ML20059A860
| ML20059A860 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 12/21/1993 |
| From: | Richard Anderson NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9401030167 | |
| Download: ML20059A860 (4) | |
Text
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Northem States Power Company 414 Nicollet Mall Minneapolis, Minnesota 55401-1927 Telephone (612) 330-5500 December 21, 1993 U S Nuclear Regulatory Commission Attn: Document Control Desk i
Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 License Nos. DPR-42 50-306 DPR-60 3rd 10-Year Interval Inservice Testing Program Draft Proposed Reaueet for Relief #5 Please find attached to this letter a draft of a Request for Relief dated i
December 17, 1993.
This draft request.was telecopied to Marsha Gamberoni of the NRC staff to facilitate a conference call to discuss our proposal to submit this request.
Following the conference call we decided not to submit the request for consideration. This letter is submitted only to place the telecopied draft on the docket.
In this letter we have made no new NRC commitments.
t Please contact Jack Leveille (612-388-1121, Ext. 4662) if you have any questions related to this letter.
h l
Roger O Anderson Director Licensing and Management Issues c: Regional Administrator - Region III, NRC Senior Resident Inspector, NRC NRR Project Manager, NRC J E Silberg
Attachment:
"5.
REQUEST FOR RELIEF" labeled Pages 38, 39, & 40 and dated 12/17/93 9401030167 931221
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- 5. REGUEST FOR REUEF i
COMPONENT FUNCTION ASME ASME CODE CLASS VLV CAT 12,22 Diesel Driven Cooling Water Pump Remove heat from components that must function 3
during accident conditions.
121 Motor driven Cooling Water Pump Remove heat from components that must function 3
during accident conditions.
CODE REQUIREMENT in measuring hydraulic performance where system resistance cannot be varied, flow rate and pressure shall be determined and compared to their respective reference values. Alert range is 0.93 to <0.95 aPr and required action range low is <0.93 APr and high is >1.10 APr.
ALTERNATE TESTING s
Pump flow and pump suction and discharge pressure are recorded. The pump differential pressure is then plotted against flow to determine a ' point" on the pump curve. This point is then compared to acceptance criteria. The acceptable range will be between.90 and 1.035 of the pump curve. The alert ranges will be from.853 to <.90 aPr of reference (Iow value) and > 1.035 to 1.05 cPr of reference (high value). The required action range will be for values less than <.853 aPr or greater than >1.05 of the pump curve.
Curves will be developed using the following methods:
A) Curves will be developed when the pumps are known to be operating properiy. Data taken to develop the curve will factor in:
- 1. Speed variability from one test to another and from one flow condition to another.
- 2. Changes in pump bay level from one test to another in determination of TDH.
- 3. Effect of measuring flow and pressure at different points in the piping system.
- 4. Effect of changes in cooling water system heat load on pump test data.
- 5. Effects of unmetered flow paths.
NOTE: These five factors are not reflected in the existing pump curves.
Page 38 Pt IST 1.4-9 3rd 10 Year Program NrNb rlo
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5.
REQUEST FOR RELIEF (CONT'D) t B) The reference points used to develop the curve will be measured with instruments that meet code accuracy, and the points wiil be as many as allowed by plant operation. River temperature affects cooling water system flow and varies between 10,000 gpm in winter to 40,000 gpm in summer. This seasonal change in cooling water system flow means it will require 6 months to generate a pump curve. The points taken wm' include points cfose to maximum pump efficiency.
C) The pump curves wi!I not be in conflict with cooling water system design requirements as described in USAR.
D) The pump curves will be revised as required by OM-6 paragraph 4.4.
The pump performance will be trended with test data. As pump wear occurs, the trending of hydraufic performance wi!! affow prediction of approach to design values and resultant scheduling of maintenance for pump overhaul.
BASIS FOR REQUESTING RELIEF A) System design does not a!!aw performance of hydraulic tests at specific reference points. Because of the numerous system loading combinations possible, it is not practical to reestablish the exact reference point for the pump test. The changing hydraulic loads are due to the numerous heat exchangers connected to the system with constantly changing coolant demands (cooling water system provides coolant to component cooling water heat exchangers, air chliters, hydrogen coolers for turbine generators, etc.). In addition, the overall hydraulic loads vary with plant conditions from one test period to the next, preventing the establishment of a specific reference point on the pump characteristic curve that could be used during each monthly test. To improve the hydraulic measurement accuracies of these pumps without disrupting the plant normal operating conditions would require the insta!!ation of 2 test loops, one for each pump, that would serve to bypass these varying hydraulic loads. The installation of these test loops involves modifying 24 inch diameter pipe systems requiring the shutdown of both units and removal of the fuel from the core.
B) Because a repeatable reference point cannot be reestablished for each test, the inaccuracles in determining the pumps' hydraulic conditions and code allowable variances in these conditions (flow and dp) compound the allowable ranges of operation when both flow and dp are compared together as described above. See A1,2,3,4 and 5. The inaccuracies will be identified and defined over the next six months.
C) Pump replacement / overhaul would be required after pump hydraulic performance has changed by 7% using Code APr ilmits. The cost of removing, inspecting and overhauling a pump is in excess of $100,000 per pump.
Page 39 Pt IST 1.4-10.
3rd le Year Program
&;. 2 f2e/93--
Dstrcrit/s7{95
5.
REQUEST FOR RELIEF (CONT *D)
JUSTIFICATION Testing in the next six months will identify unknowns of the pump testing & establish pump curves based upon test data which factors speed, flow, pressure, time varying hydraulic changes, unmetered flow paths and bay levels into the pump curves, inspection of wear rings, line bearings, volute and impeller as well as testing (vibration) data from the past 20 years indicate the cooling pumps are excellent mechanical condition.
The safeguard cooling water pumps have capacity in excess of the flow required by USAR for the design basis accident cond!tions. The interim action range of 85.3%, including 4% for instrument error, is well above the pump flow capacity required for safe operation. Therefore, when pump capac!ty greatly exceeds the " system design requirement, expanding hydraulic performance acceptance ranges [is] appropriate and justified...(since] there is a high level of confidence that the pump remains capable of performing its required function at the degraded level.* '-
- 1. Reference ' NURG/CP-0123P.287 Page 40 Pi iST 1.411
' 3rd 10 Year Prograrn S;. 2 Sfr/T Mf=T Wr7/93
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