ML20210N006
| ML20210N006 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 08/03/1999 |
| From: | Muench R WOLF CREEK NUCLEAR OPERATING CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| ET-99-0034, GL-95-07, NUDOCS 9908100257 | |
| Download: ML20210N006 (9) | |
Text
-,
W45LF CREEK NUCLEAR OPERATING CORPORATION Richard A. Muench Vice President Engineering AUG 3 1999 ET 99-0034 U.
S. Nuclear Regulatory Commission ATTN:
Document Control Desk Mail Station Pl-137 Washington, D. C.
20555
Reference:
Letter dated April 1, 1999, from K. M. Thomas, NRC, to O. L._Maynard, WCNOC
Subject:
Docket No.
50-482:
Response to Request for Additional Information Regarding Generic Letter 95-07,
" Pressure Locking and Thermal Binding of Safety-Related Motor-Operated Gate Valves" Gentlemen:
Attached is Wolf Creek Nuclear Operating Corporation's (WCNOC) response to the Request for Additional Information (RAI) contained in the Reference for the Wolf Creek Generating Station (WCGS).
The RAI requested additional information to complete the generic letter review, as discussed in a ccnference call between WCNOC staff and NRC staff on March 17, 1999.
During the development of the response to this RAI, WCNOC reassessed our current pressure locking position for certain Motor Operated Valves (MOVs).
Although WCNOC still believes the valves are capable of performing their safety function, WCNOC acknowledges the Comed approach to be more quantitative j
in design and more conservative in nature.
Thus, WCNOC has reevaluated certain MOVs using this methodology, as described in Attachment 1.
Based on the results of the use of the Comed methodology, several MOVs did not meet the Comed acceptance criteria.
As a long-term corrective action for these valves, WCNOC will either 1) enhance the margin to meet the Comed methodology acceptance criteria, or 2) eliminate the valves' susceptibility to pressure locking.
WCNOC will accomplish the long-term corrective actions i
through modifications and/or procedure revisions.
These changes will be scheduled to allow work on these MOVs to occur in conjunction with other planned outage and maintenance activities.
These activities will be completed no later than the end of the 12th refueling outage, which is currently scheduled for the Spring of 2002. discusses a change to a commitment associated to the WCNOC Generic Letter 95-07 response. provides a summary of commitments made in this submittal..
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\\m J-P.O. Box 411/ Burhngton, KS 66839 / Phone: (316) 364-8831 An Equal Opporturuty Employer M F 'He VET
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ET 99-0034 e
Pcge 2 of 2 If you have any questions concerning this matter, please contact me at (316) 364-4034, or Mr. Michael J. Angus at (316) 364-4077.
Very truly yours, Richa d A. Muench RAM /rlr Attachments cc:
J. N. Donohew (NRC), w/a W.
D. Johnson (NRC), w/a E. W.
Merschoff (NRC), w/a Senior Resident Inspector (NRC), w/a f
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. STATE OF KANSAS
)
)
SS COUNTY OF COFFEY
)
Richard A. Muench, of lawful age, being first duly sworn upon oath says that he is Vice President Engineering of Wolf Creek Nuclear Operating Corporation; that he has read the foregoing document and knows the content thereof; that he has executed that same for and on behalf of said Corporation with full power and authority to do so; and that the facts therein stated are true and correct to the best of his knowledge, information and belief.
By Richard #/. Muench Vice President Engineering SUBSCRIBED and sworn to before me this 3 dayofhi33l10
, 1999.
Q}vondo cf.&oloau mm Notar~y Public G
4 Asst es.5-//-2000 Expiration Date [1] _
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x.
- Attachment 1 to ET 99-0034
-Page 1 of 4 g
. Response to Request for Additional Information - Generic Letter 95-07, l
" Pressure Locking and Thermal Binding of Safety-Related Motor-Operated Gate Valves"
..NRC Question 1.
WCNOC's submittal dated July 3, 1996, states that the charging pump discharge to.the reactor coolant. system (RCS) cold-leg injection valves, EMHV8001A/B and EMHV8803A/B, are not susceptible to pressure locking because a charging pump is operating when the valves open.
Are EMHV8801A/B sequenced to open after EMHV8803A/B are open or could EMHV8801A/B operate at locked rotor conditions until EMHV8803A/B is initially open?.On a. loss of off-site power, are these valves sequenced to open after the charging pumps restart or could the valves operate. at locked rotor conditions until the charging pumps develop full discharge pressure?
Either clarify the basis or provide ~ appropriate actions to ensure that pressure locking is not a concern for these valves.
If applicable, explain why it is acceptable for these valves to operate at locked rotor conditions.
WCNOC Response Motor Operated Valves (MOVs) EMHV8801A/B and EMHV8803A/B are sequenced to open at the same time. These MOVs and the Centrifugal Charging Pumps (CCPs) are loaded on the electrical bus simultaneously.
Therefore, the valves are
' sequenced to open with the starting of the pumps in a Loss of Offsite Power condition.
Calculations demonstrate that'these MOVs are capable of operating under locked
. rotor' conditions until the CCP develops sufficient discharge. head to open them.
Furthermore, calculations indicate there are no adverse consequences resulting from this brief condition.
EMHV8801A/B and EMHV8803A/B have been determined to be susceptible to pressure locking.
'The Comed pressure locking (PRESLOK) methodology.has been applied and additional margin is needed to meet the standard Comed PRESLOK methodology acceptance criteria for valves EMHV8801A/B and EMHV8803B.
Valve EMHV8803A met the acceptance criteria.
As a long-term corrective action for valves EMHV8801A/B and EMHV8803B, WCNOC will either 1) enhance the margin to meet the
. Comed methodology acceptance
- criteria, or 2) eliminate the valves' susceptibility to pressure locking.
WCNOC will accomplish the long-term l
corrective actions through modifications and/or procedure revisions.
NRC Question 2.
WCNOC's submittal ' dated July 3,
1996, states that operational experience
- obtained during. plant cooldowns demonstrates that the pressurizer power
- operated relief valve (PORV)' block valves, BBHV8000A/B, are not susceptible to i
The NRC staff notes that after long periods of time, the pressure in the valves will decay and ' the valves will not pressure lock, therefore, the-operations experience 'obtained during cooldown does not j
demonstrate-that BBHV8000A/B will not-pressure lock during a steam generator L
tube rupture (SGTR). event.
These valves are a pressure locking concern at other Westinghouse plants for SGTR events.
Either clarify the basis or provide appropriate actions to-ensure that pressure locking is not a concern for these valves.
'WCNOC Response l
As the NRC Staff notes, industry experience indicates-these MOVs may pressure
' lock.
. WCNOC has reviewed our original - position, and now considers these 1
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' to ET 99-0034 Page 2'of 4 H
valves potentially susceptible to pressure locking.
Calculations have been performed using the Comed PRESLOK methodology. Additional margin is needed to meet the standard Comed PRESLOK methodology acceptance criteria for this valve type.. As a long-term corrective action for these valves, WCNOC will either
- 1) enhance the margin to meet the Comed methodology acceptance criteria, or 2) eliminate the valves' susceptibility to pressure locking.
WCNOC will accomplish the long-term corrective actions through modifications and/or procedure revisions.
NRC Question 3.
WCNOC's submittal dated July 3, 1996, provided the calculations (Commonwealth Edison (Comed) methodology) that demonstrated that the following valves would operate during pressure-locking conditions:
EJHV8811A/B Residual Heat Removal Pump Containment sump Suction EMHV8802A/B Safety Injection Pump to RCS Hot Leg Injection ENHV0001 Containment Spray Pump Containment Sump Suction ENHV0007 Containment Spray Pump Containment Sump Suction Comed recommends that, when using its methodology, minimum margins should be applied between calculated pressure-locking thrust and actuator capability.
These margins along with diagnostic equipment accuracy and methodology limitations are defined in a letter from Comed to the NRC dated May 29, 1998 l
(Accession Number 9806040164).
Explain how WCNOC is incorporating these Comed recommendations into the calculations used to demonstrate that EJHV8811A/B, EMHV8802A/B, ENHV0001 and ENHV0007 will operate during pressure-locking conditions.
Also, discuss if the valve factors, stem factors and actuator capability at reduced voltages are the same values as those used WCNOC's GL 89-10, " Safety-Related Motor-Oper~ated Valve Testing and Surveillance," program and how WCNOC determined maximum bonnet pressures.
WCNOC Response l
WCNOC has implemented the recommendations of Comed for minimum margins applied to the PRESLOK methodology (120% for " rigid" valve bodies and 140% for
" flexible" valve bodies).
The initial Comed PRESLOK methodology evaluations of actuator capabilities l
were made using GL 89-10 MOV Program design values for stem factors, valve friction coefficients, and actuator capability at reduced voltage.
With the exception of ENHV0007, the MOVs listed in NRC Question 3 did not have the necessary margins to meet the acceptance criteria of the PRESLOK methodology.
As a long-term corrective action for these valves, WCNOC will either r
- 1) enhance the margin to meet the Comed methodology acceptance critoria, or 2) l-eliminate the valves' susceptibility to pressure locking.
WCNOC will accomplish the long-term corrective actions through modifications and/or procedure revisions.
The intent of - the modifications will be to enable the actuator to meet the PRESLOK acceptance criteria using GL 89-10 design values with the Comed recommended minimum margins, or remove the pressure locking condition.
The following paragraphs discuss the methods used to determine maximum bonnet pressures for each of the valves listed in NRC Question 3.
EJHV8811A/B have air expansion chambers installed on their bonnets.
The maximum bonnet pressures for EJHV8811A/B is postulated from the RCS to Residual Heat Removal system (RHR) interface during shutdown and entrapment of RCS pressure in the bonnet.
Subsequently, the valves are postulated to experience thermally induced expansion of the volume of water in the bonnet due to.a LOCA.
This bounding scenario occurs during transition from plant operating mode four to mode three.
(
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' to ET 99-0034 Page 3 of 4 p
The maximum bonnet pressure for valves EMHV8802A/B is postulated from RCS check valve leakage and entrapment of RCS pressure in the bonnet.
The RCS pressure value envelops the bonnet pressure postulated from Safety Injection pump operation.
ENHV0001/7 have air expansion chambers installed on their bonnets.
The maximum bonnet pressure for ENHV0001/7 is postulated from the thermally induced pressure value that the bonnet of these MOVs could experience as a result of the hot containment sump fluid temperature post Loss of Coolant Accident ~(LOCA). This thermally induced pressure value envelops all other hydraulically induced bonnet pressures scenarios.
NRC Question 4.
WCNOC's technical specifications require an operable emergency core cooling system injection flow path from the refueling water storage tank (RWST) to the RCS via the residual heat removal (RHR) pump when RCS temperature is less than 350' F.
During the shutdown cooling mode of operation, the RHR pump suction valve to the RWST, BNHV8812A or B,
is shut.
Is the valve required to be opened to realign the RHR pump to inject into the RCS? If so, explain why the valve is not susceptible to hydraulic and thermal induced pressure locking?
WCNOC Response Valves BNHV8812A/B are closed when the Residual Heat Removal (RHR) System is aligned for shutdown cooling. One of these MOVs must be capable of opening to establish a flow path from the Refueling Water Storage Tank (RWST) to the RCS for RHR injection during Mode 4.
WCNOC reevaluated these MOVs in regard to pressure locking during shutdown cooling system alignment.
WCNOC concluded that these MOVs are potentially susceptible to pressure locking due to the hydraulic effects from the RCS/RHR interface and subsequent operation.
Since these MOVs are potentially susceptible to hydraulic induced pressure locking, WCNOC applied the Comed PRESLOK methodology.
Additional margin for valve BNHV8812B is needed to meet the standard Comed PRESLOK methodology acceptance criteria.
As a long-term corrective action for these valves, WCNOC will either 1) enhance the margin to meet the Comed methodology acceptance criteria, or 2) eliminate the valves' susceptibility to pressure locking.
WCNOC will accomplish the long-term corrective actions through modifications and/or procedure revisions.
These MOVs are not considered susceptible to thermally induced pressure locking during shutdown when the valves are closed with the hot RCS fluid in the main RHR suction header.
This conclusion is based on:
- 1) the existence of a check valve between the main header and the MOV, 2) the overall distance from the main header to the MOVs, 3) the portion of piping from the check valve to and including the MOV that is un-insulated, and 4) the pump room being cooled by a safety related room cooler that operates when the RHR pump operates.
This position has been verified by a calculation program that conservatively modeled the piping configuration fully insulated, without the presence of a check valve, and with no credit for room cooler operation.
NRC Question 5.
Explain why the RHR to charging and safety injection (SI) pumps' suction valves, EJHV8804A/B, and RHR to SI pump suction valves, EMHV8807A/B, are not susceptible to hydraulic and thermal induced pressure locking.
The bonnete of these valves could be pressurized during the shutdown cooling and RHR pump survuillance and injection modes of operation and these valves would be required to open later when pressure in the bonnets of the valve is greater than upstream and downstream pressures.
e.
- to ET 99-0034 Page 4 of 4 3
WCNOC Response MOVs. EMHV8807A/B ~
not normally exposed to RHR pump discharge pressure.
are These MOVs are located between the suction of the Safety Injection Pumps (SIPS) and CCPs, downstream of EJHV8804A/B.
During the recirculation phase of a LOCA,.EJHV8804A/B are opened, exposing EMHV8807A/B to the discharge pressure of the RHR Pump (s).
Then, with the RHR pump (s) still running, EMHV8807A/B are opened.
Therefore, since the RHR pump (s) are not shut off, the valve bonnets of EMHV8807A/B are not susceptible to entrapment of RHR pump discharge pressure.
The EMHV8807A/B MOVs are exposed to ambient room temperature effects only and are not susceptible to thermally induced pressure locking.
WCNOC reevaluated MOVs EJHV8804A/B for pressure locking concerns and now considers these MOVs susceptible to pressure locking due to hydraulic effects.
WCNOC also considers EJHV8804A potentially susceptible to thermally induced pressure locking.
Calculations have been performed using the Comed PRESLOK methodology and additional margin-is needed to meet the standard Comed PRESLOK methodology acceptance criteria for valves EJHV8804A/B.
As a long-term corrective action for these valves, WCNOC will either 1) enhance the margin to meet the Comed methodology acceptance criteria, or 2) eliminate the valves' susceptibility to pressure locking.
WCNOC will accomplish the long-term corrective actions through modifications and/or procedure revisions.
NRC Question 6.
Explain why containment spray pump discharge valves, ENHV0006 and ENHV0012, and spray additive eductor isolation valves, ENHV0015 and ENHV0016, are not susceptible to pressure locking following containment spray pump testing.
WCNOC Response I
Based on industry experience, WCNOC now considers these MOVs potentially susceptible to pressure locking resulting from Containment Spray Pump 1
operation.
Calculations have been performed using the Comed PRESLOK methodology.
Additional margin is needed to meet the standard Comed PRESLOK j
methodology acceptance criteria.
As a long-term corrective action for these valves, WCNOC will either 1) enhance the margin to meet the Comed methodology acceptance criteria, or 2) eliminate the valves' susceptibility to pressure
. locking.
WCNOC will accomplish the long-term corrective actions through modifications and/or procedure revisions.
' to ET 99-0034 g
Page 1 of 1 Motor Operated Valve Commitment Change In the references below, WCNOC proposed to eliminate the hot leg recirculation safety function for MOVs EMHV8802A/B and EJHV8840.
The down grading to non-safety of the hot leg recirculation function was being pursued through a Westinghouse Owners Group (WOG) initiative.
Since the commitment was made, the WCG initiative to down grade che hot leg recirculation function has been abandoned.
Therefore, WCNOC has evaluated the situation and is changing the commitment for long term resolution of pressure locking conditions associated to these valves.
Calculations have been performed using the Comed PRESLOK methodology and additional margin is needed to meet the standard Comed PRESLOK methodology acceptance criteria.
As a long-term corrective action for these valves, WCNOC will either 1) enhance the margin to meet the Comed methodology acceptance criteria, or 2) eliminate the
{
valves' susceptibility to pressure locking.
WCNOC will accomplish the long-term corrective actions through modifications and/or procedure revisions.
l
References:
l.
Letter WO 96-0023 dated February 14, 1996 to USNRC from O.
L. Maynard 2.
Letter WO 96-0107 dated July 3, 1996 to USNRC from O.
L. Maynard l
- to ET 99-0034 g
Page 1 of 1 O
List Of Commitments The following table identifies those actions committed to by Wolf Creek Nuclear Operating Corporation (WCNOC) in this document.
Any other statements in this submittal are provided for information purposes and are not considered to be commitraents.
Please direct questions regarding these commitments to Mr.
Michael J. Angus, Manager Licensing and Corrective Action, (316) 364-4077 cot 44ITMENT Due Date/ Event The following commitment has been made for valves No later than EMHV8801A/B, EMHV8802A/B, EMHV8803B, BBHV8000A/B, the end of the BNHV8812B, EJHV8804A/B,
- ENHV0001, ENHV0006/12, 12th Refueling ENHV0015/16, EJHV8811A/B and EJHV8840:
Outage As a long-term corrective action for these valves, WCNOC will either 1) enhance the margin to meet the Comed methodology acceptance
- criteria, or 2) eliminate the valves' susceptibility to pressure locking.
WCNOC will accomplish the long-term corrective actions through modifications and/or procedure revisions.
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