05000346/LER-2003-002-01, Regarding Potential Degradation of High Pressure Injection Pumps Due to Debris in Emergency Sump Fluid Post Accident
| ML040330561 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  (NPF-003) |
| Issue date: | 01/29/2004 |
| From: | Bezilla M FirstEnergy Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NP-33-03-002-01 LER 03-002-01 | |
| Download: ML040330561 (10) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii) |
| 3462003002R01 - NRC Website | |
text
FEsNOC rrstEnergy Nuclear Operating Company 5501 North State Route 2 Oak Harbor. Ohio 43449 Mark B. Bezilla Vice President - Nuclear 419-321-7676 Fax: 419-321-7582 NP-33-03-002-01 Docket No. 50-346 License No. NPF-3 January 29, 2004 United States Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555 Ladies and Gentlemen:
LER 2003-002-01 Davis-Besse Nuclear Power Station, Unit No. I Date of Occurrence - October 22. 2002 Enclosed please find Revision I to Licensee Event Report 2003-002, which was submitted to provide written notification of an issue with the High Pressure Injection pumps. The issue concerns the potential for debris from the Containment Emergency Sump impacting the High Pressure Injection pumps following a design-basis accident whereby the pump internals may be damaged to the extent they would not be able to complete their intended safety function. This issue was identified as part of the Davis-Besse Return to Service Plan inspections. This LER is being submitted in accordance with 10CFR50.73(a)(2)(i)(B), 10CFR50.73(a)(2)(ii)(B),
1 OCFR50.73(a)(2)(v) and I OCFR50.73(a)(2)(vii). This Revision provides supplemental information regarding the apparent cause and the safety significance of this occurrence based on the evaluation performed on the High Pressure Injection pumps.
Very truly yours, AWB/s Attachment Enclosure cc:
Regional Administrator, USNRC Region III DB-I NRC/NRR Senior Project Manager DB-I NRC Senior Resident Inspector Utility Radiological Safety Board
Docket Number 50-346 License Number NPF-3 NP-33-03-002-01 Attachment Page 1 of 2 COMMITMENT LIST The following list identifies those actions committed to by the Davis-Besse Nuclear Power Station in this document. Any other actions discussed in the submittal represent intended or planned actions by Davis-Besse. They are described only as information and are not regulatory
commitments
Please notify the Manager - Regulatory Affairs (419-321-8450) at Davis-Besse of any questions regarding this document or associated regulatory commitments.
COMMITMENTS
DUE DATE To prevent debris that could plug the Complete hydrostatic bearing orifices from entering the supply lines, self-flushing plates with approximately 0.050-inch diameter holes were installed on the water supply take-offs to the hydrostatic bearing.
The locations of the hydrostatic bearing supply Complete take-offs were moved from the periphery of the pump fourth stage volute to a new location on the side of the fifth stage volute across from the impeller and adjacent to the discharge wear ring, which is closer to the shaft.
A new hydrostatic bearing design was installed Complete that was based on a "figure 8" pocket configuration. Relief grooves wvere added to the hydrostatic bearing pockets to provide an "escape" path for the debris that gets into the bearing.
The parts with wear surfaces that are subject to Complete debris that were not already hardfaced were replaced with hardfaced parts. These parts are wear rings, central volute bushing (rotating and stationary parts), and the hydrostatic bearing (rotating and stationary parts).
Replaced original cyclone separators with new Complete model (with smallest clearance of 0.230-inches).
Docket Number 50-346 License Number NPF-3 NP-33-03-002-01 Attachment Page 2 of 2
COMMITMENTS
DUE DATE Scope of work was expanded to remove as Complete much as possible of the remaining fibrous insulation from containment.
Evaluations were performed, in conjunction Complete with the modifications performed on the containment emergency sump, which examined the Low Pressure Injection System, the High Pressure Injection System, the Containment Spray System, and the Boron Precipitation Control System.
Abstract
On October 22, 2002, with the reactor defueled, a potential deficiency was identified for the High Pressure Injection (HPI) pumps during the recirculation phase of postulated loss of coolant accidents (LOCA) and when HPI pump 2 is used for post-LOCA boron precipitation control.
The HPI pumps may be damaged due to potential debris generated by certain postulated LOCAs and entrained in the pumped fluid.
The HPI pumps may be subject to this debris after the pump suctions are switched over from the borated water storage tank to the discharge of the Low Pressure Injection Pumps, which are taking suction on the containment emergency sump.
The HPI pumps use a process-fluid lubricated hydrostatic radial bearing on the outboard end of the pump shaft.
The hydrostatic bearing, an inter-stage bearing, and wear rings may be damaged by debris or particles in the pumped fluid.
The HPI pumps were declared inoperable since the ability to maintain long-term core cooling while taking suction through the sump screens was in question. A non-emergency eight hour notification per 10 CFR 50.72 (b) (3) (ii)
(B) was provided to the NRC as Event Number 39740 on April 7, 2003.
Subsequently, this LER is being submitted in accordance with 10 CFR 50.73 (a) (2) (ii)
(B) as an unanalyzed condition that significantly degraded plant safety (in addition to other reporting criteria listed above).
Following analyses, (HPI) pump modifications, qualification testing, and in-plant testing, HPI Trains 1 and 2 were declared operable on December 30, 2003.
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CORRECTIVE ACTIONS (continued):
performed on the new model cyclone separator which determined that the new model cyclone separators will continue to provide cooling water flow to the mechanical seals of the ECCS pumps following a LOCA.
Reduction in Fibrous Insulation in Containment Because of testing conducted on modifications to the HPI pump hydrostatic bearing supply lines, the scope of work was expanded to remove as much as possible of the remaining fibrous insulation from containment.
Removal of in-containment sources of fiber to protect the HPI pumps hydrostatic bearings will also benefit the ECCS pump's cyclone separators by reducing the amount of fiber that could find its way into the cyclone separators.
The effort to remove as much as possible of the remaining fibrous material will also be beneficial because, as documented in LER 2002-005-02, fibrous insulation represents a potential source to clog the containment emergency sump screen if the insulation is damaged and dislodged from piping by the effects of a postulated high-energy pipe break.
The above modifications were initiated to address concerns identified with the HPI System identified during the 13th Refueling Outage.
Following the HPI pump modifications, analyses, qualification testing, and in-plant testing, HPI Trains 1 and 2 were declared operable on December 30, 2003.
Evaluations were performed, in conjunction with the modifications performed on the containment emergency sump, which examined the Low Pressure Injection System, the High Pressure Injection System, the Containment Spray System, and the Boron Precipitation Control System.
The purpose of the evaluations was to evaluate the impact of debris (less than or equal to 3/16 inch) that could pass through the screen and affect ECCS system components which are required post LOCA for emergency sump re-circulation.
The evaluations examined the piping, valves, coolers, flow elements and orifices, pumps and instrumentation for each system, as applicable.
The results determined that the debris issue does not render the subject equipment listed above incapable of fulfilling their specified safety functions in the event of a design-basis accident.
PREVIOUS SIMILAR EVENTS
There have been no LERs in the previous two years involving similar deficiencies associated potential damage of hydrostatic bearings or other pump internals due to debris entrained in the pumped fluid.
Energy Industry Identification System (EIIS) codes are identified in the text as [XX].
Energy Industry Identification System (EIIS) codes are identified in the text as [XX].
NP-33-03-002-01 CR 2002-08492, CR 2003-01738