ML20202F665
| ML20202F665 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 02/10/1998 |
| From: | Muench R WOLF CREEK NUCLEAR OPERATING CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20202F670 | List: |
| References | |
| ET-98-0003, ET-98-3, NUDOCS 9802190269 | |
| Download: ML20202F665 (3) | |
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W$LF CREEK NUCLEAR OPERATING CORPORATION j
4 Richard A Muench V6ce President Engineenng February 10, 1998 s
ET 90-0003 d
U.. S. Nuclear Begulatory Commission ATTN:
Document Control Desk 4
Mail Station Pl-137 Washington, D. C.
20555
Reference:
Subject:
Ducket No.
50-482: Acceptable Through-Wall Leakage Rate in Duried Essential Servica Water System Piping Gentlemen:
Reference 1 transmitted the Wolf Creek Nuclear Opsrating Corporation (WCNOC) request for r elie t' to use an alternative testing provi9 ion for the buried portion of the supply piping for the Essential Service Water (ESW) System.
j Reference 2 transmitted the NRC approval of the WCNOC relief request.
l Reference 1 noted that at the request of the NRC Staff, information would re submitted at a later time concerning the acceptable through-wall leakage rate in the buried ESW System piping. This letter provides this information.
Reference 1 noted that although WCNOC would submit this information, the relief request did not request any changt to the provisions for establishing acceptable leakage contained in the 1989 Edition of ASME Section XI.
Those 4
currently approved provisions require the Owner to establish the limits for acceptable leakage loss in buried piping.
WCNOC stated that the acceptable through-wall leakage rate would be established in accordance with ASME Section XI -paragraphs IWA-5244(a) and IWA-5250 (a ) (1) and would meet Wolf Creek Generating Station (WCGS) conditions for continued operations.
The "elief request proposed that for satisfactory test performance with the normally expected test boundary conditions, the acceptable difference between system makeup and identified boundary valve lethage would be set at 11 gallons per minute (gpm), -which was based on tolerances in measurement.
Any flow rate beyond 11 gpm, indicating probable through-wall leakage, was to be evaluated for acceptance in accordance with the ccrrective measures specified in IWA-5250 (a) (1).
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PDR 1.1l11!IllIlll!Illl!Illlli PO, Dox 411/ Durbngton, KS 60839 / Phone. (316) 3M 8831 i i e
An EquS Opnvtu'uty Ernpover M F HC VET
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ET 98-0003
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IWA-5150 (a ) (1) requires corrective measurcs, i.e.,
locating and repairing or replacin,g the leaking buried piping, when t% limits acceptable for continued service (Owner specified :through-wall leakage acceptance-criteria)-- have.been
- exceeded.
However, WCNOC stat sd in Reference 1 that -confirmed leakage would be monitored and evaluated -by the WCNOC; corrective. action program for appropriate. action.
1WA-5250(a)(1) requires corrective measures when the leakage losses exceed th.
limits : acceptable for-continued service.-
The limiting condition for ESW System operation at WCGS, with regard to leakage losses, is the Ultimate Heat Sink (UHS) capacity to provide cooling for.the-requi'.ed period of 30 days with no makeup water under both normal-and accident-mode operating conditions. 'The UHS has sufficient capacity - to allow -- up to 14 0 _gpm of continuousz losses (assuming maximum sedimentation levels) throughout the-30 day. period due to
' leakage from the ESW System components and other system corponents which would
- be supplied makeup from the ESW System-during accident conditiens (Updated Safety Analysis Report paragraph 9.2.5.2.5).
Leakage lossessare periodically measured and tracked-to monitor reductions in the 140 gpm allowable ' leakage loss (assuming maximum sedimentation-levels).
Sedimentation levels are periodically measured 'and ' would allow additional. increases ' in the - 140 ; gpm leakage losses by accounting for the additional inventory available in the UHS I
with less than maximum sedimentation levels.
Therefore, the Owner specified through-wall leakage acceptance criteria for the buried supply-side ESW System piping will be determined from - the allowable 3rgin-in the UHS _ _ inventory, taking ' into account projected ' sedimentation. levels and other known-leakage
-losses, but'will be limited to no more than 140 gem.
Assuming the maximum 140 gpm through-wall _ leakage is allowable (while. meeting all normal and accident conditions), tha effect of this leakage on the integrity of the buried ESW System piping has been investigated. The enclosed report by Sargent.& Lundy documents this investigation and_ concludes that the structural integrity of.the buried ESW System piping will not be impaired due to the postulated 140 gpm through-wallLleakage.
During Refuel IX at WCGS, October-November 1997,- both trains of supply-side ESW# System buried piping were. tested utilizing ~ the : test ' method proposed-in
-Reference 1-and approved by the NRC in Reference 2, with allowable measurement-tolerances reduced to match unique test boundary conditions established for 1
.. Refuel.IX. She results of these tests showed no recordable difference between system makeup and identified boundary leakage-in one train and a minor recordable difference of 0.2 gpm between system makeup and' identified boundary leakage ~in the other train,- thus-demonstrating - the integrity of. the buried
- piping.
- As : required by _ ASME Section XI, pressure ~ testing of each. train of' the ESW
-System buriedz pipint -will continue - to-be J performed within ; each - 40; month -
period. The 11-gpm acceptable difference between system makeup and identified boundaryi valve leakage,-.. based on normally-expected - test boundary conditions and 7 associated measurement ' tolerances, will bei applied in future tests - as iwed by. ' the approved relief request.
Leakage-rates above 11 gpm, Linuicating probable through-wall leakage, will be compared with the through-wall leakage acceptance criteria established above.
In accordance with IWA-5250(a) (1), ' leakage rates above' the 140 gpm through-wall' acceptance criteria wil11 require locating-andLrepairing or replacing the-11eaking hurled piping.--However,' as stated in Reference-1,~ WCNOC will monitor
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and evaluate confirmed through-wall leakage in ' accordance,with the WCNOC
-corrective actionLprogram for a determination of appropriate action prior-to 1 exceeding the'through-tall acceptance criteria.
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5 If-you should Navs any questions regarding this inforaation, please contact me s t' ( 316 )' 3 6 4 -8 0 3.1,- extension 4034,. or Mr. Michael J. Angus at-extension.4077.
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Very truly yours, h(ffgQ.f icha d A. Huench' 4.
- Ent'losure RAM /jad
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K,.M.' Thomas (NRC) r
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