IR 05000275/1991025
| ML16341G336 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 10/17/1991 |
| From: | Huey F NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | |
| Shared Package | |
| ML16341G335 | List: |
| References | |
| 50-275-91-25, 50-323-91-25, NUDOCS 9111040079 | |
| Download: ML16341G336 (20) | |
Text
U.
S.
NUCLEAR REGULATORY COMMISSION REGION V
Report Nos:
50-275/91-25 and 50-323/91-25 Oocket Nos:
50-275 and 50-323 License Nos:
OPR-80 and DPR-82 Licensee:
Facility Name:
Pacific Gas and Electric Company 77 Beale Street, Room 1451 San Francisco; California 94106 Oiablo Canyon Units
and
Inspection at:
Oiablo Canyon Site, San Luis Obispo County, California Inspection Conducted:
Weeks of. July 29 and August 19, 1991, and September 20 through October 7, 1991 Inspectors:
N, J, Royack F.
Gee, August
It 20, 1991 P. Galon, July 29 through August 2, 1991 Approved By:
~Summar:
F, R.
Huey, C ie
,
Engineering Section
)0 ]p Oat Sag e
I~ns ection conducted durino the weeks of Ju~l 29 through August 2, Ku ust 9 throu h Auaust
and Se tember 20 throu R 6ctober 7,
Areas Inspected:
The inspection included a review of randomly selected facility modifications, design change packages, licensee efforts in identifying cracked pressure blocks in Westinghouse ASL transformers, non-licensed staff training records, and open items identified during previous NRC inspections.
Inspection procedures 37701, 37702, 41400, and 92701 were used as guidance for this inspection, Safety Issues Management System (SINS) Items:
None
"O"OO7~ ~5ooo2>5
>SO18 PDR AD<<" "
p5n
Results:
Conclusions:
This inspection identified a weakness within the area of operability evaluations.
Two occasions were identified where earlier operability evaluations would have been beneficial',
An operability evaluation, addressing Unit 2 CFCU LOCA air flow conditions or degraded bus voltage, had not been performed after the licensee had observed significant CFCU high speed motor amperages following coolino coil cleaning and air inlet vane adjustments.
Subsequent operability evaluations and analysis indicated that operations at the higher CFCU motor amperages and pre-cleaning air
cooler conditions would not have degraded the systems ability to perform its design safety function, for Unit 1 or 2.
2, An operability evaluation, addressing potential seismic concerns, was not performed for safety related 4kv/480v h'estinghouse ASL dry type transformers, after it was identified to the licensee that there existed a potential problem of cracked pressure blocks in the transformers.
A subsequent operability evaluation determined that the Mestinghouse ASL transformers in Units 1 and 2 are capable of performing their design basis function with the identified potential problem of cracked pressure blocks.
Engineering management needs to ensure that events or operating occurrences from one Unit are properly evaluated for their impact on the other unit, Contributing factors to the lack of complete documented operability evaluations appears to be:
1; Lack of a clear guidance for the performance of operability evaluations.
2.
A weak communications process between site engineering organizations and corporate design engineering groups, 3.
Corporate design engineering groups not receiving, trending, or analyzing test procedure results, Summar~of Violations and Oeviations:
No violations or deviations were identified during this inspection, Open 1tems Summa'
Three open items were closed during this inspection, One new item was opened during this inspectio DETAILS Persons Contacted PGSF
"S. Santon, Plant Engineering Director 0J, Bouchard, Regulatory Compliance
"Y. Burgess, System -Engineering Director
- B. Giffin, Yianager, Maintenance Services
- J. Griffin, Senior Engineer/Regulatory Compliance S, Hamilton, Unit Supervisor/Design Control
- R. Hess, OPEG/Assistant Onsite Project Engineer
- S. Fridley, Plant Operations Director
- R, Kohout, Manager, Emergency/Safety Services
- P, Lang, QC/Senior Engineer
- C. Pendleton, Systems Engineer V. Smart, Training Coordinator/GC
- D. Taggart, Director/QP8A; QA
"J. Townsend, Vice President
-
DC Operations and Pl N. Tresler, Project Engineer NPG/NECS NRC ant Manager 4*Yi. Royack
- F. Gee
- P, Galon
" Indicates Persons attending Exit Meetings on August 2 or August 23, 1991, 4 Indicates Persons on the October 8, 1991 telephone exit meeting.
The inspectors conducted interviews with other members of the PGSE staff during the course of this inspection, Introduction The purpose of this inspection was to evaluate the licensee's design modification process, evaluate recent facility modifications, review the licensee's continued effort in identifying cracked pressure blocks in Westinghouse ASL dry type transformers, evaluate licensee non-licensed staff training, and to follow-up on NRC identified open items, Design change packages which were reviewed included a modification to the Unit 2 letdown system, a proposed class II duct repair to the containment fan cooling unit ducting, a modification to the chemical and volume control system (CVCS) letdown piping, and concrete installation for the Unit 2, 2-3 emergency diesel generator, Diablo Canyon Power Plant had purchased two Westinghouse ASL dry type transformers from Washington Public Power Supply System (WPPSS)
under
purchase order 728800.
Subsequ'ently nn Hay 13, 1991, WPPSS notified the NRC of a potential
CFR 50,55(e) deficiency concerning cracked insulators in the transformers.
This inspection'ncluded a review of the results of OCPP and Westinghouse inspections of Westinjhouse ASL transformers at OCPP.
Non-licensed staff training records were reviewed for General Construction engineering staff and mechanical maintenance personnel, Open/follow-up items identified in previous NRC inspections were reviewed
'for closure.
Open items 91-01-02 and 91-01-03 were closed during this inspection, Design Change Packages (37701 and 37702)
The following design change packages (DCPs) were reviewed by the inspector:
P-45756 Replacement of socket welded elbows in Unit
CVCS letdown line with butt welded elbows.
P-46752 Replacement of socket welded elbows in Unit 2 CVCS letdown line with butt welded elbows and replacement of a pipe coupling and adjoining piping, J-44859-RO Installation of instrumentation and data acquisition system to observe the CVCS letdown line.
EC-44295 H-47115 Nodifications to turbine building structure to facilitate the installation of sixth diesel generator.
Repair of holes in class 11 containment fan cooler unit ducting in Unit l.
Based on the review of the above design change packages and walkdowns of accessible areas the inspector made the following observations.
CVCS Letdown Line Modifications:
Design change package P-45756 appeared to be completed and performed in accordance with Diablo Canyon procedure NFNP-3,6 DC, Diablo Canyon Power Plant Design Changes, Design change Package P-45756 was initiated in response to cracking in welds in the Unit 2 CVCS letdown lines.
Design change package P-46752 appeared to be in compliance with Diablo Canyon procedure NEAP-3,6 OC.
Design change package P-46752 was initiated in response to past Unit 2 letdown line elbows and coupling cracking, The initial investigations of the first p~oblem indicated that corrosion fatigue was initiated from inside of the crevice area of the socket welds.
This modification would remove the crevice and possibly lessen the likelihood of new cracking, The inspector noted, during the review of OCP P-45756, that licensee comments provided for the response to question number nine of the "Design
Review General guestions" did not clearly establish material equivalency.
The inspector reviewed Diablo Canyon documentation and conducted interviews with the piping engineer who performed the evaluation and determined that the replacement material for the butt welded elbows and pipino were equivalent to the original socket welded elbow material.
Review of OCP 46752, by the inspector, identified that an F SAR Document revision requirement check block, for 2-Si~-46752, had been missed, The inspector also noted that the licensee's comments provided for the response to question nine of the "Design Review General (}uestions" did not cleat ly establish material equivalency.
The materials were the same materials as noted in DCP P-45756; therefore, the inspector concluded that the materials were equivalent, Containment Fan Cooler Units:
The inspector reviewed OCP-47115, NCR DCl-TN-8051, Rev. 00,
"CFCU duct cracks",
dated August 21, 1991, STP-Yi93A "CFCU Test" for Units 1 and 2, and action requests associated with the CFCUs.
The inspector noted that:
a)
the STP-H93A high speed, motor amperage data for after cleaning and adjustment of the Unit
CFCU had decreased nearly 33%,
from highs of 295. to 315 amps down to 195 to 200 amps; (b)
the post cleaning and adjustment high speed motor amps were approximately the same as, or lower than, the slow speed motor amps, 195 to 200 amps; and (c)
the pre-cleaning and adjustment motor amperages, for Units
and 2, were continuously operating within 10% of the. name plate rating of 333 amps.
Based on the data the inspector questioned whether an operability evaluation for the Unit 2 CFCUs had been performed, for degraded bus voltages and high CFCU cooler differential pressures, since the present Unit 2 CFCU high speed motor amperages were at or near the Unit
CFCU pre-cleaning and adjustment motor amperages, and that the Unit 2 cooler unit differential pressures were close to the Unit 1 pre-cleaning differential pressures.
During the period of the inspection the licensee provided the inspectors an operability evaluation which indicated that the CFCU uni ts would be able to perform their design safety function during a
LOCA condition and/or a degraded bus voltage.
The licensee's operability evaluation also conclu'ded that the CFCU motors were able to be operated continually at or near the name plate amperage without damage to the motor.
The inspectors reviewed the licensee's operability evaluations and concluded that the evaluation appeared to be accurate and have a sound engineering basis.
The licensee. provided additional documented information indicating that decreased Unit
CFCU motor amerages were identified, evaluated, and resolved by plant engineering.
The inspectors reviewed and concluded that the documentation and justification for decreased CFCU high speed
motor amperage appeared to have sound engineering basis and that no violations or deviations'ere identified.
Design change package OCP EC-44295 provides for modification to the turbine bui ldino structure to facilitate the installation of the sixth diesel generator (2-3),
The inspector's review of DCP EC-44295 concluded that the package was prepared in accordance with DCPP Procedure No ~ 3.6 OC, "Diablo Canyon Power Plant Design Changes" and that no violations or deviations were identified, Cracked Pressure Blocks ( Insulators)
in ASL Transformers Diablo Canyon Power Plant (OCPP)
was notified of a potential
CFR 50,55(e) deficiency concerning cracked insulators (pressure blocks) in h'estinghouse ASL dry type transformers.
OCPP had purchased two ASL 1000 KVA transformers from WPPSS, under purchase order 728800, as spare transformers for Units 1 and 2, Six ASL type transformers were originally purchased from Westinghouse and installed in Units 1 and 2; each unit has three transformers.
The transformers are used in the 4Kv/480volt vital busses F,
G, and H in the respective units.
The pressure blocks are located at the top and bottom of each primary coil.
They are situated between the pressure plate and the primary coil.
There are six pressure blocks at the top and six pressure blocks at the bottom of each of the three primary coils'ach transformer has a total of thirty-six pressure blocks.
The transformer coil is approximately four feet in lengthen The compressive forces that hold the transformer coils in position act through the pressure blocks.
Each pressure block is made of solid porcelain material and has a varnish coating on the surface.
Cracks on the pressure blocks are identified by visual inspection.
In response to the potential problem of cracked pressure blocks in the Westinghouse ASL dry type transformers, DCPP initiated an action request A0236940 and a nonconformance report OC0-91-EN-N063, revision 00, to resolve the potential deficiency.
Diablo Canyon Power Plant personnel conducted an inspection of the insulators in July, 1991, of the two transformers in the warehouse, and Westinghouse conducted an independent inspection of the same transformers, during the week of August 5, 1991, to determine if cracking existed in the transformer pressure blocks, Inspection of the Unit 2 transformer pressure blocks was scheduled for the outage starting September 1991.
The inspector was informed that the Unit 1 transformer had a different type of pressure block than the pressure blocks used in Unit 2 and the spare transformers.
The Unit
pressure blocks are shorter in length and have only one rib, whereas the Unit 2 and the stored transformers have a taller pressure block with 5 ribs'he inspector reviewed the results of the DCPP and Westinghouse inspections for cracked pressure blocks in the two transformers that are in storage.
The inspector identified that the Westinqhouse inspection team identified eleven cracks in the top and bottom pressure blocks for all three coils of one transformer and one crack in a pressure block at
the bottom in the other transformer and that the licensee's 'inspection identified five cracked pressure blocks in one transformer and none in the other.
The licensee's inspection of the space transformer pressure blocks occurred prior to Westinghouse inspection and was not a
comprehensive inspection and therefore did not identify all of the cracked pressure blocks.'uring the Westinghouse inspection of the, transformers, the Westinghouse inspection team provided the licensee with guidance in identifying cracks in pressure blocks, The inspector verified that the licerisee personnel were trained in the identification and recognition of cracked pressure blocks.
The inspector verified that the pressure blocks in the, Unit
transformers were different than the pressure blocks in Unit 2 and the spare transformers.
The inspector questioned whether the qualification supplied with the 'purchase order documented the qualification of both types of insulators for safety service.
Ouring a-subsequent inspection of the Unit 2 F, G,
and H 4Kv/480vol,t transformers, the licensee identified one 3/4 inch hair-line
,
circumferentially oriented crack in one pressure block in the F
transformer.
The licensee is evaluating the cracked pressure block and has committed to provide a justification for its continued use or replacement.
The inspectors noted that an operability evluation, addressing the performance of cracked pressure blocks during a seismic event,'ad not been performed for the Units 1 and 2 4Kv/480 volt Westinghouse ASL transformers.
On September 19, 1991, the licensee provided an Operability Evaluation (OE) 91-05RO, "Units 1 and 2 Westinghouse 4160 to 480 volt pressure block cracks".
Operability Evaluation 91-05RO concluded that the Unit
transformers are qualified based on previous qualifications of larger but similar transformers and that these transformers would remain operable during a design basis. seismic event, The inspectors concluded that Operability Evaluation (OE) 91-05RO appears to be adequate at this time.
In a meeting between the licensee and the inspectors, held
.on October 7, 1991, the licensee provided documentation verifying that the original equipment qualifications for the Westinghous'e ASL transformers were applicable to both Unit 1 and 2 pressure blocks.
In addition, the licensee presented an independent licensee analysis indicating that original qualifications were conservative and that the pressure blocks would be capable of performing their design function during a design basis seismic event, The inspectors reviewed the documentation and concluded that qualification of the transformer and pressure blocks'was within the envelope of the original qualification packages.
The corrective a'ctions for resolution of cracked pressure blocks for Units
and 2 will be the subject of future inspections.
(Followup Item 50-275/91-25;01).
Future inspections should review:
a)
Action Request A0236940,
b)
Nonconformance Report DC0-91-FY-N063, c)
Resolutior, of Unit
and 2 cracked pressure blocks.
Non-Licensed Staff Traininp (41400)
Non-Licensed staff training programs, requirements, and training and qualification records were reviewed for General Construction engineering staff and mechanical maintenance staff for the period of August 1989 through July 1991, The Civil-Field Engineer II and III training records were current and in compliance with General Construction Procedure GCP-2.2 and General Construction Training Matrix, Additionally, the records were reviewed for qualification, and clarity of responsibility descriptions.
Mechanical Yaintenance training records were reviewed to determine if training in the area of the use and issuance of measuring and test equipment was addressed in response to mechanical maintenance MSTE issuance and use problems noted in NRC Inspection Report (50-275, 50-323/90-29),
It was noted that MSTF training was provided for all mechanical maintenance personnel on February 26 and 27, 1991.
The inspector concluded that the. licensee appeared to be providing non-licensed technical staff personnel training sufficient to prevent events or occurrences from taking place, and provided additional trainino based on lessons learned from events or occurrences.
0~en Items (92701)
50-275 50-323/91-01-02 Lack of Appropriate Procedure For InstaT~e PDP Circuits Justification for Continued Operation (JCO) 89-13 addressed the use of the positive displacement charging pump (PDP), which would have been used in the event of a fire in the centrifugal charging pump (CCP)
room.
The JCO stated that a starting circuit for the PDP ran through the CCP room, and could be disabled if necessary during a fire.
The inspector noted that the need to address PDP starting circuits, which may have been disabled by a fire, had not been addressed in the appropriate procedure, Rev.
8 of OP AP-17, "Loss of All Charging."
The licensee agreed to review the 'procedure to address actions required for associated circuits of the PDP.
The inspector has reviewed the licensee revision 10 of OP AP-17, "Loss of All'harging," and the licensee's'ormal closure package, dated August 9, 1991, and has determined that the current revision 10 and closure package adequately address the condi tion of a failure of PDP to start from
.
control room panel YB2.
Procedure OPAP-17 has been revised to state "If the PDP will not start from control room panel VB2, then start the PDP locally at its breaker (52-HG-11)."
I Open item 50-275, 50-323/91-01-02 is closed,
50-275, 50-323/91-01-03 Plugged Fire Protection Sprinklers As a result of a fire which occurred in the security system diesel generator room, the licensee determined that a portion of the'prinkler system piping just outside of that area was plugged with corrosion products, and would not have functioned if required.
The licensee stated that the corrosion products had built up in a vertical'eg of the piping would have significantly restricted flow.
Also, the licensee considered that the plugging was a result of infrequent inspections by fire protection personnel of the security diesel and security diesel building.
The licensee root cause analysis as documented in nonconformance report, NCR OC0-90-55-N079, has determined that:,
1)
Rav. water. from the open reservoir was used to fill the security diesel generator area fire sprinkler piping, The water from the reservoir was not purified or filtered and, therefore, potentially contained silt.
2) The sprinkler piping system had not accounted for the use of unfiltered or unpurified raw water; therefore, reverse bends were not included on sprinkler drops in the original design, The licensee will continue to investigate the inclusion of reverse bends in sprinkler drops in future fire protection designs.
The licensee's investigation to date has not concluded that reverse bends in sprinkler drops would guarantee the elimination of sprinkler head silt clogging.
3) The sprinkler heads had not been inspected since installation.
The inspector verified the licensee's immediate and investigative corrective actions:
Immediate a)
An hourly roving fire watch was established.
b) Mork order C0078973 was issued to flush sprinkler piping branch lines back to valve FP-2-359.-
c) Analysis of the water quality of the fire protection system determined that particulate matter carryover from the open reservoir is minimal with the recently adopted reservoir maintenance policies.
This has been documented in PGSE Chron.
no, 140507-,
Investigative a) Conduct inspection of power plant fire protection sprinkler piping pendants to determine if other similar conditions exist.
The licensee did not identify any additional blocked sprinkler heads,-
Performed under NCR-90-55-N079 and AR A0214210.
b) Action request, AR A0-228-335, was written to evaluate the inclusion of reverse bends in future fire protection sprinkler piping designs for NFPA code complianc The inspector also reviewed a formal closure package for this item, dated July 23, 1991, and determined that all issues identified for this open item have been addressed, Open item 50-275, 50-323/91-01-03 is closed.
50-323/90-31-1 Inade9uate Root Cause An~al sis for MuTt~ip e Socket Weld FaiTures Diablo Canyon Unit 2 had experienced four socket weld failures on two of three chemical and volume contr'ol system (CVCS) letdown orifice lines, during the period of June, 1989 and December, 1990.
All of the cracks were discovered at socket welds of fittings betwen the'estricting orifices and the letdown stop valves.
An NRC inspection, documented in Inspection Report No. 50-275 and 50-323/90-31, was conducted to evaluate actions taken by the licensee in determining the root cause of the multiple weld cracks and leaks found on the Unit 2 CVCS letdown lines, NRC Inspection Report 90-31 concluded that the 'licensee had not performed a complete root cause analysis of the CVCS letdown line crackino problem.
The licensee subsequently performed a
"Summary Event Response Plan Report, Event Response Plan 91-2, CVCS Letdown Line Identified Leakage,"
which included a root cause analysis, The licensee's root cause analysis concluded that the socket weld failures were caused by vibrations induced by a failure of a pressure transmitter/controller and subsequent damage to a letdown line orifice, The inspector reviewed the root cause analysis and concluded that the analysis had a sound engineering basis and that the conclusions were acceptable, Open Item 50-323/90-31-01 is closed, Exit Neetinoes An exit meeting was conducted on August 23, 1991, with members of your staff as noted in section 1, of this report.
During the exit meetings the inspectors findings and issues were discussed.
The licensee's staff concurred that an operability evaluation for the Unit 2 CFCU should have been performed and documented and that the degraded bus voltage analysis for the CFCU should have been performed, Licensee staff members indicated that the issue of operability evaluations has been a licensee identified problem, The licensee stated that a
new procedure is in the review process which they feel will centralize and focus issues to ensure that all aspects of a problem are addressed.
The licensee, also, concurred that a contributing factor to the operability evaluation problem could have been inadequate communications between onsite engineering and corporate design engineering groups, A second exit meeting was conducted on October 8, 1991, to discuss the operability evaluatior of the Westinghouse ASL transformers,