Andrew Kee
Duke Engineering and Services Hanford, Inc.

David Dawson
Transnuclear West Inc.

Glenn Guerra
Transnuclear, Inc.

This paper describes the cask/transportation system that was designed, procured and delivered to the Hanford K-Basin site at Richland, Washington. The performance requirements and design of the various components – cask, trailer with cask tie-down system, and the cask operation equipment for the load-out pit will be discussed. The presentation will include the details of the factory acceptance testing and its results. The performance requirements for the cask/transportation system was dictated by the constraints imposed by the large number of high priority shipments and the spent fuel pool environment, and the complex interface requirements with other equipment and facility designs. The results of the testing form the basis for the conclusion that the system satisfies the site performance requirements.

The cask/transportation system design was driven by the existing facility constraints and the limitations imposed by the large number of shipments over a short two-year period. This system may be useful information for other DOE facilities that may be or will be in a similar situation.

As part of the DOE's program to remove 2090 metric tons of spent N Reactor fuel assemblies currently stored in the two Basins (spent fuel pools) located at Hanford's K-Reactor site, Westinghouse Hanford Company contracted with Transnuclear, Inc. of Hawthorne, New York for the design and fabrication of a cask/transportation system into which multi-element spent fuel containers will be loaded for transport of the spent fuel to a dry storage vault facility called the Canister Storage Building (CSB). Though the spent fuel movements will be confined to the Hanford Reservation and therefore not subject to NRC transportation regulations, the cask/transportation system is designed to meet the "intent" of 10CFR71 regulations. The truck shipments will occur specifically between the two K-Reactor Basins and the CSB, a distance of about 16 km (10 miles). Each shipment will consist of one cask and fuel canister. Portions of the transportation system will also be used to support both the actual loading of spent fuel into the 400 multi-element containers and an initial drying process performed under cold vacuum conditions prior to transport.

The spent nuclear fuel is currently stored underwater in both sealed and open storage canisters at the two K-Basins. As part of the repackaging effort, the fuel elements will be removed from the current canisters and cleaned of loose corrosion and sludge. The fuel elements will then be placed in special baskets that will allow for an optimum loading configuration inside the larger storage containers. These storage containers, called multi canister overpacks or MCOs, will provide a redundant containment barrier during transportation and will serve as the primary containment barrier during storage at the CSB. The empty MCOs are pre-staged inside a transport cask prior to fuel loading operations at the basins. Following installation of a mechanically sealed shield plug in the fueled MCO, the loaded casks will be removed from the K-Basin load out areas, placed on their trailers, and taken to the vacuum drying station. Here the cask and MCO will be drained, dried, and prepared for transport to the CSB. The trailer is designed to transport the cask in the vertical position to facilitate the vacuum drying operation, minimize operator dose by eliminating cask upending/downending operations, and eliminate the need for heavy cranes in the vacuum drying facility.

The design of the Cask/Transportation System and the associated Operations Equipment was completed in December 1996. Two Systems were fabricated and delivered to Hanford in July 1997 after successfully completing the performance testing of each system. Delivery of two sets of Operations Equipment was completed in September 1997 after system integration testing. By the end of September 1997, the support structure of the Operations Equipment was installed into one K-Basin loadout pit without interference with the site. Transnuclear is presently fabricating an additional three Cask/Transportation Systems which are scheduled for delivery in mid-1998.

Removal of all spent fuel from the K-Basins has been established as a very high priority activity of the Hanford site cleanup effort by DOE and other State and Federal agencies. Current plans are to initiate removal of the spent fuel from the two basins by the end of July 1999, and to complete the transfers to the CSB in early 2003. Loading, drying, and transport of the 400 MCOs with occur with the five Cask/Transportation Systems and will require 80 shipments per System.

The total shipment quantities discussed above dictate a ramp-up to a rate of about four shipments per week or a cycle time of about one per day for all operations performed in the basins. A combination of this short cycle time and extremely high contamination levels in the basins created a challenge to design special operations equipment which will eliminate the need for decontamination of the outer cask surfaces by isolating the cask from the contaminated pool water. The Operations Equipment relies on a rigid immersion pail system into which the cask is placed prior to submersion. An inflatable seal at the top of the pail prevents basin water leakage into the pail/cask annulus. Short cask turnaround times were also driven by the general background radiation in the basins as well as the expected dose rate from the casks during loading and following removal from the pools.

Three major factors that influenced the design of the cask as well as the operations equipment are the limited lifting capacity of the cranes that serve each of the two basins (27.3 metric tons); the requirement to limit operating staff exposures to ALARA (the project performance specification established a limit of 100 mrem/hour at the surface and 10 mrem/hr at 2 meters from the surface); and the requirement to maintain the working level of the immersion pail system within 0.3 m off the floor level.

The major safety requirement for the cask design was the need to maintain "confinement" within the cask of the MCO under all conditions. This requirement drove the structural design of the cask.

The Hanford Spent Nuclear Fuel Project required that the design of the cask and all supporting equipment, the safety analysis report for packaging (SARP) development and approval, and system fabrication be completed on an 18 month timeline. Uncertainties in the packaging contents and MCO processing locations dictated that the performance requirements of the cask be verified through analytical approaches rather than by demonstration through physical tests.

The on-site use enabled implementation of a risk-based approach to developing packaging design requirements. The packaging was required to meet the intent of 10 CFR 71 with respect to criticality control and containment of radioactive contents under normal and hypothetical accident conditions. The design requirements were developed with a special emphasis on the minimization of dose to workers since the packaging is used only within controlled access areas on the Hanford site. Table I compares the specific normal and accident conditions identified in 10 CFR 71 Subpart F to the conditions applicable to the specific transportation route.

In order to comply with these requirements, both the Cask/Transportation Systems and the Operations Equipment are of unique designs. In addition to the primary function of isolating the cask from the pool water, the Equipment must provide:

• buoyancy for height and lifting weight control
• minimal cycle times
• precise control of cask positioning during the various fuel loading and closure operations
• minimal waste generation
• minimal hands-on operational requirements near the cask top and circumferences

The Cask/Transportation System consists of a stainless steel cask designated the TN-WHC and its trailer with the cask tiedown system and workplatform. The System layout is shown on Figure 1.

The TN-WHC cask consists of a cylindrical body fabricated from stainless steel forging(s). The lifting system is an integral component of the bolt-on stainless steel closure lid. This design was driven by the existing facility cask crane hook configuration and dimensional limitations with the Operations Equipment. The solid stainless steel design was selected in order to facilitate and expedite cask fabrication, to minimize cask maintenance, and maximize in-service time.

The structure of the cask is a right circular cylinder with a bottom and a closure lid. The overall dimensions of the cask are 4.26 m (190.25 in.) long and 1.01 m (39.81 in.) in diameter. The cask cavity has a length of 4.08 m (160.50 in.) and a cavity ID of 0.64 m (25.19 in.). The general arrangement of the cask is depicted in Figure 2. The basic components of the cask are the cask body, closure lid, the lid bolts and the lid/penetration cover butyl seals. The cask body consists of the cylindrical shell and the shop-welded bottom plate. The closure lid is attached to the cask body with twelve 0.038 m (1.5 in.) diameter bolts. Three penetrations into the containment are provided to support cask operations. Two are located at the top end of the cask body and the remaining is located in the cask bottom. The maximum gross weight of the loaded cask is about 26,089 kg (57,500 lb.) dry including a payload of 8312 kg (18,320 lb.). The cask is designed to allow all operations (i.e. lifting, loading, closure, draining, vacuum drying, transport, and MCO removal at CSB) to be performed in a vertical orientation.

The cask lifting system is the primary crane interface for all cask handling operations. The layout of the assembly is shown on Figure 2. Two lifting trunnions are attached to the integrated lifting system which is welded to the cask lid. The lift assembly is used for lifting the cask from the trailer, placing the cask into the Operations Equipment prior to immersion into the pool, lifting the cask from the Operations Equipment, and placement on the trailer in the vertical position. The lifting system is also used to handle the cask lid and to lift the cask from the trailer into the MCO unloading position at the CSB.

The conveyance system is a semi-trailer which can be attached to a standard tractor. The trailer’s cask tiedown system provides the necessary supports and attachment points for securing the cask in the vertical orientation during drying operations and transport. The cask is supported in the vertical orientation on the trailer by an upper collar and a lower cup shaped retainer. The collar is essentially a clamp that restrain the cask in the horizontal direction and is provided with a hold down device to restrain the cask in the vertical direction. The trailer is also designed to minimize the flex due do changes in weight between a loaded and unloaded cask/MCO configuration. An additional performance feature of the trailer is to provide seismic restraint at the Cold Vacuum Drying Facility during a seismic event. The conveyance system is provided with a workplatform to allow operators access to the cask lid region. The workplatform contains removable planks that can be raised and lowered so that the cask can be removed from or installed on the conveyance system. A winch system is used to raise an lower the removable planks. Layout of the work platform arrangement is shown in Figure 3.

The K-Basins loadout pit Operations Equipment consists of the cask immersion pail, a support structure for the immersion pail, a guide rail system that controls vertical cask/pail positioning in the loadout pits and a lift beam/slings for the operation of the immersion pail using the site crane. This equipment will be installed in the cask loadout pit of each basin.

The immersion pail is a thin walled reinforced structure housing a buoyancy foam 0.69 m (176 in.) long with four base beams and four vertical support components to provide the safety-related load path to the Loadout Pit floor. The buoyancy foam improves working level control of the pail when in the raised position and reduces the maximum load to be lifted by the facility cranes. The immersion pail sealing lid encloses the cask in a clean demineralized water cavity. The entire immersion pail/cask/MCO assembly is lowered to the K-Basin loadout pit floor for loading of the fuel baskets into the MCO. Contamination of the cask and MCO outer surfaces is precluded by the sealed immersion pail and a positive 34.5 kPa (5 psig) pressure maintained within the immersion pail.

The immersion pail is supported by a steel support structure which rests on the floor of the loadout pit. Four actuated square lock pins are used to support the immersion pail in the full up position during initial placement of the empty cask/MCO into the immersion pail and during installation/removal of the pail sealing and cask closure lids. The facility crane is used to lower and raise the immersion pail to and from the loadout pit floor. Guides are mounted to the lower end of each support rail to eliminate binding during immersion pail movement. The immersion pail support structures are passive structures that will remain in the loadout pits throughout the fuel removal campaign. Compressed air and demineralized water supply are required to support the operation of the Equipment. Figure 4 presents the K-Basin loadout pit Operations Equipment

The immersion pail sealing lid is handled by the facility crane during installation and removal for each loading cycle. Four lifting lugs are provided for moving the immersion pail lid to and from the immersion pail using slings. The pail lid is lowered in place, deionized water flow is established, and seals are pressurized. Seal integrity verification occurs at this point in the operation.

The pail lid is fabricated of stainless steel to mitigate concerns about corrosion and abrasion. The lid is held in place through seal pressure, dead weight and four bolts to the main pail structure. Seal pressure of 172 kPa (25 psig) activates the silicone seals which have been rated to withstand radiation environments of 150 rem/hr. The lid design minimizes seal crevasses and pool water entrapment, permits flushing of the seal surface prior to breaking the seal and permits clean immersion pail water to flow from the seal boundary when seal pressure is removed. Each of these features supports ease of decontamination during the operation sequence.

As discussed above, the cask design’s compliance with regulation-derived performance requirements was verified by analytical techniques, not physical testing.

Thermal, criticality, shielding and structural analyses on the packaging design were checked by at least two independent analytical approaches. As an example, compliance with structural requirements was verified by the use of EPRI NP-4830 "Effects of Target Hardness on the Structural Design of Concrete Storage Pads for Spent Fuel Casks" guidelines to assess cask and content accelerations, and independently verified through the use of a nonlinear finite element code (Abaqus Explicit) model to assess the packaging and target response to the free drop events.

Note that the MCO packaging complies fully with Paragraph 71.71, Normal Conditions of Transport, except for the one foot drop that used an 8 inch thick high strength reinforced concrete pad.

In order to demonstrate that the TN-WHC Cask/Transportation System would function as designed, Transnuclear required the fabricators to perform a comprehensive list of acceptance tests. This testing is in addition to the NDE testing required by the ASME Code for the cask material and the welds. The following acceptance testing was performed:

Hydrostatic test. The cask cavities was hydrostatically tested in accordance with the requirements of the ASME Code to a pressure of 1.55 MPa (225 psig) for a period of fifteen minutes. No visible leakage and no pressure drop was observed during the duration of the test.

Shielding test. The shielding integrity of the sidewalls of the casks were verified by the performance of UT scanning of the forgings. The results of the testing confirmed the lack of voids in the forging material. This result coupled with dimensional verification of the final machined sidewalls demonstrated the shielding integrity of the cask body.

Seal leakage test. The containment seals for the lid and the penetration covers were leak tested in accordance with the requirements of ANSI N14.5 and an acceptance criteria of 1 x 10^-7 std cc/sec air. The testing was performed using a helium mass spectrometer.

Lifting trunnion load test. The cask is maneuvered using the two lifting trunnions of the lift system that is an integral component of the cask lid. The lifting trunnions were loaded tested to 1.5 times the design load of 27,217 kg (60,000 lb.) to comply with ANSI N14.6 requirements and examined for defects and permanent deformation. At the conclusion of the test, the load bearing welds and the critical load path of the lift system were non-destructively tested.

Cask lid bolt load test. Since the lid bolts provide a load path to the cask body during the lifting of the cask, the bolts were overtorqued to develop the equivalent 150% design load in the bolts. After the test, the bolts were examined for defects/permanent deformation and nondestructively tested.

Assembled cask weight test. Each cask was fully assembled and the weight recorded. The acceptance criterion was a weight limit of 17,691 kg (39,000 lb.), which will allow a payload of 9,072 kg (20,000 lb.) without exceeding the maximum loaded cask weight limit of 27.3 metric tons.

Cask assembly/disassembly test. The complete cycle of cask assembly and disassembly was performed to verify that the lid, penetration covers, and all fittings can be installed and removed without interference, damage or unusual observations.

Trailer frame 120% static load test. The trailer frame was load tested by applying 38,104 kg (84,000 lb.) i.e., 120% of the design load which included the 27.3 metric ton maximum design load of the cask and additional weight for the tie-down system and the workplatform) static load. Deflections of the main beam were recorded at 0, 27.3 and 38.1 metric ton loading conditions. After the test, the frame welds were nondestructively inspected. The deflection data for the load test was evaluated against that predicted by analysis and concluded to be acceptable.

Trailer road test. The completed Conveyance System was loaded with a mock-up of the cask and loaded to 27,300 kg. A maneuverability test was conducted to demonstrate that the Conveyance System can negotiate turns, and start/stop without any interference. The trailer equipment was checked for proper operation. The final road test was performed without the cask mock-up at highway speeds.

Operations Equipment load test. All components that provide a load path to support/lift the cask were loaded tested to 1.5 times the cask design load of 27,300 kg to comply with ANSI N14.6 requirements and examined for defects and permanent deformation. These components included the support structure, the immersion pail, the slings and the lift beam. At the conclusion of the test, the load bearing welds and the high stress areas were non-destructively tested.

Operations Equipment floation leak test. The foam shell enclosure of the immersion pail was leak tested using the bubble test method to verify the absence of pin holes in the foam shell. This test was performed after the nondestructive testing of the welds of the foam shell.

Operations Equipment assembly/disassembly/fit-up test. This acceptance testing consisted of the verification of the following:

• Fit-up of the upper and lower support structures (The immersion pail support structure was made in two piece for ease of fabrication, shipment and ease of installation at the
  K-Basin loadout pit.).
• Assembly and disassembly of immersion pail and lid.
• Fit-up of immersion pail with assembled support structure including the verification of "free travel" of the pail within the structure.

Cask-trailer fit-up test. The cask fabricator was supplied with the conveyance system. The fitup test consisted of lifting a cask and installing it on the trailer. The operation of workplatform and the

clamping system including the hold down device was verified. The support/tiedown system of the trailer and cask was examined for damage and potential interference during the test.

Integrated Cask/Immersion Pail test The purpose of this test was to demonstrate the immersion pail/TN-WHC cask fit-up, the immersion pail lid seal function, fit-up of the pail lid to the MCO, and to record crane hook loads as the cask is inserted and removed form the immersion pail. This test also demonstrated the use of the applicable sections of the operations manual for the Operations Equipment. The equipment used for the test included the immersion pail and its lid, a TN-WHC cask and a mock-up of the MCO. The immersion pail was anchored in a vertical stable position for the test. The test included the following steps:

1. Preparation of the pail to receive the cask including the addition of water (as required by the operations manual) in the pail.
2. Installation of the cask into the pail.
3. Removal of the cask lid to its storage location.
4. Installation of the pail lid and seal testing.
5. Removal of the pail lid and installation of the cask lid.
6. Removal of the cask from the pail.

The results of the test demonstrated that

• water in the pail did not spray or splash out of the immersion pail during the installation of the cask in the pail;
• the lid seals performed as designed;.
• the load on the crane hook always remained below the dead weight of the cask.

The K-Basins Cask/Transportation System including the Operations Equipment delivered to Hanford performed as designed and satisfies the Hanford Site performance and safety requirements. This System is expected to operate with minimal risk in the Hanford environment that is dictated largely by the existing facility constraints and requirements imposed due to the large number of shipments required.