05000285/LER-2012-003
| Fort Calhoun Station | |
| Event date: | 03-12-2012 |
|---|---|
| Report date: | 11-16-2012 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition |
| 2852012003R01 - NRC Website | |
BACKGROUND
Fort Calhoun Station (FCS) is a two loop Combustion Engineering, pressurized water reactor. The FCS Safety Injection (SI) system consists of three High Pressure Safety Injection (HPSI) pumps, associated piping and valves; three Containment Spray (CS) pumps, associated piping and valves; and two Low Pressure Safety Injection (LPSI) pumps, associated piping and valves. During accident conditions Emergency Operating Procedures (EOPs) and Abnormal Operating Procedures (A0Ps) are used to ensure safe operation of the plant.
The primary function of the LPSI system is to provide emergency core cooling following a loss-of coolant-accident (LOCA). The LPSI system is designed to achieve this in conjunction with the operation of one HPSI pump and one emergency diesel generator during worst case accident conditions.
Long-term cooling and recirculation are mainly accomplished by the HPSI system. However, the LPSI pumps can be used to obtain increased recirculation cooling flow once the reactor coolant system pressure is reduced to approximately the same as the containment building pressure. The LPSI pumps may be used to inject uncooled water, or a portion of their discharge may be diverted through the shutdown cooling heat exchangers before being injected back into the Reactor Coolant System (RCS).
If only one HPSI pump is available, one LPSI pump in conjunction with the available HPSI pump will be used for simultaneous hot and cold leg injection in accordance with EOP/AOP Attachment 11, "Alternate Hot Leg Injection," via the shutdown cooling flow path. Hot leg injection is normally accomplished with two HPSI pumps via a cross tie to the Chemical and Volume Control System (CVCS).
EVENT DESCRIPTION
A non-conservative error was identified in the input calculation for post-LOCA cooling flow (post-RAS (recirculation actuation signal)). The calculation used an incorrect (non-conservative) input for LPSI pump performance. The associated procedure (EOP/AOP Attachment 11) as written does not provide adequate direction during the Alternate Hot Leg Injection mode of operation. Therefore, the procedural guidance may not ensure the completion of the safety function of providing adequate core cooling during the Alternate Hot Leg Injection mode of operation under a worst case scenario during the recovery phase of the accident The minimum analyzed flow for a LPSI pump is 150 gpm. The calculation does not clearly demonstrate that this flow is maintained during some accident conditions. The associated procedure (EOP/AOP Attachment 11) as written does not provide adequate direction during the Alternate Hot Leg Injection mode of operation to ensure this requirement is met.
EOP/AOP Attachment 11 requires that RCS pressure be less than 140 pounds per square inch absolute (psia) as the entry point for the procedure. The LPSI pumps may not be able to meet minimum flow requirements for long term pump operation at this pressure, which could result in pump damage. The minimum analyzed RCS hot leg injection flow of 134 gpm may not be met with current procedural guidance and instrument accuracy limitations. Therefore, procedural guidance may not ensure completion of the safety function of providing adequate core cooling during the Alternate Hot Leg Injection mode of operation under a worst case scenario.
On April 25, 2012, at 1622 Central Daylight Time (CDT) an eight-hour notification per 10 CFR 50.72(b)(3)(ii)(B) was made to the Headquarters Operation Office (H00) (Event Number 478620). This report is being made per 10 CFR 50.73(a)(2)(ii)(B).
CONCLUSION
The apparent cause was identified to be inadequate use of vendor oversight when the design information for calculation FC06644,"LPSI Pump SI-1A and SI-1B Performance, IST Acceptance and Hot Leg Injection (HLI) EOP/AOP Attachment 11," (In-Service Test (IST)) was transmitted to the vendor. The analysis also identified a contributing cause of inadequate review of the calculation provided by the vendor during the owner acceptance process.
CORRECTIVE ACTIONS
The corrective action for the apparent cause was to incorporate a procedural requirement in PED-QP-3, "Calculation Preparation, Review and Approval" and PED-QP-5,Engineering Analysis Preparation, Review, and Approval," to use PED-QP-38, "External Transmittal of Design Information," when transmitting design information to vendors and contractors preparing safety-related calculations. This corrective action has been completed. Additionally, FCS has incorporated a more extensive owner acceptance procedure and an owner acceptance review checklist into PED-QP-3.
Additional corrective actions will revise calculation FC06644 (due November 30, 2012) and EOP/AOP Attachment 11, Alternate Hot Leg Injection (due November 16, 2012).
SAFETY SIGNIFICANCE
The Updated Safety Analysis Report (USAR) described post-recirculation actuation signal safety function of the LPSI pumps may be affected by this condition. Part of the LPSI pump function as described in USAR Section 6.2 is to deliver core cooling and makeup water following a LOCA or MSLB via the alternate hot leg injection flow path. This safety function is implemented by EOP/AOP Attachment 11. Based on the correct pump curve for the LPSI pumps, the flow and pressure requirements stated in EOP/AOP Attachment 11 cannot be achieved. This is because RCS pressure is too high and the pumps will be operating at or near shut off head. Operation of the LPSI pumps at these conditions for an extended period of time could cause pump degradation or failure. As noted in the background information, long-term cooling and recirculation are mainly accomplished by the HPSI system. Failure of the HPSI system and the normal LPSI hot leg injection path requiring use of the alternative flow path is very unlikely. Therefore, this event had minimal impact on the health and safety of the public.
SAFETY SYSTEM FUNCTIONAL FAILURE
This event does not result in a safety system functional failure in accordance with NEI-99-02.
PREVIOUS EVENTS
No previous qualifications issues with hot leg injection have been identified.
� FORT CALHOUN STATION NOD-QP-9.2
QUALITY PROCEDURE FORM RO
LICENSING CORRESPONDENCE REVIEW FORM
LIC-12-0166 �Date Issued: 11/6/12� Requested Return Date:� 11/9/12 Review/Approval Information L. Cortopassi Lynn Smith Terrence W. Simpkin V. Naschansky S. Miller Corey Cameron S. Swearngin A. Hackerott Subject LER 2012-003 Rev1, "Non-Conservative Error in Calculation for Alternate Hot Leg Injection Results in Unanalyzed Condition" Please review and approve the attached draft correspondence (referenced above). I n order to document your review for our records, please sign this form and return it to the Licensing Coordinator. If n o notification is received by the requested return date, your concurrence with no comment will be assumed.
Erick Matzke � 6855 Technical Coordinator (Ext.)� Licensing Coordinator (Ext.) [ ] Approved with no comment.
�[ ] Approved pending resolution of comments as noted.
Comments:
Reviewer's Signature� Date � FORT CALHOUN STATION NOD-QP-9.2
QUALITY PROCEDURE FORM RO
LICENSING CORRESPONDENCE REVIEW FORM SUMMARY
LIC-12-0166 � Date Issued:�11/6/12 Requested Return Date:�11/9/12 Name Date Comments Received No Comments' Comments - How Resolved2 L. Cortopassi none T. Simpkin 11/7/12 Corrected S. Miller 11/7/12 X S. Swearngin none C. Cameron 11/9/12 X V. Naschansky none L. Smith none A. Hackerott 11/8/12 Corrected as able.
Subject LER 2012-003 Rev1, "Non-Conservative Error in Calculation for Alternate Hot Leg Injection Results in Unanalyzed Condition" NOTE — This submittal does�does not�X include documents/files on CD-ROM.3 NL Comment Coordinator Signature Date Responsible Dept. Manager (if required) Date Review by Nuclear Licensing Supervisor Date 1 Attach only signed Licensing Correspondence Review Form.
2 Attach necessary documentation.
3 Ensure that the CD-ROM files are formatted properly for electronic information exchange (EIE) to the NRC. (Reference NL-17)