REACTOR REFUELING - INTERIM DECAY STORAGE (FFTF)
The IDS facility is located between the CLEM rails and within the FFTF containment building. It is located in a rectangular steel-lined concrete cell which lies entirely below the 550 ft floor level with the top flush with the 550 ft floor level. The BLTC rails within containment traverse the IDS cover (H-4-38001). The facility consists of a rotatable storage basket submerged in liquid sodium which is contained in a stainless steel tank. The storage positions within the basket are arranged so that it is not physically possible to achieve a critical array. The primary vessel is enclosed in a secondary guard tank of such size and arrangement that, should a leak develop in the primary tank, the sodium level would not fall below the top of the fueled section of the stored core components or test assemblies. The atmosphere outside the primary vessel, but within the concrete cell, is nitrogen which also serves as a heat transfer medium to control the cell temperature. To provide space for the storage of test assemblies such as the OTA and CLIRA, 10 storage tubes (each approximately 43-1/4 ft long) are included near the center of the basket. This arrangement requires that the center of the primary vessel be quite deep. In this region, the primary vessel extends downward to elevation 501 ft 6 inches while the guard tank reaches 500 ft 4 inches. The floor of the cell is at 499 ft a inches which is 51 ft below the operating room floor. Storage positions are provided for 112 core components in the upper section of the storage basket. These positions are arranged in four circles, all of which are concentric with the test element array and the storage basket. The primary vessel and the guard tank are shaped to provide the necessary space with a minimum of excess volume. Both these vessels have a relatively small cylindrical lower section connected to a larger upper cylinder by a conical transition. The primary vessel is supported from a top flange by a vessel support structure. The guard tank is supported by a skirt which rests on a ledge at elevation 527 ft 2 inches. The skirt is an extension of the upper cylinder of the guard tank. The storage basket is supported by a gear-driven, mechanically indexed, ball bearing that rests on the bearing support, which in turn rests on the vessel support structure. The interior of the primary vessel above the sodium level is blanketed with argon at 6 inches of water gage pressure. The vessel is designed to allow the pressure to be increased to 3 psig to assist drainage of the sodium from the vessel. The structure which supports the primary vessel also serves as the cover to the IDS cell. The support structure rests on a shelf cast into the cell wall at the 544 ft 6 inch level. In addition to supporting the primary vessel and the storage basket bearing, this structure also provides support for the top shield which is a 16 inch thick by 15 ft 10 inch diameter laminated steel assembly, which in turn supports the impact absorber neutron shield, and the BLTC tracks where they cross the IDS. Storage position access ports are provided on the centerline of the IDS facility between the BLTC rails. Basket rotation and indexing allows any storage position to be located in alignment with its proper access port. Double buffered seals are provided for the removable plugs and removable lids for all components and access ports where necessary to seal between the vessel cover gas and the FFTF containment atmosphere. Buffering gas for these seals is argon. Capability of a 10 cfm argon purge rate is provided although normal argon flow into the cover gas cavity will be less than 1 cfm. Argon cover gas exits through a vapor trap located in the southwest corner of the support structure and then to the Cell Atmosphere Processing System. Vessel overpressure protection is provided by rupture discs on the inlet and outlet argon piping. Rupture discs vent to the IDS cell. Biological shielding is provided to maintain the radiation contribution in the operating area below 0.2 mrem/h. The primary gamma shield directly above the IDS is the 16 inch thick steel top shield and the 4 inch steel striker plate. Neutron attenuation is provided by 4 inches of polyethylene directly below the impact absorber tubes. Control instrumentation and power junction boxes are provided in the top cover. Instrumentation includes basket position sensor and indicator, interlocks, thermocouples, sodium level indicator, sodium leak detector, and a cover gas pressure indicator. Means for visually checking the position of and manually rotating the storage basket are also provided. Decay heat is dissipated during normal operation by either the primary sodium system or the backup nitrogen cooling system. The sodium system circulates approximately 30 gpm of sodium from near the top of the primary vessel to an intermediate heat exchanger and returns the cooled sodium to near the bottom of the vessel.
- Research Organization:
- Hanford Site (HNF), Richland, WA (United States)
- Sponsoring Organization:
- USDOE; USDOE Assistant Secretary for Environmental Management (EM)
- DOE Contract Number:
- DE-AC06-76FF02170
- OSTI ID:
- 991932
- Report Number(s):
- SDD-41-5 Rev 11; TRN: US201021%%473
- Country of Publication:
- United States
- Language:
- English
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