Part 21 Report - 1997-370

ACCESSION #: 9702030199 LICENSEE EVENT REPORT (LER) FACILITY NAME: Clinton Power Station PAGE: 1 OF 5 DOCKET NUMBER: 05000461 TITLE: Failure of Nuclear Fuel Supplier to Analyze Turbine Pressure Regulator Downscale Failure Event in the Off- Rated Condition Results in Operation in an Unanalyzed Condition EVENT DATE: 01/03/97 LER #: 97-001-00 REPORT DATE: 01/28/97 OTHER FACILITIES INVOLVED: None DOCKET NO: 05000 OPERATING MODE: 5 POWER LEVEL: 000 THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR SECTION: 50.73(a)(2)(ii) & OTHER LICENSEE CONTACT FOR THIS LER: NAME: R. W. Chickering, Engineering TELEPHONE: (217) 935-8881, Projects Extension 3334 COMPONENT FAILURE DESCRIPTION: CAUSE: SYSTEM: COMPONENT: MANUFACTURER: REPORTABLE NPRDS: SUPPLEMENTAL REPORT EXPECTED: NO ABSTRACT: Because of a nuclear fuel supplier error, the Turbine Pressure Regulator Downscale Failure (PRDF) event for 40 to 80 percent of rated thermal power had not been quantitatively analyzed during past operation. The fuel supplier issued a revision to the power-dependent operating limit for the cycle 7 Minimum Critical Power Ratio (MCPR) to correct the previous limit which was not adequate for conditions between 40 and 80 percent of rated thermal power for the PRDF event. Utility engineers reviewing the documentation identified that there was some potential to exceed the Safety Limit MCPR if the PRDF event had occurred during any of the past 5 fuel cycles. The engineers identified that the plant had operated in an unanalyzed condition during fuel cycle 6 and may have operated in unanalyzed conditions during fuel cycles 2, 3, 4, and 5. The cause of this event is attributed to an error by the nuclear fuel supplier in determining which events were the limiting anticipated operational occurrences that required analysis for the fuel design. Corrective action includes implementing corrected power-dependent operating limits for the MCPR. This event is also reportable under 10CFR, Part 21. END OF ABSTRACT TEXT PAGE 2 OF 5 DESCRIPTION OF EVENT On January 3, 1997, the plant was in Mode 5 (REFUELING) and the sixth refueling outage (RF-6) was in progress. Reactor [RCT] coolant temperature was being maintained between 75 and 185 degrees Fahrenheit and pressure was atmospheric. Because of a nuclear fuel supplier error, the Turbine Pressure Regulator Downscale Failure (PRDF) event for 40 to 80 percent of rated thermal power had not been quantitatively analyzed during past operation for fuel cycles 2, 3, 4, 5, and 6. The PRDF event leads to a larger change in the power-dependent operating limit Minimum Critical Power Ratio (MCPR) than any of the other Anticipated Operational occurrence. This condition is unique to the Boiling Water Reactor (BWR)-6 reactor type because a single failure may cause the pressure regulation system to fail downscale. The fuel supplier issued a revision to the power-dependent operating limit for the MCPR for fuel cycle 7 to correct the previous limit which was not adequate for conditions between 40 and 80 percent of rated thermal power in the PRDF event. Utility engineers were performing an approval review of the fuel supplier documentation for the fuel cycle 7 Supplemental Reload Licensing Report and the core performance monitoring computer [CPU] [IO] data bank. ,The review identified that there was some potential to exceed the Technical Specification Safety Limit MCPR if the PRDF event had occurred during any of the past 5 fuel cycles. At about 1520 hours, while comparing fuel cycle 6 actual operating data with the new limits for fuel cycle 7, the engineers identified that the plant had operated in an unanalyzed condition during fuel cycle 6 and may have operated in unanalyzed conditions during fuel cycles 2, 3, 4, and 5. Investigation of the condition identified that the PRDF event should have been analyzed for power levels between 40 and 80 percent of rated thermal power during fuel cycles 2, 3, 4, 5, and 6 because the impact of PRDF is more limiting than the other events used for establishing the operating limit for MCPR. Because the standard margins for uncertainty land instrument error for the calculations were not maintained, if a PRDF event occurred while operating near the operating limit for MCPR, the Safety Limit MCPR could have been violated. During fuel cycle 6, non-conservative power-dependent operating limits for the MCPR were used to monitor the reactor. On several occasions during reactor startups, the reactor was in a condition that placed the MCPR on a few lead fuel bundles close to the power-dependent operating limit for the MCPR. The power-dependent operating limit for the MCPR would have been exceeded if it had been correctly calculated for fuel cycle 6. The error in the analysis of the power-dependent operating limit for the MCPR has been applicable since the first refueling outage (RF-1) when the Maximum Extended Operating Domain (MEOD) modification was implemented. The MEOD modification eliminated the conservative Total Peaking Factor requirements and replaced them with the power-dependent operating limit for the MCPR. The Operations Shift Supervisor was notified about the non-conservative power-dependent operating limit for the MCPR at about 1545 hours. TEXT PAGE 3 OF 5 Condition Report 1-97-01-030 was initiated to track a cause and corrective action determination for this event. No automatic or manually initiated safety system responses were necessary to place the plant in a safe and stable condition. No equipment or components were inoperable at the start of this event to the extent that their inoperable condition contributed to this event. CAUSE OF EVENT The cause of this event is attributed to an error by the nuclear fuel supplier, GE Nuclear Energy, in determining which events were the limiting Anticipated Operational Occurrences that required analysis for the fuel design. The error occurred in the generic design of MEOD which was completed long before its installation at Clinton Power Station (CPS). Previous CPS reviews of the MEOD modification and fuel design changes did not identify the GE error. The fuel supplier has informed CPS that it plans to perform a root cause analysis of the error. CORRECTIVE ACTION Corrected power-dependent operating limits for the MCPR will be implemented in the core performance monitoring computer and incorporated into the Core Operating Limits Report of the CPS Operating Manual after the fuel cycle 7 Supplemental Reload Licensing Report is approved. ANALYSIS OF EVENT This event is reportable under the provisions of 10CFR50.73(a)(2)(ii)(A) due to the plant being in an unanalyzed condition that could have compromised plant safety. An assessment of the safety consequences and implications of this event indicated that this event had potential nuclear safety significance. The potential to exceed the Safety Limit for the MCPR in fuel cycles 2, 3, 4, 5, and 6 due to a PRDF event was not conservatively analyzed for conditions between 40 and 80 percent of rated thermal power. If a PRDF event had occurred while operating near the non-conservative power-dependent operating limit for the MCPR in those fuel cycles, the potential would have existed to exceed the Safety Limit for MCPR for fuel bundles that were near the power-dependent operating limit for the MCPR. However, CPS has not experienced any Turbine Pressure Regulator Downscale Failure events while operating between 40 and 80 percent of rated thermal power during fuel cycles 2, 3, 4, 5, or 6. Additionally, at low power levels and at near 100 percent rated thermal power, the power-dependent operating limit for the MCPR was adequate. Further, the reactor was not operated for long periods of time close to the power-dependent operating limit for the MCPR. Following completion of RF-6, and during fuel cycle 7, the power-dependent operating limit for the MCPR will be correct. TEXT PAGE 4 OF 5 ADDITIONAL INFORMATION No equipment or components failed during or as a result of this event. CPS has not issued LERs for similar events in recent history; however, GE Nuclear Energy has reported similar fuel design errors regarding the Safety Limit MCPR under the provisions Of 10CFR, Part 21. For further information regarding this event, contact R. W. Chickering, Engineering Projects, at (217) 935-8881, extension 3334. 10CFR, PART 21 REPORT 21-97-003 While performing an approval review of GE Nuclear Energy documentation for the fuel cycle 7 Supplemental Reload Licensing Report and core performance monitoring computer data bank, Illinois Power (IP) determined that there was some potential during the past 5 fuel cycles to exceed the Safety Limit MCPR if a PRDF event had occurred. Review of fuel cycle 6 actual operating data identified that CPS had operated in an unanalyzed condition during fuel cycle 6 and may have done so in fuel cycles 2, 3, 4, and 5 as well. The cause of this condition is an error in the MEOD analysis performed by GE Nuclear Energy, the nuclear fuel supplier for CPS. IP has evaluated this issue and concludes that it is reportable under the provisions of 10CFR, Part 21. IP is providing the following information in accordance with 10CFR21.21(c)(4). Initial notification of this matter will be provided by facsimile of this letter to the NRC Operations Center in accordance with 10CFR21.21(c)(3) within 2 days of the date the responsible officer approves this report. (i) Wilfred Connell, Vice President of Illinois Power Company, Clinton Power Station, Post Office Box 678, Clinton, Illinois, 61727, is informing the Commission by means of this report. (ii) The basic component involved in this report is the reload core. The core was to be designed to operate with adequate margins during all conditions as described by the CPS Updated Safety Analysis Report (USAR). This includes the conditions of the MEOD. one of the conditions the core design Must meet is operating limits for MCPR that provide margin to the Safety Limit MCPR for all Anticipated Operational occurrences between 40 and 80 percent of rated thermal power. The PRDF event is a limiting transient for a region of the MEOD. (iii) The reload core designs with the MEOD for fuel cycles 2, 3, 4, 5, and 6 were supplied by GE Nuclear Energy. TEXT PAGE 5 OF 5 (iv) As discussed in the DESCRIPTION OF EVENT portion of this document, the nature of the defect is the failure of the fuel supplier to include the PRDF event for 40 to 80 percent of rated thermal power in the MEOD analysis. If the PRDF event had occurred during any of fuel cycles 2, 3, 4, 5, or 6, while operating near the non-conservative power-dependent operating limit for the MCPR, the potential would have existed to exceed the Technical Specification Safety Limit MCPR on fuel bundles that were at or near the power-dependent operating limit for the MCPR. (v) GE Nuclear Energy notified CPS about the deficiency in the MEOD analysis in a letter dated December 22, 1996. The letter reported that the GE evaluation of reportability under 10CFR, Part 21, concluded that the condition was not reportable. On January 3, 1997, while comparing fuel cycle 6 actual operating data with the new limits for fuel cycle 7, IP engineers identified that the plant had operated in an unanalyzed condition during fuel cycle 6 and may have operated in unanalyzed conditions during fuel cycles 2, 3, 4, and 5 as well. This event was determined to be potentially reportable under the provisions of 10CFR, Part 21 at that time. (vi) The GE Nuclear Energy letter reports that the deficient reload core analysis applies to Clinton Power Station and other BWR-6 reactor types. (vii) The corrective action that IP is taking for this event is discussed in the CORRECTIVE ACTION section of this document. (viii) IP expects that GE Nuclear Energy will notify or has notified affected reactor owners and has no additional advice to offer. ATTACHMENT TO 9702030199 PAGE 1 OF 1 Illinois Power Company Clinton Power Station P.O. Box 678 Clinton, IL 61727 Tel 217-935-5623 Fax 217-935-4632 WC-075-97 January 28, 1997 Wilfred Connell Vice President ILLINOIS POWER U-602685 2C.220 Docket No. 50-461 10CFR50.73 10CFR21.21 Document Control Desk Nuclear Regulatory Commission Washington, D.C. 20555 Subject: Clinton Power Station - Unit 1 Licensee Event Report No. 97-001-00 and 10CFR, Part 21 Report.No. 21-97-003 Dear Madam or Sir: Enclosed is Licensee Event Report (LER) No. 97-001-00 and 10CFR, Part 21 Report No. 21-97-003: Failure of Nuclear Fuel Supplier to Analyze Turbine Pressure Regulator Downscale Failure Event in the Off-Rated Condition Results in Operation in an Unanalyzed Condition. This report is being submitted in accordance with the requirements of 10CFR50.73 and 10CFR21.21. Sincerely yours, Wilfred Connell Vice President RSF/krk Enclosure cc: NRC Clinton Licensing Project Manager NRC Resident Office, V-690 Regional Administrator, Region III, USNRC Illinois Department of Nuclear Safety INPO Records Center GE Nuclear Energy *** END OF DOCUMENT ***

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