05000373/FIN-2009003-02
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Finding | |
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| Title | Review of Rod Control Management System 50.59 Evaluation |
| Description | The inspectors identified an unresolved item (URI) associated with a potential failure to conduct an adequate 10 CFR 50.59 evaluation for the U2 RCMS. This item remains unresolved pending further review by the NRC staff. The inspectors identified a URI associated with the 50.59 evaluation for theU2 RCMS. Specifically, Revision 1 of L-06-036 did not specifically address the example questions contained in NEI 01-01 Appendix A, Supplemental Questions for Addressing10 CFR 50.59 Evaluation Criteria for all allowed fuel loading conditions. The RCMS was designed and built to allow gangs of up to four rods to be moved simultaneously. The licensee confirmed that the software installed within the RCMS is currently configured to allow control of four rods, but the capability to control more than one rod was disabled, the software password protected and the capability additionally prevented via operating procedures. The inspectors were concerned that the licensee had not properly evaluated questions associated with software common cause failure and the potential for uncommanded withdrawal of four control rods. Subsequently the licensee revised the evaluation and addressed the supplemental questions in Revision 3 ofL-06-036, and Revision 11 of EC 349628.In response to concerns about the potential consequences of uncommanded rod withdrawal, the licensee provided analytic results to the inspection team. These analyses considered spurious, ganged control rod withdrawal in both at-power and low-power/startup conditions and demonstrated acceptable performance following this type of reactivity anomaly for the current fuel cycle. The at-power analyses consider bundle minimum critical power ratios and fuel enthalpy for comparison to licensing and design limits to demonstrate acceptable fission product barrier performance during the postulated transient. These parameters were evaluated using the MICROBURN-B2 code system. The initial conditions assumed for the transient pertained directly to operating conditions present in or planned for the LSCS Unit 2 13th fuel cycle, which is the current LSCS Unit 2 operating cycle. The analyses assumed that the postulated transients would be terminated by the high flux reactor trip. The analyses for the at-power conditions demonstrated that the high flux trip would terminate the postulated, spurious, high-worth control rod withdrawal error without exceeding the minimum critical power ratio or the linear heat generation rate safety limits. The inspectors did not identify any significant issues precluding these analyses from justifying continued operation for the current fuel cycle at LSCS Unit 2.The low-power analyses consider fuel enthalpy as a demonstration of acceptable fission product barrier performance, instead of the linear heat generation rate and minimum critical power ratio, because the fuel enthalpy is a generally accepted indicator for fuel cladding performance at low-power conditions. The licensee used the RAMONA5-FAtransient thermal-hydraulic computer code to evaluate the low-power cases, demonstrating that fuel enthalpy addition would not exceed 170 calories per gram for the postulated transients. These low-power analyses were also specific to the LSCS Unit 2 13th fuel cycle, and the inspection team did not identify any issues precluding these analyses from justifying continued operation in a low-power condition during the LSCS Unit 2 13th fuel cycle, or subsequent restart following an unplanned reactor shutdown during the 13th fuel cycle. An unresolved item is open pending further review by the NRC staff. (URI 05000374/2009003-02 |
| Site: | LaSalle  |
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| Report | IR 05000373/2009003 Section 4OA2 |
| Date counted | Jun 30, 2009 (2009Q2) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71152 |
| Inspectors (proximate) | J Yesinowski P Smagacz G Roach F Ramirez K Riemerf Ramirezg Roach J Yesinowski K Riemer P Smagacz |
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Finding - LaSalle - IR 05000373/2009003 | |||||||||||||||||||||||||||||||
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Finding List (LaSalle) @ 2009Q2
Self-Identified List (LaSalle)
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