ML17059C643
| ML17059C643 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 04/21/1999 |
| From: | Abbott R NIAGARA MOHAWK POWER CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML17059C644 | List: |
| References | |
| GL-95-07, GL-95-7, NMP2L-1862, NUDOCS 9904300067 | |
| Download: ML17059C643 (14) | |
Text
CATEGORY 1y REGULAT RY INFORMATION DISTRIBUTION SYSTEM (RIDS)
ACCESSION NBR:990%300067 DOC.DATE: 99/04/21 NOTARIZED NO DOCKET ¹ FACIL:50-410 Nine Mile Point Nuclear Station, Unit 2, Niagara Moha 05000410 AUTH.NAME AUTHOR AFFILIATION ABBOTT,R.B.
Niagara Mohawk Power Corp.
RECIP.NAME RECIPIENT AFFILIATION Records Management Branch (Document Control Desk)
SUBJECT:
Forwards response to NRC 990208 RAI re NMPC 961121 submittal or revised previous responses to GL 95-07 based upon further Q
review of method for evaluating pressure locking
& thermal binding.Supproting calculation encl.
A DISTRIBUTION CODE: A056D COPIES RECEIVED:LTR ENCL SIZE:
0 TITLE: Generic Ltr 95-07
&, Thermal Binding of Safety Rela E
NOTES:
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N NOTE TO ALL "RIDS" RECIPIENTS:
PLEASE HELP US TO REDUCE WASTE. TO HAVE YOUR NAME OR ORGANIZATION REMOVED FROM DISTRIBUTION LISTS OR REDUCE THE NUMBER OF COPIES RECEIVED BY YOU OR YOUR ORGANIZATION, CONTACT THE DOCUMENT CONTROL DESK (DCD)
ON EXTENSION 415-2083 TOTAL NUMBER OF COPIES REQUIRED:
LTTR 8
ENCL 8
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5Mohawk'ichard B. Abbott Vice President Nuclear fngineering April21, 1999 NMP2L 1862 Phone: 31 5.349.1812 Fax: 315.349.4417 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 Nine Mile Point Unit 2 Docket No. 50-410
Subject:
Generic Letter 95-07, "Pressure Locking and T/dermal Binding ofSafety-Related Potver-Operated Gate Valves" Gentlemen:
On August 17, 1995, the NRC issued Generic Letter (GL) 95-07, "Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves," to request that licensees take actions to ensure that safety-related power-operated gate valves susceptible to pressure
'locking or thermal binding, are capable of performing their safety functions.
By letters dated October 16, 1995, and February 13, 1996, Niagara Mohawk Power Corporation (NMPC) provided responses to GL 95-07.
The NRC Staff requested additional information on May 21, 1996, to which we responded on June 20, 1996.
On November 21, 1996, NMPC revised previous responses to GL 95-07 based upon further review of our method for evaluating pressure locking and thermal binding. By letter dated February 8, 1999, the Staff indicated that additional information was required concerning our November 21, 1996, submittal.
The Attachment to this letter provides the requested information.
Sincerely, Richard B. Abbott Vice President - Nuclear Engineering RBA~JMTikap,'qoes00067 v904.2x Attachment I
PDR ADOCK 05000410 i
P PDR xc:
Mr. H. J. Miller, NRC Regional Administrator Mr. S. S. Bajwa, Director, Project Directorate I-l, NRR Mr. G. K. Hunegs, Senior Resident Inspector Mr. D. S. Hood, Senior Project Manager, NRR Records Management Nine Mile Point Nuclear Station PO. Box 63, Lycoming, New York 13093 0063
~ www.nimo.corn
Your November 21, 1996, submittal states that the RCIC-steam-exhaust-to-suppression-pool valve, 2ICS*MOV122, is susceptible to thermal binding. It also states that no correciive'ction is required because the valve would be declared inoperable and a Technical Speci+cation PS) action statement would be entered.
Please clarify when the valve ~ould be declared inoperable (i.e., the instant the valve closed or when the valvefailed to open?).
Resyaasa:
The relationship of this valve to Reactor Core Isolation Cooling (RCIC) System operability and Technical Specification actions needs to be clarified. During surveillance testing, or any other situation that would require this valve to be closed, prior to closing the valve the RCIC system is declared inoperable due to the function of this valve as a turbine exhaust pathway.
Once the RCIC System is declared inoperable, the plant is in a 14 day action statement.
At the end of this action statement, ifthe valve is not reopened, a plant shutdown is required.
Therefore, the situation under which the valve is subject to thermal binding (i.e., closed) is the same situation which requires entry into the shutdown action statement due to RCIC System Technical Specification requirements.
You performed calculations for numerous valves to demonstrate that they could operate without pressure locking. Ifadditional calculations have been performed that change the November 21, 1996 results regarding the valves listed below, then provide those calculations.
You evaluated the following valves as having adequate actuator capacity to overcome pressure locking scenarios at the specific point ofoperation during an accident; therefore, you plan no modijfcationforpressure locking mitigation:
2CSH*MOV101 2CSL*MOV107 2ICS*MOV121 2ICS*MOV122 2ICS*MOV129 2ICS*MOV128 2RHS*MOV4A/B/C High Pressure Core Spray (HPCS) Pump Suction Isolation Low Pressure Core Spray (LPCS) Pump Minimum Flow Bypass Isolation Reactor Core Isolation Cooling (RCIC) Steam Supply Outboard Isolation RCIC Steam Zxhaust to Suppression Pool RCIC Pump Suction Isolation RCIC Steam Supply Inboard Isolation Residual Heat Removal (RHR) Loop Pump Minimum Flow Isolation
2RHS*MOV115 2RHS*MOVI16 2SWP*MOVI7A/B 2S WP*MOV18A/B 2SWP*MOV21A/B 2SWP*MOV66A/B 2SWP*MOV67A/B 2SWP*MOV94A/B Service Water (SW)/RHR Containment Flooding Cross Tie SW/RHR Containment Flooding Cross Tie Isolation SW to Spent Fuel Cooling (SFC) Heat Exchanger Isolation SWfrom SFC Heat Exchanger Isolation SW Spent Fuel Pool Makeup Isolation SW Return Isolation From Diesel Generator (DG) Cooler SW to Control Room Chiller Isolation SW Return From HPCS DG Cooler Isolation Regarding the methodology used for these calculations, discuss:
2.1 Minimum margins that should be applied beoveen calculated pressure-locking thrust and actuator capability, 2.2 Any diagnostic equipment accuracy requirements, and 2.3 Methodology limitations.
2.4 Is this methodology used forflexible and/or double disk gate valves?
2.5 Hoiv did you validate this methodology?
In November 21, 1996, Niagara Mohawk Power Corporation (NMPC) indicated that twenty three (23) valves have adequate actuator capacity to overcome the applicable pressure locking scenarios. This was based on the methodology used by NMPC at that time. NMPC has re-evaluated (see Enclosure for a revised calculation and the calculation disposition) these 23 valves as described below:
(1)
Eight (8) valves meet the Commonwealth Edison methodology plus an additional 20% margin.
(2)
One (1) valve has already been modified to meet the Commonwealth Edison methodology plus an additional 20% margin.
(3)
Three (3) valves meet the Commonwealth Edison methodology, but not the additional 20% margin and willbe modified. However, the methodology used to determine the pressure increase in the bonnet is very conservative. Iffurther evaluation of the valve(s) confirm(s) that modification(s) is (are) not required, NMPC willnotify the Staff.
(4)
Six (6) valves do not meet the Commonwealth Edison methodology and willbe modified. However, the methodology used to determine the pressure increase in the bonnet is very conservative. Iffurther evaluation of the valve(s) confirm(s) that modification(s) is (are) not required, NMPC willnotify the Staff.
(5)
Five (5) valves have been further evaluated and have been determined not to be subjected to pressure locking or thermal binding at the time when they are required to operate to fulfilltheir safety function. Therefore, no modification is required.
These five categories of the 23 flexible wedge gate valves are discussed in greater detail below.
2ICS*MOV122, 21CS*MOV128, 2SWP*MOV17A/B, 2SWP*MOV18A/B, 2SWP*MOV94A and 2SWP*MOV67A These valves have a positive open thrust margin using the Commonwealth Edison methodology plus an additional 20% margin.
2SWP*MOV67B This valve's normal position is either open or closed and was modified during RFO6 providing sufficient opening thrust margin to satisfy the Commonwealth Edison methodology plus an additional 20% margin.
2SWP*MOV66A/B These are normally closed valves with an active safety related function to open and permit service water return flow from the respective Emergency Diesel Generator.
These valves are capable of opening against the temperature induced pressure locking force using the Commonwealth Edison methodology, but not sufficient to account for the additional 20% margin.
These valves willbe modified prior to the end of Refueling Outage 7 (RFO7) to provide additional margin.
However, iffurther evaluation of the valve(s) confirm(s) that a modification(s) is (are) not required, NMPC willnotify the Staff.
2SWP*MOV94B This is a normally closed valve with an active safety related function to open, allowing service water return flow from the respective Emergency Diesel Generator.
This valve is capable of opening against the temperature induced pressure locking force using the Commonwealth Edison methodology, but not sufficient to account for the additional 20%
margin.
This valve willbe modified prior to the end of RFO7 to provide additional margin.
However, iffurther evaluation of the valve confirms that a modification is not required, NMPC willnotify the Staff.
2CSL*MOV107 This is the Low Pressure Core Spray (LPCS) pump minimum flow valve. It is a normally open valve which is required to close for maximizing injection flow after pump flow is established greater than the required minimum flow. The valve willbe modified prior to the end of RFO7 to meet the Commonwealth Edison methodology plus an additional 20%
margin.
However, iffurther evaluation of the valve confirms that a modification is not required, NMPC willnotify the Staff.
2RHS*MOV4A/B/C These are the minimum flow valves for the three Residual Heat
Removal (RHR) pumps. They are normally open valves which remain open during pump start and must close to maximize injection flow into the reactor.
After closure, these valves may have to reopen for other system functions. These valves willbe modified prior to the end of RFO7 to meet the Commonwealth Edison methodology plus an additional 20% margin.
However, iffurther evaluation of the valve(s) confirm(s) that a modification(s) is (are) not required, NMPC willnotify the Staff.
2RHS*MOV115 and 2RHS*MOV116 These valves are positioned in series and are normally closed. They open to provide an RHR intertie. with Service Water in case containment flooding is required.
These valves willbe modified prior to the end of RFO7 to meet the Commonwealth Edison methodology plus an additional 20% margin.
However, if further evaluation of the valve(s) confirm(s) that modification(s) is (are) not required, NMPC willnotify the Staff.
2ICS*MOV121 This is the RCIC outboard containment isolation valve. This is a normally open valve with an active safety related function to close upon an isolation signal (RCIC line break). Once closed, there is no design basis requirement that the valve be re-opened.
No valve modification is required.
2ICS*MOV129 This is the RCIC suction valve from the Condensate Storage Tank (CST). It is a normally open valve with an active safety related function to close for transferring suction from the CST to the suppression pool. Once the valve is closed and the suction transfer is accomplished, there is no design basis requirement that the valve be re-opened.
No valve modification is required.
2SWP*MOV21A/B These are normally closed valves with an active safety related function to open and provide Service Water makeup to the spent fuel pool. The ambient temperature at the location of these valves willbe sufficiently reduced such that the pressure locking conditions no longer exist when the valves are required to function. No valve modification is required.
2CSH*MOV101 This is the High Pressure Core Spray (HPCS) suction valve from the CST Tank. It is a valve which is normally open with an active safety related function to close for transferring HPCS pump suction from the CST to the suppression pool. Once the valve is closed and the suction transfer is accomplished, there is no design basis requirement that the valve be re-opened.
No valve modification is required.
- Any diagnostic equipment accuracy requirements The random measurement uncertainty for the static unseating thrust is assumed to be no more than +/-15%.
- Methodology limitations.
The Commonwealth Edison pressure locking methodology is valid for all flexible wedge gate valves.
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d I gy dj'l ill dl d ll Ch*kg The methodology was used on flexible gate valves.
There are no double disk gates subject to pressure locking conditions.
- How did you validate this methodology?
NMPC used the NRC endorsed Commonwealth Edison methodology including a 20% margin.
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