ML20059M560
| ML20059M560 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 08/17/1993 |
| From: | Rueger G PACIFIC GAS & ELECTRIC CO. |
| To: | |
| References | |
| OLA-2-I-MFP-007, OLA-2-I-MFP-7, NUDOCS 9311190163 | |
| Download: ML20059M560 (10) | |
Text
f
& 2 75/3 z3 -Ce A 1~.-ppp-7 gj{q CQ'lg t
y 8
Pacific Gas and Electric Company 77 Beale Street Room 1451 Gregory M. Rueger P 0. Box 770000 Senior Vice Presidentand San Fra'tisco CA 94177
' Generhi Manhd 0 415/973 4684 Nuchar F5h/ Generation f ax 415/973-2313
'93 GT 28 PS :15 July 26, 1993 1
PG&E Letter No. DCL-93-185 "7/ 7
.i t U.S. Nuclear Regulatory Commission
._j.J ATTN: Document Control Desk
'fCO Washington, D.C.
20555
- .u~
Docket No. 50-275, OL-DPR-80 j
.m.
Docket No. 50-323, OL-DPR-82 Diablo Canyon Units 1 and 2 i
Licensee Event Report 1-84-047 Technical Specification 3.0.4 Not Met Due to Inadequate-. Inservice Testing of Safety Injection Pump Discharge Check Valves j
1 Gentlemen-Pursuant to 10 CFR 50.73(a)(2)(1)(B), PG&E is submitting the enclosed Licensee Event Report concerning inadequate inservice testing of safety injection pump discharge check valves due to deficiencies in the scope J
of the Inservice Testing Program Plan reviews.
Sincerely,
$6dt.dUlt l
./
regory M. Rueger i
cc:
Bobby H. Faulkenberry Ann P. Hodgdon Mary H. Mil kr, c3 W
c.n.
Sheri R. Peterson CPUC Diablo Distribution INP0 l
DCO-93-TP-N028 Enclosure fu
'^'m Cte 11395/85K/SDL/2246
~ 2 5 1 M y g.uu inF0 1 pecn+5t1eEMASfailfCTD10 Co h :s.m n
sw
_ _ u _2.. __ wu s v'
V;.q v y
V v'
. e _ _ __
s.
N'
.. $,f)
'^'
4 c =.,.
--.. ~ - _
'C kFmd 9311190163 930817' kwter PDR ADOCK.05000275.
)
G PDR~:
- q,, _,
/
LICENSEE EVENT REPORT (LER)
FOCIUTY N AME til DOCA ET NUMBER f71 PAGE (31 DIABLO CANYON UNIT 1 0l5l0l0l0l2l7l5 1l'l 9 TECHNICAL SPECIFICATION 3.0.4 NOT MET DUE TO INADEQUATE INSERVICE TESTING OF SAFETY mtE m INJECTION PUMP DISCHARGE CHECK VALVES EVENT DaTE lli LIR NUMBER (el REPORT DATE (71 OT HE li FACILIT1(5 INVOLVED (8)
MON DAY YR YM SEQUINTIAL REVI&lON MON DAY YR DOCKET NUMBER ($1 NuusER NUMBER DIABLO CANYON UNIT 2 03 03 84 84 0l4l7 0l0 07 26 93 0
5 0
0 0
c TNIS REPORT !$ 5VBMITTED PUR5UANT To THC REQUIREMENTS OF 10 CFR: (11) yagc.
1 LtIEL x
10 CFR 50,73(a)(?)(1)(B) 1 l 010 OTHER -
(Specify in Abstract below and in text, NRC Form 366A)
UCEN8Ff CONT ACT FOR THE LER (171 TELfPHON[ NUMPfR
^"'" c 5 DAVID P. SISK, SENIOR REGULATORY COMPLIANCE ENGINEER (805) 545-4420 COMPLETE ONE UNE FOR EACM COMPONENT FAILURE DESCRIBED IN TMS REPosti(13)
CaVSE l SYSTEM COMPONENT MANUFAC.
0 0
(
CAUSE SYSTEM COMPONENT MANUFAC.
R O A C l
lll ll l l
lll lll l
lll lll l
Ill III SUPPLEMENT AL REPORT EAPECTED (141 D"'
EXPECTED SUBMISSION l l YES (if yes, conclete EXPECTED SUBMISSION DATE) lX l NO QBSTRaCT (16)
On Mmh 3,1984, for Unit I and on July 25, 1985, for Unit 2, Technical Specification 3.0.4 was not met when initial entr,y into Mode 3 (Hot Standby) was made without reverse flow testing of safety injection (SI) pump discharge check valves 1-8922A, 1-89228, 2-8922A, and 2-89228.
On he 25,199T, a Technical Review"uroup determined thE the testing prograffor SI pump discharge check valves 1-8922A, 1-8922B, 2-8922A, and 2-8922B was inadequate to verify their safety function for reverse flow seating in accordance with ASME Section XI inservice testing (IST) requirements.
The root causes of this event include deficiencies in the scope of the IST Program Plan review, miscommunication, and personnel error (cognitive).
The SI pump discharge check valves were not identified as required to be periodically reverse flow tested during the development of the IST Program Plan or subsequent reviews of the IST Program Plan.
Subsequent tests performed on Units 1 and 2 SI discharge check valves verified reverse flow seating in accordance with ASME Section XI IST requirements.
Periodic reverse flow testing requirements for the SI pump discharge check valves will be added to the IST Program Pltn. Other check valves will be reviewed for compliance with ASME Section XI requirements.
l ll395/85K
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION
! ' f.nemy..nu ooem muusa m t= =t=== m mar m ma o
a 0l4l7 0l0 2 l'l9 DIABLO CANYON UNIT 1 0l5l0l0l0i2l7l5 84
)
sw on I.
Plant Conditions Unit 1 and Unit 2 operated in various modes at various power levels while i
this condition existed.
i II.
Description of Event A.
Summary:
On June 25, 1993, following discussion with the SI pump discharge check valve vendor a Technical Review Group (TRG) determined that I
testing of the SI pump (BP)(P) discharge check valves (BP)(V), which relied upon reverse pump rotation to identify reverse flow, may not I
have been adequate to meet the reverse flow seating requirements.
]
Although the SI pump discharge check valves were not reverse flow i
tected in accordance with ASME Section XI, the information provided in j
Section IV of this LER demonstrates that the SI pump discharge check valves have always been capable of performing their intended safety s^
functions since initial Mode 3 (Hot Standby) entry.
However, because i
SI pump discharge check valves 1-8922A, 1-8922B, 2-8922A, and 2-8922B j
are required to be operable to meet the requirements of Technical Specification (TS) 3.5.2, PG&E has conservatively taken the position that Diablo Canyon Power Plant (DCPP) had entered into an operating
,i mode not permitted by TS 3.0.4.
)
B.
Background:
}
The SI pumps deliver water from the refueling water storage tank (RWST)(BP) to the reactor coolant system.(RCS)(AB) during the injection phase or from the cont.'nment recirculation sump (BE)(RVR) i to-*Che RCS during the post loss-of-coolant accidnt (LOCA) i recirculation phase.
In this capacity, SI pump discharge check valves i
1-8922A, 1-8922B, 2-8922A, and 2-8922B have a safety function-to open.
SI pump discharge check valves 1-8922A,1-89228, 2-8922A, and 2-8922B also serve to prevent pump-to-pump interaction during SI single pump 4
operation, thus ensuring stable miniflow operation for each SI pump.
]
In this capacity, SI pump' discharge check valves-1-8922A,-1-8922B,
]
2-8922A, and 2-8922B have a safety function to close.
1 i
TS 3.5.2 requires that two emergency core cooling system (ECCS)(BP) subsystems shall be operable with each subsystem comprised of: (a) one i
operable centrifugal charging pump (CB)(P); (b) one operable SI pump; (c) one operable residual heat removal heat exchanger (BP)(HX);
(d) one operable residual heat removal pump (BP)(P); and (e) an operable flow path capable of taking suction from the RWST on a SI signal and manually transferring suction to the containment i
recirculation sump during the recirculation phase of operation.
7 5
ll39S/85K
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION
~m
- y...,
,- -. m
--n, DIABLO CANYON UNIT 1 0l5l0l0l0l2l7l5 84
- 0l4l7 0l0 3~l'l9 1 EXT V h TS 3.0.4 states that entry into an operational mode shall not be made when the conditions for the limiting condition for operation are not met and the associated action requires a shutdown if they are not met within a specified time interval.
TS 4.0.5 requires that inservice inspection of ASME Code Class 1, 2, and 3 components and inservice testing of ASME Code Class 1, 2, and 3 p=ps and valves shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code.
Section XI of the ASME Boiler and Pressure Vessel Code specifies required testing intervals for Class 1, 2, or 3 valves that perform a function in mitigating the consequences of an accident or in bringing the plant to a cold shutdown condition..The DCPP Inservice Testing (IST) Program Plan was developed to meet the requirements of ASME-Section XI.
Surveillance Test Procedure (STP) P-18, " Routine Surveillance Test of Safety Injection Pumps," is performed on a nominal quarterly frequency.
STP P-1B verifies the operability of SI pumps in accordance with ASME Section XI.
In addition, STP P-1B fully strokes SI pumps to RWST check valves SI-8919A and SI-8919B and partially strokes RWST to SI pumps suction check valve SI-8977.
STP P-1B is relied upon to satisfy the requirements of TS 3.5.2 and to verify that the non-operating SI pump does not rotate in reverse.
STP V-15, "ECCS Flow Balance Test," is performed on a nominal 18-month i
refueling frequency.
STP V-15 verifies the proper setting of the ECCS cold leg runout valves (BP)(V) to assure proper flow using a single SI pump.
STP V-15 also verifies the full-stroke opening of SI pump discharge check val. : 1 8922A, 1-8922B, 2-8922A, and 2-8922B in accordance with ASME Section XI.
IST Program Plan Relief Request No. 7 documents the acceptability of refueling outage test frequency for full-stroking these valves.
The IST Program Plan does not currently specify reverse flow closure testing requirements for SI pump discharge' check valves 1-8922A, 1-8922B, 2-8922A, and 2-8922B.
C.
Event
Description:
On March 3, 1984, for Unit I and on July 25, 1985, for Unit 2, initial entry to Mode 3 was made without reverse flow testing of safety-related SI pump discharge check valves 1-8922A, 1-89228, 2-8922A, and 2-89228. These discharge check valves were forward flow tested during STP V-15 testing.
On April 17, 1993, a review of STP P-1B identified a potential SI leak path that could affect the minimum ECCS cold leg injection flows, ll395/85K
44 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION norm my =
i oocm au=a m
- acun awa m DIABLO CANYON UNIT 1 0l5l0l0l0l2l7l5 84
- 0l4l7 0l0 4 l 'l 9 TEXT UM This review also identified that the IST Program Plan did not include reverse flow testing of the SI pump discharge check valves 1-8922A, t
l 1-89228, 2-8922A, and 2-89228.
On April 19, 1993, PG&E performed an operability assessment on the Unit 1 SI pump discharge check valves.
SI Pump 1-1 was started, pressurizing the discharge piping to approximately 1600 psig.
The pump was then shut down, and the discharge piping pressure was monitored for a decrease in pressure. The pressure held at approximately 1600 psig for 20 minutes.
Since the suction pressure of the pump is 30 psig, both SI discharge check valves 1-8922A and 1-8922B held a differential pressure of approximately 1570 psid.
This test demonstrated that the valves do not leak.
If the valves had leaked even a small amount, the pressure would have decayed rapidly.
Therefore, SI discharge check valves 1-8922A and 'l-8922B will reverse flow seat.
In addition, prior to entering Mode 3 following the Unit 2 fifth efueling outage (2RS), similar tests were performed on SI dischan ge check valves 2-8922A and 2-8922B and the test results were consistent with the Unit 1 test'results.
On June 25, 1993, following discussions with the SI pump discharge check valve vendor, a TRG determined that the SI pump discharge check valve testing that relied upon reverse pump rotation to identify l
reverse flow may not have been adequate to meet the reverse flow i
seating requirements. Although the SI pump discharge check valves were not reverse flow tested in accordance with ASME Section. XI, the information provided in Section IV of this LER demonstrates that the SI pump discharge check valves have always been capable of performing their intended safety functions since initial Mode 3 entry.
- However, because SI pump discharge check valves 1-8922A,1-8922B, 2-8922A, and 2-8922B are required to be operable to meet the requiremt a of TS 3.5.2, PG&E has conservatively taken the position that DCPP entered l
into an operating Mode not permitted by TS 3.0.4.
i D.
Inoperable Structures, Components, or Systems that Contributed to the Event:
None.
E.
Dates and Approximate Times for Major Occurrences:
1.
March 3, 1984:
Event date.
Initial entry of Unit 1 into Mode 3.
TS 3.0.4 was not met.
l l
2.
July 25, 1985:
Event date.
Initial entry of Unit 2 into Mode 3.
TS 3.0.4 was not met.
l 3.
April 17, 1993:
Reverse flow testing requirements for SI discharge check valves 1-8922A and B and.
(
11395/85rs
--m
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION I
F ACluTV N AMg (y DOCKET NUMBE (2)
LER NUMBER (St PAOf (35 t
veAn at tu A
N 3
0l4l7 0l0 5 l'l9 DIABLO CANYON UNIT 1 0l5l0l0l0l2l7l5 84 TEXT (171 2-8922A and B were determined not to be included in the IST Program Plan.
4.
June 25, 1993:
Discovery date.
The TRG determined that STP P-1B is inadequate to meet the ASME Section XI i
reverse flow IST requirements.
4 F.
Other Systems or Secondary Functions Affected:
None.
G.
Method of Discovery:
On April 17, 1993, during a review of STP P-18, Plant Engineering-identifiec' a potential SI leak path that could affect the minimum ECCS j
cold leg injection flows. On June 25, 1993, the TRG' determined that
{
since SI pump discharge check valves 1-8922A,1-89228, 2-8922A, and 2-8922B are required to be operable to meet the requirements of TS 3.5.2, entry into Mode 3 is not permitted by TS 3.0.4 without
{
verification of operability.
H.
Operator Actions:
None.
Safety System Responses:
None.
III.
Cause of the Event A.
Immediate Cause:
Inservice testing required by ASME Section XI to verify reverse flow seating was not performed on SI pump discharge check valves 1-8922A, 1-89228, 2-8922A, and 2-89228.
B.
Root Cause:
ASME Section XI, Subsection IWV-3522,-states that check valves shall be exercised to the position required to fulfill their function.
Valves that are normally open during plant operation and that function to prevent reverse flow shall be tested in a manner that proves that the disk travels to the seat promptly on cessation or reversal of flow.
Valves that are normally closed during plant operation and that function to open on reversal of pressure differential shall be tested by proving that the disk moves promptly away from the seat when the closing pressure differential is removed and flow through the. valve is-initiated. The SI pump discharge check valves 1-8922A,1-89228, ll39S/85K
.=
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION mar m uy =
acm au=== m 1Weun==<m DIABLO CANYON UNIT 1 0l5l0l0l0l2l7l5 84
- 0l4l7 0l0 6 l"l9 TEXV O 71 2-8922A, and 2-8922B perform a safety function in both the open and closed positions. Because the SI pump discharge. check valves are normally closed during plant operation and the SI pumps are idle, the check valves normally do not have a reverse pressure differential.
Plant Engineering did not interpret the above requirements as requiring that both open and closed positions of the SI discharge check valves be verified by testing.
Consequently, because the SI pump discharge check valves are normally closed during plant operation, the valves were classified as normally closed Category C valves and tested for full-stroke open capabilities.
During the development of the IST Program Plan a personnel error occurred because responsible personnel did not recognize the need to reverse flow test the check valves.
Reverse flow testing of these valves was not identified as an IST requirement by plant engineers during the detailed design review of the DCPP IST Program Plan in a working session with the NRC_in 1983. At that time, the NRC reviewed the adequacy of testing procedures for all components in the IST Program Plan. Where testing deficiencies were identified, plant engineers revised appropriate STPs and the IST Program Plan.
The NRC followed up with several safety evaluation reports, ultimately providing approval of the current IST Program Plan in December 1988.
In summary, the root causes of this event include deficiencies in the scope of the IST Program Plan review, miscommunication, and personnel error (cognitive).
IV.
Analysis of the Event Dur.ng single pump operation, SI pump M icharge check valves 1-8922A, l-89228,'2-8922A, and 2-89228 serve to prevent leakage from the operating SI pump discharge back through the non-operating SI pump during the injection phase.
The following operating and maintenance history summary indicates that SI pump discharge check valves 1-8922A, 1-8922B, 2-8922A, and 2-8922B (on both Units 1 and 2, respectively) are operable and capable of performing their intended safety function to close upon reversal of flow since initial Mode 3 entry.
1.
SI pump discharge check valves I-8922A,1-8922B, 2-8922A, and 2-8922B have been observed to be leaktight on an incidental basis.
Following performance of STP P-1B, the discharge pressure was often observed to remain at SI pump discharge pressure. This indicates that the SI pump discharge check valves 1-8922A,1-8922B, 2-8922A, and 2-8922B were leaktight.
2.
The Unit 1 SI pump discharge check valves 1-8922A and.I-8922B were disassembled and inspected during the Unit I fifth refueling outage.
Il39S/85K
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION
==
7-q mm.,-,,,
mm - m DIABLO CANYON UNIT 1 0l5l0l0l0l2l7l5 84
- 0l4l7 0l0 7 l"l9 I
VLKT (171 The inspection determined that there was no internal valve damage and a 360 seating surface blue check was satisfactory.
3.
The Unit 2 SI pump discharge check valve 2-8922A was. inspected during the Unit 2 second refueling outage (2R2). The inspection determined that there was no internal valve damage and a visual inspection of the valve seat was satisfactory. The Unit 2 SI pump discharge check valve 2-0922B also was disassembled and inspected during 2R2.
The inspection determined that there was no internal valve damage and a 360 seating surface blue check was satisfactory.
The Unit 2 SI pump discharge check valve 2-89228 was disassembled and inspected during both the Unit 2 fourth refueling outage and 2R5, with similar results.
4.
A review of maintenance histories determined that no corrective maintenance has been required for SI pump discharge check valves 1-8922A, 1-8922B, 2-8922A, and 2-8922B.
5.
STP V-15, currently performed on an 18-month basis to meet the requirements of TS 4.5.2 action h.,
ensures that the stringent ECCS flow criteria (including single SI pump operation) are met.
In accordance with the single failure criterion defined by the NRC in SECY 77-439, total valve disk failure or failure in the fully open position is not considered to be a credible failure mode based on the maintenance history of the valve, inspection results, and the service environment.
Therefore, any potential valve impairment is considered to be in the form of backleakage.
STP V-15 is currently performed on a nominal 18-month l
frequency and verifies adequate cold leg injection flows for single pump operation.
Verification of these flows by performance of STP V-15 I
demonstrates that the discharge check valve of the non-operating SI pump has seat J, is not exhibiting umsive backleakage, and is not degrading the ability of the system to perform its safety function.
During a LOCA, the SI pumps deliver water from the RWST to the RCS after the RCS pressure is reduced.
During single pump operation, SI pump discharge check valves 1-8922A, 1-8922B, 2-8922A, and 2-8922B serve to prevent leakage from the operating SI pump discharge back through the non-operating SI pump.
If the discharge check valve of the opposite SI pump leaks, the fluid will flow through the idle SI pump, thereby potentially reducing the overall ECCS flow to the cold legs below the minimum acceptable amount.
In the event that both SI pumps are operating, reverse flow in either SI pump discharge check valve is not possible.
Surveillances performed in accordance with STP V-15 on an 18-month basis to meet the surveillance requirements of TS 4.5.2 action h. ensure that ECCS injection flow for single pump operation is within the TS minimum and maximum flow rates.
Thus, the failure to perform periodic reverse flow inservice testing on SI pump discharge check valves 1-8922A, 1-8922B, 2-8922A, and 2-8922B did not adversely affect the health and safety of the public.
Il395/85K
i LICENSEE EVENT REPORT (LER) TEXT CONTINUATION oociar==m m ta=== =
noe m
) wurr =we m DIABLO CANYON UNIT 1 0l5l0l0l0l2l7l5 84
- 0l4l7 0l0 8 l"l9 ruron V.
Corrective Actions A.
Immediate Corrective Actions:
On April 19, 1993, testing was performed demonstrating that SI pump discharge check valves 1-8922A and 1-8922B are leaktight. Between April 19 and 23, 1993, SI pump discharge check valves 2-8922A and 2-8922B were tested and demonstrated satisfactory results.
B.
Corrective Actions to Prevent Recurrence:
1.
A pressure drop test has been added to the unscheduled outage item lists to be performed during a Mode 5 (Cold Shutdown) forced outage for Units 1 and 2.
The pressure drop test will verify reverse flow seating of SI pump discharge check valves 1-8922A, 1-89228, 2-8922A, and 2-8922B.
2.
The IST Program Plan will state the function and the type of periodic testing required for SI pump discharge check valves 1-8922A, 1-8922B, 2-8922A, and 2-89228, and the appropriate procedures will be revised prior to the Units 1 and 2 sixth refueling outages.
3.
The DCPP IST Program Plan for the second ten-year period will be revised and submitted to the NRC. As part of this process, safety-related pumps and valves will be reviewed for compliance with the requirements of ASME Section XI.
VI.
Additional Information m,
A.
Failed Components:
None.
B.
Previous LERs on Similar Problems:
LER 1-84-044-01, Check Valves Inservice Testing Deficiencies Due to Personnel Error (submitted to the NRC on July 16, 1990)
As a result of review in response to NRC Information Notice 88-70, " Check Valve Inservice Testing Program Deficiencies,"
PG&E determined that on February 20, 1984, for Unit 1 and on July 19, 1985, for Unit 2, initial entry to Mode 4 (Hot Shutdown) was made without complete inservice testing of certain check valves. Also, on March 3,1984, for Unit 1 and on July 25,1985, for Unit 2, initial entry to Mode 3 was made without closure testing of check valves MS-5166 and MS-5167.
The check valves were not being tested to verify their safety 11395/85K
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION a
mc=v===m oocan=== m un=== =
==m j
DIABLO CANYON UNIT 1 0l5l0l0l0l2l7l5 84
- 0l4l7 0l0 9 l'l9 TEXT (1D function in the closed position in accordance with ASME Section AI i:T requirements.
The IST deficiencies were caused by a personnel error.
Plant Engineering did not correctly identify testing requirements for these check valves in the closed position.
Corrective actions to prevent recurrence included: (1) reviewing the testing requirements of components in the IST Program Plan to ensure consistency with the guidance of NRC Generic Letter (GL) 89-04,
" Guidance on Developing Acceptable Inservice Testing Programs;"
(2) revising the IST Program Plan to accurately reflect the proper testing requirements for these check valves; and (3) reviewing check valves in the IST Program Plan to confirm that the GL 89-04 review considered all appropriate design basis requirements. The corrective actions described in LER 1-84-044-01 could rat have prevented the event described in this LER since the corrective actions were performed several years after the event date of this LER, but should have identified the condition described in this LER at an earlier date.
LER l-92-001-00, Violation of Technical-Specification 4.0.5 Due to a Previously Unidentified Check Valve Safety Function On April 1, 1992, PG&E determined that Units 1 and 2 were in violation of IS 4.0.5, since volume control tank (VCT)(CB)(TK) outlet check valve CVCS-8440 (CB)(V) was not being t::ted in accordance with ASME Section XI.
The root cause for the exclusion of CVCS-8440 from the ASME Section XI IST Program Plan was that its safety function had not previously been identified.
a
~
Corrective actions to prevent recurrence included a review of all valves in the post-LOCA recirculation flow path to determine if any other valves perform a previously unidentified safety function due to a similar configuration.
This review would not have identified the condition described in this event because the review was limited to post-LOCA recirculation flow paths that may potentially leak to the atmosphere; the.nonconformance described in this LER did not fall into the scope of the review associated with LER l-92-001-00.
1 ll395/85K _
- -