ML20059C870
| ML20059C870 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 08/19/1993 |
| From: | AFFILIATION NOT ASSIGNED |
| To: | |
| References | |
| OLA-2-I-MFP-104, NUDOCS 9401060164 | |
| Download: ML20059C870 (13) | |
Text
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Iteractivity Containment Fan Coolers 3.
Peference 5.
Descriptaon of Nonconf orma.nce:
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Questionable maintenance practice regarding the re-use of locking nuts, and b.
I (2)
Inadequate maintenance instructions related to relative tightness of damper I
weichts.
This is Considered a nonconformance per DAP 15.b. paragraph ~2.1.8.
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N Plant Conditions III. Cause of Problem V.
Corrective Actions A
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Description of Protlam IV.
Ar.alysis of Froble:n VI.
Additional Inf oar.ation L
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- 18. 10CFR50.9
- 19. Reference Other C
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- 23. Notified By 26 Time
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- 27. Time Limit
- 28. LER Ho.
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Other Agencies Rotified 31.
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Chairman (p/ s )
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Date 40.
Other (p/s) al. Date F
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Date 42.
Other (p/s) 63.
Date R
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Other (p/s)
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Date A
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Reg. Ccep. f or DCFP NCRs 19.
Date A6.
Other (p/s) 67.
Date only (p/s) seenees mese PSRC l64.
Mee t ing Da t e :
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GObFh.AC hot ti) cat 3on Date :
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Date Action 9401060164 930819 i
PDR ADOCK 05000275 hs trityt t en G
PDR Dn%
Materials
} P5Rc Sec retary Manager. OA Station / Hydro Constru:t ton Instaator P l.a.n t Kar.ager. DCfP TES Appreprnate QC CCFPRAC 5ec retary Authorized Inspecter, llOtaer Lre s tw e r ing if app 1ncable Other
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DCO-92-MM-N007 RO DRAFT:
February 12, 1992 MANAGEMENT
SUMMARY
LAST TRG
SUMMARY
On February 12, 1992, the TRG reconvened in the Blue Conference Room at 3:00 pm PST to discuss the results from the instrumentation of BD 1-2, and plans to replace the BD blades on Unit 2 during 2R5.
The TRG will raconvene after 2R5, during approximately the last week of May 1993.
EVENT ONE:
Unit 2:
On January 22, 1992 during the weekly containment inspection, a counterweight from the containment fan cooler unit (CFCU) 2-1 backdraft damper (BD) was found on the 117' elevation grr_ing.
Further investigations found that on CFCU 2-1 a total of 9 counterweights assemblies were either missing or lacking locknuts to secure the counterweight to the counterweight arm.
Additionally one counterweight assembly was missing from CFCU 2-5.
The other three CFCUs were verified to have all counterweights properly attached.
Unit 1:
On January 23, 1992 a walkdown was performed to ensure that there were no missing weights on the Unit 1 CFCUs.
All counterweight assemblies were verified to be attached to the counterweight arms.
However, the counterweights appeared to be instal'ed too tight when compared to the design drawings.
)
i Further walkdowns and inspections in Unit 1 identified
'at the backdraft damper linkage assemblies we.c not installed c.
functioning as designed (backdraft dampers were stuck open) on CFCUs 1-1, 1-2, and 1-5.
On February 19, 1992, CFCUs 1-1, 1-2, and 1-5 were declared inoperable and a 1-hour non-emergency report was made to the NRC under 10 CFR 50.72 (b) (1) (ii) as a condition (prior to discovery) that was outside the design basis of the plant.
As discussed in the 5/19/92 TRG, all Unit 1 and 2 CFCU BDs have been inspected and overhauled, and are per design with minor discrepancies and wear identified.
However, these minor discrepancies may allow some BD binding and fan reverse rotation, if there is not sufficient backpressure on the dampers.
STP M-51A sets forth acceptance criteria for reverse rotation.
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7 DCO-92-MM-N007 RO DRAFT:
February 12, 1992 The root cause of this event is failure to perform proper maintenance.
The corrective actions will include:
(1) formation of a CFCU High Impact Team; (2) revision of CFCU surveillance test and post-maintenance testing procedures; (3) preparation of a detailed maintenance procedure; (4) formation of an Integrated Problem Response Team; (5) training in evaluating degraded plant conditions; (6) assuring maintenance personnel are qualified in HVAC systems; and (7) deve3oping an action plan to ensure the adequacy of attention to HVAC systems.
EVENT TWO:
On September 25, 1992, September 27, 1992 and on October 3, 1992 backdraft (BD) damper blades on CFCOs 1-5, 1-2 and 1-4, respectively, were found to have cracks during planned inspections.
The CFCU BD damper blade material exhibits brittle fracture characteristics including a high sensitivity to defects.
Evaluation of the cracks, verified by laboratory tests, has concluded that longitudinal cracks that existed in the blades were of sufficient length to have resulted in blade failure caused by blade loading from a postulated RCS loop piping double ended guillotine LOCA pressure wave.
On October 17 and 18, 1992, visual inspections of the Unit 2 CFCU damper blades discovered a crack in,one blade of CFCU 2-1 and one crack each in two blades of CFCU 2-2.
This inspections also identified one broken blade bolt of CFCU 2-4.
l
- PROPOSED - The root cause of the CFCU BD blade cracking was fatigue cracking during normal operating conditions.
The CFCU BD blading in both Unit 1 and Unit 2 will be replaced with blades of similar dimensions made of a material more resistant to fatigue cracking.
J 9mcawrmuusanJCN Page 2
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i DCO-92-MM-N007 R0 DRAFT:
February 12, 1992 NCR DCO-92-MM-N007 CONTAINMENT FAN COOLERS l
EVENT ONE:
I.
P_lant conditions 1
i E
power.
II.
Description of Event A.
Summary:
Unit 2:
On January 22, 1992 during the weekly containment inspection, a counterweight from the containment fan cooler unit (CFCU) 2-1 backdraft damper (BD) was found on the 117' elevation grating.
Further investigations found that on CFCU 2-1 a total of 9 counterweights assemblies were either missing or lacking locknuts to secure the counterweight to the counterweight arm.
Additionally one counterweight assembly was missing from CFCU 2-5.
The other three CFCUs were verified to have all counterweights properly attached.
i Unit 1:
On January 23, 1992 a walkdown was performed to ensure that there were no missing weights on the i
Unit 1 CFCUs.
All counterweight assemblies were verified to be attache? 'o the counterweight arms.
However, the counterweights appeared to be installed too tight when compared to the design drawings.
i Further walkdowns and inspections in Unit 1 identified that the backdraft damper linkage assemblies were not installed or functioning as designed (backdraft dampers were stuck open) on CFCUs 1-1, 1-2, and 1-5.
On February 19, 1992, CFCUs 1-1, 1-2, and 1-5 were declared inoperable and a 1-hour non-emergency report was made to the NRC under 10 CFR 50.72 (b) (1) (ii) as a condition (prior to discovery) that was outside the design basis of the plant.
i As discussed in the 5/1L/92 TRG, all Unit 1 and 2 CFCU BDs have been inspected and overhauled, and are per design with minor discrepancies and wear identified.
92NCRWB97MMN007.JCN Page 3
of 51 e...-,
1 DCO-92-MM-N007 R0 DRAFT:
February 12, 1992 However, these minor discrepancies may allow some BD binding and fan reverse rotation, if there is not sufficient backpressure on the dampers.
STP M-51A sets forth acceptance criteria for reverse rotation.
The root cause of this event is failure to perform proper maintenance.
The corrective actions will include:
(1) formation of a CFCU High Impact Team; (2) revision of CFCU surveillance test and post-maintenance testing procedures; (3) preparation of a detailed maintenance procedure; (4) formation of an Integrated Problem Response Team; (5) training in evaluating degraded plant conditions; (6) assuring maintenance personnel are qualified in HVAC systems; and (7) developing an action plan to ensure the adequacy of attention to HVAC systems.
B.
Background:
There are five CFCUs in the containment which provide cooling during normal and emergency conditions.
The five CFCOs share a common diutribution duct work system.
The backdraft dampers are installed between the CFCUs and the distribution duct.
The backdraft dampers open under the discharge pressure of the operating CFCU and close on reverse flow of air (with gravity assist) when the associated CFCU is shut down.
The normal function of these dampers is to prevent excessive backflow of air through the CFCU when it is not running.
This prevents excessive CFCU fan reverse rotation during normal plant operation and minimizes cool air bypass.
The safety-related function of the backdraft dampers is to isolate the CFCUs from the ventilation distribution ducting during a design basis accident.
This protects each CFCU from reverse flow from a postulated transient 7 psi differential pressure across the CFCUs.
The backdraft dampers prevent excessive reverse rotation of the fan and motor that could affect the starting capability of the fan motor.
Following a loss-of-coolant accident (LOCA) or steam line break, the CFCUs, in conjunction with containment spray, reduce the containment ambient temperature and pressure and promote mixing between the lower and. upper ecawmmmmxw Page 4
of 51
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DCO-92-MM-N007 RO DRAFT:
February 12, 1992 containment areas to help prevent the localized accumulation of hydrogen.
Technical Specification (TS) 3.6.2.3 requires that, for Modes 1 through 4 (Hot Shutdown), at least three electrically independent groups of CFCUs with a minimum of one CFCU be operable in each group or at least two electrically independent groups of CFCUs with a minimum of two units be operable in each group.
I C.
Event
Description:
Between February 1 and March 27, 1991 (during the Unit 1 fourth refueling outage), maintenance was performed on all five CFCUS and their associated backdraft dampers.
On March 23, 1991, CFCU 1-2 backdraft damper was found to have broken bolts on the blade-to-axle connection.
This condition was repaired.
A Quality Evaluation report was initiated requiring all other Units 1 and 2 CFCU internal bolting to be inspected in the next respective refueling outages.
Internal inspections were performed.
l On March 25, 1991, Operations personnel found CFCU 1-5 i
rotating backwards.
This condition was determined to i
be acceptable.
On March 27, 1991, Unit 1 entered Mode 4 and TS 3.6.2.3 became applicable.
On January 22, 1992, Operations found a counterweight from the CFCU 2-1 backdraft damper on the grating at the 117 foot elevation of Unit 2 containment.
Further investigations by Mechanical Maintenance identified a total of seven counterweight assemblies missing from CFCU 2-1 backdraft damper and one assembly missing from CFCU 2-5 backdraft damper.
The as-found condition was evaluated by Design Engineering, documented in a Prompt Operability Assessment (POA), and determined not to affect the safety-related function of the CFCUs.
The cause of the loosening of the counterweights was determined to be the improper reuse of the locknuts.
On January 23, 1992, following the identification of the missing Unit 2 backdraft damper counterweights, 9?NCRWP 92MMNW7 )CN page 5
of 51 D
1 4
DCO-92-MM-H007 R0 DRAFT:
February 12, 1992 Mechanical Maintenance and Operations performed a walkdown to determine the condition of the Unit 1 backdraft damper counterweights.
There was no evidence of missing counterweights as were discovered on Unit 2; however, the counterweights were tightly fixed in their counterweight arm slot, whereas the design provides for relative motion between the counterweights and the slot.
Also, CFCU 1-3 was found to have nuts missing on the bolts of two damper linkage assemblies and CFCU 1-4 was found to have three bolt / nut assemblies missing l
from the damper linkage assembly.
Design Engineering was immediately notified.
Between January 23 and February 7, 1992, the as-found condition was documented and an Action Request was issued to Design Engineering to analyze the sign ticance of the condition.
Design Engineering discussed the design basis and qualification testing of the backdraft dampers with the original vendor's design engineer.
This conversation provided additional insight into the design features of the backdraft dampers.
On January 31, 1992, during a walkdown of the CFCUs in Unit 2, CFCU 2-1 was found to have reverse rotation of approximately 30 rpm.
An evaluation performed by Design Engineering showed that the CFCU remained operable with the identified reverse rocation.
On February 7, 1992, Design Engineering issued a POA, which concluded that the Unit 1 backdraft dampers were cperable based on the knowledge th't the counterweights were tightened with the backdraft damper in the closed position.
The POA required verification of weight positions to ensure proper damper operation.
On February 13, 1992, as a means for verifying that the tight condition of the counterweights would not prevent correct damper operation, another Unit 1 CFCU inspection was conducted by Mechanical Maintenance.
Each CFCU was sequentially stopped to observe if reverse rotation was present.
The CFCU 1-1, 1-2, and 1-5 fans were discovered to be rotating in reverse at speeds of 132, 143, and 114 rpm, respectively.
The reverse rotation was evaluated by preparation of a POA, and the CFCUs were determined to be operable based on information (later found to be incorrect) that reverse 92NCRWI'92MMNLU7)CN Page 6
of 51 l
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- r DCO-92-MM-N007 R0 DRAFT:
February 12, 1992 rotation was due to backleakage through the dampers and not as a result of dampers being stuck open.
On February 19, 1992, as a follow up to the POA of February 13, 1992, Mechanical Maintenance entered containment to evaluate the CFCU 1-5 damper performance.
The damper was discovered to be stuck open due to external linkage assembly problems.
The remaining CFCUs were inspected for similar problems and CFCUs 1-1 and 1-2 also were found to be stuck open.
CFCUs 1-3 and 1-4 were found to have proper linkage assembly and some degraded bolting problems.
Based on this new information, at 1933 PST, CFCUs 1-1, 1-2, and 1-5 were declared inoperable and TS 3.6.2.3 action "a" was entered (7-day action).
Because this condition had potentially existed since Unit 1 entry into Mode 4 on March 27, 1991, a one-hour, i
1
e made in accordance with 10 CFR 50.72 (b) (1) (ii) (B) as a condition (prior to discovery) that was outside the design basis.
This condition was outside the design basis of the plant since only two CFCUs were operable upon entry into Mode 4.
On the evening of February 19, 1992, CFCU 1-1 was returned to operable status after the backdraft damper was manually closed and the CFCU placed in standby.
On February 20, 1992, the backdraft damper was verified to open by starting CFCU 1-1.
The CFCU was shut down and returned to standby, with the backdraft damper closed.
Work was initiated to sequentially restore CFCUs 1-2, 1-5, and 1-1 to proper design configuration.
By February 26, 1992, the linkage arm configuration and tight counterweight condition of Unit 1 CFCUs 1-1, 1-2, and 1-5 were corrected and these CFCUs were declared operable.
No reverse fan rotation of those three CFCUs was observed after the deficient conditions were corrected.
Tight counterweight assemblies and loose or missing bolts remained on CFCUs 1-3 and 1-4.
- However, the dampers were functioning correctly and no reverse rotation was observed.
During the repair activities on the CFCU 1-5 damper, some looseness was noted on three bearing / blade assemblies and one damper arm demonstrated looseness which could indicate loose bolting in the blade-to-axle connection.
In addition, during the corrective maintenance, one damper blade on the CFCU 1-1 backdraft damper was observed from below, ymenwes7uem xw Page 7
of 51
't DCO-92-MM-N007 R0 DRAFT:
February 12, 1992 through an opening in the duct, to be partially open when the other blades were closed.
Inspection indicated that the blade was moving relative to the axle due to missing connection bolts.
However, an evaluation indicated that its position assured closure upon exposure to the transient pressure condition.
These conditions were formally evaluated and determined not to affect CFCU operability.
On March 2, 1992, a re-evaluation was performed and CFCU 1-1 was conservatively declared inoperable due to the potential for the blade to rotate to a position that would prevent damper closure.
The re-evaluation differed from the February 26 evaluation in that the blade was postulated to move to a position that could create interference with adjacent blades, thus preventing damper closure.
Further analysis was performed which demonstrated that one free blade would not prevent proper operation.
During a forced outage on March 6, management decided to repair the remaining identified exterior mechanical deviations on CFCUs 1-3 and 1-4 dampers and to conduct an internal inspection of all CFCU dampers.
The internal inspections of the five CFCUs were performed.
Observations were made of the axle / blade bolting, as well as the blade position.
ine summary of significant inspection results showed deficient conditions of the axle / blade connections on CFCUs 1-1, 1-2, 1-3 and 1-5 as follows:
CFCU 1-1 Two broken bolts on one blade that allowed the blade to move relative to the axle.
CFCU 1-2 One broken bolt.
CFCU 1-3 Four broken bolts.
One loose blade.
CFCU 1-5 Six broken bolts on three blades.
One blade had movement relative to the axle.
One loose bolt on another blade.
The loose blade conditions on the CFCU backdraft esen rmuumm;cs Page 8
of 51 1
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DCO-92-MM-N007 RO DRAFT:
February 12, 1992 dampers were previously evaluated for CFCU 1-1 and found not to adversely affect the operability of the CFCUs.
Between March 6 and March 9, 1992, all deficient internal bolting was replaced and design conditions were restored.
Also, the tightly installed counterweight assemblies and the missing or loose shoulder bolts were corrected on CFCUs 1-3 and 1-4.
On March 9, 1992, after internal and external mechanical deficiencies were corrected, post-maintenance testing and exercising of all CFCU dampers was completed.
Each damper was cycled twice while being observed for proper operation.
Proper damper operation was demonstrated on all CFCUs.
All CFCU; and dampers were operable.
Between March 17 and March 20, 1992, internal inspections of the CFCUs, similar to those performed for Unit 1, were performed for Unit 2.
Minor bolting deficiencies, none of which affected operability, were corrected.
On April 8, 1992, Unit 1 CFCUs were inspected via STP l
M-51A with no reverse rotation identified (ref. 7).
On April 15, 1992, STP M-51? tas conducted on Unit 2.
j CFCU 2-2 was observed to have reverse rotation of 132 rpm.
As part of the STP require'ments, the BD was verified to be in the closed position.
All otF'- CFCUs had no reverse rotation (ref. 7 ar. ' A0263766).
On April 16, 1992, a comprehensive inspection of the 2-j 2 CFCU BD did not 1
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would contribute to the reverse rotation.
However, the inspection did identify that the counterweights were installed tight in the counterweight arm slot.
This condition was not in accordance with the approved design and was contrary to previous inspection results (ref. 7 and C0099168).
On April 17, 1992, a similar inspection of the 2-2, 2-l 3,
and 2-4 CFCU BDs confirmed the fully tightened condition of BD 2-2 as well as identifying this same condition on BD 2-4.
A POA was generated (ref.
7, A0264097, and A0264099).
.q MNCRWMMMN3DKN Page 9
of 51
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t DCO-92-MM-N007 R0 DRAFT:
February 12, 1992 On April 20, 1992, an investigation into the conflict between the previous and current inspection results initiated a question regarding the validity of previous inspections on the 2-2 thru 2-5 CFCU BDs.
As a result, another inspection of these four CFCU BDs was performed, which identified that the all four BDs I
appeared to have washers installed in the linkage / linkage bar bolt connections and the ccunterweight connections, contrary to the design (ref.
7 and A0264155).
On April 22, 1992, prior to overhauling the 2-2 BD, an investigation re-created the conditions under which CFCU 2-2 exhibited reverse rotation on 4/15/92.
This investigation found that the BD exhibited some binding problems when only two other CFCUs were running, but performed as required when three CFCUs were running.
The initial binding was attributed to the washers on the linkage assembly creating a tighter-than-required joint between the linkage bar and linkage arm.
Subsequently, CFCU BDs 2-3, 2-4, and 2-5 were each verified to perform as required with two CFCUs running (ref. 7 and A0264925).
On April 22, 1992, during the disassembly and inspection of 2-2 BD, an additional internal binding problem was discovered with the inside edge of one of the damper blades.
This condition and possibly, the installation of washers, were the factors causing the damper to hang up under certain conditions, which resulted in reverse rotation of the fan (ref. 7 and
- A0264097, AF^"\\.
The overhaul was completed and the damper returned to its design condition with minor (not unusual) wear of the linkage and counterweight arms identified.
The post-maintenance testing (PMT) verified proper damper operation with no reverse flow and the required design CFCU flow (ref. 7).
On April 24, 1992, overhaul of the 2-4 BD was completed.
Some unusual wear was identified, but evaluated to be acceptable pending successful completion of the PMT.
The PMT verified proper operation with no reverse rotation, but identified that few of the BD counterweights were not resting a
completely on their bumpers (ref.
7,
- A0264615, 9mcawrmmewucs Page 10 of 51 i
r DCO-92-MM-N007 RO DRAFT:
February 12, 1992 A0264617).
On April 25, 1992, overhaul of BD 2-3 was completed with successful completion of the PMT.
In addition, evaluation of the gap between the BD 2-4 counterweights and their bumpers was completed and it was concluded that the gap was small enough so that the function of the damper would not be compromised (ref.
7,
- A0264617, and 1.0264623).
On April 26, 1992, overhaul of the 2-5 BD was completed and verified to be per design with some minor (not unusual) wear, and the PMT verified proper damper operation (ref. 7 and A0264660).
As of April 26, 1992, all Unit 1 and Unit 2 BDs had been completely overhauled on the exterior and have had internal inspections and repairs performed on internal axle / blade connections.
All BDs were per design with minor discrepancies and wear identified (ref. 7).
On May 12, 1992, STP M-51A on Unit 1 identified CFCUs 1-3 and 1-4 to be rotating in the reverse direction.
The reverse rotation of CFCU 1-4 was within the STP acceptance criteria, but the left half of the CFCU 1-3 damper remained open under some conditions.
After manipulating the configuration of operating and shutdown CFCUs, MM, OPS, and NECS Engineering determined that the 1-3 BD closed and CFCUs 1-3 and 1-4 met the STP acceptance criteria when the other three CFCUs were running (ref.
7, A0265979, and A0266026).
On May 14, 1992, an internal and external inspection of the 1-3 and 1-4 BDs did not identify any conditions that were not previously identified (ref.
7,
- A0266210, and A0266333).
However, as discussed in the 5/19/92 TRG, the existing conditions could cause enough minor binding to explain the observations, but would allow the dampers to close fully upon a slight increase in backpressure on the dampers.
As of May 15, 1992, OE 92-01 will be revised to address the existing condition, and will remain open until the discrepancies are repaired during 1R5 and 2RS and the root cause of the axle / blade bolting is determined.
D.
Inoperable Structures, Components, or Systems that mcxwmuunm7;cN Page 11 of 51 m
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DRAFT:
February 12, 1992 Contributed to the Event:
None.
E.
Dates and Approximate Times for Major Occurrences:
1.
March 23, 1991: A plant problem report was initiated to document broken bolts on CFCU 1-2.
2.
March 25, 1991: A plant problem report was initiated to document reverse rotation observed on CFCU 1-5.
3.
March 27, 1991: Event data.
Unit 1 entered Mode 4, and TS 3.6.2.3 became applicable.
4.
February 19, 1992:
Discovery date. CFCU 1-1, 1-2, and 1-5 backdraft dampers were found stuck open.
TS 3.6.2.3 action "a" was entered.
A one-hour, non-emergency report was made under 10 CFR 50. 72 (b) (1) (ii) (B).
5.
February 19, 1992:
CFCU 1-1 was placed in an operable configuration, and TS 3.6 ' 3 was exited.
6.
February 26, 1992:
Repair work on CFCUs 1-1, 1-2, and 1-5 was completed.
Minor design dicarepancies still existed on CFCU 1-1 and 1-5 backdraft dampers.
7.
March 9, 1992:
All five CFCUs were completely restored to design configuration during a Unit 1 forced outage.
8.
April 15, 1992: CFCU 2-2 was observed to have a reverse rotation of 132 rpm (ref. 7 and A0263766).
9.
April 16-26, 1992:
Inspection and overhaul of CFCU BDs 2-2 thru 2-5.
All CFCUs verified to be per design, with some minor discrepancies (ref.
4 92NCRWI*97MMN0(17.JCN Page 12 of 51
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February 12, 1992 7).
- 10. May 12, 1992:
Reverse rotation was observed on CFCUs 1-3 and 1-4 (ref.
7, A0265979, and A0266026).
J
- 11. May 14, 1992:
Additional inspections of CFCUs 1-3 and 1-4 did not identify any new conditions (ref.
7,
- A0266210, A0266333).
F.
Other Systems or Secondary Functions Affected:
None G.
Method of Discovery:
This condition was discovered by plant personnel during an inspection of the Unit 1 CFCUs.
H.
Operator Actions:
None.
3 I.
Safety System Responses:
I None.
III.
Cause of the Event Immediate Cause:
n.
The immediate cause of the plant being outside design basis was that the backdraft dampers on CFCUs 1-1, 1-2, and 1-5 were stuck open.
B.
Determination of Cause:
For the Unit 1 CFCUs, the proper orientation of the linkage bar and the condition of its stop assembly is critical to the damper's operability.
The proper configuration of these items was not readily apparent on the design drawing and was not mentioned in the work packages.
Therefore, the craft personnel did not receive the proper direction to correctly reassemble the damper linkages.
Additionally, three separate Containment maintenance crews were responsible for the I
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DCO-92-MM-N007 R0 DRAFT:
February 12, 1992 disassembly and inspection of the linkage bar and counterweights in addition to their other work.
For the Unit 2 CFCUs, no Maintenance Engineer was dedicated to the support of the backdraft damper maintenance creating a lack of " engineering" direction.
This led to an oversight on the reuse of old fasteners which caused the counterweights to come loose.
C.
Root Cause:
The root cause has been detarmined to be failure to perform proper maintenance.
D.
Contributory Cause:
1.
Management underestimated the importance of the backdraft damper to the overall safety function of a CFCU, and therefore did not provide for adequate maintenance.
This resulted in:
a.
Poor planning of CFCU backdraft damper work.
I b.
Inadequate work instructions.
c.
Inadequate job turnover.
d.
No Quality Control direct involvement in inspection of CFCU backdraft damper work.
j e.
Inadequate Plant System and System Design engineer involvement.
2.
Post-maintenance testing was not adequately i
implemented.
3.
The CFCU STP did not adequately test the critical backdraft damper function.
4.
Missed opportunities from prior problems and observations relative to backdraft damper design and maintenance.
IV.
Analysis of the Event V2NCRW792MMNOWJCN Page 14 of 51 4
'l DCO-92-MM-N007 R0 DRAFT:
February 12, 1992 A.
Safety Analysis:
The FSAR Update Chapter 6 containment analysis models two CFCUs and a single containment spray train to mitigate a design basis LOCA.
Because the backdraft dampers for CFCUs 1-1, 1-2, and 1-5 were stuck in the open position, they were initially assumed to be inoperable.
Internal and external inspections of CFCUs 1-3 and 1-4 performed prior to and on March 7,
- 1992, identified that these CFCUs also had minor deviations from the design configuration.
However, these deviations were evaluated and determined not to impact the ability of the CFCUs to perform their intended safety function.
PG&E has analyzed the safety significance of CFCUs 1-1, 1-2, and 1-5 backdraft dampers being stuck open during the fifth operating cycle of Unit 1.
As discussed below, PG&E concludes that the TS requirements and accident analysis assumptions for the number of operable CFCUs were met since entry into Mode 4 (TS applicability for CFCUs) on March 27, 1991, through March 9, 1992 (Unit 1 CFCU backdraft dampers restored to proper design configuration).
4 PG&E's conclusion regarding CFCU operability is based on a recently completed evaluation which demonstrates that a CFCU with a stuck open backdraft damper remains operable as long as it is operating at the time of the initiation of the LOCA.
The evaluation considered the case where the CFCU is operating at low speed (600 rpm) and is automatically tripped-off at the initi tion of the LOCA.
The evaluation concluded that the assumed LOCA generated pressure differential will cause the fan to decelerate to zero rpm and then begin to accelerate in the reverse direction.
The calculated reverse rotation at the end of the pressure transient is approximately 90 rpm.
The evaluation performed for the CFCU in low speed also bounds the case of a CFCU in high speed (1200 rpm).
Additional evaluations also determined that the CFCUs can restart with reverse rotation up to 400 rpm and that the pressure transient would not have any adverse consequences on the CFCU enclosure, fan or motor.
Therefore, as long as a fan with a stuck open backdraft damper was operating, it was operable.
nsenwrwn m anacN Page 15 of 51
=-
t DCO-92-MM-N007 R0 DRAFT:
February 12, 1992 PG&E has reviewed the operating history for the Unit 1 CFCUs for the period of time from March 27, 1991 (CFCU TS applicability), through February 19, 1992 (the identification of stuck open backdraft dampers).
Based on the operability of CFCUs 1-3 and 1-4, and because an operating CFCU with a stuck open backdraft damper is operable as long as the fan is operating, it was determined that the requirements of TS 3.6.2.3 were met at all times.
Therefore the public health and safety were not adversely affected by the condition of the CFCU backdraft dampers.
B.
Reportability:
1.
Rsviewed under QAP-15.B and determined to be non-conforming in accordance with Section 2.1.2 and 2.1.8.
2.
Reviewed under 10 CFR 50.72 and 10 CFR 50.73 per NUREG 1022 and originally determined to be reportable in accordance with 10 CFR 50.73 (a) (2) (ii) (B).
The associated LER is 1-91-019-00.
Based on the safety analysis performed by PG&E and Westinghouse, this event was determined not to be reportable per 10 CFR 50.73.
However, this event is bcli.g reported voluntarily in accordance with NUREG 1022.
3.
This problem does not require a 10 CFR 21 rc srt.
e 4.
This problem does require reporting via an INPO
]
Nuclear Network entry.
)
i 5.
Reviewed under 10 CFR 50.9 and determined event was not reportable under 10 CFR 50.9.
6.
Reviewed under the criteria of AP C-29 requiring the issue and approval of an Operability Evaluation (OE) and determined that an OE is required.
See OE 92-01 (Attachment Two) for more information.
V.
Corrective Actions A.
Immediate Corrective Actions:
nNcawvwuusmuen Page 16 of 51
I
' l DCO-92-MM-N007 R0 DRAFT:
February 12, 1992 1.
The backdraft damper on CFCU 1-1 was manually closed and verified to properly open upon a slow speed start signal.
The CFCU was placed in standby for slow speed auto start when required for LOCA accident mitigation.
By March 9, 1992, deficient conditions were restored to design, and i
subsequently, there have been additional overhauls of the backdraft dampers.
On March 9, 1992, after internal and external mechanical deficiencies were corrected, post-maintenance testing and exercising of all CFCU dampers was completed.
Each damper was cycled twice while being observed for proper operation.
Proper damper operation was demonstrated on all five CFCUs.
All CFCUs and dampers were operable.
Operability Evaluation OE 92-01 discusses the continuing operability of the CFCUs with this problem.
A compensatory action for the OE is to perform monthly walkdowns of Unit 1 and Unit 2 CFCUs to inspect for reverse rotation (A0260047, A0265979, AE03).
B.
Investigative Actions:
1.
Provide a summary of preventative maintenance and recurring task work orders related to the CFCUs for the last two outages.
RESPONSIBILITY:
Ken "-lmer DEPARTMENT:
PGMA Tracking AR:
A0258408, AE #1 STATUS: COMPLETE 2.
Provide a summary of the maintenance procedure for the CFCUs as well as a copy for the TRG.
The TRG determined the AE was no longer required.
1 3.
Contact the manufacturer of the bolt and lock nuts used on the backdraft dampers to determine whether they are adequate for the vibration environment for a full fuel cycle.
RESPONSIBILITY:
Ling /Rosales DEPARTMENT:
NCEM nscnemmmmKN Page 17 of 51
. - - - - - ~.
t DCO-92-MM-N007 R0 DRAFT:
February 12, 1992 Tracking AR:
A0258408, AE #3 STATUS: COMPLETE 4.
Interview Roger Moy, Gregory Porter, Warren Jacks, Thomas Brattin to understand CFCU maintenance problems encountered during the last few outages.
RESPONSIBILITY:
R.
Waltos DEPARTMENT:
PGMA Tracking AR:
A0258408, AE #4 STATUS: COMPLETE 5.
The CFCUs problems being addressed by this NCR may, in large part, have been caused by a lack of appreciation for the importance of the CFCU system function resulting in system not receiving appropriate attention.
Request input from a cross section of the QA organization regarding other systems which also may not be receiving the appropriate level of attention.
RESPONSIBILITY: Mark Dewitt DEPARTMENT:
QAAS Tracking AR:
A0258408, AE #6 STATUS: COMPLETE 6.
The CFCUs problems being addressed by this NCR may, in large part, have been caused by a lack of appreciation for the importance of the CFCU system function resulting in systen not receiving appropriate attention.
Request input from a cross section of LPa QC organization regarding other systems which also may not be receiving the appropriate level of attention.
RESPONSIBILITY: Neal Koellish DEPARTMENT:
PQCE Tracking AR:
A0258408, AE #7 STATUS: COMPLETE 7.
The CFCUs problems being addressed by this NCR may, i
in large part, have been caused by a lack of i
appreciation for the importance of the CFCU system function resulting in system not receiving appropriate attention.
Request input from a cross section of the Mechanical Maintenance organization regarding other systems which also may not be emenwr9mMNONKN Page 18 of 51
l r
a DCO-92-MM-N007 RO DRAFT:
February 12, 1992 receiving the appropriate level of attention.
RESPONSIBILITY: Ken Palmer DEPARTMENT:
PGMA Tracking AR:
A0258408, AE #8 STATUS: COMPLETE 8.
The CFCUs problems being addressed by this NCR may, j
in large part, have been caused by a lack of appreciation for the importance of the CFCU system function resulting in system not receiving j
appropriate attention.
Request input from a cross section of the System Engineering organization l
regarding other systems which also may not be receiving the appropriate level of attention.
i RESPONSIBILITY: Brent Pogue ECD: 3-30-92 DEPARTMENT:
PTEB Tracking AR:
A0258408, AE #9 STATUS: RETURN 9.
The CFCUs problems being addressed by this NCR may, in large part, have been caused by a lack of appreciation for the importance of the CFCU system function resulting in system not receiving appropriate attention.
Request input from a cross section of the OSRG organization regarding other i
systems which also may not be receiving the appropriate level of attention.
RESPONSIBILITY: Brian LoConte DEPARTMENT:
PTPM Tracking AR:
A0258408, AE #10 STATUS: COMPLETE
- 10. The CFCUs problems being addressed by this NCR may, in large part, have been caused by a lack of appreciation for the importance of the CFCU system function resulting in system not receiving appropriate attention.
Request input from a cross section of the Engineering Design organization regarding other systems which also may not be receiving the appropriate level of attention.
RESPONSIBILITY: Bob Waltos DEPARTMENT:
NCFN Tracking AR:
A0258408, AE #11 92Ncawr92uxNoo7.scN Page 19 of 51
i DCO-92-MM-N007 R0 DRAFT:
February 12, 1992 STATUS: COMPLETE
- 11. Provide a copy of the Integrated Problem Response Team report on the results CFCUs investigations.
RESPONSIBILITY: Jeff Kelly DEPARTMENT:
NCEM Tracking AR:
A0258408, AE #12 STATUS: COMPLETE C.
Corrective Actions to Prevent Recurrence:
1.
A CFCU High Impact Team will be formed to assure adequate planning and coordination of maintenance activities and identification of spare parts.
REfroNSIBILITY: Bob Waltos DEPARTMENT:
PGMA Tracking AR:
A0258408, AE #13 q
Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? No STATUS: COMPLETE 2.
The CFCU surveillance test procedure will be revised to specifically verify backdraft damper operability and to include eteps to test backdraft damper critical safety function.
RESPONSIBILITY: Brent Pogue DEPARTMENT:
PTES Tracking AR:
A0258408, AE #14 Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? Yes STATUS: COMPLETE 3.
Procedures will be developed for backdraft damper maintenance with appropriate QC hold points.
RESPONSIBILITY: Bob Waltos DEPARTMENT:
PGMA Tracking AR:
A0258408, AE #15 Outage Related? No OE Related?
No
I DCO-92-MM-N007 R0 DRAFT:
February 12, 1992 NRC Commitment? Yes CMD Commitment? Yes STATUS: COMPLETE 4.
A multi-disciplinary Integrated Problem desponse Team was formed to review the containmenc CFCU system maintenance history, design, and design basis to determine if an underlying cause has contributed to the problems of this system.
As part of this effort, recommendations will be made regarding maintenance of the backdraft dampers.
RESPONSIBILITY: Jeff Kelly DEPARTMENT:
NCEM Tracking AR:
A0258408, AE #16 Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? No STATUS: COMPLETE 5.
Training will be provided for engineers, supervisors, and licensed operations personnel in evaluating degraded plant conditions.
RESPONSIBILITY: Bruce Terrell DEPARTMENT:
PATT Tracking AR:
A0258408, AE #17 Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? No STATUS: RETURN 6.
Maintenance personnel will be qualified to perform maintenance on HVAC systems. The HVAC systems used in this context are specifically the CFCU backdraft dampers.
RESPONSIBILITY: Bob Waltos DEPARTMENT:
PGMA Tracking AR:
A0258408, AE #18 Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? No STATUS: COMPLETE nscawr.nuwvxrucw Page 21 of 51
I DCO-92-MM-N007 R0 DRAFT:
February 12, 1992 7.
An action plan will be developed to review the adequacy of the System Engineering, Design Engineering, Nuclear Operations Support, Maintenance, and Quality Control organizations attention to HVAC systems.
RESPONSIBILITY: Bob Waltos DEPARTMENT:
PGHA Tracking AR:
A0258408, AE #19 Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? No STATUS: COMPLETE 8.
Revise AP C-29 to incorporate recommendations as follows:
1.
record POAs in SF logs, 2.
QC Director to review active POAs during daily management meetings and will be updated to reflect the findings of the IPRT and TRG.
RESPONSIBILITY: Don Behnke DEPARTMENT:
PTRC Tracking AR:
A0258408, AE #20 Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? No STATUS: COMPLETE 9.
Track metallurgical failure analysis of failed bolts and _..;+ porate findings in maintenance procedures and/or design changes.
RESPONSIBILITY: Bob Waltos ECD:12/31/94 DEPARTMENT:
PGMA Tracking AR:
A0258408, AE #21 Outage Related? No OE Related?
Yes NRC Commitment? No CMD Commitment? No
- 10. Determine basis for post maintenance testing (PMT).
What procedure (s) need to be revised to improve the effectiveness of post maintenance testing.
RESPONSIBILIT : Brent Pogue 9mcawrmetmKN Page 22 of 51
f
~
DCO-92-MM-N007 RO DRAFT:
February 12, 1992 DEPARTMENT:
PTEB Tracking AR:
A0258408, AE #22 Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? No STATUS: COMPLETE
- 11. A maintenance service policy will be prepared on prompt closure of work orders.
RESPONSIBILITY: Bob Waltos DEPARTMENT:
PGMA Tracking AR:
A0258408, AE #23 Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? No STATUS: COMPLETE
- 12. Reliability engineering will provide component failure data to system and maintenance engineers.
Results to be included in joint guarterly walkdown reports.
RESPONSIBILITY: Bruce Patton DEPARTMENT:
PTMT Tracking AR:
A0258408, AE #24 Outage Related? No 1
OE Related?
No NRC Commitment? Yes CMD Commitment? No l
STATUS: COMPLETE
- 13. Issue a memo to re-emphasize face-to-face communications between system, design, maintenance, reliability and plant engineers (including
,I supervisors).
This memo should be coordinated with MJ Angus, MR Tresler, and BW Giffin.
1 1
RESPONSIBILITY: Mike Angus DEPARTMENT:
PMMT Tracking AR:
A0258408, AE #25 Outage Related? No OE Related?
No NRC Commitment? Yes nucawemMMNW7EN Page 23 of 51 P
,9
-.m-,
--,.y,.
-m
l DCO-92-MM-N007 RO DRAFT:
February 12, 1992 CMD Commitment? No STATUS: COMPLETE
- 14. Improve definitions of roles by issuing a t
discipline engineer support program directive covering system design, maintenance, reliability i
and plant engineers.
RESPONSILILITY: Bob Waltoc DEPARTMENT:
PGMA Tracking AR:
A0258408, AE #26 Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? No l
STATUS:
RETURN
- 15. Perform periodic audits on the effectiveness of l
system engineering.
RZSPONSIBILITY: David Taggart DEPARTMENT QAAX Tracking AR:
A0258408, AE #27 Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? No l
STATUS:
COMPLETE
- 16. Reassess the scope of work order review for inspection activities performed by non quality organizations to assure proper in_pection planning, clarity and acceptance criteria.
RESPONSIBILITY: Richard Cramins DEPARTMENT:
PQCI Tracking AR:
A0258408, AE #28 Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? No j
STATUS:
COMPLETE
RESPONSIBILITY: Phillip Lang vmenwr92uscari>cn Page 24 of 51
[
i
.v-e
,2 e-
-r-e
.... ~
=.
I 4
4 DCO-92-MM-N007 R0 DRAFT:
February 12, 1992 DEPARTMENT:
PQCE Tracking AR:
A0258408, AE #29 Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? No l
STATUS:
COMPLETE
- 18. Re-emphasize management expectations to aggressively question responses in ARs and QEs.
RESPONSIBILITY: Phillip Lang DEPARTMENT:
PQCE Tracking AR:
A0258408, AE #30 Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? No l
STATUS:
COMPLETE
- 19. Improve inspection selection criteria through the use of equipment failure trending which will be performed by reliability engineering.
RESPONSIBILITY: Richard Cramin DEPARTMENT:
PQCI Tracking AR:
A0258408, AE #31 Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? No l
STATUS:
COMPLETE
- 20. Issue a revised LER to reflect new information.
RESPONSIBILITY: Raymond Thierry DEPARTMENT:
PTRC Tracking AR:
A0258408, AE #32 Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? No
}
STATUS:
COMPLETE
- 21. Review Westinghouse Assumptions, inputs, methods and results utilized in support of Westinghouse letter dated May 28, 1992, PG&E 92-587.
vmcawre m w nw Page 25 of 51
-i 1
e DCO-92-MM-N007 RO DRAFT:
February 12, 1992 RESPONSIBILITY: Jeff Kelly DEPARTMENT:
NCEM Tracking AR:
A0258408, AE #33 Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? No STATUS: COMPLETE
- 22. Clarify management expectations for QC/QA: To maintain independent perspective, to continually ask "the big picture" question and to rapidly identify substantive concerns directly to management.
RESPONSIBILITY: James Sexton DEPARTMENT:
NSVP Tracking AR:
A0258408, AE #34 Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? No STATUS: COMPLETE
- 23. Increase System Engineering staff by six positions and expeditiously fill vacancies.
l RESPONSIBILITY: McCoy Burgess ECD:
3/1/93 DEPARTMENT:
SYSENG Tracking AR:
A0258408, AE #'36 Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? No
- 24. AP A-350 to be revised to include a requirement for Joint Quarterly System walkdown reports to highlight immediate and long-term priorities and address repetitive problems.
RESPONSIBILITY: Daniel Stermer DEPARTMENT:
SYSENG Tracking AR:
A0258408, AE #37 i
Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? No 92NCRWM92MMNOMJCN Page 26 of 51
o DCO-92-MM-N007 RO DRAFT:
February 12, 1992 j
STATUS:
COMPLETE i
- 25. NRC letter dated 6/19/92 contained 3 severity level IV violations regarding the CFCUs. Response is due within 30 days.
RESPONSIBILITY: Tom Deuriarte DEPARTMENT:
NSARA Tracking AR:
A0258408, AE #35 Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? No STATUS: COMPLETE
- 26. Address actions of this NCR credited for by QE Q0009552.
RESPONSIBILITY: Bob Waltos DEPARTMENT:
PGMA Tracking AR:
A0258408, AE #39 Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? No
]
STATUS: RETURN D.
Prudent Actions (not required for NCR closure)
None.
{
VI.
Additional Information A.
Failed Components:
Backdraft dampers manufactured by American Warming and Ventilating Inc. Model No. SHW-P-7900-18 failed to close as designed.
B.
Previous Similar Events:
None.
C.
Operating Experience Review:
1.
NPRDS:
escawrouumm;m Page 27 of 51 l
i DCO-92-MM-N007 RO DRAFT:
February 12, 1992 Reviewed as part of the Integrated Problem Response Team Evaluation and documented in Chron # 191670.
2.
NRC Information Notices, Bulletins, Generic Letters:
Reviewed as part of the Integrated Problem Response Team Evaluation and documented in Chron # 191670.
3.
Reviewed as part of the Integrated Problem Response Team Evaluation and documented in Chron # 191670.
D.
Trend Code:
i Responsiale department MM, ano cause codes A1, A2, A3, A4, AS, B1, B2, B3, B4, C1, C2, C3, C4, C5.
E.
Corrective Action Tracking:
1.
The tracking action request is A0258408.
2.
Are the corrective actions outage related?
No.
F.
Footnotes and Special Comments:
1.
None.
G.
References:
1.
Technical Specification 3.6.2.3 Containment Cooling System 3.6.2.1 Containment Spray 3.0.4 LCO l
2.
Initiating Action Request A0256600 QE Q0009461 Counter Balance Weight off of CFCU 2-1
& 2-5 E-mail, "CFCU BD Damper Condition," from GJP1 (G.
Porter) to various, dated January 22, 1992 A0256869 CFCU Back Draft Dampers:
Report on Walkdown Unit 1 A0257430 Walkdown:
Unit 2 CFCU Counter Balance Weights 92NCR%7.92MMNtXTlJCN Page 28 of 51
=
DCO-92-MM-N007 RO DRAFT:
February 12, 1992 A0257556 W/O to Document Walkdowns A0259076 1-Hour Non-Emergency Report Unit 1 CFCUs A0260849 Inspect / Repair CFCU 2-1 BD Blade-to-Axle Fasteners A0261583 CFCU 2-1 Reverse Rotation Found A0261584 CFCU 2-2 Reverse Rotation A0260856 Inspect / Repair CFCU 2-4 BD Blade-to-Axle Fasteners 1
A0260861 Inspect / Repair CFCU 2-5 BD Blade-to-Axle Fasteners A0260850 Inspect / Repair CFCU 2-2 BD Blade to Axle Bolting A0209034 STP M-93A Revise Refuel 3.
DCPP Event Notification Form dated 2/19/92 4.
Chronological Description of Events Related to Loss of Counterweights Off the CFCU BD's 2-1 & 2-5 (chronology from 1/22/92 to 1/31/92) 5.
Unit 1 CFCU Backdraft Damper Inspection 2/20/92 6.
E-mail, " NIGHT SHIFT TURNOVER, 2/20/92, THURSDAY,"
from DVP1 to SS Unit 1 Containment Fan Coolers Backdraft 7.
Dampers Chronology of Events Unit 2 Containment Fan Coolers Backdraft J
Dampers Chronology of Events "CFCU Back-Draft Da Ters" (discussed in the 5/19/92 TRG) 8.
A0224682 CFCU 1-5 Rotating Backwards 3/25/91 E-mail, " Containment Crew Dayshift Turnover...," from TCS1 to various, dated March 25, 1991 9.
Monthly Operating Report for March, 1991
- 10. Safety Significance of Containment Heat Removal (buses F, G,
H component unavailability 3/91 -
2/92) i
- 11. Operability Evaluation (OE) 92-01, " Containment Fan Cooler Unit Operation with Mechanical Deviations on One Unit 2 Backdraft Damper" 92NCRWP92MMNOLD h"N Page 29 of 51
.~..
DCO-92-MM-N007 R0 DRAFT:
February 12, 1992
- 12.
2," from Mechanical Maintenance (R. Powers) to Regulatory Compliance (T. Grebel), dated March 1
s
.,r...
a.~.,-
.,n--,,._,.
..v.
, =,.,_,___ _,._,_ -_. _ __
._m 6
J Documents supporting POAs (includes attachments to above memorandum, plus add'l documents dated 3/18/92 and 4/17/92)
- 13. FSAR Update Sections 6.2.2.3.3.3 and 9.4.5
- 14. A0258712 CFCU 1-5 Backdraft Repair A0259244 CFCU 1-2 Backdraft Repair A0259246 CFCU 1-1 Backdraft Repair i
A0263766 A0264097 A0264099 A0264155 A0264214 A0264217 A0264623 A0264617 A0264615 A0264660 A0264925 A0260047 A0265979 A0266026
.A0266210 A0266333
- 15. Lessons Learned - CFCU Backdraft Dampers
- 16. A0224521, QE Q0008787 CFCU 1-2 Damper Blade Broken & Half of BD Stuck Open (3/23/91)
A0218339 CFCU 1-4 Linkage Arm Repairs A0167401 CFCU 1-2 Broken Bolt & Linkage Hole i
Oval 1
- 17. Senior Resident Issues l
E-mail, "Part 1-3/19 NRC Exit," from JJG1 to various, dated March 24, 1992 E-mail, "SR Items," from JJG1 to various, dated 4
February 26, 1992 E-mail, "NRC/CFCU Backdraft Dampers," from RAW 2 to f
9:scawrotumm)CN Page 30 of 51
DCO-92-MM-N007 R0 DRAFT:
Februar 12, 1992 i
various, dated. January 24, 1992
- 18. Previous Problem Reports:
Startup Problem Reports from 1983 re: stuck-l open backdraft dampers on CFCUs 2-1 and 2-2 Nuclear Plant Problem Reports l
DC1-81-OP-P1170 DC1-83-OP-P0165 DC1-84-OP-P0063 DCJ -8 4 -OP-PO4 63 l
DC1-84-OP-P1953 DC1-85-OP-P0944/AR A0003656
- 19. NECS Calculations:
205A-DC 92-04 92-03 92-05 92-OL l
- 20. Unit 2 Internal Inspection Results 3/20/92
- 21. E-mail from Jim Tomkins regarding Enforcement l
Conference on CFCUs: May 28, 1992.
- 22. NRC Special Inspection of Diablo Canyon Units 1 and 2: Report No. 92-17.
4
- 23. Westinghouse Letter No. PGE-92-542 dated March 26, 1992: CFCU Backdraft Damper closure Assessment Containment Integrity Analysis.
- 24. Westinghouse Letter No. PGE-92-578 dated May 18, 1992: CFCU Backdraft Damper Evaluation Summary Report.
- 25. Westinghouse Letter No. PGE-92-587 dated May 28, 1
1992: Assessment of Differential Pressure Pulse on CFCU Fan Speeds.
- 26. PG&E letter DCL-92-161, NOV Response, dated l
7/20/92.
action #22)
\\
92NCR%7.92MMN007.3CN Page 31 of 51
D'3-92-MM-N007 RO DPAFT:
February 12, 1992
- 28. Training documentation for Corrective Actions #17 and #18.
- 29. Maintenance Services Policy on work order closure. (Corrective action #11)
- 30. Memorandum from M. Angus " Face-To-Face Communication." (Corrective Action #13)
- 31. Integrated Problem Response Team Evaluation (Chron
- 191670).
- 32. Work Order Inspection Criteria memorandum (Corrective Action #16).
- 33. Note from QA documenting applicable trend codes.
H.
TRG Meeting Minutes:
1.
On February 18, 1992, the TRG convened and discussed the condition of the Unit 1 and Unit 2 CFCUs.
It was agreed that the Unit 2 CFCUs will be walked down on a weekly basis to ensure proper counterweight conditions (this will be done for a total of 4 weeks and, if no change in counterweight conditions are observed, the walkdowns will be change to monthly).
For Unit 1, monthly tests will be performed to ensure that reverse rotation has not increased.
The TRG agreed to reconvene on March 4, 1992.
2.
On February 25, 1992 the TRG reconver.ed to consider new information regarding the Unit 1 CFCUs identified on February 19, 1992.
The TRG concluded that the Unit 1 event is reportable under 10 CFR
- 50. 73 (a) (2 ) (ii) (B) as a condition outside the design basis of the plant.
The start of the clock for the required 30-day report is February 19, the date of reporting under 10 CFR 50.72 (b) (1) (ii).
The TRG agreed to reconvene on March 4 to review the results of investigative actions and consider root cause.
3.
On March 4, 1992 the TRG reconvened to discuss root cause and the status of repair activities on the Unit 1 CFCUs.
The chairman stated that the dampers on CFCUs 1-1, 1-2, and 1-5 have been repaired.
vmcawmuunarucu Page 32 of 51
,3
+_,---y-r-.-
,3-
DCO-92-MM-N007 RO i
DRAFT:
February 12, 1992 CFCU 1-1 was found to have a loose vane and declared inoperable.
The Unit 2 CFCUs are all operable with only CFCU 2-1 having deficiencies (missing counter weights).
During the discussion of root cause, it was noted that CFCU maintenance work had no QC involvement and no QA surveillance.
The post maintenance i
testing was written up well in the work order packages but, implementation may not have been good.
Investigative actions 5 through 11 were assigned to identify other systems which, like the CFCUs, might not be receiving adequate attention.
The chairman provided a preliminary Barrier Analysis and the System Engineer provided a preliminary root cause analysis (Attachments 1 and 2 to NCR writeup dated 3/9/92, distributed 3/11/92).
No conclusions were made regarding root cause and the TRG agreed to reconvene on March 11, 1992 to further consider root cause land review the results of investigative actions.
4.
On March 18, 1992 the TRG reconvened to discuss root cause and corrective actions of the improper maintenance of the CFCUs which resulted-in reverse installation of the damper linkage tie-bars, the tie-bar being installed on the outside of the damper linkage, missing or inadequate stops, and re-use of locknuts and degradstion of the vane to axle bolting.
The TRG also assigned a new investigatis
'" tion to have the Integrated Problem Response Team provide a copy of the report i
documenting their findings to the TRG.
The TRG agreed to reconvene on April 9,
1992 to assign the corrective actions.
I 5.
On April 10, 1992, the TRG reconvened to review the root cause and corrective actions developed for Licensee Event Report (LER) 1-91-019-00.
The root cause and corrective actions were added to the NCR and applicable personnel were assigned the corrective actions.
See items 1-10 in the Corrective Action section above.
The issues raised by the Senior Resident on thursday, 2/27/92, during an interim exit were discussed and it was determined that the current investigative and l
92NCRWP97MMNarrxw Page 33 of 51 i
- -. = _ _.
4
-4 DCO-92-MM-N007 RO DRAFT:
February 12, 1992 f
corrective actions adequately address his concerns.
The IPRT investigation results are due June 15, 1992.
The TRG will reconvene on June 23, 1992, to review the results of the corrective and l
investigative actions assigned.
6.
On May 19, 1992, the TRG reconvened to bring the TRG up to date on recent events and compensatory actions.
The TRG discussed the observed reverse rotations and BD overhauls since the last TRG (ref.
14), and the proposed revision to STP M-51A to start an additional CFCU if an open damper /reverce rotation is observed.
If this additional backpressure on the damper is sufficient to close it, then the damper would also close upon the postulated LOCA pressure wave (which would be of an even greater magnitude).
Information from Westinghouse currently indicates that the CFCUs would be able to start without a thermal overload trip, assuming up to 400 rpm reverse rotation and degraded (85%) voltage.
Practical experience indicates that with both halves of the BD stuck open, maximum reverse rotation was only approx. 170 rpm, and no problems i
were noted stopping / starting the CFCU.
Preliminary analysis of the shoulder bolt failures by the Plant Metallurgist and TES indicates the primary cause to be high cycle fatigue.
Corrosion and rubbing on the fracture = faces indicates at the fracture existed for a long time.
The conclusion is that any bolts subject to failure would have failed prior to the current point in time and therefore, the remaining intact bolts would not be subjected to failure in the remaining 1
fuel cycle.
Investigations and corrective actions are ongoing; this TRG will reconvene in July 1992.
7.
On June 2, 1992 the TRG reconvened to review the commitments made during the 5/19/92 meeting between the NRC and PG&E.
The commitments were summarized in the Electronic Mail from Jim Tomkins dated May 28, 1992.
Each of the commitments were reviewed l
9arawrmwwxw Page 34 of 51
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DCO-92-MM-N007 R0 DRAFT:
February 12, 1992 f
and a corrective action assigned or verified to l
already exist.
The TRG will reconvene at the chairman's discretion.
8.
On July 22, 1992 the TRG reconvened to review the NOV response dated July 20, 1992.
To fully comply with the NOV response, AE due dates were revised to be consistent with the NOV response. Additionally some AE action statements were clarified.
The following revisions to the outstanding AEs have been made:
a.
AE #02, The TRG determined that the AE was no longer required.
b.
.he following AE ECDs have been changed:
AE #15, new ECD 9/13/92 AE #18, new ECD 9/13/92 AE #21, new ECD 12/31/94 AE #26,-new ECD 12/31/92 AE #34, new ECD 8/31/92 c.
AE #18, Add the line "The HVAC systems used in this context are specifically the CFCU backdraft dampers."
d.
AE #21, The last line should read " Track metallurgical failure analysis of failed bolts and incorporate findings in maintenance procedures ana/or design changes."
e.
AE #20, The line should read "2. QC Director to review active POAs during daily management meetings and will be updated to reflect the findings of the IPRT and TRG."
The following new corrective actions were also identified at the meeting:
f.
Increase System Engineering staff by six positions and expeditiously fill vacancies.
g.
AP A-350 to be revised to include a requirement for Toint Quarterly System walkdown reports to highlight immediate and long-term priorities nncawnnwuse;cs Page 35 of 51
P
~
DCO-92-MM-N007 R0 DRAFT:
February 12,.
1992 and address repetitive problems.
The TRG agreed to reconvene on 8/14/92.
8.
On August 21, 1992, the TRG reconvened to review the progress made on the assigned corrective actions. The TRG wanted to make sure that the actions with ECDs before IRS were on schedule.
The TRG agreed to reconvene on 9/3/92 to review the corrective actions that are scheduled to be completed by 9/1/92.
9.
On September 3, 1992, The TRG reconvened to review the status of the action evaluations associated with this NCR.
In addition to the actions already taken to fulfill corrective action #5, memorandums will be generated to: (1) State the TRG's position that DCPP does not need to provide any " follow-up" training for C-29 and (2) To remind department directors of those subordinates that have not received the training that DCPP had committed to the NRC.
i The TRG Chairman agreed to acquire a hard copy of the memorandum generated by Mike Angus to satisfy corrective' action #13.
Regulatory Compliance will update AEs #29 and #30 to document the locatic-of training session records in this NCR.
The TRG agreed to reconvene after 1R5 to review the remaining corrective actions.
i i
- 10. On October 1, 1992, the TRG reconvened in room 302 of the adminictration building at 1:00 pm PDT to 4
discuss cracking of backdraft damper blades in CFCU.
1-5 and 1-2 found on September 25 and 27, 1992 during planned inspections.
The agenda for the TRG reconvene was:
I a.
description of the new findings b.
implications of these new findings c.
new investigative actions 92NCRWl*,91MMNiM7.KH Page 36 of 51
)
_ ~,
'DCO-92-MM-N007 RO DRAFT:
February 12, 1992 d.
reportability of the newly found conditions.
Five new investigative actions as noted above were identified to assist determination of the previous and current operability of the CFCUs with the identified backdraft damper blade cracking.
i Resolution of the CFCU's condition is a Unit 1 1R5 Mode 4 restart constraint.
The TRG plans to reconvene on Wednesday, October 7, 1992 at 1:00 pm PDT to discuss the status of the identified investigative actions.
- 11. On October 7, 1992, the TRG reconvened in room 316 l
of the administration building at 1:30 pm PDT to discuss the progress of investigative actions identified in the last TRG reconvene.
A blade in CFCU 1-4, VAC-1-BD-46, was identified on October 3, 1992 as having cracks (see ref. 36 and Attachment Three).
Blade samples have been received by TES.
No identical replacement blades are available for these BDs, thus investigative action has been assigned to determine if an alternate material and fabrication method can be identified and a design change specifying acceptable repair details will be issued (see actions in Section V. above).
The TRG will reconvene on Thursday, October 15, 1992 at 1:0L p~
co evaluate the results of identified investigative actions.
I.
Remarks:
None.
J.
Attachments:
None.
+
E 92NCRWM92MMN00DCN Page 37 of 51 f
DCD-92-MM-N007 RO DRAFT:
February 12, 1992 EVENT TWO:
I.
Plant Conditions Unit 1 was in Mode 6 (Refueling) and Unit 2 was in Mode 1 at 100% power.
j IT.
De-~rintion nf Event A.
Summary:
On September 25, 1992, during planned inspection of the 1-5 CFCU during 1RS, blade seven-left of backdraft damper BD-47 was found to have a piece broken about the center bolt hole; see AR A0278039 (ref. 34) and Attachment Four.
On September 27, 1992, during planned inspection of the 1-2 CFCU during 1RS, blade six-right of backdraft damper BD-44 was found to have cracks; see AR A0278376 (ref. 35) and Attachment Four.
On October 3,
1992, during planned inspection of the 1-4 CFCU during 1R5, blade four-left of backdraft damper BD-46 was found to have cracks; see AR A0279388 (ref.
- 36) and Attachment Four.
t B.
Background:
See references 34, 35 and 36.
C.
Event
Description:
l See OE 92-20 (Att. 4).
D.
Inoperable Structures, Components, or Systems that i
Contributed to the Event:
None.
i E.
Dates and Approximate Times for Major Occurrences:
1.
September 25, 1992: Inspection of CFCU 1-5 finds cracks in a BD-47 blade.
1 2.
September 27, 1992: Inspection of CFCU 1-2 finds cracks in a BD-44 blade.
}
vaScRwr92MMNW J(w Page 38 of 51
-y
+ -,
I DCO-92-MM-N007 RO DRAFT:
February 12, 1992 3.
October 3, 1992:
Inspection of CFCU 1-4 finds cracks in a BD-46 blade.
F.
Other Systems or Secondary Functions Affected:
1 None.
G.
Method of Discovery:
1 This condition was discovered by plant personnel during an inspection of the Unit 1 CFCUs.
l H.
Operator Actions:
None required.
I.
Safety System Responses:
None required.
III.
Cause of the Event
)
A.
Immediate Cause:
j The immediate cause of this event was cracking identified in BD-44, 46 and 47 blading during 1R5 CFCU inspections.
B.
Determination of Cause:
1.
Human Factors:
a.
Communications: N/A.
b.
Procedures: N/A.
c.
Training:
N/A.
d.
Human Factors:
N/A.
e.
Management System:
N/A.
2.
Equipment / Material:
a.
Material Degradation:
TBD.
b.
Design: TBD.
92NCR%1*92MMN007)CN Page 39 of 51
DCO-92-MM-N007 R0 DRAFT:
February 12, 1992 c.
Installation:
N/A.
d.
Manufacturing:
N/A.
e.
Preventive Maintenance: N/A.
4 f.
Testing:
N/A.
g.
End-of-life failure:
TBD.
t C.
Root Cause:
TBD.
D.
Contributory Cause:
L TBD.
IV.
Analysis of the Event A.
Safety Analysis:
See OE 92-20 (Att. 4).
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 per NUREG 1022 and determi.2d to be reportable in accordance with 10 CFR 50.72 (b) (1) (li) (B) and 10 CFR 50.72 (b) (2) (i).
See LER 1-92-023 for more information.
3.
This problem does not require a 10 CFR 21 report.
4.
This problem has been reported via an INPO Nuclear Network entry (MI 10117, 10/17/92).
5.
Reviewed under 10 CFR 50.9 and determined event was not reportable under 10 CFR 50.9.
6.
Reviewed under the criteria of AP C-29 requiring the issue and approval of an OE and determined that an OE is required.
See Attachment Two for more information.
9menwr.9 uumo7;cw Page 40 of 51
I DCO-92-MM-N007 R0 DRAFT:
February 12, 1992 V.
Corrective Actions A.
Immediate Corrective Actions:
1.
NECS Engineering in coordination with TES and American Warming and Ventilation to determine if blade R6 in BD VAC-1-BD-44 and L7 in BD VAC-1-BD-47 would have performed their design function in their "as-found" condition (described in ref. 34 and 35).
RESPONSIBILITY:
F.
Ling DEPARTMENT:
NCEM AR A0258408, AE # 40 l
STATUS:
RETURN Blade L4 in BD VAC-1-BD-46, as described in ref.
36, will also be evaluated for performance of its design function in the "as-found" condition.
2.
NECS Engineering in coordination with TES and American Warming and Ventilation to determine whether the remaining Unit 1 and Unit 2 BD-blades i
are susceptible to the same failures as those identified in references 34 and 35.
RESPONSIBILITY:
F.
Ling DEPARTMENT:
NCEM AR A0258408, AE # 41 l
STATUS:
COMPLETE 3.
TES to perform a failure analysis of the BD blades identified urieferences 34 and 35 (consideration should be made for instrumenting damper blades for data acquisition to support the failure analysis).
RESPONSIBILITY:
S.
Friedrich DEPARTMENT: TEMT AR A0258408, AE # 4 2 l
STATUS:
COMPLETE 4.
Mechanical Maintenance to review information on previously identified failed, loose or missing bolting in backdraft damper blading to assist in determining if the recently identified cracking could be attributed to stresses imposed by degraded bolting.
vmcawn9;mwxnacw Page 41 of 51 f
,..,c
=_-._
DCO-92-MM-N007 R0 DRAFT:
February 12, 1992 RESPONSIBILITY: Bob Waltos DEPARTMENT:
PGMA AR A0258408, AE # 43 STATUS:
COMPLETE No relationship between the cracked damper blades and the deficient bolting condition could be l
identified.
5.
Mechanical Maintenance to coordinate with ISI to perform magnetic particle testing of a sample of Unit 1 BD blades.
RESPONSIBILITY: Bob Waltos DEPARTMENT:
PGMA AR A0258408, AE # 44 STATUS:
RETURN i
Testing completed and reported in work order C0105227 (ref. 38).
6.
NECS/TES to identify potential alternate CFCU BD blade material and fabrication method for replacement blades.
RESPONSIBILITY:
F.
Ling DEPARTMENT:
NCEM AR A0258408, AE # 45 l
STATUS:
RETURN B.
Investigative Actions:
1.
Review license and previous JCO commitments for activities to be included in any forced Unit 2 outage resulting from CFCU concerns.
RESPONSIBILITY:
J.
Nolan DEPARTMENT: Regulatory Compliance (PTRC)
AR A0258408, AE # 48 Outage Related? Yes, Unit 2 forced outage.
OE Related?
Yes, OE 92-20.
NRC Commitment? No.
CMD Commitment? No l
STATUS:
RETURN 2.
Review QEs to identify commitments for activities to be included in any forced Unit 2 outage CNCRWY.92MMNCC7 JCN Page 42 oi 51 4
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DCO-92-MM-N007 R0 DRAFT:
February 12, 1992 resulting from CFCU concerns.
RESPONSIBILITY:
N.
Koellish DEPARTMENT: Quality Control (PQCE)
AR A0258408, AE # 49 Outage Related? Yes, Unit 2 forced outage.
OE Related?
Yes, OE 92-20.
r NRC Commitment? No.
CMD Commitment? No 1
l STATUS:
RETURN 3.
Review operating experience for similar events (see section VI.B and C below).
i RESPONSIBILITY:
J.
Nolan DEPI'TMENT: Regulatory Compliance (PTRC)
AR a0258408, AE # 50 Outage Related? No.
OE Related?
Yes, OE 92-20.
NRC Commitment? No.
CMD Commitment? No l
STATUS:
RETURN 4.
Determine if an OE is required, and if required, prepare and present OE to the PSRC for concurrence.
RESPONSIBILITY:
D.
Marburger DEPARTMENT: Regulatory Compliance (PTRC)
AR A0258408, AE # 47 Outage Related? No.
OE Related?
Yes, OE 92-20.
NRC Commitment? No.
CMD Commitment? No l
STATUS:
RETURN 5.
Review previous maintenance history.
Document why past inspections failed to identify cracking in the BD blades.
RESPONSIBILITY:
R. Waltos ECD: 2/28/93 DEPARTMENT: Mechanical Maintenance (PGMA)
AR A0258408, AE # 51 Outage Related? No.
OE Related?
Yes, OE 92-20.
NRC Commitment? No.
CMD Commitment? No STATUS: ASIGND 92NCR%7.92MMNotT1)CN Page 43 of 51
DCO-92-MM-N007 RO DRAFT:
February 12, 1992 4
6.
Determine the feasibility of and, if feasible, perform Unit 2 CFCU BD blade inspections for cracking.
RESPONSIBILITY:
J. Hinds DEPARTMENT: Mechanical Maintenance (PGMA)
AR A0258408, AE # 52 Outage Related? No.
OE Related?
Yes, OE 92-20.
NRC Commitment? No.
CMD Commitment? No l
STATUS:
COMPLETE 7.
Document contact and information received from other plants regarding CFCUs.
RESPONSIBILITY:
D.
Stermer DEPARTMENT: System Engineering (PTEB)
AR A0258408, AE # 53 Outage Related? No.
OE Related?
No.
NRC Commitment? No.
CMD Commitment? No l
STATUS:
COMPLETE 8.
Issue an AT EWR type AR to NECS to request a determination whether continuous operation of all five CFCUs with BDs blocked open is acceptable.
RESPONSIBILITY:
R. Waltos DEPARTMENT: Mechanict Maintenance (PGMa)
J AR A0258408, AE # 59 Outage Related? No.
OE Related?
Yes, OE 92-20.
NRC Commitment? No.
CMD Commitment? No l
STATUS:
COMPLETE 9.
Mechanical Maintenance to determine if BD blade bolting is adequate to assure an acceptable blade connection.
RESPONSIBILITY: J. Hinds DEPARTMENT: Mechanical Maintenance (PGMA)
AR A0258408, AE # 54 Outage Related? No.
OE Related?
Yes, OE 92-20.
92NCRWM2MWKXUJCN Page 44 of 51 l
d
~ _..
- - =. -
DCO-92-MM-N007 R0 DRAFT:
February 12, 1992 NRC Commitment? No.
CMD Commitment? No l
j STATUS:
COMPLETE
- 10. TES to evaluate blade cracking and bolt breakage failure mechanisms based on the operating data collected from instrumentation of CFCU 1-2 BD.
RESPONSIBILITY:
J.
Schletz ECD: 2/28/93 DEPARTMENT: TEMT AR A0258408, AE # 61 Outage Related? No.
OE Related?
No.
NRC Commitment? No.
CMD Commitment? No STATUS: ASIGND C.
Corrective Actions to Prevent Recurrence:
1.
DCP H-47687 to be issued and implemented to provide acceptable repair details for cracked BD blades.
See AR A0279386 (ref. 37) for DCP implementing information.
RESPONSIBILITY:
S.
Khosla NECS ENGINEERING - VENTILATION (NCFM)
AR A0258408, AE / 4 6 Outage Related? YES - 1R5 OE Related?
YES - OE 92-01 NRC Commitment? YES - LER 1-91-019-01 CMD Commitment? YES STATUS:
usT"'R 2.
Mechanical Maintenance to issue an AT EWR type AR to request Unit 1 CFCU BD blade replacement.
RESPONSIBILITY:
J. Hinds DEPARTMENT: Mechanical Maintenance (PGMA)
AR A0258408, AE # 55 Outage Related? Yes, 1RS.
OE Related?
No.
NRC Commitment? No.
CMD Commitment? No l
STATUS:
COMPLETE 3.
Develop a schedule for Unit 1 CFCU BD blade replacement.
92NCRWB92MMN(XT13CN Page 45 of 51
4 DCO-92-MM-N007 R0 DRAFT:
February 12, 1992 RESPONSIBILITY:
J. Hinds DEPARTMENT: Mechanical Maintenance (PGMA)
AR A0258408, AE / 56 Outage Related? Yes, 1RS.
OE Related?
No.
NRC Commitment? No.
CMD Commitment? No l
STATUS:
COMPLETE 4.
Raise RCP stator temperature alarm setpoint for Units 1 and 2 in support of Unit 2 CFCU BD blade inspections.
RESPONSIBILITY:
D.
Stermer DEPARTMENT: System Engineering (PTEB)
AR A0258408, AE # 57 Outage Related? No.
OE Related?
No.
NRC Commitment? No.
CMD Commitment? No l
STATUS:
COMPLETE 5.
Develop an action plan for replacing Unit 2 CFCU BD blades during an unplanned Unit 2 forced outage of sufficient length.
7 l
RESPONSIBILITY:
J. Hinds ECn-5/31/93 DEPARTMENT: Mechanical Maintenance (PGMA)
AR A0258408, AE # 58 Outage Related? Yes, Unit 2 unplanned outage.
OE Related?
Yes, OE 92-20.
I NRC Commitutnt? No.
CMD Commitment? No STATUS: ASIGND 6.
Issue an FC to DCP H-48719 permitting installation of Site-modified CFCU BD blades (part of DCP H-47728) in Unit 2 and specify the required fabrication details for BD blade installation using square washers for mounting.
RESPONSIBILITY:
C.
Pfau ECD: 2/28/93 DEPARTMENT: Mechanical Maintenance (PGMA) i AR A0258408, AE # 62 Outage Related? Yes, 2RS.
OE Related?
No.
NRC Commitment? No.
92NCRuT9?MMN007)CN Page 46 of 51
4 DCO-92-MM-N007 R0 DRAFT:
February 12, 1992 CMD Commitment? No STATUS: ASIGND D.
Prudent Actions (not required for NCR closure):
1.
Post an INPO Nuclear Network entry regarding CFCU inspections, results and evaluations.
RESPONSIBILITY: J.
Nolan DEPARTMENT: Regulatory Compliance (PTRC)
AR A0282461 Outage Related? No.
OE Related?
No.
NRC Commitment? No.
CMD Commitment? No ST/*US:
COMPLETE 2.
Incorporate lessons learned from 1R5 and 2R5 CFCU BD work into DCPP Maintenance procedures.
RESPONSIBILITY:
C.
Pfau ECD: 6/30/93 DEPARTMENT: Mechanical Maintenance (PGMA)
AR A0287497 Outage Related? No.,
OE Related?
No.
NRC Commitment? No.
CMD Commitment? No STATUS:
ASIGND 3.
Document which CFCU BD blades are installed in which BDs (including blade position),
e.g.,
L e-slotted blades versus vendor slotted blades.
RESPONSIBILITY:
C.
Pfau ECD: 6/30/93 DEPARTMENT: Mechanical Maintenance
I i
i 1
4 AR A0287498 Outage Related? No.
OE Related?
No.
l NRC Commitment? No.
CMD Commitment? No STATUS:
ASIGND VI.
Additional Information A.
Failed Components:
None.
92ncawwnuusawacN Page 47 of 51
DCO-92-MM-N007 RO DRAFT:
February 12, 1992 B.
Previous Similar Events:
None.
C.
Operating Experience Review:
1.
NPRDS:
None.
2.
NRC Information Notices, Bulletins, Generic Letters:
None.
3.
None.
D.
Trend Code:
TBD.
E.
Corrective Action Tracking:
1.
The tracking action request is A0258408.
2.
Corrective actions are outage related.
F.
Footnotes and Special Comments:
None.
G.
References:
- 36. AR A0278039.
- 37. AR A0278376.
- 38. AR A0278388.
- 39. AR A0280335.
- 40. AR A0280848.
- 41. AR A0281393.
9:scR4P92WNan xw Page 48 of 51 r
s
. _. _ ~. - _
DCO-92-MM-N007 RO f
DRAFT:
February 12, 1992 4
- 42. AR A0281396.
- 43. ERP 92-9.
H.
TRG Meeting Minutes:
1.
This entry combines the ERP/TRG meetings held between October 15, 1992 and October 23, 1992.
There were 10 meetings held during this period.
l ERP 92-9 (Att. 43) contains the investigative and corrective actions identified during the October 15 through October 23 ERP/TRG meetings.
OE 92-20 (Att. 4) was initially presented to the PSRC on October 21, 1992 as an incomplete document with a request for concurrence on the progress to date.
The PSRC concurred with the information and direction of the OE to that point in time.
On October 23, 1992, a completed draft OE was presented to the PSRC and was rejected due to disagreement on the proposed schedule for removal of CFCU BD blades from Unit 2.
2.
On December 3, 1992, the TRG reconvened in room 533 of the administration building at 10:00 am PST to discuss the results of NDT (mag particle) performed on Unit 1 CFCU BD blades.
Nine additional cracked blades were identified, eight of which had cracks that would likely have resulted in blade failure during a design basis LOCA.
The decision was made to remove all Unit 2 CFCC BD blades.
Maintenance procedures will be revised to incorporate lessons learned.
TES will instrument a BD to assist in root cause determination.
An FC will be issued to permit installation of Site-modified CFCU BD blades (part of DCP H-47728) in Unit 2 and specify the required fabrication details for BD blade installation using square washers for mounting.
The TRG will reconvene on February 1, 1993 to discuss root cause.
+
3.
On February 12, 1992, the TRG reconvened in the Blue Conference Room at 3:00 pm PST.
The TRG l
9?NCHWI".92MMNtU7)CN Page 49 of 51 I
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, t DCO-92-MM-N007 R0 DRAFT:
Febraary 12, 1992 discussed the results of the data obtained from instrumentation of the 1-2 BD.
There is little vibration when the CFCU is in slow speed, but in i
fast speed (normal operation) there appears to be resonant vibration in primarily two modes (bending i
and torsional vibration about two different axes).
The resonant frequencies for these two modes are similar to those found.in the empirical model.
Using the model to evaluate the combination of these stresses, TES estimates a cyclic 15,000 psi at the point of highest stress.
With the material currently in Unit 1 and to be installed in Unit 2, we have a factor of safety of approximately two f
I i
i f
i t
P l
t
+
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i l
4 4
l 6
i Based on these findings, NECS, TES, and the plant have decided to replace the Unit 2 blades during 2RS, in the same manner as we did Unit 1 in 1RS.
TES will continue their evaluations with an actual BD blade (rather than the model) in an attempt to verify the mechanical properties of the new blade material and thereby possibly increase the calculated safety factor.
Under consideration is a design change to add a stiffening bracket to the l
blade for additional margin.
1 NDT testing of all of the original Unit 2 blades showed cracks only in the areas we had already identified visually.
The data from Unit 1 instrumentation appa rs to be represencative, su there are no plans to instrument 2ny Unit 2 CFCU j
BDs.
The TRG will reconvene after 2RS, during approximately the last week of May 1993.
If our evaluations can assure an adequate safety factor, i
j the TRG will begin the process of closing the NCR.
i I.
Remarks:
None.
J.
Attachments:
a 1.
Diagram of Identified Backdraft Damper Blade Cracking for CFCU 1-2 and 1-5.
nucawnnmeuxnxw Page 50 of 51 e
,--4 m.,
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..*.e,,r
f DCO-92-MM-N007 RO DRAFT:
February 12, 1992 2.
OE 92-01, " Containment Fan Cooler (CFCU) Operation With Mechanical Deviations On One Unit 2 Backdraft Damper."
3.
Unit 1 CFCU BD Current and Historical Inspection Results.
l 4.
Operability Evaluation 92-20, " Cracking of i
Backdraft Damper Blades in Containment Fan Cooler Units (CFCU)."
9 3
9.'scRWPS2mtNan n Page 51 of 51
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