ML20059M696
| ML20059M696 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 08/17/1993 |
| From: | AFFILIATION NOT ASSIGNED |
| To: | |
| References | |
| OLA-2-I-MFP-011, OLA-2-I-MFP-11, NUDOCS 9311190251 | |
| Download: ML20059M696 (23) | |
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April 12, 1991
'93 rr.: 23 P6:i5 i
l MANAGEMENT
SUMMARY
Check valves 9002A, 9002B, 8924, 8977, 8981, MS-5166, and MS-5167 were not besi,9 tested to' verify their safety function in the closed position I
in accordance with ASME Section XI inservice test (IST) requirements.
The IST deficiencies were caused by a personnel error because plant engineering did not correctly identify testing requirements for these check valves in the closed position.
To prevent recurrence, the testing requirements of components in the IST Program were reviewed to ensure consistency with the guidance of NRC Generic Letter 89-04. The IST l
Program has been revised to accurately reflect the proper testing requirements for these check valves.
Check valves in the IST program will be reviewed to confirm that the Generic Letter 89-04 review l
considered all appropriate design basis requirements.
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NCR DCO-91-TN-N026 April 12, 1991~
i stroked quarterly and full-stroked every cold shutdo m to verify that the valves will open when needed.
However, these tests do not verify the check valves' closure capability following actuation.
To address this concern, a new testing requirement was conservatively added to the IST Program which consisted of disassembly and inspection of MS-5166 and MS-5167 on a rotational refueling outage frequency to verify their capability to close following actuation. The Plant Staff Review Committee (PSRC) approved the revised IST Program Plan on February 15, 1991.
Since disassembly inspections are not part of ASME Section XI testing requirements, PG&E submitted a relief request to the NRC in letter DCL-91-042, dated February 27, 1991.
In a letter to PG&E dated March 5, 1991, the NRC granted interim relief ~for a period of 60 days.
On February 28, 1991, based on discussions between DCPP and NECS system engineering, it was confirmed tnat check valves MS-5166 and MS-5167 Hve a safety function in the closed position because they prevent on intact steam generator from blowing down to containment through the turbine-driven AFW pump steam supply line following a main steam line break (MSLB).
Because these valves are required to be operable in Mode 3, the event date is considered to be the first time that Units 1 and 2 entered Mode 3, on March 3, 1984 and July 25, 1985, respectively.
On April 2, 1991, LER l-84-044-01 was submitted to the NRC to report the IST deficiencies for check valves MS-5166 and MS-5167.
B.
Inoperable Structures, Components, or Systems that Contributed to the Event:
None.
o C.
Dates and Approximate Times for Major Occurrences.
1.
June 15, 1990:
Check valves 9002A and 9002B were confirmed to have a safety function in the -
closed position during post-LOCA-recirculation.
2.
June 15, 1990:
Discovery date - Phone call with the NRC indicated that these IST deficiencies constitute a violation of ASME Section XI and Technical Specification 4.0.5.
3.
June 29, 1990:
Check valves 8924, 8977, and 8981 were confirmed to have a safety function in the closed position during post-LOCA recirculation.
91NCRWP\\91TNN026.DB1 Page 4 of 19
t l
'NCR DCO-91-TN-N026 l T'.
April 12, 1991 i
4.
July 16, 1990:
LER 1-84-044, "ECCS Chec' Valves Back Flow k
Inservice Testing Deficiencies Due to Personnel Error"_was-issued.
5.
February 28, 1991: MS-5166 and MS-5167 were confirmed to have a safety function _ in the closed position.
6.
April 2, 1991:
LER 1-84-044-01, " Check Valves -Inservice i
Testing Deficiencies due to Personnel' Error" was issued.
D.
Other Systems or Secondary. Functions Affected:
E None.
E.
Method of Discovery:
1.
The IST deficiencies for valves 9002A, 9002B, 8924, 8977, and 8981 were discovered as a result of PG&E's' review of-an information letter from Westinghouse dated August 4,- 1989
+
regarding potential leakage paths to the RWST during post-LOCA recirculation.
2.
The IST deficiencies for valves MS-5166 and MS-5167 were-discovered during a review of testing' requirements for AFW system check valves contained in the IST Program to ensure consistency with NRC Generic Letter-89-04 as committed in LER-1-84-044-00.
l F.
Operators Actions:
None.
G.
Safety System Responses:
None.
-l 1
i III.
Cause of the Event t
A.
Immediate Cause 1.
Five check valves on each unit' (8924, 8977, 8981, 9002A, and '
9002B) were not tested'in'accordance with ASME Section XI to verify their safety-functionlin the closed position.-
2.
Check. valves MS-5166 and MS-5167 in the. steam supply tolthe' turbine driven AFW pump on each unit were not tested in.
~
accordance with ASME Section'XI to' verify their. safety
't function in the closed position.
1 B.
Root Cause:
l 91NCRWP\\91TNN026.DB1 Page 5 of 19
..a
NCR DCO-91-TN-N026 April 12, 1991
'T Personnel error.
During the initial development of the Diablo Canyon IST Program which included a detailed review of the draft IST Program in a working session with NRC Staff in 1983, plant engineering did not correctly identify testing requirements for these check valves in the closed position.
C.
Contributory cause:
1.
Plant engineering misinterpreted ASME Section XI requirements for testing normally closed check valves. ASME Section XI, subsection IWV-3522(b), requires that normally closed check valves be tested to verify proper valve disc opening.
Plant engineering believed that meeting the testing requirements of subsection IWV-3522(b) was sufficient for normally closed check valves.
However, as clarified by the NRC Staff in recent generic correspondence, all check valves must be evaluated against the broader requirements of subsection IWV-3522, which requires that check valves be exercised to the position required to fulfill their safety function (i.e.,
open and/or closed position).
2.
Closure testing of valves 9002A, 9002B, 8924, 8977, and 8981 was not considered necessary because it was thought that the valves' safety function in the post-LOCA recirculation mode (at least 30 minutes after a LOCA) was beyond the scope for ASME Section XI inservice test requirements.
IV.
Analysis of the Event A.
Safety Analysis:
RWST isolation check valves 9002A. 90028. 8924. 8977. and 8981 Following is the said: 2nalysis for operation of Units 1 and 2 with containment spray discharge pump check valves 9002A and 9002B and safety injection check valves 8924 (RWST to charging pumps),
8977 (RWST to safety injection pumps), and 8981 (RWST to residual heat removal pumps) not being tested properly in accordance with ASME Section XI requirements.
i.
Safety Function Potentially Affected FSAR Section 6.3.1.4.4.3 states the RWST is protected from reverse flow of reactor coolant from the RCS.
The RWST is redundantly protected from reactor coolant reverse flow during post-LOCA recirculation by MOVs and by the operation of check valves 9002A, 90028, 8924, 8977, and 8981.
In the event of a single failure of the check valve or the MOV located between the RWST and check valve, the check valve or the M0V will be the only valve remaining to limit reverse flow to the RWST.
Reverse flow of reactor coolant into the RWST provides the potential for an unfiltered release to the
- environment through t': RWST vent. Any reverse flow through 91NCRWP\\91TNN026.DB1 Page 6 of 19
4 NCR DC0-91-TN-N026 April 12, 1991 p.
the valves may affect the control room and offsite dose calculations that are presented in the FSAR if unfiltered leakage exceeds the FSAR value.
These valves do not serve to prevent accident initiation.
ii. Affect of Condition on Safety Function To determine the potential for failure and leakage of the check valves and MOVS, a maintenance history search was performed.
No past or present problems related to seat leakage or operators were noted that would affect the operability of the MOVS. Therefore, failure of the MOVs or for them to leak significantly is not expected.
Following is a summary of the operating and maintenance history for the check valves (Note: Complete documentation of maintenance history is filed in NCR package.)
1.
The check valves operate in a very clean environment, with no significant amounts of crud in the system which 2
could cause valve degradation.
2.
The check valves consistently pass their full-stroke open exercising tests without evidence of disc binding and with no corrective maintenance required.
3.
These valves are included in the DCPP check valve disassembly inspection program. While none of the valves have been inspected as part of this program to date, disassembly inspections of identical types of valves in similar applications have not produced any significant findings regarding seat conditions.
4.
SI-1-8981 was demonstrated to be leak-tight during the Unit 1" third refueling outagicfrom observations uuring 4
the RHR pump surveillance test.
5.
SI-2-8924 was disassembly inspected in 1988 to ensure proper operation of the valve following observed
)
pulsations in the line caused by the positive i
displacement pump.
The valve internals were detern.ined to be in good condition, and no corrective maintenacca was required.
i 6.
A review of NPRDS data has not identified any failures of swing check valves in similar applications.
Documentation of this review is filed with the NCR package.
7.
Discussions with the valve manufacturers have indicated that these valve models have not had any history of problems which would affect their closure capability.
91NCRWP\\91TNN026.DB1 Page 7 of 19
l NCR DCO-91-TN-N026 April 12, 1991 T
The preceding summary indicates that the check valves were operable and capable of performing their intended safety function, i.e., to close on reversal of pressure di fferential.
To ensure that the check valves will continue to perform their intended safety function of preventing reverse flow to the RWST, the IST Program Plan has been revised to require that the valves be disassembled and inspected during refueling outages.
In the event of reverse flow past che valves, although not expected as described above, the flow would be very small, l
most of which would be contained in the piping and RWST, and would eventually be isolated.
1.
The differential pressure across the valves would be approximately 150 psid when corrected for elevation head A ring post LOCA recirculation.
These valves were ested at the manufacturer per MSS SP-61 at a differential pressure of at least 165 psid and passed.
2.
The check valves are in series with MOVs which provides single failure protection.
Given that a single failure of a check valve or M0V would affect only one line, any I
fluid leaking past the check valves in the other two lines would also have to leak past the closed MOV l
upstream of the check valve.
3.
Any gas dissolved in the fluid which would leak past the check valve and MOV would have to diffuse through stagnant water in more than 150 feet of horizontal pipe and 14 feet of vertical pipe before being released into the RWST.
This would significantly reduce the quancity of gas which wouTd be released to tnF RWST if reverse flow were to occur through the check valve.
4.
Any gas that would be released into the RWST would be contained in an essentially stagnant volume.
Unless the tank were filled, the gas would diffuse slowly through the contained volume.
The gas would have to diffuse out the vent or be expelled due to thermal expansion or eduction due to local winds.
The amount of gas leaking out the vent would be a smaller amount than the gas leaking into the RWST.
5.
Since the gases would have a definite residence time in the RWST, there would be plate out of iodine on the inside of the tank.
This would also tend to reduce the amount of radioiodine that would be released from the ECCS.
6.
During the time frame following initiation of post-LOCA recirculation, the recovery manager could direct 91N:RWP\\91TNN026.DB1 Page 8 of 19
d i
NCR DCO-91-TN-N026
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April 12, 1991 1
activities to ensure that any leakage detected by routine detection surveys through these valves be i
isolated.
As described above, the MOVs and check valves would have performed and will continue to perform their safety function of preventing reverse flow to the RWST.
Any reverse flow would be very small, mostly contained in the piping and RWST, and be detected and isolated shortly after initiation.
Although not expected, the impact of potential reverse flow past these valves on the control room and offsite dose calculations is discussed below.
Post-LOCA recirculation dose analysis provides. a margin of 0.10 gpm leakage for. control room dose limits and 0.38_ gpm for exclusion area boundary dose limits.
The previous discussions regarding reverse flow past the valves' indicate that any leakage past.the MOVs or check valves would be within these margins and would not result in dose values-exceeding 10 CFR 50 Appendix A, General Design Criteria 19 or the 10 CFR 100 limits. The dose analysis also conservatively assumes releases over a 30 day period.
As discussed above, a leaking valve would most likely be detected and isolated in a time frame much shorter than 30 days.
Based on the factors discussed above, the dose contributions due to leakage past these check valves would be a negligible contributor to the offsite and control room doses, and the current calculation of offsite and control room doses remains
- bounding, iii. Alternate Methods of Safety Function Performance The RWST is redundantly protWed from reactor cooiant
reverse flow during post-LOCA recirculation ty-MOVs and these check valves.
Any leakage past' the check valves is blocked by the MOVs and the column of water in the suction pipe and the water remaining in the RWST.
Emergency operating procedure EP E-1.3, " Transfer to Cold Leg Recirculation," steps 8 and 9, instructs the operator to close M0Vs 9001A, 9001B, 8976, 8980, 8805A, and 88058 from the control room following transfer of RHR pump suction to l
'the recirculation sump and_ restart of the RHR pump.
If the MOVs fail to close remotely, the procedure-instructs the operator to manually close the MOVs.
iv. Compensatory Measures EP E-1.3, steps 8 and 9, was revised to require closure of the manual RWST stop valve (CS-100 or SI-1) if remote and -
manual closure of the MOVs is unsuccessful.
v.
Conclusion 91NCRWP\\91TNN026.DB1 Page 9 of 19
NCR DCO-91-TN-N026 April 12, 1991 wT.
i The review of the operating and maintenance history of the MOVs and check valves indicates that the valves would not fail or leak significantly, if at all, when performing their j
safety function of preventing reverse flow to the RWST.
Any reverse flow past the valves would be insignificant and within the assumptions of the dose calculations. Also, any reverse flow would mostly be contained.in the piping and RWST, detected, and isolated.
It-is,therefore concluded that the health and safety of the public were not adversely affected by the failure to' test these valves in the closeo
,1 position in accordance with ASME Section XI requirements.
In the future, the check valves will be disassembly. inspected as j
part.of the IST Program Plan.
This will provide further assurance that the check. valves will perform their safety.
function in the closed position and is sufficient tofcontinue to protect the health and safety of the public..
j AFW steam supolv check valves MS-5166 and MS-5167 Following is the safety analysis for operation of Units 1 and 2-with the Terry Turbine steam supply check valves MS-5166 and MS-5167 not being tested properly in accordance with ASME Section XI requirements.
'1 1.
Safety Function Potentially Affected j
FSAR Section 10.3.3 states "The steam' supply to the auxiliary feedwater pump turbine (Terry Turbine) is safety-related' because of the engineered safety requirements of the auxiliary feedwater system.
The steam supply lines from two of the four generators are interconnected upstream'of the steam line stop valve to provide both redundancy and balanced steam flow.
Both isolation and check valves in series in each of these lhu provide the required; valve redundancy that acts to prevent reverse flow." The safety function that is potentially affected is preventing an intact steam generator (SG) which supplies steam to the turbine driven AFW pump from blowing down through the break following a 4
steamline. break in the other SG that supplies steam to the.
turbine driven AFW pump.
If the check valve were to fail, the adverse affects of.the steamline break would be worse since higher steam flows would result; This would increase.
the plant cooldown and increase mass and energy releases.. A failed check valve would_also allow steam to go out the, break instead of going through the turbine.
ii. Affect of Condition on Safety Function The ability of the check valves to perform their intended safety function in the closed position has been confirmed.
each refueling outage based on disassembly inspections for maintenance purposes.
These disassembly inspections have verified that the ched valves were closed, with the 91NCRWP\\91TNN026.DB1 Page 10 of 19-
c NCR.DCO-91-TN-N026 y',
April 12, 1991 exception of valve MS-2-5166 which was found in the partially open position on two occasions, during the Unit 2 second refueling outage (2R2) and Unit 2 third refueling outage (2R3),respectively.
It was determined that the valve would 1
1 have closed under reverse flow conditions.
The force applied to seat the valve after it was found in the partially open l
position was less than would be generated by reverse flow of steam in the line and, therefore, the valve would have closed if required.
These check valves were replaced during the Un'it'l third refueling outage.(1R3) and the Unit 2 third refueling outage (2R3), respectively, with a different model check valve due l
to accelerated wear experienced with the original valves in l
this application. MS-1-5166.was disassembled and inspected l
during the Unit 1 fourth refueling outage (1R4) per MP M-l 51.14, " Check Valve Inspection Program." The results of the inspection satisfactorily verified the. closure capability of the valve.
To ensure that the valves will continue to perform their l
intended safety function of preventing reverse flow of steam, the IST Program Plan was revised to require that check valves I
MS-5166 and MS-5167 be disassembled and inspected on a rotational refueling outage frequency.
If problems are 3
identified, the other valve will be disassembled and checked.
The check valves would have performed and will continue to perform their safety function of preventing reverse flow of steam.
iii. Alternate Methods of Safety Function Performance-Motor operated valves (valve numbers FCV-37 and 38) are in series with thbck valves 5166 and'5167.
Emergency Praedure
~
E-2, Faulted Steam Generator Isolation," instructs the I
operator to close these valves to isolate a faulted steam i
generator.
I iv. Compensatory Measures No compensatory measures are required.
v.
Conclusion The review of the operating and maintenance history of_the-check valves indicates that the valves would not' fail.when
~
performing their safety function of preventing reverse flow to a faulted SG.
It is therefore concluded that the health and safety of the public were not adversely affected by the -
l failure to test these valves in accordance with ASME Section h
XI requirements.
In addition, the check valves will be J
disassembly inspected to verify their closure capability as'-
part of the.IST Program Plan..This will provide further 91NCRWP\\91TNN026.DB1 Page 11 of 19
NCR DCO-91-TN-N026 April 12, 1991 assurance that the check valves will perform their safety function in the closed position and is sufficient to continue to protect the health and safety of the public.
B.
Reportability:
On June 15, 1990, a telephone conference was held between PG&E and the NRC to discuss the method for reporting these IST deficiencies.
The NRC indicated that omission of a test or component required by ASME Section XI constitutes a violation of Technical Specification 4.0.5, and is reportable to the NRC in accordance with 10CFR50.73.
Since the safety injection, residual heat removal, and containment spray. systems are required to be operable in Mode 4, the event date is considered to be the first time that Unit 1 entered Mode 4, on February 20, 1984.
Unit 2 initially entered Mode 4 on July 19, 1985.
The IST deficiencies for the RWST isolation check valves were reported te the NRC via LER 1-84-044-00 dated July 16, 1990.
The IST deficiencies for the AFW steam supply check valves 5166 and 5167 were reported to the NRC in Revision I to LER l-84-044, dated April 2, 1991.
V.
Corrective Actions A.
Immediate Corrective Actions:
1.
As an immediate corrective action for RWST isolation check valves 9002A, 9002B, 8924, 8977, anu 8981, emergency operating procedure EP E-1.3 was revised to require the following steps when transferring to the post-LOCA recirculation mode:
COMPLETE NRC Commitment - LER l-84-044 Tracking AR: A0147828 AE#7 a.
Step 8 of EP E-1.3 was revised to require manual closure of RWST outlet stop valve CS-100 if the containment spray pump discharge MOVs.(9001A, 90018) fail to close remotely and if manual closure is unsuccessful.
(Note:
Because of this procedure change, operation of containment spray pump discharge check valves 9002A and 90028 in the closed position are no longer relied upon to protect the RWST from reverse flow of reactor coolant from the RCS.
Therefore, 9002A and 9002B do not needed to be tested to verify their capability to close.)
b.
Step 9 of EP E-1.3 was revised to require manual closure of RWST outlet stop valve SI-l if the RWST suction MOVs (8805A, 8805B, 8976, 8980) fail to close remotely and if manual closure is unsuccessful.
This change is 91NCRWP\\91TNN026.DB1 Page 12 of 19
NCR DC0-91-TN-N026 y,
April 12, 1991 considered temporary and will be deleted from EP E-1.3 following 1R4 and 2R4 disassembly inspections of RWST isolation check valves 8924, 8977, 8981 to verify their capability to close.
Responsible Organization: Operations /M. Abramovitz-l Tracking Document: AR A0221486 AE#5 l
ECD:
12/01/91 Firm Outage Related: YES/2R4 CMD: No l
NRC Commitment - LER l-84-044-01 2.
No immediate corrective actions are needed for check valves MS-5166 and MS-5167 because the valves' capability to perform their intended safety. function.in the closed position has been confirmed each refueling outage based on-disassembly inspections for maintenance purposes.
3.
Evaluate the ASME Section XI categorization of check valves i
8924, 8977, 8981, and 9002A&B to determine whether or not-they should be reclassified as Category A/C. valves.
l Tracking AR: A0147828 AE#6 NRC Commitment - LER l-84-044 COMPLETE: These valves do not need to be reclassified as Category A/C. 8924, 8977,-and E981 need to be tested in the open and closed position in accordance with Category C requirements of ASME Section XI.
9002A&B need only be tested in the open position.
4.
Revise LER 84-044 to reflect the new valves identified and to i
be consistent with the current corrective actions.
COMPLETE Tracking AR: A0221486 AE#4
~
B.
Corrective actions to prevent recurrence:
1.
The testing requirements of all pumps and-valves in the DCPP i
IST Program have been reviewed to ensure consistency with the guidance of NRC Generic Letter 89-04.
COMPLETE Tracking AR: A0221486 AE #10-(transferred from A0147828 AE
- 10)
NRC Commitment - LER l-84-044 2.
The DCPP IST Program was revised and submitted to the NRC on February 27, 1991.
The revised IST Program contained the following new testing requirements:
a.
Relief requests nos. 9, 13, and 14 were revised to require disassembly inspections of RWST isolation check valves 8924, 8977, and 8981'on a rotating refueling outage frequency to verify their closure capability.
91NCRWP\\91TNN026.DB1 Page 13 of'19
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NCR DCO-91-TN-N026 April 12, 1991
't b.
Relief request no. 23 was added to require disassembly inspections of AFW steam supply check valves MS-5166 and MS-5167 on a rotating refueling outage frequency to verify their closure capability.
COMPLETE Tracking AR: A0147828 AE #8 NRC Commitment - LER l-84-044 3.
The testing requirements of relief request no. 23 were initially implemented for Unit I during the Unit I fourth refueling outage (IR4) via disasstmbly and inspection of MS-1-5166 per maintenance procedure MP M-51.14, " Check Valve Inspection Program." The results of the inspection satisfactorily verified the closure capability of the valve.
The testing requirements of relief request no. 23 will be initially implemented for Unit 2 during the Unit 2 fourth refueling outage (2R4) in accordance with surveillance test procedure STP V-18, " Check Valve Inspection." This STP will be revised by 2R4 to include check valves MS-5166 and MS-5167 in the DCPP check valve disassembly inspection program.>
Responsible Organization: Mechanical Maintenance /S Allen Tracking Document: AR A0221486 AE #2 ECD:
09/15/91 Firm Outage Related: YES/2R4 CMD: NO NRC Commitment - LER l-84-044-01 4.
The testing requirements of revised relief request nos. 9, 13, and 14 were initially implemented for Unit I during IR4.
Check valves 1-8924,1-8977, and 1-8981 were disassembled and inspected in accordance with STP V-18.
The results of the inspection satisfactorily verified the closure capabilities of the valves.
The testing requirements of relief request nos. 9, 13, an: 14 will be initially implemented for Unit 2 check valves 2-8924, 2-8977, and 2-8981 during 2R4 per STP V-18.
Responsible Organization: Mechanical Maintenance /S. Allen Tracking Document: AR A0221486 AE #6 ECD:
12/01/91 Firm Outage Related: YES/2R4 CMD: N0 NRC Commitment - LER l-84-044-01 5.
NECS and DCPP system engineering will review check valves in the DCPP IST Program Plan to confirm that the Generic Letter 89-04 review performed in corrective action B.1 considered appropriate design basis requirements.
Responsible Organization: NECS and DCPP system engineering Tracking Document: AR A0221486 AE #7 (Lee /NCEN), AE #8 (Tateosian/NCEH), AE #9 (Groff and Burgess /PTET) i ECD:
08/01/91 Target Outage Related: NO CMD: NO 91NCRWP\\91TNN026.DB1 Page 14 of 19
i.-
NCR DCO-91-TN-N026 April 12, 1991
],
1
!!RC Commitment - LtR 1-84-044-01
~
C.
Investigative corrective actions:
l l
1.
Investigate the safety function of containment spray while on recirculation following a LOCA.
i COMPLETE Tracking Document: AR A0221486 AE #1 VI.
Add Jonal Information A.
Failed Components:
None.
B.
Previous NCRs on similar events:
3 l
1.
LER l-84-036, dated 3/10/86: Missed Surveillance of BIT Recirculation Check Valve 8912.
Normally open check valve 8912 was not stroke tested to the l
fully closed position per ASME Section XI, thereby violating TS 4.0.4 and 4.0.5.
The event was caused by procedural l
deficiency. A surveillance test procedure (STP) required the l
valve to be stroke tested open; however,'there was no STP to require stroke testing the valve closed. Plant engineers failed to identify the.need to stroke the valve closed.
To prevent recurrence, the' appropriate STP was revised to l
include the testing of check valve 8912 in the fully closed position for both units, and the IST Program was revised.
The corrective actions for this event should have included a requirement to review other check valves for similar testing deficienciesv> Therefore, the corrective actions taken ~. tere l
not adequate to prevent recurrence of this event.
2.
NCR DCO-89-TN-N049, " Check Valve Back Flow Inservice Testing Deficiencies."
Check valves 8998A&B were not being tested to verify their safety function in the closed position in accordance with ASME Section XI inservice test (IST) requirements.
The IST. deficiencies were caused by_ a personnel error.
because plant engineering did not ~ correctly identify testing requirements for.these check valves in the closed position.
The IST Program has been revised to accurately-reflect the proper testing requirements for these check -
valves.
To prevent. recurrence, the IST Program Plan was reviewed for consistency with the guidance in NRC Generic Letter 89-04, and check valves 5165 and 5167 testing deficiencies were identified, as discussed in NCR DCO TN-N026.
l l
91NCRWP\\91TNN026.DB1 Page 15 of 19 i
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I NCR DCO-91-TN-N026 April 12, 1991
't 3.
NCR DC2-90-MM-N023, " Check Valve MS-2-5166."
MS-2-5166 was found to be in the partially stuck-open position during 2R3 maintenance inspections.
The valve was subsequently replaced during 2R3 due to excessive wear.
The root cause was determined to be inappropriate machining of the check valve oushings performed in 1984.
Because, the valve had b er, inspected every refueling outage for maintenance purposes and because it was determined that the valve would have performed its intended safety function if needed, the adequacy of ASME Section XI testing requirements was not considered to be of concerr..
Therefore, the IST deficiency for the valve was not discovered at that time.
This maintenance information has been evaluated and added to the safety analysis in NCR DCO-91-TN-N026.
4.
NCR DC0-90-TN-N069, " Pump Test Requirements" During a review of a corrective action from LER l-84-044 to revie'. the IST Program against the guidance in GL 89-04, inconsistencies were discovered in pump STPs regarding bearing temperature measurements.
These inconsistencies were not related to the GL guidance on check valves and, therefore, this problem is not considered to be related.
C.
Operating Experience Review:
1.
Not reportable to NPRDS, as these problems did not involve component failures.
2.
NRC Information Notices, Bulletins, Generic letters, Safety Evaluation Reports.
-n.
n a.
NRC Information Notice 88-70: Check Valve Inservice Testing Program Deficiencies, issued August 29, 1988 b.
NRC Generic Letter 89-04: Guidance on Developing Acceptable Inservice Testing Programs, issued April 3, 1989.
The attachment to the GL identifies 11 generic IST programmatic deficiencies that affect plant safety.
Item 3 of the GL attachment, "Back Flow Testing of Check Valves," identifies the same concerns as NRC Information Notice 88-70. The GL does not require a written response from PG&E because the NRC has issued a safety evaluation report (SER) for the DCPP IST Program Plans.
To date, several IST program changes have been made to ensure consistency with position 2 of the GL attachment,
" Alternative to Full Flow Testing of Check Valves."
These changes included adding several valves to the check valve disassembly / inspection program, as described in section 2.d below.
91NCRWP\\91TNN026.DB1 Page 16 of 19
NCR DCO-91-TN-N026-April 12, 1991 1-c.
Minutes of the Public Meetings on Generic Letter'89-04, dated October 25, 1989 d.
.NRC SER dated December 22, 1988 provided'the Staff's SER on Revisions 6 and 3 of the DCPP Unit I and 2 IST i
Program Plan, respectively.
The SER identified several potential check valve testing deficiencies at DCPP.
i These problems were considered generic testing deficiencies and were the subject of NRC Generic Letter 89-04.
Although none of these. items were documented in NCRs, they are mentioned here because they are related problems:
1.
The'NRC Staff doubted.the ability of DCPP to perform functional testing of check valves 8948A-D i
and 8818A-D because of design constraints.
As a result,. PG&E added these check valves to the DCPP disassembly inspection program.
1 2.
Likewise, check vaives 8740A-B were also added to the disassembly inspection program.
3.
Check valves 9002A-B testing schedule changed from every refueling outage to every cold shutdown.
3.
INP0 SOERs and SERS.-
J None 4.
LERs from other utilities on Section XI check valve IST deficiencies.
I a.
Duke Power submitted LE'R 87-033-01 on April 18, 1988 for McGuire Nuclear Station " nit I to report check valve testing deficiencies identified by the NRC during an AE0D audit.
Following the audit, McGuire performed a design basis review and determined that six Category C check valves in the current IST program also performed a safety function in the reverse direction and, therefore,-
should be backseat tested.
1 b.
The LER database was searched to determine if any i
utilities reported check valve IST deficiencies resulting from their required' review of GL'89-04. 'No hits were found. While many utilities submitted responses to GL 89-04 and reported many changes to their IST programs, there was.no. indication these were reported via an LER in addition to the GL response.
D.
Trend Code TN, Nuclear Engineering i
A.4, personnel error due to programmatic deficiency 91NCRWP\\91TNN026.DB1 Page 17. of' 19
NCR DCO-91-TN-N026 Aprii 12, 1991 t
E.
Corrective Action Tracking The tracking action request is A0221486 F.
Problem Identification ARs:
RWST isolation check valves:
A0192545, A0193857 AFW steam supply check valves:
A0125276-G.
Additional Information Management decided a new NCR would be generated to cover some of the check valves initially identified in NCR.DCO-89-TN-N049,.
" Check Valve Back Flow Inservice Testing Deficiencies." The separation is due to the differences in classification of the.
valves.
Valves 8998A&B were reclassified as. Category A/C in the closed position and will be leak rate tested.
The other valves, 8924, 8977,. and 8981, were reclassified as. Category C and will only be tested to verify closure.
This NCR will cover all check valves but 8998A&B.
The TRG of NCR DCO-89-TN-N049 on 03/01/91' determined the following which will be included in this NCR:
1.
Two more check valves (5166 and 5167) were identified as having a safety function in the closed position.
These check valves are in the steam supply lines from the steam generators to the turbine driven AFW pump. The safety function is prevention of blow down of an intact steam:
generator through check valve to a faulted steam generator.
The Description of Event and Safety Analysis sections will-be updated to cover these two valves-Currently, the valves are inspected via % =stembly and inspection during refueling outages as part of maintenance practice.
This current practice will be added to the IST program as a corrective action.
~
2.
IST of check valves using disassembly and inspection for reverse flow testing requires NRC-approval prior to implementing the testing.
It was previously thought that this practice for IST of ~ check valves did not. require NRC approval prior to implementation. -The fact that. prior NRC approval is needed is documented in the response to Question 17 in the Minutes of the Public Meetings on Generic Letter 89-04, dated October 25,.1989. The question and response are listed below.
Question 17 May the valve testing by disassembly / visual inspection identified in Position 2 of Generic Letter 89-04 be applied to reverea flow testing of check valves? ~
91NCRWP\\91TNN026.DB1 Page 18 of 19
l l.'
NCR DCO-91-TN-N026 April 12, 1991 l
Response
Position 2 of Generic Letter 89-04 addresse: the use of disassembly and inspection as an alternative to forward flow testing of check valves. The use of disassembly and inspection to verify closure capability (i.e., back flow) may be found to be acceptable depending on whether l
verification by flow or pressure measurements is practical. As the generic letter doet. not address this use, however, the submission and approval of a relief request before implementation is required.
Disassembly and inspection is not acceptable for demonstration of l
leak-tight integrity.
A letter was sent to the NRC requesting approval of the use of disassembly and inspection for check valves 8998A&B, 8977, 8981, 5166 and 5167 to verify their safety function in the closed position. The NRC will review and approve the use of disassembly and inspection on an interim basis until a more formal review of the request can be performed. The interim approval will be complete prior to Unit 1 Mode 4 entry.
3.
It was determined that valves 9002A & B no longer have a safety function for preventing flow in the closed position since EP E-1.3 was revised to require manual closure of RWST l
outlet stop valves CS-1-100 and CS-2-100 if MOVs 9001A and B could not be automatically or manually closed. Therefore, the TRG decided to revise the NCR corrective actions to delete closure testing requirements for 9002A&B.
4.
The TRG decided to revise corrective action A.2 as documented in the NCR (AR A0147828 AE#6) " Check valves 9002A&B, 8924, 8977, and 8981 were reclassified as ASME Section XI Category C valves in the reverse flow direction" to delete valves 9002A&B since they do not have a vsafety function in t' 1
reverse flow direction and to replace "in the reverse flow direction" with "in the open and closed position."
5.
The TRG decided to revise corrective action B.2 as documented in the NCR write up (AR A0147828 AE#8) "The IST Program Plan will be revised to reflect reverse flow testing require,nents for valves 8998A, 8998B, 9002A, 9002B, 8924, 8977, and 8981" to a) replace " backflow" with " closure verification;" b) i delete valves 9002A&B since they do not have a safety i
function in the reverse flow direction and 8998A&B since they l
will be classified as Category A, C and leak tested; and c) add valves 5166 and 5167.
6.
The TRG identified the following new corrective actions:
a.
Develop or revise STPs to verify closure capability for valves 8924, 8977, and 8981.
1 Responsible: Systems Engineering 91NCRWP\\91TNN026.DB1 Page 19 of 19 i
l 1
NCR DC0-91-TN-N026
' April'12, 1991 t
ECD: 03/12/91 Not outage related Tracking AR: A0221486 AE#6 b.
Revise LER 84-044 to reflect the new valves identified-and to be consistent with the current corrective actions.
I Responsible: D. Behnke ECD: 04/10/91 (60 days from discover'date)
Not outage related Tracking AR: A0221486 AE#4 Additionally,.the following corrective actions were reassigned i
from NCR DCO-89-TN-N049.
A.
Immediate' Corrective Actions:
l 1.
Emergency operating procedure EP E-1.3 will be revised
'o provide additional actions to be taken if the-RWST MOVs fail to close when. transferring to the post-LOCA recirculation mode.
If the MOVs do not close from the control room, they will be locally closed, or valve SI-l 1-1 will be closed (RWST outlet stop valve).
COMPLETE
. Tracking AR: A0147828 AE#7.
t 2.
Check valves 8924, 8977, and 8981'were reclassified'as l
ASME Section XI Category C valves in-the open and' closed position.
COMPLETE Tracking AR: A0147828 AE#6 4
)
B.
Corrective Actions to-Prevent Recurrence:
1.
The IST Program Plan will be revised to. reflect closurei verification. testing' requirements for valves 8924, 8977, 8981, 5166, and 5167..
i COMPLETE Tracking AR: A0147828 AE# 8 R
2.
The desig'n basis of all check valves in the.IST Program Plan will be reviewed against surveillance; test ~
1 procedures to determine the ' adequacy ~of inservice -
testing to verify that the valves are capable of performing their intended' safety function.
Responsible: M. Burgess ECD: 01/30/91 Not outage related Tracking AR: A0147828 AE# 9 91NCRWP\\91TNN026.DB1 Page 20 of 19 m..
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NCR DCO-91-TN-N026 April 12, 1991 A-3.
The DCPP IST Program Plan will be reviewed to ensure consistency with NRC Generic letter 89-04.
l COMPLETE Tracking AR: A0147828 AE# 10 The TRG of 3/11/91 determined the following:
1.
The NRC has granted interim approval of the use of disassembly and inspection for check valves 8998A&B, 8977, 8981, 5166 and 5167 to verify their safety function in the reverse flow direction.
The NRC requested additional information within 60 days prior to granting approval beyond the interim time period.
Preparation of the submittal will be tracked by this NCR:
Responsible Organization: NSARA/J. Arhar Tracking Document: AR A0221486 AE #3 l
ECD:
5/6/91 NRC Commitment, FIRM I
Outage Related: NO CMD: NO I
2.
The safety function of MS-5166 and MS-5167 was discussed.
It was determined that failure of one of these valves would not affect minimum AFW flow assumed in the safety analyses.
Due l
to the arrangement of the power supplies to FCV-37, FCV-38, and the motor driven AFW pumps, eith:r power is available to close FCV-37 or FCV-38 and the turbine driven AFW pump is available, or one motor driven AFW pump is available to feed two intact steam generators.
Therefore, the only safety function is to prevent an intact steam generator from blowing down through the break following a steamline break.
3.- The point was discussed that the Emergency Procedures do not instruct the operator to close MOVs (FCV-37 and FCV-38) which are in series with check valves MS-5166 and MS-5167.
- This, however, is not true.
Emergency Procedure E-2, Faulted Steam Generator Isolation," instructs the operator to close these valves to isolate a faulted steam generator.
4.
The safety function of valves 9002A&B was discussed.
It was previously thought that containment spray operation was not necessary while on recirculation.
However, it was identified that the FSAR Update states in Section 6.2.3.2.1 that containment spray must be operated following transfer to recirculation for a period of at least 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.
The following investigative corrective action.was identified:
a.
Investigate the safety function of containment spray while on recirculation following a LOCA.
Responsible Organization: NECS/T. Baldwin Tracking Document: AR A0221486 AE#1 91NCRWP\\91TNN026.0B1 Page 21 of 19
I NCR DCO-91-TN-N026 April _12, 1991-6 4
ECD: 3/20/91 Outage Related: NO CMD: NO 5.
An audit of the IST program by QA was discussed.
It was determined that a programmatic audit would not be effective.
The QA audit of the AFW system did not identify.MS-5166 and MS-5167 as not being appropriately inservice tested.
The TRG of 3/20/91 determined the following:
1.
The draft LER was reviewed to report the IST deficiencies-for MS-5166 and MS-5167.
The root cause~was agreed to be personnel error during the initial development of.the ~IST Program Plan.
Two contributory causes were identified to address missed opportunities 1to identify the testing-deficiency on a more timely basis: (1) communication deficiency between NECS and_the plant and (2) misinterpretation of ASME Section XI. testing requirements for normally closed category C check valves.
2.
Mechanical maintenance added that MS-2-5166 had been the subject of a previous NCR because it had been' found partially open during 2R3 inspection of the valve.
The NCR was pulled,l and the safety analysis for the LER was updated to reflect this past maintenance.
3.
A corrective action was agreed upon by NECS and plant engineering to perform a coordinated review of components in the IST program to ensure that the recently completed GL 89-04 review considered appropriate design basis requirements.
The TRG of 4/12/91 determined the following:
1.
The following was listed in the write up as a contributory cause:
A communication deficiency existed between plant system engineering and NECS system engineering regarding the need for verifying closure of check valves MS-5166 and MS-5167.
The TRG determined that this was not an appropriate contributory cause for the IST deficiencies.
The identified-communication deficiency will be handled by a QE at the discretion of QA.
i 2.
The ECD date for corrective action to prevent recurrence #5
-(AR A0221486, AEs #7, #8, and #9) was changed to 08/01/91.
3.
The following action was removed as a corrective action to prevent recurrence bacause'it would not prevent recurrence.
91NCRWP\\91TNN026.DB1 Page 22 of. 19
NCR DCO-91-TN-N026 April 12, 1991 4'
Respond to NRC request for information regarding exemption from IST requirements.
Responsible Organization: NSARA/J. Arhar Tracking Document: AR A0221486 AE #3 ECD:
5/6/91 FIRM Outage Related: NO CMD: N0 4.
AEs will be written under AR A0221486 to cover AE# 9 and AE#
10 from AR A0147828.
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1 91NCRWP\\91TNN026.DB1 Page 23 of 19 i