ML20147H690
| ML20147H690 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 03/02/1988 |
| From: | Van Brunt E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| To: | Martin J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| Shared Package | |
| ML20147H688 | List: |
| References | |
| 161-00851-EEVB, 161-851-EEVB, NUDOCS 8803090040 | |
| Download: ML20147H690 (5) | |
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Arizona Nuclear Power Pro ect I
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- PMCsNir. Ani20%A te4M@H March 2, 1988 161-00851-EEYB/MRO Mr. John B. Martin, Regional Administrator Office of Inspection and Enforcement U.S. Nuclear Regulatory Ce:missien, Region V 1450 Maria 1.ane, Suite 210 Valnut Creek, CA 94596 5368
Dear Sirs:
subject:
Palo Verde Nuclear Generating Station Unit i Request for Additional Information. Justification for Continued Operation: Re: Inability of CEA $6 to Drop File: 88.A.056 026
Reference:
(a) Letter (16100826.EEVS/JRP), Dated February 25, 1988 from E. E. Van Brunt to J. B. Martin, Justification for Continued Cperation. Inability of CEA $6.To Drop Ajustification for continued operation on Palo Verde Unit I was forwarded in Reference (a).
This was discussed in a meeting at Valnut creek, C4 on February 20, 1988. At the nesting, additional inforEation on Caintenance histbry was requested.
This letter addresses the following issues:
Maintenance History of the Multi Stud Tensioner. Stud Handling Vehicle (MST.SHV) caster bearings Reason for bearing replacement, if replaced I
location of easter bearit,5 repair I
$MffBg plek fAOutes dut[ng replacement Engineerins History for MST.SHV failure In order to address these issuas and as a part of the ANFP Special Plant Event i
Evaluation Report process, extensive research was required.
The course of research included:
A review of all available work orders vuitten s' gainst the MST since' the initill U81 1986.
A review of the Engineering Evaluation Roquests since 1984 on componer.ts classified within the Reactor Coolant systen and containment.
00N 0j 1
Mr. J. 's. Martin Page 2 March 2, 1988 161-00851 ER B/MR0 Interviews with available Maintenance Supervision, Torenen and Mechautes who bearing replacement prior to head lift. performed work on the MST durin and Interviews with a Planner / Coordinator on MST.
responsible for Work Order preparation Review of the MST Technical Manual overhaul the MST.
to determine the scope of requirements to Maintenance History of MST SHV Canter Bearinaa A review of the available work orde was performed to determine the maintenance history of the MST SNV.
Repairs of this type are normallyThis review identified several Work orders on the M performed as
- Minor Maintenance," since the M5T is classified as a tool.
In the case of Minor Maintenance on tools no documentatio'n of activities performed is required. Therefore, the exact number of bearing repairs is indeterminate.
W review of Vork Orders periermed on the MST identified three work orders of major significance.
1)
In 1986 the MST was r6 built in the fuel building in preparation for refueling:
tyl[ndersonceeveryfouryeaft.The manufacturer of the MST re During this process, the MST was overhauled
)
in order to prepare it for the first refuelina outage.
As part of the work performed, three er four caster bearinge were replaced due to their being "locked.up".
The easter bearing or baaring assembly is an integral unit consisting of a bearing housing, ball bearings, a roller ball, a felt' ring, and a cap. A total of five or six caster bearings were locked up but there were only spare parts for three or four bearings.
Interviewees have stated that during the replacement of the three or four easter bearings in the fuel building they did not notice any small ball bearings falling out of the caster bearing.
The toch manual reconsenda that the caster bearings be tested for freedom of movement. Maintenance personnet removed a caster bearing that was locked up and took it apart in the fuel i
building in an attempt to repair it.
It was not repaired due to broken ball bearings within the bearing housing. No ball bearings were lost.
It was at that time ti,at the design of the caster bearing was first recognised by the maintenance personnel doing this work.
(The vendor's technical manuel. dose j
not include any specifics on the design of this bea' ring).
Just prior to refueling, the MST was moved into the containment building on to its stand though two caster bearings still required future replacement, I
l
^
l Mr. J. B. Martin Fase 3 krch2,1M8 161-00651-IIVB/MRO 2)
A work order was written for performance of the Reactor Vessel head lift in October, 1987.
During final preparation of the Kst for the head lift, the back ordered replacement bearings arrived.
Verk vae accomplished prior to establishment of cleanliness zone 3 and p-tor to the head lift, keplacement 1
of two bearings was done insido containisent on the MST storage stand.
Maintenance personnel that performed the replacement were interviewed and stated that the first castar bearing removed from the SHV came apart during removal, spilling numerous ball bearings.
The caster bearing that case was located such that it was at the farthest position from the upper guide apart structure pit, 7' ; 9 1.
Th5y cleaned up all the small ball bearings found on the MST and on t r
' s r and they disposed of them. The MST was then placed o
on the Reactor I m,
head and the studs were detensioned. The maintenance crew found mors 21 bearings at that time on the MST.
4 station setvices to clean the reactor head and pool seal area prior to renovalThey r of the head.
The cleaning was then accomplished.
It is possible that one of the ball bearinn lost at the time the work
..,. r.
order was perforued while the MST vas on the steat Sund its way into CEA 56.
investigation is continuing en Unit 1.
The 3) n a MST was inspected subsequent to the recent discovery of the ball bearing in the CIA guide tube in February,1988.
During this Unit 1 inspection seven (7) easter bearin6s were determined to be faulty (there at's a totgl of 16 C& Stet belfings on the M$I) and removed in the containment building.
Thore were no reports that any ball bearings came apart in the course of this bearing removal.
The caster bearings were determined to be faulty if they exhibited "too much" movement or "no" movement.
The fadty caster bsarings all showed no movement.
The seven caster bearinge v*Te removed in containment, taken to the service building and disassembled.' Three of the caster bearings showed no wear.
Two of those were replaced and one returned to service. The other four exhibited a considerable amount of voar (including "destroyed ball bearings, split ball bearings, an insufficient number of ball bearings and a fractured bearing cup").
ENGINEER 1NC HISTORY OF MST.SHV Fall.URES A review was performed of the Engineering Evaluation Requests since 1984 for the reactor coolant system components and the contain:aent building.
There are no records of Engineering Evaluation Requests to evaluate any MST SHV ball bearing losses.
BEARING TAliURE INFORMATION. VENDOR i
A representative of X1eiber and Schulz, the licensed broker for Klochner Recorit (the manufacturer of the MST) was contacted. He stated that there is no record of bearing failures of the type that OGCE ftd AC M CS (loose bear {ngs).
Star Manufacturing the manufacturer of the bearing, is being contacted to provide an assessment of the failure mode experienced at PVNGS.
I
v 1
Mr. J. B. Martin Page 4 March 2, 1988 161-00851-EEVB/NR0 EG001Y Results of the investigation to date have found one instance where small were released to the containment during bearin$ caster replacement on the MS bearings in October, 1987 prior to head removal.
post maintenance activities in the units. Purther investigations are continuing on The results of the investi ation to date cdd weight to the conclusion reached in the 5
JCo, Reference (a) and adds more conclusive evidence to the source of bearing release from the bearing casters.
ANPP continues to believe that, as stated in the JCO, identified with the foreign material exclusion pro 5 ras in that it was notareas of concern have be er intended to exclude material from designed component failure e.g.,
KST caster bearing failure.
In addition, as stated in the JCO, the caster bearings on the NST have been replaced with a new design that Vill OllElRAtt 2 f&llure of this type significant information becomes available If any notify you.
during further investi ation, ANPP will 5
Very truly ours.
.S.
4ULTG^JL
~
r E. E. Van Brunt, Jr.
Executive Vice President Project Director EEVB/KRO/ls Attachment cc:
- 0. M. De Michele J. G. Haynes G. W. Kni hton 5
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