September 27, 1994 The Honorable Thomas P. Grumbly Assistant Secretary for Environmental Management Department of Energy Washington, D.C. 20585 Dear Mr. Grumbly: Enclosed for your information and use are two reports issued by our staff on seismic and structural stability issues concerning the CPP-603 and CPP-666 spent fuel storage basins at the Idaho National Engineering Laboratory. Mr. Andrew Stadnik of the Defense Nuclear Facilities Safety Board will be available to provide any additional information you may require. Sincerely, John T. Conway Chairman c: The Honorable Tara O'Toole, EH-1 Mr. Mark Whitaker, Acting EH-6 Ms. Jill Lytle, EM-30 Mr. John Wilcynski, Acting Manager, ID Operations Office Enclosures (2) DEFENSE NUCLEAR FACILITIES SAFETY BOARD August 22, 1994 MEMORANDUM FOR: G. W. Cunningham, Technical Director COPIES: Board Members FROM: C. H. Keilers SUBJECT: Idaho National Engineering Laboratory - Structural and Seismic Review of CPP-603 Spent Fuel Storage Basins 1. Purpose: This report documents the status of on-going reviews by the Defense Nuclear Facilities Safety Board (DNFSB) staff and outside experts of a structural scoping study for the Chemical Processing Plant (CPP)-603 spent fuel storage basins at Idaho National Engineering Laboratory (INEL). The DNFSB staff will separately report the status of a concurrent series of structural reviews of the CPP-666 basins. 2. Summary: The DNFSB staff and outside experts have reviewed a scoping study on the structural adequacy of the CPP-603 spent fuel storage basins and have several observations discussed below. The study identifies a large number of structural deficiencies and, furthermore, provides little justification for accepting them. The Department of Energy (DOE) contractor, Westinghouse Idaho Nuclear Co. (WINCO), is preparing a recommendation to DOE on the disposition of these deficiencies. WINCO has done a value engineering study on possible resolution options, but more effort may be warranted that considers quick, low-cost structural upgrades that improve safety without impacting the fuel removal schedule. The DNFSB staff will review the recommendation when it becomes available. 3. Background: CPP-603 is a 1950's era facility consisting primarily of three unlined concrete basins, all covered by a steel frame superstructure with asbestos shingle siding. By court order, all spent fuel must be removed from two of the basins by the end of 1996 and from the third basin by the end of 2000. As of June 6, 1994, about one-fifth of the fuel had been removed, meeting the schedule. In 1991, WINCO contracted Advanced Engineering Consultants (AEC) to perform a scoping study on the basin structural adequacy for use beyond the year 2000. Since then, the DNFSB staff and outside experts have been reviewing progress on this study. The most recent review was performed on June 6-7, 1994, by DNFSB staff members A. Hadjian and C. Keilers, and by outside experts J. Haltiwanger and J. Stevenson. 4. Discussion: DOE, WINCO, and AEC briefed the DNFSB staff and outside experts on the purpose of AEC's analyses for the CPP-603 basins, as well as on the models, load combinations, geotechnical evaluations, and final analysis and results . WINCO stated that the primary purpose of the scoping study was to identify major structural deficiencies that could affect continued use of these basins beyond the year 2000. However, such use is no longer an option, and fuel is being removed expeditiously. AEC identified several areas that are inadequate for seismic or high wind loads such as: the South Truck Bay crane, the North and Middle Basin walkway support frames, some South Basin superstructure truss webs, and the asbestos shingle siding. AEC, through a subcontractor (R. Cloud and Associates), also evaluated mechanical and electrical distribution systems and components and determined that they would require significant upgrades to be seismically qualified. AEC is separately evaluating a newer dry storage vault that is also part of this facility, contains irradiated graphite-based fuel, and will be used beyond the year 2000. WINCO is preparing a recommendation to DOE on the disposition of these deficiencies. WINCO indicated that it intends to administratively control the crane to park it in a position that avoids a seismic hazard. WINCO may propose no action be taken for the other deficiencies since installing structural upgrades could slow down fuel removal. Furthermore, WINCO expects that effective upgrades may be difficult to design and install in the remaining service life of the basins (three to six years). Observations: The DNFSB staff and its outside experts have the following observations: a. The scoping study identified a large number of structural deficiencies. It did not prioritize the deficiencies. It also did not provide justification for accepting the deficiencies, other than stating that many of these are expected to show ductile, non-catastrophic behavior. b. The DNFSB staff believes that, given the large number of deficiencies, a more detailed structural evaluation may ensure that all major weaknesses have really been identified that could warrant near-term resolution, such as quick, low-cost structural upgrades discussed below. c. The assumed seismic and high wind loads in the CPP-603 scoping study are lower than those assumed in recent CPP- 666 basin evaluations. The DNFSB staff believes that an adequate review of safety of the CPP-603 basin would require that these discrepancies be explicitly recognized and resolved. d. The AEC documentation does not specify how the demand and capacity values cited were determined. Several other documentation deficiencies that are discussed in the DNFSB staff report on CPP-666 are also applicable to the CPP-603 reports. e. WINCO has done a value engineering study on possible resolution options. However, the DNFSB staff believes that more effort may be warranted that considers quick, low-cost structural upgrades that enhance safety without impacting the fuel removal schedule. To be worthwhile, the DNFSB staff also believes that such an investigation would need to be conducted expeditiously by highly experienced personnel applying sound technical judgement and would need to include the following: 1. Identifying effective structural upgrades or other measures that would remediate each identified weakness. 2. Estimating the level of effort, the time required, and the cost to implement each remedial measure and to design and install each potential modification. 3. Determining for each measure if it would delay fuel removal, and if so, by how much. 4. Estimating for each deficiency or group of possibly interacting deficiencies what the consequences of an extreme loading event would be if no action is taken and whether recovery actions would be feasible. 5. Weighing the advantages and disadvantages of each remedial measure using a systems engineering approach and implementing those actions needed to enhance safety, considering the remaining service life of the facility. 6. Prioritize possible mechanical and electrical system and component upgrades to assure necessary safety- related function during or following an evaluation basis seismic event. 5. Future Planned Activities: The DNFSB staff intends to review the WINCO recommendation for the CPP-603 wet basins when it becomes available. The DNFSB staff will also evaluate the trade-offs that are being made between structural upgrades in the CPP-603 basins and the remaining service life of the facility. DEFENSE NUCLEAR FACILITIES SAFETY BOARD August 22, 1994 MEMORANDUM FOR: G. W. Cunningham, Technical Director COPIES: Board Members FROM: C. H. Keilers SUBJECT: Idaho National Engineering Laboratory - Structural and Seismic Review of CPP-666 Spent Fuel Storage Basins 1. Purpose: This report documents the status of on-going reviews by the Defense Nuclear Facilities Safety Board (DNFSB) staff and outside experts of structural/seismic evaluations for reracking the Chemical Processing Plant (CPP)-666 spent fuel storage basins at Idaho National Engineering Laboratory (INEL). The DNFSB staff will separately report the status of a concurrent series of structural reviews of the CPP-603 basins. 2. Summary: The DNFSB staff and outside experts consider that the proposed reracking of some CPP-666 pools to increase fuel loading may be found to be structurally acceptable; however, this is difficult to determine from the structural/seismic evaluations provided. Significant uncertainty exists in the evaluation conclusions because of some of the assumptions made and the methods applied and because of inadequate documentation. The Department of Energy (DOE) contractor is initiating efforts to improve the evaluations. Even if the current evaluations were conclusive, they are limited in scope. Since this facility will be used for decades for interim spent fuel storage, the DNFSB staff believes there will be a need for a comprehensive evaluation that addresses the structural adequacy of all CPP-666 safety- related structures, systems, and components. The DNFSB staff also believes that this evaluation would reasonably extend beyond the areas affected by reracking and would consider updated ground motion and other extreme loading events (both natural and man-made). 3. Background: CPP-666 was constructed in 1984 and is DOE's newest wet storage facility for spent fuel. It consists of stainless steel-lined concrete basins enclosed by a concrete shear wall superstructure with a cast-in-place roof supported by precast, prestressed girders. CPP-666 receives fuel from many sources, including naval reactors and CPP- 603. Westinghouse Idaho Nuclear Co. (WINCO) contracted Advanced Engineering Consultants (AEC) to evaluate the structural adequacy of the CPP-666 spent fuel storage pools with proposed new fuel racks. The new racks are still being designed and could eventually permit quadrupling the amount of fuel stored in some pools. Since 1991, the DNFSB staff and outside experts have been reviewing progress on the AEC evaluations. The most recent review was performed on June 6-7, 1994 by DNFSB staff members A. Hadjian and C. Keilers, and by outside experts J. Haltiwanger and J. Stevenson. 4. Discussion: DOE, WINCO, and AEC briefed the DNFSB staff and outside experts on the purpose of the analyses for the CPP- 666 basins, as well as on the models, load combinations, geotechnical evaluations, and final analysis and evaluation results. Also, a team from EQE International (EQE) provided a briefing on their independent review of AEC's evaluations. WINCO stated that the primary purposes of AEC's evaluations were to determine the facility's ability to accommodate additional fuel loading from reracking and to develop seismic inputs for the rack designer. The basins are being evaluated as "Performance Category 4" for natural phenomena hazards. This is the highest performance category, which was selected to be consistent with the facility's original design basis. AEC did not evaluate parts of the facility assumed to be unaffected by reracking. EQE independently reviewed AEC's reports and performed appropriate analyses by alternate methods. EQE stated that their comments have since been resolved. EQE did not challenge fundamental assumptions and evaluation parameters in the reports, such as the ground motion in the site's Architectural Engineering Standard. EQE concluded that, given the evaluation basis, AEC's analyses were acceptable, that the new rack seismic inputs are conservative, and that the basin structure with full and loaded pools is adequate. Observations: The DNFSB staff and outside experts believe that the basins may be found to be adequate for increased fuel loading, but it is difficult to determine from the evaluation documents provided. As discussed below, significant uncertainty exists in the evaluation conclusions because of some of the assumptions made and the methods applied and because of inadequate documentation. WINCO and AEC have initiated efforts to improve the evaluations. Even if the current evaluations were conclusive, they are limited in scope. Since this facility will be used for decades for interim spent fuel storage, the DNFSB staff believes that there will be a need for a comprehensive evaluation that addresses the structural adequacy of all CPP- 666 safety-related structures, systems, and components. The DNFSB staff also believes that this evaluation would reasonably extend beyond the areas affected by reracking, and would consider updated ground motion and other extreme loading events (both natural and man-made). Some general deficiencies in the current evaluations and documentation, together with specific examples, are as follows: a. The reports include few physical interpretations of the analytical results. For example, few structural deformation plots are provided. Such interpretations would facilitate reasonability checks. No explanation is given for why it takes 75 modes below 19 Hz to capture half the mass participation for a fixed base structure (EQE's explanation for this was unsatisfactory, and the question remains unanswered). Earthquake induced soil pressures from the computer code SASSI are used, but they were not compared to those of the applicable standard (ASCE 4-86) and were not validated as being adequate. The artificial seismic acceleration time histories generated were not compared to available records from the 1983 Borah Peak earthquake. b. The sensitivity of parameter variations is not adequately explored in the reports. For example, the effect of using uncracked and cracked concrete material properties in different analyses is not examined. The consequence of assuming dry instead of saturated soil conditions in seismic analyses was not determined. The adequacy or effect of using SASSI predicted loads when most of the mass participation occurs at frequencies above the SASSI cutoff frequency was not confirmed. The sensitivity of assuming rack attachment to the basin floor, when actually the racks will be permitted to slide, was not evaluated. c. The reports are not specific enough on some of the procedures and acceptance criteria used. For example, not all the live loads in the cited standard (ASCE 7-88) were actually used in the analyses. The analyses were also strictly linear elastic with no correction for ductility; this is conservative but inconsistent with the cited standard (UCRL-15910). Furthermore, the reports do not specify how the demand and capacity values cited were determined. Subsequently, AEC stated that they would document six representative examples of their demand and capacity calculations, which still have not been received by the DNFSB staff. d. The effects of other accident or off-normal conditions were not fully evaluated. For example, extreme loading events other than earthquakes or high winds, such as realistic missile impact, aircraft crash, malevolent vehicle effects, or accidental explosion, were not evaluated. A lower bound design basis tornado may also be appropriate (i.e., a Fujita Class 2 with 159 mph winds). As another example, the seismic adequacy of having a flooded pool without fuel next to one loaded with fuel was evaluated implicitly but may warrant an explicit evaluation. Explicit seismic evaluations of a dry basin next to a flooded and loaded basin indicated that a plastic hinge could develop in the separating wall (WINCO plans to procedurally control dry basin activities to avoid this). Explicitly confirming that similar behavior will not occur for a flooded basin without fuel next to one loaded with fuel would be desirable. For these analyses and the dry basin analyses, the maximum allowable strain criteria in the rebar and in the stainless steel basin liner may need to be revised to ensure the basins not only retain structural integrity but also remain leak-tight (e.g., consider ACI-359 criteria for joint rotations and liner strains). 5. Future Planned Activities: As information becomes available, the DNFSB staff and outside experts intend to review updated CPP-666 structural/seismic evaluations, capacity and demand computational examples, the new rack designs, and any subsequent comprehensive evaluations of safety-related structures, systems and components.