IR 05000271/1990012
| ML20062H033 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 11/19/1990 |
| From: | Blumberg N, Drysdale P NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | |
| Shared Package | |
| ML20062H032 | List: |
| References | |
| 50-271-90-12, NUDOCS 9012040051 | |
| Download: ML20062H033 (14) | |
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S. NUCLEAR REGULATORY COMMISSION
REGION I
. Report No.:
50-271/90-12
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- DocketfNo.:
50-271-License-No.:
OPR-28
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Licensee:
Vermont Yankee Nuclear Power Corporation-
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Brattleboro, VT 05301
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-r Facility Name: Vermont Yankee Nuclear Power Station
_ Inspection:At: Vernon, Vermont m
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Inspection Conducted:
~' October'T
"5, 1990
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- Inspector:
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P. DrysdaTe,. Sr. - Reactor Engineer, OPS,. ORS
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2 Approve'd by:
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TBTumberg, Chief-
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Operational Programs-Section f -
Operations ~ Branch, DRS-
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' Inspection ~ Summary: _ Inspection;on October 1-5, 1990-(Inspection Report No.
50-271/90-12)
y LArea's: Inspected:
Routine announced safety inspection by=one region based
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inspector to. review the status of/ unresolved items'and maintenance program
- weaknesses identified in the maintenance' team ' inspection (Report. No. 50-271/ -
189-80)L ti
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Results: No deficiencies were identified._'Alicunresol~ved items' identified in
NRC inspection.50-271/89-80: have:been; satisf actorily) resolved by the~ licensee.
Seven maintenance? program weaknesses:have_been_ adequately addressed and. improve--
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- ments in these areas havelbeen implemented, or'are-in progress.
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DETAILS-1 0_ P_ersons Contacted
Vermont Yankee-Nuclear Power Corporation
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J.~0urborow, Operations Engineer
- R. Loprior, Maintenance Supervisor-R. McCullough, Assessment Coordinator
- R. Pagodin, Technical Services Superintendent D. Phillips, Sr. Electrical Engineer
- D. Reid,.. Plant Manager
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.E. Taintor, Quality Assurance-Coordinator.
- R. Wanczyk, Operations Superintendent i
M. Watson, Sr,xI&C Engineer
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T. Watson, I&C Supervisor
' Yankee Nuclear Services Division
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'*R..Gippardt, QA Supervisor United States Nuclear Regulatory Commission E*H. Eichenholz, Sr. Resident Inspector
T~~Hiltz, Resident Inspector
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(Duringthe-courseof_theinspection,theinspectoralsocontactedother
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members of the111censee % Operations, Technical and Qual % Assurance staff.
- Denotes those present at.the exit meeti_ng on October 5, 1990.
- 2.0 1 Background
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The NRC-maintenance team inspection (MTI), report 50-271/89-80, identified
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one. Violation, three unresolved-items, and seven maintenance program:
weaknesses.
This report provides a current statusion all findings from the MTI an'd I
. consolidates-in one location all_inspe'ction activity conducted to_date.to follow-up on these findings.
' 3.0 Review of. Maintenance Team Inspection-Findings
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'To: evaluate the : licensee's. response to the MTI' findings, the inspector;
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inter' iewed representatives and reviewed documentation -that was revised v
or initiated in response to the findings. The resolution of some. findings a
~ resulted in ~long. term project ef forts which sxtended over several months or years.
If_the completion of activities in response to the MTI findings had not.yet been completed, the inspector identified sufficient management l
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commitments to-implement activities and establish goals to ensure that the activities are tracked and progress monitored to ensure timely completion.
- The documentation reviewed'to verify items described in this report are listed in Attachment A.
In some cases, MTl findings have been closed by previous inspection activity.
Their reporting here serves to consolidate l
and summarize the total of activities to date conducted to resolve the MTI
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findings.
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4 '. 0 Follow-up on licensee's actions __to items previously identified in the Maintenance Team inspection (IP 25597)
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4.1 (Closed) Unresolved Item 89-90-01 - Potential for peeling drywell I
paint to clog the ECCS pump suction screens
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The potential for the drywell liner topcoat material to adversely
effect ECCS pump performance was originally questioned in 1983 by the NRC resident inspectors af ter a tour of the drywell revealed that large areas of the topcoat (epoxy paint) had blistered, peeled away,.
and fallen to the bottom of the drywell. The' inspectors' concerns.
were. increased during a subsequent inspection when another tour of
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the drywell revealed approximately 5% of the upper drywell topcoat had peeled away.
The licensee's evaluation. indicated that clogging of:the ECCS pump suction strainers was not credible.
Further NRC inspector. concerns were expressed after it.was determined that
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approximately 20% of the upper drywell surfaces had peeled away and
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excessive debris was accumulating at the bottom of the drywell.
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licensee responded.by correspondence (letter VY 89-124, 7/1/89) to an NRC-request for formal documentation of the. bases for their evalu-
- ation of this issue, and for' the-establishment of site instructions Lto; conduct periodic inspections, scraping.'away peeled areas as neces-
- sary.
UNR 85-40-02 was closed by NRC inspection report-no. 50-271/
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87-02-after the licensee's: actions were determined to be. adequate.
During the maintenance team inspection in 1988, it was noted by visual inspection that many additional iarge areas (up to 1. f t. in
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diameter) of peeled and chipped paint existed on drywell surfaces.
UNR 89-80-01 was generated due to inspector's concerns regarding both the amount of paint debris; generated after an 18 month operating cycle, and the need for further NRC review of theylicensee's evalu-ation of'the potential for ECCS suction screen clogging.= On August t
2,'1990, the NRC (NRR/EMCB) issued the results of.a safety evaluation ~
l performed to assess this potential, The report concurred with the licensee'.s evaluation and concluded that the amount of epoxy paint material'likeiy to be transported to Residual Heat Removal and Core
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Spray sys'.em pump strainers during post-LOCA conoitions would be
insufficient to adversely effect pump performance.
This evaluation.
is contained in Attachment 'B'
to this report.
Based upon these results, this item is close _
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4.3 Unresolved Item 89-80-02, Maintenance team inspectors developed a concern about personnel access to the drywell during transfer of spent fuel since lethal dose rates could be present in some locations if a postulated fuel drop accider.t occurred.
Drywell access controls during refueling were also a general concern expressed by Inspector Follow Item 88-02-03.
NRC inspection report 50-271/89-16 addressed this UNR; report 50-271/90-06 addressed both the UNR and the IFI and closed the IFI; and report 50-271/90-09 closed this UNR.
4,4 Unresolved Item 89-80-03 concerned the need for strengthening admin-istrative controls over "tagouts" to specify methods for adding addi-tional work parties to an existing tag.
This item was closed by NRC inspection report 50-271/90-05.
4.5 Violation 89-80-04 identified three instances of the licensee's failure to fbT17w procedures, for example, by not using the most current revision of calibration data sheets to document the calibra-tion of a torque wrench, The corrective actions taken by the licen-see to address this issue were reviewed by the NRC and the violation was closed in inspection report no. 50-271/90-05 after it was deter-mined that the specific deficiencies had been corrected and that appropriate revisions to administrative procedures had been made to prevent recurrences.
However, after the MTI, one incident of out-of-date data sheets were noted to be in use at the site.
In addition, in August 1990, the plant operations department authorized and issued a change to aux-iliary operator round sheets adding an item to be checked during rounds.
The change was made by a temporary clerk on a version which did not contain the last change. When copies of the form were added to the operations department files, forms which did contain the previous change were removed from the files and destroyed.
This caused auxiliary operators to perform rounds for 4 days using in-correct round sheets, Potential Reportable Occurrence (PRO)-26 was issued to determine if this incident was reportable to the NRC; however, it was not.
The inspector reviewed the existing administrative controls and the long term corrective actions identified in the licensee's response to violation 89-80-04 (letter BVY 89-58, June 30, 1989) to determine if current instructions for processing revisions were adequate to prevent the use of outdated forms to perform work or to create official records.
The inspector also interviewed the maintenance, I&C, and operations department managers, supervisors, technicians, and administrative personnel to determine if cheir current-practices aid level of understanding of current requirements were consistent with existing administrative procedures, No instances of improper practice or inadequate administrative control were identified. The incident with the operator round sheets was caused by a temporary administrative clerk who inadvertently went to the wrong location to
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obtain what she thought was the most recent version of this form.
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Also, all_ departments on site perform regular monthly audits of
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procedure files to ensure that they contain only the most recent revisions.
The QSD auditors on site also perform random audits-of
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procedure files for the same purpose.
The ir.spector determined that-this incident was isolated, that the potential for recurrence is low, and-that no additional actions by the licensee are considered neces-sary. at' this time.
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4.5 Weakness #1; Lack of comprehensive and formally documented mainte-nance plan and policies:
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The inspection team found that the licensee did not have a unified comprehensive document or set of documents that clearly spelled out
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policies, objectives, and other elements of the plant!s maintenance-
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program. _The maintenance program was scattered in various admin-istrative and departmental procedures, instructions, flow charts, etc., which also contained the organizational structure, personnel responsibilities, and duties.
In addition, no corporate directive or policy statement existed which required the establishment-of a
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comprehensive maintenance' plan. -Although the elements of an adequate
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main _tenance' program appeared to be in place, they were-not.readily i
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apparent from documented procedures.
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On October 1, 1990, the licensee issued the~" Vermont Yankee Nuclear Power Corporation Maintenance Program"_ document.
This. document
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contains a comprehensi_ve outline of maintenance department policies and states'the purpose, objectives, scope, and responsibilities for the program.
It also_contains a description of requirements for m_ajor program elements such: procedures, training, major types of
. maintenance, coordination and control of' maintenance work -' post-maintenance testing =, root cause analysis, and-corrective actions.
Thelinspector noted that this document also contains a program
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mission statement which defines the general _ goals of maintenance
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performed at the facility -and provides a corron focus and a consis-
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tent: approach for all licensee personnel in achieving the program-
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objectives. Although:the document was not developed or' issued as a
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corporate; directive,.it does have the concurrence of.the Senior Vice-
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President.
The document has not yet been-incorporated into the 1 station Administrative Procedures System; however, this is currently planned toJoccur so that other APs.can incorporate it directly by
-reference.
The inspector determined that the developr=nt and issuance of-this document satisfies the need to'have a comprehensive policy documeat
'for'the conduct of maintenance. The weakness has been adequately
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4.6 Weakness #2; Lack of comprehensive and structured reviews for the adequacy and applicabili_ty of the plant's maintenance requirements:
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The maintenanca ;nspection team determined that the licensee had not
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performed a comprehensive and structured review of the applicability and. adequacy of the plant's maintenance requirements, Maintenance requirements in place at the beginning of commercial operation appeared to remain.as the basis for the overall program. -Individual
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improvements on the program since then were implemented without the advantage of periodic and coherent formal review to determine their applicability within the overall program.
The inspector reviewed the most recent version of AP-0200, " Conduct
of Maintenance. Activities," which outlines and specifies major Main-
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tenance Department functions in the areas of maintenance planning and J
administration, equipment records, preventive and corrective mainte-
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nance, surveillance inspections, equipment trending, root cause fail-
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ure. analysis, and the Equipment Technical Information Program (vendor manual packages).. Responsibilities for periodic reviews in all of
.these program areas have been explicitly defined and structured to ensure that changes to program requirements and activities are reviewed, that they ref. lect actual and current needs,-are applicable
to the overall maintenance program, and are implemented in a consis-
tent manner,. These responsibilities have been given primarily= to the
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Senior Maintenanc' Engineers who are also required to provide annual reports to the Ma',ntenance Department Supervisor-summarizing the activities in each of these areas by evaluating the ef'ectiveness,_
the correctness, and the applicability of major changes and accom-plishments :The Maintenance Department Supervisor is required to
periodically / review the entire maintenance program to identify
.necessary changes-to requirements on an.on going basis.
A formal
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biennial review of all maintenance department administrative proce-
. dures 'is :also conducted which requires program content to be evalu-
ated and approved by department supervisors, managers, and the Plant n
Operations: Review Committee.
In addition,_the. licensee's-Operating
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Experience Review and Assessment /Committment Tracking system-
' (AP-0028);provides a mechanism.whereby-equipment' problems, mal-functions,- and: failures are evaluated within the maintenance depart-cment to ensure that current maintenance requirements,and practices-are appropriate to maximize equipment reliability and availability.
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1 Based upon the above actions, the inspector considers that this.
j-weakness has been adequately addressed and..that improvements have
.been adequately implemented.
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4.7 Weakness #3; Reviews for the appropriateness and technica1' adequacy of completed maintenance activities were not being performed in a
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timely manner:
Maintenance inspectors noted that the technical adequacy of mainte-
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nance activities were not being reviewed in a timely fashion and that the backlog-of Maintenance Requests (MRs) awaiting such review was
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large. The licensee was compiling information on equipment perform-a ance trends; however, the information was not being communicated to or reviewed by upper management.
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The inspector noted that the licensee issued a complete revision to AP-0021, " Maintenance Requests," (MRs) which now provide means 'or identifying, assigning, planning, approving, tracking documenting, and certifying all corrective and preventive maintenance (CM & PM)
c performed on plant equipment. With regard to this weakness, the most significant change in this procedure was a revision to the overall method by which MRs are processed. Of key importance was the crea-tion of an Operations Planning Coordinator. This individual is responsible for coordinating and processing all corrective mainte-nance requests (CMRs) and preventive maintenance requests (PMRs)
after they have been initiated and continuing through the final steps i
of work certification and closeout.
This individual maintains a CMR and PMR log to track the status of all active MRs.
MR$ that have completed repair work and post-main-tenance testing, and are pending final maintenance department super-visory review are tracked by the Operations Planning Coordinator.
MRs which di not receive a timely review and closeout are given the appropriate amount of attention at the management level to orevent the growth of backlogged MRs and to ensure timely closeout.
Based upon the licensee's implementation of the MR processing and tracking methods required by AP-0021, the inspector regards this weakness to be adequately addressed with corrective actions fully implemented.
4.8 Weakness #4; Lack of effective policy and procedures for controlling a
and updating manufacturer's technical manuals-
a Maintenance inspectors observed that the licensee had no effective mechanism to update manufacturer's technical manuals for equipment.
Formal manual revisions were infrequent due to several factors relat-ing to the sources of information, and the means by which technical information was received by the licensee.
The manner in which up-dated technical information was orcanized, filed, and disseminated in procedures were also noted problems during the maintenance inspection.
To address this weakness the licensee daveloped the " Equipment Technical Information" system (AP-0312) to establish a consistent program to control the preparation, review, revision, and approval of Vermont Yankee Equipment Manuals (VYEMs). AP-0312 was issued in December 1989, and establishes the administrative requirements and responsibilities for the conduct of the program.
The licensee has contracted out the initial project to create, revise and update all VYEMS and to establish a consistent format for maintaining them.
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Each VYEM is placed under the control of a cognizant person who has
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both technical awareness of the equipment and an understanding of this responsibilities under AP-0312 for maintenance of the manuals.
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Under the equipment technical information program, all VYEMs become y
"centrolled" documents and, therefore, fall within the administrative n
controls defined by Ap-6805, " Document Control," and AP-0200, " Main-t tenance Program". The cognizant person is responsible to ensure that
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new technical information received from vendors and manufactures is reviewed for applicability to plant equipment Md that the informa-tion is reviewed within the AP-0028 Experience Assessment process, h
the licensee's Design Change Review process, or another formal review process as applicable.
As of this inspection, approximately 75% of the safety related VYEMs had completed the revision process and had been entered into the site document control system.
The remainder of these are expected to be incorporated under formal controls by the end of 1990.
The inspector reviewed five different completed VYEMs on plant
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components and found them to be well structured, organized, accurate, and readily useable for the support of maintenance activities at the site.
Based upon the actions identified Jove, tr e inspector con-siders the licensee's resolution of this weakness to be adequate and proceeding in a timely manner.
4.9 Weakness #5; PRA concepts are not incorporated into Vermont Yankee's maintenance program.
One objective of the maintenance team inspection was to determine the
extent to which PRA concepts and methodology were considered in maintenance program elements such a planning, scheduling, and prioP-
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E itizing work, it was determined that the licensee did not have
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either a formal program or documented goals to incorporate PRA concepts into the maintenance program.
In October 1989, Vermont Yankee responded (letter DVY 89-100) to NRC Generic L.etter 88-20, Supplement 1
" Initiation of the Individual Plant Examination (IPE) for Severe Accident Vulnerabilities - 10 CFR 50.54 (f)," by stating their intention to develop a plant-specific IPE, in part, to understand the most likely severe accident sequences and to gain a more quantitative understanding of the overall probab-ilities of core damage.
This letter also outlined the purposes, methods, and schedule for achieving these objectives.
The principle method the licensee intends to use will be to develop a plant-specif-ic Level 1 Probabilistic Risk Assessment (PRA).
This project has
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been assigned to the 11ctinsee's primary engineering support organi-zation, Yankee Atomic Electric Company's (YAEC) Safety Assessment Group. Work commenced in January 1990, and it is currently expected to be completed before January 1994.
In July 1990, the Safety Assessment Group presented the licensee with an overview of the PRA
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work in progress whi
<ncluded a listing of future applications for the PRA. Although m atenance was not specifically listed as an application, system reliability was listed as a key application.
The maintenance department supervisor indicated that plant-specific
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information derived from maintenance activities was provided to the i
Safety Assessment Group.
However, other than maintaining syste-
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relibility as one of the maintenance department's primary goal:.
there are still'no documented plans or goals to incorporate specific PRA concepts into the maintenance program.
The PRA effort has not developed to aa extent that would make this possible. The PRA i
project is currently proceeding on a system-by system basis, and no
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conclusions have yet been reached which would be of value for plan-ning, scheduling, or prioritizing maintenance wJrk.
Based upon the above actions, the inspector considers that this weak-
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ness has received only preliminary attention. Although the initial steps have been taken toward development of the PRA, it appears that a full resolution of this weakness can be addressed only over an extended time period.
The progress made to date is considered to be
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satisfactory; however, this item will remain subject to further NRC review as the PRA develops and useable conclusions become available to the plant maintenance department.
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4.10 Weakness #6; No integrated Master Equipment List (MEL) existed for Vermont Yankee.
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The maintenance inspection identified that Vermont Yankee does not have a single Master Equipment List that meets generally accepted i
industry standards (INPO) for such lists.
The licensee had several discrete lists in use by different departments and at least three
major equipment lists in use by the maintenance and I&C departments
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that were referred to as the " Master Equipment List" by approved
'I plant procedures.
In recognition of the need for improved information technology both at the plant and the corporate of fices, licensee management directed
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the development of corporate-wide information system improvements.
This plan-included the development of a centralized " Maintenance and-Materials Management" (3M) computerized database system to provide Vermont Yankee personnel with improved maintenance planning, schedul-
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ing, preparation, eificiency, and communications.
One key feature of m
this system will be a component database able to accommodate a detailed information file on approximately 50,000 plan _t components.
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In January 1990,-the Information. Systems St'eering Committee (ISSC)
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approved the 3M System Objectives document which outlined the prin-ciple objectives and a basic schedule for the development of this system. The inspector reviewed the current status of this project with the lead project engineer directing its development. -Project personnel were currently assembling information on all plant equip-v
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Records, the ISI/IST index, EQ lists, vendor manuals, technical i
specifications, et. al.
This effort will systematically standardize
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all available component information into an " Engineering Databan" and a " Maintenance Database," both of which will eventually be combined by the 3M system into a " Total Database." The Total Data-base is expected to be completed by December 1990 and will essen-tially comprise a Master Equipment List available for use by all site
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and corporate departments.
The 3M system will be further developed to adapt software applications for each user department. Maintenance and I&C department planning, scheduling, prioritizing, and work control will eventually be managed through the use of the 3M system.
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Based upon the above actions, the Inspector considers that this weakness has been addressed and that the development of the 3M project p_rovides necessary improvements in this area.
This item has
.been adequately resolved.
4.11 Weakness J7; Post-Maintenance Testing requirements were not proce-
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-duralized in administrative procedures.
Maintenance team inspectors noted that the licensee did not have I
proceduralized requirements for their post-maintenance testing (PMT).
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Although PMis were being accomplished in a sati'sfactory manner, a
formalized comprehensive. approach to this activity was not provided.
The: licensee subsequently assembled a special task force to review the PMT.needs for all types of maintenance requests at the plant.
The results of this task force culminated in June 1990 with a major revision to the site instruction for processing MRs, i.e., AP-0021,
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" Maintenance Requests."
- In addition'to addressing PMT requirements throughout this procedure,
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a special appendix was added to provide all crite'ia.for the speci--
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fication and documentation of-PMis for all types of preventive and-
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corrective maintenance (PM & CM) at the plant.
Thi s - appendix contains a complete set of instrc tions for determining specific PMT requirements and provides an extenlive list of types of maintenance
activities (e.g., circuit breaker epair, MOV operator repair, sole-noid valve repair, air compressor rebuild or repair, et. al.) and
correlates a detailed listing of ecommended PMT items for each
activity.
Y The inspector considers that the incorporation of the this revision
.into.the processing of all MRs at the rlant resolves the need for improvements in this area.
This 1 7 he L..T 6 +.:1y resolved.
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5.0 Management Meetings (IP 30703)
Licensee-management was informed of the purpose and scope of this inspec
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tion at an entrance meeting conducted on October 1, 1990.
The findings of
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the-inspector.were discussed periodically with licensee representatives j-c,
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. presented to the: station management.
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At'no time during the inspection did the inspector-provide written i.
material to the licensee, nor did the licensee indicate that any of the areas' covered in this report contain proprietary information.
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i Attachment A
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Documents Reviewed
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Administrative Procedures i-
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-AP0021, Rev. 17, Maintenance Requests
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AP0028, Rev. 12, Operating Experience Review and Assessment /Committment
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. Tracking
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AP0200, Rev. 12, Conduct of Maintenance Activities AP0310, Rev. 6, Surveillance, Preventative, and Corrective' Maintenance Program
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AP0312, Rev. 0,- Equipment Technical Information
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-AP0625,-Rev. 2, Quality Control / Independent Inspection j
..M_emoranda
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L VY Memo BVY 89-58, 6/30/89, Response to Int.pection Report 89-80, Notice of f
Violation
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E VY Memo BVY 89-100,-10/24/89, Vermont Yankee Response to Generic letter 88-20,
- Supplement 1-VY Memo BVY 89-75,.8/11/89, Additional Response to-Inspection Report 89-80,
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Request for Information-
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VY Memo, 4/26/90, 3M Plant Staff Goals 1990
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VY Memo,-'12/29/90, MMMS Subcommittee Progress Report
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QA Surveillance Reports
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.90-119, Corrective Actions Associated with NRC Maintenance Inspection 89-80
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b 90-33, Post-Maintenance Testing
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i Other
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Vermont Yankee Strategic Plan, 8/10/90
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- VYNPC Maintenance-Program Misston
- Document, Rev. 1, 10/1/90
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LVYNPC Maintenance Materials Management Objectives Document,:1/4/90
- NRC Inspection Report 50-271/89-80
~ Safety Assessment Group Presentation to Vermont Yankee, 7/11/90
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L Potential: Reportable Occurrence - 26, 8/20/90,_ Incorrect: version of VYAPF-0150.01-in use.
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i ATTACHMENT B l
Vermont Yankee Drywell Topcoat Degradation (ECMB)
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NRR evaluated the potential problem resulting from the transport of paint chip g
debris following a loss-of-coolant accident (LOCA). We conclude that the amount of paint chips that peel off the upper drywell region and is likely to
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eventually deposit on~RHR and core spray suction strainers is insufficient to
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adversely affect ECCS pump performance in a post-LOCA condition.
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During the_short term transport phase, i.e., initial 30 seconds following the LOCA while the reactor vessel depressurizes, steam, gas, and water at a high velocity are vented through the downcomers to the torus.
Since the degraded
topcoat paint; which is subject to debris formation, is in the upper section of
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the drywell, which is not exposed to the turbulent flow, insignificant quan-tities of paint chips should be transported to the torus.
Paint topcoat chips that~ may.have settled in the drywell prior to the LOCA should be broken up into small-fragments by the heavy turbulence produced during the first 30 seconds of LOCA blowdown because of the observed brittle nature of the chips.
These small paint chip fragments could_be transported from the drywell to the torus via the
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downcomers.
Because of the small paint chip particle size, most of the chips should pass'through the 1/8' inch ECCS suction. strainers.
The small quantity of paint chips that may be transported to the suction strainers collect on the thermal insulation mat and should not significantly reduce the NPSH of the RHR and Core Spray Pumps.
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During the.iong term transport phase, i.e., after the 30 seconds of LOCA L
'depressurization through continuing ECCS pump flow for days or weeks, addi-l, tional quantities of paint chips may be released from the drywell surfaces due to the LOCA environment.
The paint debris generated during this phase is not likely to_be transported to-the ECCS suction strainers because of the following factors:
Paint chips have a higher density than water and should settle out
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on.the floor of the drywell.
The settled paint chips should not be re-suspended in the drywell
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bottom and_ transported through the downcomers due to the low veloc-ities generated by the ECCS flow.
.The entrance to the downcomer: vents is protected by a blast shield.
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and.the downcomer openings are about 9 inches above the drywell floor.
These factors'should restrict plint chip transport to the torus.
The downcomers distribute drywell flow-via spray headers into the 16
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torus bays (4 of which contain ECCS intakes).
'Due to low torus transport velocities, paint chips should settle out
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in the bays which are separated by ring girders that should restrict particle transport between bay m,
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- Attachment 8'
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The ECCS suction strainers are located a few feet from the torus
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bottom.
Therefore, any paint chips entering the bays with these suction strainers are likely to settle to the torus bottom.
Trans-port to the suction strainers-is not likely due to the low velocities.
It_ is concluded that'the peeling of topcoat paint in the upper drywell area should not affect ECCS pump performance in 4. post-LOCA condition. NRR concurs
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with the Vermont Yankee's paint consultant, that surveillance of the drywell.
surfaces should be carefully performed each refueling outage and.that all loose
topcoat 1 material should be removed by thorough scraping without damaging the
,
+
prime r.~
Damaged or degraded Carbozine-11 primer should be repaired with
!
approved procedures since this primer is relied upon for primary containment.
interiorfsurface corrosion protection.
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