ML20059M878
| ML20059M878 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 08/18/1993 |
| From: | AFFILIATION NOT ASSIGNED |
| To: | |
| References | |
| OLA-2-I-MFP-038, OLA-2-I-MFP-38, NUDOCS 9311190413 | |
| Download: ML20059M878 (26) | |
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SUMMARY
Event 1 (Unit 1):
On January 18, 1991, at 1700 PST, the FHB ventilation system was declared inoperable because the system failed to maintain a negative 1/8 inch water gauge pressure in the building.
The root cause of event 1 was determined to be the degradation of the FHB. Contributory causes were determined to be dirty exhaust fan ducts, failure to maintain a flow difference between the exhaust and supply flows of 19.8 percent, and blocking of a FHB exhaust duct.
Corrective actions to prevent recurrence for event 1 include rebalancing the flows in the FHB to provide for a greater margin for meeting the negative pressure requirement, sealing the movable crane wall, and investigating the acceptability of the 19.8 percent flow mismatch.
Event 2 (Unit 2):
On August 7, 1991, the Unit 2 FHB failed to pase STP M-41A.
The root cause of event 2 was determined to an imp r understanding of the required calibration frequency of the supply fan inlet vane controller.
Corrective actions to prevent recurrence include defeating the controller function by failing the inlet dampers open and adjusting the supply fan speed to provide the correct flow with that condition. The controller setpoint function is not used in any other application at DCPP.
91NCRWP\91tnn007.ptn Page 1 of 26 l 9311190413 DR 930818 ADOCK 05000275 PDR (f fl } - }>
'o t
NCR DC1-91-TN-N007 Rev.00 December 11, 1991
- 2. October 15, 1989: Event date -
Fuel and heavy loads moved over the spent fuel pool with the FHB ventilation system inoperable.
- 3. January 18, 1991, at 1700 PST: Discovery date
- FHB Ventilation system declared inoperable.
LCO for TS 3.9.12 entered.
Event 2 (Unit 2):
- 4. August 7, 1991: Unit 2 FHB failed to pass STP'M-41A.
D. Other Systems or Secondary Functions Affected:
None.
E. Method of Discovery:
Utility personnel, during the performance of a scheduled STP, identified the problem.
F. Operators Actions:
Operators declared the FHB ventilation system inoperable.
G. Safety System Responses:
None required.
l III. Cause of the Event l
l A. Immediate Cause:
l 91NCRWP\91tnn007.ptn Page 4 of 26
, , , , - = '^
6-NCR DC1-91-TN-N007 Rev.00 December- 11,-1991 i
i The immediate cause was determined to be excessive leakage into the FHB.
B. Determination of Cause: t
- 1. ' Human Factors:
- a. Communications:
' Event 1:
t During start up for.the FHB,. fasteners for ,.
the siding'near.the crane rail were i tightened regularly. This practice ceased after the building was turned over to the plant, as it was never communicated that a ;
proLiem with the lasteners existed.
Event 2: I l N/A
- b. Procedures: N/A ;
1
- c. Training: N/A
- d. Human Factors: N/A
- e. Management System:. 1 1
l Event 1:~
.,, ...~ *
. . . ~
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The System Engineer had identific ' that the FHB ventilation system.had a low ~ i margin for meeting the negative 1/8. inch. l WG pressure requirement and had requested l a design change to improve the margin '(by !
reducing the supply flow, thus,11ncreasing the mismatch between supply and exhaust flows). The funding to implement this design change was' denied by Plant'-
Management due to a lack of failure _
history. This action is not considered a-contributing cause to'this event although it could-have aided in preventing the failure.
- Have the System Engineering Quarterly-91NCRWP\91tnn007.ptn Page 5 of 26 I
- I
's -
.NCR DC1-91-TN-N007 Rev.00 i
December'11, 1991 Reports for the FHB identified adverse trends in the pressure for the FHB?
The system engineering quarterly reports have not identified any trends with.the pressure.~for the FHB. .
However, NOS trending of the exhaust:
flows from-the FHB has noted a-continual decline in exhaust flow-volume.- This-decline amounts to approximately 10 percentLcapacityL inL 15 years.. The flow, however,. is still within acceptable. limits.
Event 2:
N/A >
- 2. Equipment / Material:
- a. Material Degradation: -p Event'1:
Walkdowns have identified degradation of- l materials used in the FHB boundary. .;
In-leakage has'been identified lat areas-of ~
corrosion of the steel-siding,- :
deteriorated gasket material around doors, boots around piping penetrations, and {
general sealing materials.(e.g.,'between .
.. plating and' concrete, and'between ster' siding and concrete) . 'The .walkdown also identified a missing seal between the fuel handling building movable and fixed walls, which contributed significantly to the leakage.- The combination of the-leakage- ,
is considered to be the root cause.s Was the failure of the FHB ventilation '
system due to normal degradation.of the ventilation' system?
Corrosion of the siding of'the'FHB_was !
noted:as a. source of in leakage for .
the FHB. . Degradation of doorfands l penetration. seals was-also noted. '
However, several' larger gaps.in the 91NCRWP\91tnn007.ptn Page 6 of 26 l t
, - . , . . , , .w.-~,
s-NCR DC1-91-TN-N007 Rev.00 December 11, 1991 FHB ventilation boundary were noted that have existed since the performance of the last STP, including seals around CST piping and between the fixed and movable walls in the FHB.
Event 2:
N/A
- b. Design:
Event 1:
The negative pressure expectations for a structure are dependent on having a high.J exhaust flow than supply flow, and the magnitude of the mismatch is based on the building materials used. A-verification of the design of the ventilation system:
(currently specified exhaust / supply flow mismatch) adequacy to meet a negative 1/8 inch WG pressure considering the building materials used is being performed.
However, at most this would be'a contributory cause since PG&E accepted the existing Technical Specification requirements, and the building.has been demonstrated to be capable of meeting the Technical Specification requirements during previous surveillance tests.rw w
- What variables have a significant effect on the ability of the FHB ventilation system to maintain a negative 1/8 inch WG pressure in the FHB (i.e., temperature, barometric pressure, cloud cover, wind. speed and direction, season,.etc.)?
All weather conditions can have an effect on the pressure in the FHB, most notably, wind speed and- 4 direction. These variables cannot be controlled.'Also,-opening doors for personnel access has a significant effect on the pressure in the FHB, 91NCRWP\91tnn007.ptn Page 7 of 26' 1
i
'.L E
NCR DCl-91-TN-N007-Rev.00 l December 11, 1991-i though the effect'is temporary..
- What experience have other utilities ,
had in maintaining the appropriate pressure in the FHB?
Other. utilities' experiences vary depending on the-design of;the FHB' (concrete vs. sheet raetal) .
- Did. design drawings for-the'FHB
- include a seal for the movable wall?
original design drawings.for the FHB included an inflatable seal for-thel ;
movable wall.. The seal is no longer ;
installed, and a DCN search did not identify any time that the seal was removed.
Event 2:
-* - What past experience-exists with the=
design setpoint of the controller'for. ,
the inlet vanes? '
The setpoint on the~ inlet vanes has ,
l never beenJa-concern in'the past as the vane position in other- .
applications is not relevant. The DCN :
that adjusted 1the supply flow to the Unit 2.FHB'used'.the setpoint.
- c. Installation: N/A
- d. Manufacturing: N/A
- e. Preventive Maintenance:
l Event 1: +
l
- Do PMs for-the FHB ventilation l boundaries (i.e.,.FHB walls,. ;
j penetrations, etc.) exist?
PMs exist-for the FHB: doors. STPs '
exist for monitoring the. ventilation '
system components. However, a PM 91NCRWP\91tnn007.ptn Page 8 of . 26 L
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! NCR DCl-91-TN-N007 Rev.00 l December 11,_1991 program for the building or its sealing capabilities does not exist.
Note that Civil / Architectural Engineering has a program to monitor
, the condition of the buildings, and,is l planning upgrades based on the observed condition.
Event 2:
l l N/A
, f. Testing:
Event 1:
( The current surveillance test (STP M-41) l adequately verifies the ability of the l Fuel Handling building to meet the
! surveillance requirements'specified by the TS, and at the frequency specified in the l TS. Past surveillances on the Unit 1 FHB have always demonstrated acceptable results, and have not demonstrated any l useful. trends which would have predicted l this failure. Based on the degradation in negative pressure seen, increased surveillance testing is recommended until long term corrective actions can be implemented. This increased testing should be performed specifically when the
^^
system is required (i.e., when moving fuel in the spent fuel pool, or crane operations with loads over the spent fuel pool).
- When was the last successful STP M-41 performed for the FHB ventilation system?
The last successful test was performed in August, 1989.
l l
- What work was performed that could affect the FHB ventilation system subsequent to the performance of the last successful STP M-41 (i.e.,
dampers, damper actuators, fans, 91NCRWP\91tnn007.ptn Page 9 -of 26 l
NCR DC1-91-TN-N007 Rev.00 December 11, 1991 penetrations, etc.)?
No work was identified which would change the ventilation capabilities of the FHB.
- Is testing performed frequently enough to accurately trend. degradation of the building?
In the past, testing frequency'was adequate. However,' the frequency has been increased to assure that adequate negative pressure exists in the' building prior to. movement of fuel or heavy load over the pool. .The need for sustaining the frequency will be -
re-evaluated after the building 1is resided..
- Is the testing method adequate to accurately determine the'overall ,
pressure:of the building?
The testing method provides a-representative measure of_the pressure ;
at the surface of the spent fuel pool.-
Negative. pressure at the surface of, s the pool is necessary to assure that, ' .
in the event of an accident,- !
radioactive' material will not be '
released unfiltered.
Does the test method. measure a.
localized pressure only? j The test pressure measured is:the pressure of concern for the FHB.
- Is testing adequate to assure that a negative 1/8 inch WG' pressure is maintained any time fuel is moved in the pool or heavy loads.are moved over the pool?
No. STP M-41 verified the negative j pressure of the FHB every.18 months.
The OP B-8 series of. procedures do not. i 91NCRWP\91tnn007.ptn Page 10 of- 26 l
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. . --m-. -
- ~ - ~ #
NCR DC1-91-TN-N007 Rev.00
. December 11, 1991 require that the negative pressure of the FHB be physically verified prior to starting fuel movement, or during fuel movement.
Event 2:
N/A
- g. End-of-life failure:
Event 1:
Note that to date, the actions taken to correct the problem of the FHB ventilation system's inability to maintain a negative 1/8 inch WG pressure were to seal the small identified leaks that have i developed, and to seal openings which were j not required to be sealed during previous ;
satisfactory performances of the STP M-41.
- Did normal aging cause a penetration to fail?
Normal aging of the FHB siding and the ,
adhesive degraded due to aging and '
contributed to the problem. !
Event 2:
NlA , , , ,
- 3. A copy of the Root Cause Analysis may be found in Attachment 1.
C. Root Cause:
Event 1:
i l The root cause was determined to be degradation of l the FHB sealing material. This degradation j includes: (ref. 4, 9 and 10)
- 1. Gaps between sections of sheet metal siding
- 2. Unsealed piping penetrations
! 3. Missing or degraded door and piping. seals
{ 4. Gaps between the FHB movable crane wall and i 91NCRWP\91tnn007.ptn Page 11 of 26 l
l
NCR DC1-91-TN-N007 Rev.00 December 11, 1991 the FHB fixed walls
- 5. Through wall oxidation of FHB sheet metal siding Performance of FHB pressure tests has identified that the sealing of the pressure boundary significantly affects the building pressure.
After sealing all identifiable through wall oxidation of the building, the building would not maintain a negative 1/8 inches WG pressure.
However, sealing of the FHB movable wall provided sufficient sealing to allow the building to pass its surveillance test. Therefore, since sealing the building provided adequate margin to pass the surveillance test, the root cause was determined to be degradation of the sealing of the building.
Past surveillance test data did not indicate a trend in maintaining the required negative pressure of the FHB. Past data from the Unit 1 FHB indicates that the pressure differential between the FHB and the atmosphere was negative 0.25 inches WG in 1986, negative 0.33 inches WG in 1988, and negative 0.15 inches WG in 1989. The lack of an adverse trend in FHB pressure may not have been identified because several. variables affecting the results of the test, such as test performer, weather conditions, door position, and instrument inaccuracies, were not consistent (uring the three tests.
A request was initiated to reduce the building supply flow to provide a greater margin for passing the surveillance test; however, it was concluded that the action was not necessary because the buildircJ had always passed the surveillance test in the past, and past data _did not indicate a negative trend in maintaining the required negative pressure. Though reducing the supply flows is not required and does not directly ;
address the root cause (seal degradation), the action will be performed as a Corrective Action to Prevent Recurrence because it provides additional margin above the Tech. Spec. and STP requirements.
Event 2:
The root cause of the controller setpoint drift -l 91NCRWP\91tnn007.ptn Page 12 of 26 l l
l, NCR DC1-91-TN-N007 Rev.00 i December 11, 1991 was determined to be inadequate understanding of the proper calibration interval for the controller.
D. Contributory Cause:
Event 1:
- 1. tontributory cause of the failure of the FHB 2aintain a negative pressure is reduced 1 vw through the FHB exhaust fans due to accumulation of dirt in the ducts.
! 2. A contributory cause of the failure of the FHB to maintajn a negative pressure is the failure to mainta ' 19.8 percent difference between
~
the supp: . exhaust flows as required by the FSAR.
i 3. A contributory cause of the failure of the FHB l to maintain a negative pressure is the l blocking of a FHB exhaust duct by plastic l sheeting.
Event 2:
No contributs y cause was identified.
IV. Analysis of the Event A. Safety Analysis:
In order to assure that all potential rc eases from the spent fuel pool are exhausted through the FHB exhaust filters, the fuel pool area must be maintained at a negative pressure. The TS bases for the FHB ventilation system states, "The limitations on the FHB ventilation system ensure that all radioactive material released from an irradiated fuel assembly will be filtered through the HEPA filters and charcoal adsorber prior to discharge to the atmosphere. The operability of this system and the resulting iodine removal '
I capacity are-consistent with the assumptions of the safety analysis."(ref. 17 and 6) )
1 Final Safety Analysis Report (FSAR) Update Section j 9.4.4.1 goes on to say "...The requirements for i i
91NCRWP\91tnn007.ptn Page 13 of 26 l
)
t NCR DCl-91-TN-N007 Rev.00 December 11, 1991 the system design are as follows:...(3) Remove more air than is supplied so that all potential air leakages will be inward..." The FSAR accident analysis assumes that the fuel pool area at the 140 foot elevation is at a negative pressure with respect-to the ambient, which will assure that near the area of the spent fuel' handling accident there would be infiltration ~of air from the ambient "ather than exfiltration which could by-pass-the FHB exhaust filters, in accordance with the TS bases (ref. 18 and 6).
The FHB ventilation system was able to maintain a negative. pressure in the spent fuel pool area between 0.05 inches and 0.09 inches WG.- The differential pressure-for Unit 1 is measured in the northeast' corner of the FHB on the same elevation as the surface of the spent fuel pool.
The pathway between the instrument and the-pool is unobstructed. The low pressure leg.of'the instrument is located in the northeast corner of-the building on the same elevation as.the surface of the spent fuel pool. 'The high pressure leg of the instrument is located outside the northeast corner of the FHB, and is shielded from wind effects (ref. 6).
The FHB ventilation system creates a sweeping effect across the surface of_the pool. The ventilation path is also_ unobstructed. As a result, the effect of stagnant _ air pockets is minimized. Considering the ventilation path 'nd the location of the measuring instruments, the measured pressure is indicative of the pressure at the surface of the spent fuel pool (ref. 6 and 18).
Although the negative pressure requirement of the TS was not met, sufficient negative pressure was maintained to prevent gross air exfiltration from the spent fuel pool ~ area.- This conclusion is based on a qualitative evaluation performed for:an analogous Unit 2 event described in NCR-DC2-90-TN-N015 (ref. 6). Therefore, since the FHB_ spent fuel pool area was maintained at a negative pressure, the assumptions in the FSAR Update' regarding a postulated 1 fuel handling accident are q i
maintained, and the health and safety of the l i
91NCRWP\91tnn007.ptn Page 14 of 26 i l
I I
NCR DC1-91-TN-N007 Rev.00 December 11, 1991 l public were not affected by this event.
B. Reportability:
- 1. Reviewed under QAP-15.B and determined to be non-conforming in accordance with Section 2.1.2.
- 2. Reviewed under 10 CFR 50.72 and 10 CFR 50.73 I per NUREG 1022. The event is reportable as fuel was moved just prior'to the. event, and i evidence does not indicate that the condition
! did not exist during this time, even though
! the FHB doors were checked each day prior to fuel movement. Evidence does not indicate that work was performed on the building which would alter the pressure boundary, 'Thereft.e, the FHB ventilation system is considered to have been inoperable since the last successful performance of STP M-41. Since fuel was moved subsequent to the test, the event'is reportable in accordance with 10 CFR 50.73 (a) (2) (1) (B) . The report was issued as LER 1-89-019-01.
- 3. This problem does not require a 10 CFR 21 report.
- 4. This problem does not require reporting via an INPO Nuclear Network entry.
- 5. Reviewed under 10 CFR 50.9 and determir.ed to se be not reportable since this event does not have a significant implication for public health and safety or common defense and security.
- 6. Revise LER 1-89-019-00 to report root cause determination.and corrective actions.
RESPONSIBILITY: Hug, MT l ECD: COMPLETE I Tracking AR: A0214837 AE#9 l
V. Corrective Actions l
A. Immediate Corrective Actions:
! 91NCRWP\91tnn007.ptn Page 15 of 26
\
NCR DC1-91-TN-N007 Rev.00 f December 11, 1991 I Event 1:
- 1. The FHB ventilation system-was declared inoperable, and fuel movement suspended.
- 2. Identified leaks will be sealed, and STP M-41 re-performed to assure that the FHB' negative 1/8 inch WG pressure can be satisfied.
- 3. The pressure of the FHB'will be monitored.more frequently during: fuel movement to assureLthat the. negative pressure requirement for the FHB is satisfied. This requirement'is-included in !
Operating Procedure (OP) B-8D, "Non-refueling Fuel Handling Instructions." ;
- 4. Previous STP datarwill be reviewed to l determine if current flow mismatch is bounded by previous flow mismatches.
RESPONSIBILITY: C. Pendleton-i ECD: COMPLETE-l Tracking AR: A0214837 AE #1 Outage Related: NO JCO Related: NO ,
NRC Commitment: YES CMD Commitment: NO ,
l 5. Meteorological data for the days of pont '
l performances of successful STPs will be reviewed to identify trends'that'may effect i the performance of STP M-41.
l RESPONSIBILITY: C. Pendleton l ECD: COMPLETE Tracking AR: A0214837 AE #2 i
Outage Related: NO i JCO Related: NO NRC Commitment: YES l CMD Commitment: NO f
- 6. NECS to evaluate a reasonable margin above negative 0.135 inches to assure that TS negative pressure is maintained in the building. i 1
RESPONSIBILITY: ~ R. Waltos l ECD: ' COMPLETE 91NCRWP\91tnn007.ptn Page 16 of 26
,.. , _ - _ - , _ - . _ _ - . , , . _.I
I t
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a NCR DC1-91-TN-N007 Rev.00 December 11, 1991 Tracking AR: A0214837 AE #4 Outage Related: NO l JCO Related: NO NRC Commitment: NO CMD Commitment: NO
- 7. NECS to determine what rebalancing can be done on the Unit 2 FHB prior to fuel receipt.
f RESPONSIBILITY: R. Waltos I ECD: COMPLETE Tracking AR: A0214837 AE #5 Outage Related: NO
! JCO Related: NO l NRC Commitment: YES CMD Commitment: NO l
Event 2:
i No investigative actions were identified as the l investigation could not be completed before the controller is abandoned in place during 2R4. The setpoint for the controller is not used in any other application at DCPP.
l B. Corrective Actions to Prevent Recurrence:
Event 1:
- 1. The flows in the Units 1 and 2 FHB will be rebalanced and the supply flows reduced to provide greater margin for passing STP M-41.
RESPONSIBILITY: R. Allen ECD: COMPLETE for Unit 2 1R5 for Unit 1 Tracking AR: A0214837 AE #6 and 16 Outage Related: NO JCO Related: NO l
NRC Commitment: YES l CMD Commitment: NO l
- 2. The accuracy-and acceptability of the 19.8 percent flow difference stated in FSAR Update Section 9.4.4.1 will be investigated.
RESPONSIBILITY: R. Allen ECD: COMPLETE 91NCRWP\91tnn007.ptn Page 17 of 26 I
I NCR DC1-91-TN-N007 Rev.00 December 11, 1991 Tracking AR: A0214837 AE #7 Outage Related: NO JCO Related: NO NRC Commitment: YES CMD Commitment: NO
- 3. A DCN will be initiated to seal the FHB movable wall with the fixed portion of the building.
RESPONSIBILITY: C. Pfau ECD: COMPLETE Tracking AR: A0214837 AE #8 Outage Related: NO JCO Related: NO NRC Commitment: YES CMD Commitment: NO
- 4. An AT EWR will be initiated to install permanent differential-pressure instrumentation in the Units.1 and 2 FHB to allow'for more frequent monitoring of the building differential pressure.
RESPONSIBILITY: R. Allen ECD: COMPLETE Tracking AR: A0214837 AE #10 and 11 Outage Related: NO JCO Related: NO NRC Commitment: YES CMD Commitment: NO
- 5. STP M-41A was created to require that differential pressure of the FHB be measured ,
within 7 days of movement of fuel or heavy loads over the spent fuel pool. l i
RESPONSIBILITY: R. Allen ECD: COMPLETE Tracking AR: A0214837 AE #12 ,
Outage Related: NO '
JCO Related: NO NRC Commitment: YES CMD Commitment: NO
- 6. A DCN will be issued to replace the Units 1 and 2 FHB to atmosphere roll up doors.
91NCRWP\91tnn007.ptn Page 18 of. 26
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1 i-NCR DC1-91-TN-N007 Rev.00 December 11, 1991 RESPONSIBILITY: R. Allen ECD: 12/31/91 Tracking AR: A0214837 AE #13 and 14 Outage Related: NO JCO Related: NO NRC Commitment: YES CMD Commitment: NO Event 2:
- 7. A DCN will be implemented to change the speed of the Unit 2 supply fans to allow normal operation of the fans with the inlet dampers failed.
RESPONSIBILITY: R. Allen ECD: COMPLETE Tracking AR: A0214837 AE #15 l Outage Related: NO JCO Related: NO NRC Commitment: YES CMD Commitment: NO C. Prudent Action
- 1. The FHB will be resided.- A membrane will be installed over the existing siding to seal the building, and new siding placed over the top of the membrane.
RESPONSIBILITY: R Allen Tracking AR: A0230700 <* e l
VI. Additional Information A. Failed Components: ;
l i None.
B. Previous Similar Events:
NCR DC2-90-TN-N015 Unit 2 FHB Ventilation System Inoperable.
In this event, fuel was moved when the pressure of I l the FHB was greater than negative 1/8' inch WG.
l This problem occurred due to several personnel doors being blocked open for outage work. The 91NCRWP\91tnn007.ptn Page 19 of 26 j l
t
's NCR DC1-91-TN-N007 Pev.00 December 11, 1991 corrective action included posting signs on the FHB doors stating that the door is a pressure boundary, and that it can only be blocked open with the permission of the shift foreman. As the corrective actions only addressed doors, they would not have prevented the recent event.
C. Operating Experience Review:
- 1. NPRDS:
Not applicable.
- 2. NRC Information Notices, Bulletins, Generic Letters:
None identified.
SER 60-81 Spent Fuel Pool Ventilation System.
This notice addressed a problem with maintaining the negative pressure in the FHB required by TS at Calvert Cliffs. The pressure could be maintained with both supply fans shut down, but not with either. supply fan running. The notice provided no cause for the problem.
The PG&E response stated that.due to design differences, the issue was not a problem at DCPP. The response also stated that existing surveillance procedures were sufficient to assure that a problem would be identified.
The problem with the FHB was identified during the performance of an STP. Therefore the response did accurately identify the_ fact that the STPs would identify the problem. At the time of the review of the SER, no problems.had been identified regarding the FHB. However, had the problem identified during startup been known, the evaluation should have considered increasing the surveillance interval for the STP.
I 91NCRWP\91tnn007.ptn Page 20 of 26
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NCR DC1-91-TN-N007 Rev.00 December 11, 1991 D. Trend Code:
Responsible department TN, and cause code C5.
E. Corrective Action Tracking:
- 1. The tracking action request is A0214837.
F. Footnotes and Special Comnents:
None.
j G.
References:
l
- 1. Control Room logs dated 1/18/91 j 2. AR A0215407 l
- 3. AR A0414500
- 4. AR A0215074
- 5. LER 2-90-002-01
! 6. Letter to file from D. Tateosian on impact of open doors on FHB ventilation system dated 2/6/91
- 7. AR A0214837
- 8. E-mail from Roger Moy to Regulatory Compliance dated 2/6/91
- 9. E-mail from Roger Moy to John Gisclon dated 2/4/91
- 10. AR A0216092
- 11. E-mail from Roger Moy to John Vranicar dated 1/29/91
- 12. STP M-41
,, 13. AR A0183967 .
i
- 14. Control Room Logs oated October, 1C39. l
- 15. TS 3.4.9.12 i
- 16. AR A0217821 l
- 17. TS B-3.4.9.12 l
- 18. FSAR 9.4.4.1 l
- 19. LER 1-89-019-01 1 1
H. TRG Meeting Minutes: '
On January 24, 1991, the TRG convened and i considered the following:
- 1. The TRG discussed the issue of the. operability of the FHB ventilation system. System engineering stated that investigation was in progress to determine the reason for the 91NCRWP\91tnn007.ptn Page 21 of 26
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NCR DC1-91-TN-N007 Rev.00 December 11, 1991 l
1 failed STP. No information was available by the time of the TRG. The TRG agreed to address the questions in the determination of l cause section at the next TRG, as more information would be available at that time.
- 2. The TRG will reconvene 1/31/91 to discuss the results of investigative actions and reportability, on January 31, 1991, the TRG reconvened and discussed the following: I
- 1. The TRG discussed the results of Walkdowns of the FHB. The walkdowns identified degradation I of the building siding, and several missing or {
degraded piping penetration seals. l
- 2. The TRG discussed increasing the surveillance requirement for the negative pressure of the j FHB. The TRG could not reach a consensus for the increased frequency. The-chairman stated l he would let the APM-Technical Services i decide.
- 3. The chairman stated that, after discussions with the Regulatory Compliance Supervisor, the )
issue would be brought before the NRC for a reportability clarification.
4.
The TRG will reconvene on 2/6/91 to discuss results of the performance of STP M-41.
On February 6, 1991, the TRG reconvened'and discussed the following:
- 1. Results of recent STP performances were discussed. The FHB still had not passed STP M-41, though improvement had been made. Upon reaching Mode 4, the supply fans were turned l off to achieve sufficient negative pressure to allow fuel movement during the outage.
t j 2.
The TRG discussed comments from NECS Civil /
Architectural. NECS feels that the building design is not sufficient for it to be leak tight. The question was then raised by the TRG as to the appropriateness of maintaining a 91NCRWP\91tnn007.ptn Page 22 of 26 i
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NCR DC1-91-TN-N007 Rev.00 December 11, 1991' negative 1/8 inch pressure in the building.
- 3. The'TRG discussed correlating the previous data with current data. Due to changes in door management policies, weather conditions, test performers, etc., the data is difficult to correlate. Weather data _will be identified to attempt to eliminate ~one' variable affecting the correlation.
- 4. The exhaust ducts were cleaned. The pressure improved, but not sufficiently to pass the STP.
- 5. The TRG discussed the differences-in flow.
mismatch between the recent STP and previous STPs. The previous data will be obtained and reviewed to determine if current data is within'the bounds of past data.
- 6. The TRG will' reconvene approximately 4/1/91 to-discuss the results of further investigation.
The TRG reconvened on April 1, 1991, and discussed the following:
- 1. The TRG discussed the operability of the Unit 2 FHB. The Unit 2 FHB is in the same condition as tne Unit 1 FHB. .This problem l must be corrected prior to fuel receipt in May- l for 2R4. As in the case of Unit 1, a partial STP M-41 will be performed an a seven*" day ""
frequency during fuel movement.
- 2. Weather effects on-the building were discussed. MET data from previous performances of STPs is not available in detail. However,-it was stated that wind conditions can have significant effects cn1 the building pressure. Other variables which affect the pressure measured are the instrumentation used and the' individual performing the test. These variables make it difficult to correlate past data.
- 3. The TRG discussed quantifying the effects of' the different contributors to-the decreased pressure. Syct.em engineering agreed to look 91NCRWP\91tnn007.ptn' Page 23 of H26 g m
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~l NCR DC1-91-TN-N007 Rev.00
-December 11, 1991 into the issue.
- 4. Several actions were discussed at the meeting. '
The results from these actions will be discussed at the next TRG.
- 5. The TRG will reconvene on 4/11/91 to finalize and sign off the NCR.
The TRG reconvened April 11, 1991, and. discussed the following:
- 1. The TRG reviewed the NCR for consistency with~
the associated LER. The TRG determined the immediate cause, root cause, and contributory causes of the event.
- 2. The TRG discussed a discrepancy between the TS and the FSAR. The TS-provides a range of flow values for the' supply and exhaust-fans.-
However, this does not ensure' compliance with the flow difference between the exhaust and supply fans cited in the FSAR. This issue will be investigated under-a_ corrective action.
- 3. The NCR will be routed for: signature. The overall due date of the NCR is 12/31/92. The NCR will lxt sent to the PSRC after the' associated'LER is sent to the'NRC.- . (NOTE : -
See below for revised'NCR due date.).
The TRG reconvened May 13', 1991 and: discussed the.
following:
- 1. Corrective action to reside building was~ moved-from CAPR section to a Prudent: Action. The TRG agreed that residing the~ building was a conservative measure and'that the balance of the corrective actions ~ would lxa sufficient to preve.nt recurrence.
- 2. The TRG discussed-AR A0229795 which documents.
measurements'taken in the Unit 2 FHB. 'Recent-measurements taken indicate a negative ventilation pressure of_less than the TS requirement. STP.M-41 will be run in the upcoming week. No operations; involving 91NCRWP\91tnn007.ptn Page 24 of- 26
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NCR DC1-91-TN-N007 Rev.00 December 11, 1991 movement of fuel within the SFP or crane operations with loads over the pool will be.
conducted until resolution of the problem has been determined.
- 3. The TRG will not reconvene. The NCR will be routed for signature and sent to the PSRC when the LER is revised.
On August 8, 1991, the TRG reconvened and discussed the following:
i 1. The TRG discussed the failure of STP M-41A.
The' failure was the result of inlet vane i controller setpoint drift.
- 2. The iRG agreed that any action '.aken for the controller:would be fruitless as the controller function will be defeated when the inlet vanes are failed open. The TRG-assigned l an action to adjust theLsupply fan speed to allow operation of the fan with the inlet vanes failed open.-
- 3. The TRG identified several corrective actions for event 1.
l 4. The TRG will not reconvene unless the' building j fails its STP aga3n.
On October 30, 1991, the TRG reconvened'and l ,_ discussed the following: ~
m
- 1. The TRG reconvened to review the NCR corrective actions against the commitments- )
made in the LER. AE #05 will be closed and- l the action tracked by AE #16. AEs'#13 and #14 required only that DCNs be " initiated" (not
" implemented"), which has been.done. Since j some modifications to fix the seals'have i already been done as immediate corrective actions, the TRG agreed that initiating the >
DCNs is sufficient and AEs #13 and #14 can be
! closed.
- 2. The TRG also determined that a paragraph in the NCR root cause needed clarification.
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NCR DC1-91-TN-N007 Rev.00 December 11, 1991 ;
- 3. Overall ECD for NCR closure will be 6/1/92.
I. Remarks:
1 None.
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