reactors is to be repackaged for interim storage at the Idaho National Engineering and Environmental Laboratory operated by the United States Department of Energy.
During the last 40 years, the US Department of Energy (DoE) and its predecessor agencies have generated, transported, received, stored, and reprocessed spent nuclear fuel at facilities in the DoE’s nationwide complex. This spent fuel was generated from various sources, including production reactors; research and test reactors; special-case commercial power reactors; and foreign research reactors.
The DoE ended reprocessing in 1992, but some 265t of Heavy Metal (tHM) of spent fuel is still stored at the Idaho National Engineering and Environmental Laboratory (INEEL). The INEEL spent fuel is currently stored onsite in pools, dry wells and above ground storage. Current storage facilities are not adequate to meet the mission need through 2034. The current storage facilities are located over the Snake River aquifer, a major water source for the region. The government is committed to repackaging spent fuel for more stable interim dry storage and future shipment to a storage location outside the state of Idaho.
A Settlement Agreement signed on 17 October, 1995 by the DOE, the US Navy and the state of Idaho requires that all INEEL spent fuels be transferred to dry storage by 31 December, 2023 and removed from Idaho by 1 January, 2035. The agreement includes fuel from Peach Bottom and Shippingport reactors, and TRIGA fuel from various sources. Foster Wheeler has been employed as the design, license, build and operate contractor, and will transfer the fuel to a modular vault dry storage facility designed by ALSTEC. AEA is responsible for conceptual design of the transfer area where fuel will be removed from DoE shipping casks and placed in canisters designed by Foster Wheeler that meet the ASME Section III requirements. Utility Engineering is responsible for several aspects of balance of plant design including fire protection, security, emergency plan and structural steel design, and will provide leadership for the operating phase of the facility.
To accomplish this scope of work, Foster Wheeler must design a facility, licensable by the NRC under 10 CFR 72, which can receive, repackage and store the Peach Bottom, Shippingport, and TRIGA spent fuel.
The spent fuel storage canisters must be compatible with the requirements of the proposed national high level waste repository. The preliminary canister specifications were designed by DoE and its contractors to accommodate a wide range of fuels currently stored by DoE. The ISF will use two different diameter storage canisters, 18 inch and 24 inch. The 24 inch canisters are required to accommodate the Shippingport fuel assemblies, while the 18 inch canisters will be used for the remaining fuel types.
Once the facility design is complete, an application for a license to receive, repackage, and store the fuel will be submitted to the NRC. Once license approval is obtained, Foster Wheeler will construct the facility, and perform pre-operational testing before beginning to receive fuel. Construction of the facility is scheduled to occur in 2004 and 2005 with fuel receipt to begin in 2005.
The ISF facility provides for year round operations. Due to the weather extremes in Idaho, all operations occur inside the facility. The ISF facility design provides for specific operations to occur within discrete areas of the facility. These areas include the Receipt Area, Transfer Area, Canister Closure Area, and Storage Area which are further described hereafter.
Foster Wheeler will also provide a conceptual transportation cask design compatible with the ISF storage canisters. This conceptual transportation cask will allow the spent fuel canisters to be removed from storage and placed in the transportation cask for rail or road shipment. Ultimately, the packages will be transferred off site, but this operation is not included in the scope of this project.
Fuel Type Summary
The fuel to be stored in the ISF facility consist of the following:
•Peach Bottom 1600 Fuel Assembles 3.8% by weight total heavy metal
•Shippingport 16,721 Fuel Rods 95.8% by weight total heavy metal
•TRIGA 1600 Fuel Elements <1% by weight total heavy metal
Characterisation of Spent Fuel
The Peach Bottom Core 1 fuel consists of 813 individual elements (assemblies) differentiated into four types of varying enrichment and materials. The elements are packaged into 814 sealed aluminium storage canisters with stainless steel liners. The canisters are contained within 46 aluminium storage baskets, and stored in the underground vaults in dry storage. Failed fuel elements were placed in sealed canisters, inerted, and leak-tested. In the event of positive leak detection, the canister was packaged into a second aluminium storage canister (a salvage canister).
Most canisters contain intact fuel with assembly components, instrumentation, and scrap. One element has been disassembled and is stored in two separate canisters. The intact fuel canisters are approximately 153 inches long and 4.48 inches in diameter, while the salvage canisters are 158 inches long and 4.73 inches in diameter.
Some fuel storage positions were visually inspected using remote cameras. The inspection discovered that there has been some water infiltration into the vaults, and there was corrosion of both baskets and canisters. Water may have infiltrated the aluminium canisters, but this has not been confirmed. One basket failed when it was removed for inspection in 1988, but this was due to improper handling and not corrosion. This fuel has since been repackaged and stored in the new second-generation vaults at the site. It is assumed that all baskets and their canisters have been corroded to some extent. As a result, all the spent fuel was scheduled to be moved to second generation storage vaults.
Each transfer basket received in the transfer cask will contain between 1 and 18 Peach Bottom Core 1 fuel assemblies(each individually canned) per transfer from DoE. The fuel assemblies must be removed from the aluminium cans, staged in the ISF basket assembly, and placed in the ISF canister. The ISF canister will go through drying/inerting and sealing processes prior to placing the canister in the Storage Area. Elements will be inspected and inventoried. The aluminium cans, tools, and non-fuel waste debris will be disposed of as waste and the basket assembly will be returned to DoE in the transfer cask.
The Peach Bottom Core 2 fuel consists of 787 individual elements of the same basic type as the Peach Bottom Core 1 fuels. The major difference is that the fuel particles are coated with pyrolytic carbon.
The elements are packaged dry into 70 unsealed, carbon steel canisters within the dry side of the fuel storage area. Each canister, around 129 inches long and 18 inches in diameter, contains 11 to 12 elements and their removed reflectors. None of the Core 2 fuel has undergone internal inspection since they were placed in storage. However, external inspection of the canisters in 1997 showed no corrosion and the fuel condition is assumed to be good. The spent fuel will be transferred to the ISF with each cask containing from 1 to 12 Peach Bottom Core 2 fuel elements in a carbon steel canister. Foster Wheeler will remove the fuel, repackage it, and place it in the dry storage facility, inspecting and drying/inerting the fuel as necessary. The carbon steel canisters will be disposed of as waste.
The spent fuel to be handled from the Shippingport LWBR consists of 16,721 rods consisting of 15 reflector modules and 127 loose reflector rods. The modules and rods have been packaged into 43 canisters, and kept in dry storage within underground vaults. The canisters, approximately 158 inches long and 25.5 inches in diameter, variously contain intact modules, partially filled modules, bare intact rods, sectioned rods and scrap. The canisters were dried, sealed, and inerted before storage. The modules and rods are thought to be in good condition, although they have not been inspected.
Foster Wheeler will receive one fuel canister per shipment and will remove the fuel module assembly from each canister, and place them in new storage canisters to be placed in the Storage Area. The rods will be inspected, inventoried, vacuum dried, and inerted. The existing canisters and non-fuel materials from the individual module assemblies will be disposed of as waste.
TRIGA fuel rods are made of uranium-zirconium hydride, with a cladding of aluminum or stainless steel. There are currently 1,159 TRIGA fuel rods placed in three storage locations at the Idaho Nuclear Technology and Engineering Center (INTEC). Some 303 rods in 67 cans are currently in wet storage, but will have been transferred to dry storage before the ISF facility is completed. There are already 576 rods in 14 canisters in dry storage. Finally, there are 280 rods in 19 buckets in wet storage and fuel is still being brought to the INEEL from domestic and foreign sources.
The scope of this contract includes 1600 TRIGA elements. It is estimated that 320 cans, each containing five rods (totalling 1600 elements) will be delivered to the ISF during the planned campaign within this contract. The fuel assemblies are 28.94 inches long and 1.48 inches in diameter. Fuel arriving at the INEEL from off-site sources has likely been stored in water for some time, but will be placed in dry storage upon arrival at the INEEL. Assembly components may have experienced some corrosion, but the fuel itself is expected to be in good condition.
In each cask shipment Foster Wheeler will receive up to 28 fuel canisters, each containing up to 5 fuel elements. The fuel will be removed from the receipt canisters, inspected, inventoried and placed in storage canisters. The internal volume of the canisters will be subjected to a vacuum to remove moisture from the fuel. Once this vacuum drying is complete, the canister will be back-filled with helium, and placed in storage.
The Receipt Area houses the equipment necessary to receive shipments of spent fuel from DoE. The major equipment in this facility consists of an overhead hoist and a transfer trolley. The fuel arrives at the ISF facility in a transfer cask, which was formerly licensed by the NRC for transportation of Peach Bottom fuel over public highways. The transfer of the fuel to the ISF facility does not traverse public roadways since the transfer is from an adjacent DoE facility. The Receipt Area hoist is a single failure proof hoist to minimize the probability of drop accidents associated with cask handling. The transfer cask is lifted from the transport vehicle and placed in a rail-mounted trolley, which will restrain the cask from tipping even in the unlikely event of an earthquake. The transfer cask provides radiation shielding for the fuel to reduce personnel exposure. The cask trolley moves the cask from the Receipt Area down a tunnel to the Transfer Area where the building structure provides not only the required shielding but also a ventilation system designed to prevent release of radioactive material under credible accident scenarios.
The Transfer Area is designed to allow remote handling and unloading of the transfer casks containing the spent fuel. The fuel will be remotely handled during inspection and repackaging into the storage canisters. The process involves removing the cask lid and reusing the inner canister containing the spent fuel. This canister is placed in a shielded port located in the floor of the transfer area. The canister lid is removed to allow access to the spent fuel. The spent fuel assembly is then removed, inspected, and placed in a “basket” which is designed to hold the fuel within a fixed location when placed inside a new storage canister that meets ASME Boiler and Pressure Vessel Code requirements. Once a basket is loaded, it is placed inside a storage canister.
Canister Closure Area
The loaded storage canister, restrained to prevent tip-over accidents in a radiation shielded, rail-mounted trolley, is then transferred to the Canister Closure Area where a lid is welded to the canister. Once the canister lid is welded, an access port allows the interior volume of the canister to be placed in a vacuum. This vacuum drying process removes any residual moisture and air. The canister is then backfilled with helium to provide an inert atmosphere, which minimises corrosion and improves heat transfer. Once the canister closure and inerting are complete, it is ready for storage.
The canister, ready for storage, is transferred to the Storage Area in the canister transfer trolley in which it has remained since fuel loading. This trolley is moved to the Storage Area and located under a specially designed Canister Handling Machine (CHM). The CHM provides shielding and remote handling of the canister to minimise personnel radiation exposure. The CHM is also designed to preclude drop accidents, as it is designed as a single failure-proof crane in accordance with NRC guidance. The storage canister is placed within a mechanically sealed storage tube whose primary purpose is to provide a redundant confinement barrier for the stored fuel. The vault system provides for a self-regulating passive cooling of the fuel canisters as well as shielding to limit personnel exposure, and protection of the fuel canister confinement boundaries from all credible accident scenarios.
Off-site Transfer of Casks
To prepare for eventual transfer of the fuel canisters to a national repository or other storage location, Foster Wheeler will prepare a conceptual design for a transport system. This conceptual design will be compatible with the storage canisters and integrated with the ISF facility operations and equipment. The conceptual transport cask design will provide for off-site shipment of the packaged spent fuel in accordance with the requirements of 10 CFR Part 71. To accommodate the transport system, the ISF facility will have a staging area for loading off-site transportation casks onto either a truck or rail car. It will be able to handle a cask envelope 128 inches in diameter, 308 inches long, and weighing 260,000 pounds.
Foster Wheeler will design, license, construct and operate an Independent Spent Fuel Storage Installation adjacent to INTEC within the INEEL, approximately 50 miles west of Idaho Falls, Idaho. This Idaho Spent Fuel (ISF) facility will receive, repackage, and store spent nuclear fuel provided by DoE.
Foster Wheeler will own and operate the ISF until the end of the contract when the site and NRC license would be transferred to the DoE. Further activities may involve additional fuel transfer and storage, expansion of the facility for additional fuel types, extension of the term of the contract, export to repository operations, and eventual decontamination and decommissioning. The ISF facility is designed to provide for the interim storage of the spent fuel for a minimum of 40 years.