ML20235N322
| ML20235N322 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 02/16/1989 |
| From: | Murphy W VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| BVY-89-17, GL-88-14, NUDOCS 8903010160 | |
| Download: ML20235N322 (13) | |
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e VERMONT YANKEE NUCLE 5R POWER CORPORATION RD 5 Box 169, Ferry Road Brattleboro, VT 05301 BVY 89-17 i
s 9
REPLY TO ENGINEERING OFFICE 580 MAIN STREET BoLToN, MA 01740 (508)779-6711 February 16, 1989 U.S. Nuclear Regulatory Commission Washington, D.C.
20555 Attn:
Document Control Desk
References:
a)
License No. DPR-28 (Docket No. 50-271) b)
Letter, USNRC to All Holders of Operating Licenses or Construction Permits for Nuclear Power Reactors, NVY 88-177,
" Instrument Air Supply System Problems Affecting Safety-Related Equipment (Generic Letter 88-14)," dated 8/8/88 c)
Letter, Byron Lee, Jr. (NUMARC) to NUMARC Board of Directors, "NRC Generic Letter 88-14, Instrument Air Supply System Problems Affecting Safety-Related Equipment," dated 11/8/88 d)
NUREG 1275, Volume 2, " Operating Experience Feedback Report, Air Systems Problems," Published December 1987 i
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Dear Sir:
Subject:
Vermont Yankee Response to NRC Generic Letter 88-14:
" Instrument Air Supply System Problems Affecting Safety-Related Equipment" By Generic Letter 88-14, dated August 8, 1988 [ Reference b)), the Nuclear l
Regulatory Commission (NRC) requested all licensees / applicants to review NUREG I
1275, Volume 2 [Peference d)], and perform a design and operations verification of the Instrument Air System. The subject Generic Letter stated that the veri-fication should include the following:
l 1.
Verification by test that actual instrument air quality is consistent with the manufacturer's recommendations for individual components served.
2.
Verification that maintenance practices, emergency procedures, and training are adequate to ensure that safety-related equipment will function as i
intended on loss of instrument air.
j j
3.
Verification that the design of the entire Instrument Air System including l
air or other pneumatic accumulators is in accordance with its intended l
function, including verification by test that air-operated, safety-related components will perform as expected in accordance with all design basis events, including a loss of the normal Instrument Air System.
This design verification should include an analysis of current air-operated component failure positions to verify that they are correct for assuring required safety functions.
8903010160 890216 goa aoocx 0s000271
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VERMONT YANKEE NUCLEAR POWER CORPORATION U.S. Nuclear Regulatory Commission February 16, 1989 Page 2 In addition to the above, it was requested that each licensee / applicant provide a discussion of their program for maintaining proper instrument air quality.
The purpose of this letter is to notify the NRC that Vermont Yankee has completed the required review of NUREG 1275, Volume 2 [ Reference d)) and to pro-vide, as Enclosure 1, the results of our design and operations verification of l
the Instrument Air System concerning each of the specified action items.
Specifically, Enclosure 1 provides the following:
o A detailed response to the three required action items as pertair; to both Instrument and Containment Air Systems, o
A description of Vermont Yankee's program for maintaining proper instrument air quality.
o A description of the testing which has been completed to date and Vermont Yankee's plans for future testing.
l In addition, Enclosure 2 provides a schedule for completion of all remaining action items. describes the actions taken, or planned to be taken, to ensure that intended safety functions are accomplished as well as describing the results of our investigation concerning the Reactor Building to torus vacuum breakers.
With regard to testing performed in response to the subject Generic Letter, Vermont Yankee utilized the NUMARC guidance of November 8, 1988 [ Reference c)]
-l to clarify the requirements of Generic Letter 88-14.
This letter provided clarification that it is not the intention of the Generic Letter to require the performance of gradual loss of air tests. Accordingly, Vermont Yankee has not and does not intend to perform any gradual loss of air tests other than those on specific safety-related accumulator systems. As far as performing tests to verify proper component failure positions on loss of air, Vermont Yankee has utilized existing component testing programs. Where it has been determined, as described in Enclosure 1, that existing testing is sufficient to verify proper component operation and position when air is vented, no additional testing is performed.
For components (other than those supplied with safety-related accu-mulator systems) that are not presently tested for operation by venting air, or where testing is not adequate to verify component position when air is vented, additional tests will be performed to verify safe failure positions when air is vented. Additionally, should this testing identify any components that cannot accomplish their intended safety function, corrective actions will be taken.
When Vermont Yankee has completed all requirements of Generic Letter 88-14, a written notification indicating such will be provided to the NRC.
As requested, all documentation pertaining to the subject design and verification effort will be retained on-site for a minimum of two years from the date of this submittal.
/
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VERMONT YANKEE NUCLEAR POWER CORPORATION I
UIS.-NuclearRegulatoryCommission February 16, 1989 Page 3 l
l.
I We trust this letter and Enclosures are responsive to the subject generic letter;.however, should you have any questions or require additional infor-mation, please do not hesitate to contact us.
Very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATION Y'
w Warren P.
urphy i
Vice President and Manager of Operations Enclosures
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USNRC Regional Administrator, Region I USNRC Resident Inspector, VYNPS STATE OF VERMONT)
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WINDHAM COUNTY- )
Then personally appeared before me, Warren P. Murphy, who, being duly sworn, did state that he is Vice President and Manager of Operations of Vermont Yankee Nuclear Power Corporation, that he is duly authorized to execute and file j
the foregoing document ~in the name and on the behalf of Vermont Yankee Nuclear 2
Power Corporation and that the statements therein are true to the best of his knowledge and belief.
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ENCLOSURE 1
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VERMONT: YANKEE RESPONSE TO NRC GENERIC LETTER NO. 88-14
'" INSTRUMENT AIR SUPPLY SYSTEM PROBLEMS AFFECTING SAFETY-RELATED EQUIPMENT"-
INTRODUCTION Instrument and Service Air Systems-at Vermont Yankee are described in FSAR Section 10.14 and consist of_the following:
A.
A Station Instrument and Service Air System comprised of four air compressors connected in parallel with two air receiver tanks to provide the station with compressed air for pneumatic instruments and' controls and general station services.. The compressed air of the Instrument Air System-passes through two parallel branches both of which contain a separator, pre-filter,' dryer, and after_ filter.
B.
A separate Containment' Air System which is either supplied with nitrogen-from a compressor which takes suction from the inerted drywell or from a nitrogen; bulk storage tank (backed up by nitrogen' bottles) to provide compressed nitrogen required for pneumatic instruments and controls located within the drywell. The Containment Makeup System (nitrogen bulk storage tank) is the normal supply with the Containment Air Compressor System serving as a backup..The Nitrogen Make-Up System can be cross-connected with the Instrument-Air System to provide another source for the contain-ment air subsystem.
C.
A separate Emergency Diesel Generator Air Starting System consisting of an air compressor and two redundant air storage tanks for each diesel-genera-tor.
Vermont Yankee's design and operations verification of'the Instrument Air System consisted of a detailed review of flow diagrams for the Instrument and Containment Air Systems to identify, safety-related air-operated components.
For each component, two worksheets were generated. One worksheet was used to iden-tify the required failure positions upon loss of air and provided the supporting analysis for that position. An example of the type of information appearing on this worksheet is shown in Figure 1.
The second worksheet was used to record instrument air quality requirements based upon discussions with manufacturers and a review of manufacturer literature.
An example of the type of information appearing on this worksheet is shown in Figure 2.
LThe Diesel Generator Air Starting System was included in a recent self-initiated Safety System Functional Inspection (SSFI). The results of this effort determined that all design requirements of the Starting Air System are satisfied.
Presently, surveillance performed on these systems verify starting air receiver tank pressure and blowdown the air receivers and filters on a daily basis.
In addition, weekly tests are made to ensure that the diesel generator compressors start upon a reduction in air pressure within the receiver tanks.
Enclosuri l Page.2 l
A.
REQUIREMENT No. 1 l
f-Verification by test that actual instrument air quality is consistent with the manufacturer's recommendations for individual components served.
RESPONSE
Vermont Yankee determined requirements for instrument air quality for air-operated components identified as critical components. These requirements l
were based on discussions with equipment. manufacturers and a review of manufacturers' literature pertaining to instrument air quality require-ments. Presently, Vermont Yankee has a procedure for determining that levels of oil and moisture.in both the instrument air and containment instrument' air supplies are within acceptable limits. The procedure requires taking air samples to verify that the air has a dew point of less-than or' equal to -40*F and no detectable oil exists. Testing of instrument air is procedurally required to be performed monthly, and testing of con-tainment instrument air is required to be performed quarterly.
Since early_
1988, instrument air sampling has been performed weekly; samples are taken at the outlet of dryers and at sample points located in the chemistry lab.
The procedure requires the notification of Chemistry supervision if accep-tance criteria is exceeded.
The determination of manufacturer's recommendations for instrument air quality verified that requirements for air dew point and oil content are satisfied for all safety-related, air-operated components identified uti-lizing the acceptance criteria in the ex' sting Vermont Yankee procedure.
In fact, based upon a review of documentation and drawings pertaining to the capabilities and design of the Vermont Yankee Air Supply Systems, it was determined that all vendor requirements for air quality could be satisfied, assuming periodic maintenance was performed, without any design modifications. However, additional air quality testing was performed. The results of these tests at approximately a dozen sample points were used to give a representation of air quality throughout the system and are pre-sently being reviewed and evaluated.
Preliminary results on dew point indicate that all vendor requirements for this aspect of air quality are being satisfied. The review and evaluation of all air quality testing results is expected to be completed by June 1, 1989 [ Enclosure 2, Item (1)].
Based upon the evaluation of air quality testing results, Vermont Yankee will perform a comprehensive review of the existing Air Quality Testing Program [ Enclosure 2, Item (4)].
B.
REQUIREMENT NO. 2 Verification that maintenance practices, emergency procedures, and training are adequate to ensure that safety-related equipment will function as intended on loss of instrument air.
5 b
Page 3
RESPONSE
o Maintenance Practices Vermont Yankee has a maintenance program for performing preventive and corrective maintenance on the Instrument and Containment Air Systems.
The emergency diesel generators and the main steam isolation valves, have separate procedures for performing periodic preventive main-tenance.
These procedures for preventive maintenance include air-operated components, the air compressors, dryers, and a number of associated components, l
In many cases, surveillance testing will identify equipment that, although functional, may require maintenance. During the performance of surveillance procedures, Vermont Yankee personnel observe the general condition of the equipment being tested which includes such items as evidence of moisture or oxidation, wear, and leaking.
Inadequate equipment conditions result in Maintenance Requests being issued.
i l
In an effort to determine the effectiveness of Vermont Yankee's existing maintenance programs on maintaining air-operated safety-related equipment functioning as designed, a review of the following Vermont Yankee documents, for at least the last five years, was per-formed:
Licensee Event Reports (LER's)
Potential Reportable Occurrences (PRO's)
Plant Information Reports (PIR's)
Maintenance Requests (MR's)
I
' Design Change Modifications From this review and based upon equipment availability over the past five years, it has been determined that existing maintenance practices are adequate to ensure that air-operated safety-related equipment will function as intended.
However, two improvements were identified which could enhance system operation and will be incorporated into station I
procedures. The additional items to be incorporated into the main-tenance programs are:
Filters existing within individual air filter regulators located in air lines to safety-related equipment will be periodically inspected and cleaned / replaced, as required (Enclosure 2, Item (8)].
Instrument air lines will be periodically blown down, including air accumulator draining [ Enclosure 2 Item (9)).
I t.
o Page 4 I
o Emergency Procedures Vermont Yankee presently has a procedure which is used to respond to a reduction in air pressure in the instrument / scram air header.
This procedure was reviewed and determined to be adequate. However, several enhancements were identified and the procedure will be revised to assist operators in the identification, control, and recovery from a partial or total loss of instrument air. The revision to this pro-cedure is expected to be completed by June 1, 1989 [ Enclosure 2, Item (2)].
o Trainina An assessment was performed on the Vermont Yankee Training Program regarding the station instrument air systems, and the existing training was determined to be adequate. Training on the revised operations procedure described above will be incorporated into the existing Licensed Operator Requalification training schedule.
This training is expected to be completed by September 1, 1989 [ Enclosure 2, Item 3).
This training will re-emphasize the importance of the Instrument Air Systems on the operation of safety-related equipment as well as the potential for common-mode failure of air-operated com-ponents as a result of poor air quality. These same topics will also be incorporated into the. appropriate Initial Operator Training program curriculum prior to commencement of the next class.
C.
REQUIREMENT NO. 3 Verification that the design of the entire Instrument Air System, including air or other pneumatic accumulators, is in accordance with its intended function, including verification by test that air-operated safety-related components will perform as expected in accordance with all design-basis events, including loss of the normal Instrument Air System. This design verification should include an analysis of current air-operated component failure positions to verify that they are correct for ensuring required safety functions.
RESPONSE
i l
l A review of station drawings was performed to identify safety-related com-ponents fed by either instrument or containment air (nitrogen).
For each applicable component identified, an analysis was performed to determine the component's function and required safe failure position upon loss of air.
This analysis considered specific design basis requirements applicable to each component. A review of vendor drawings and existing specifications, and in some cases, walkdowns were performed to see if they suoported the required safe failure positions. From this effort, it was verified that the design of all safety-related, air-operated components identified is in
1 Page 5 accordance with its intended function. The details of these analyses were documented on an individual worksheet for each component.
However, as described in Enclosure 3, it was determined that air-inflated seals for Reactor Building doors may not be adequate by themselves.
A review of existing testing procedures was performed to identify safety-relateo air-operated components which are currently tested in a manner which verifies correct position when operated by venting air.
This review did not include the main steam isolation and safety relief valves which have safety-related accumulator systems and are discussed below.
For any components which are presently not tested or operated to verify operation upon venting of air, and which have been determined to require testing, verification of correct position operation will be accomplished by a one-time function test [ Enclosure 2, Item (6)]. A total of ten components were determined to require testing to verify failure positions upon loss of air.
The current outage schedule is being reviewed to determine if the testing of any of these ten components can be accomplished during the ongoing outage.
Testing of the components this outage will be completed to the extent possible without impact on the established schedule at this late date. As indicated in Enclosure 2, Item (6), the testing of all components l
will be completed before startup from the 1990 outage.
Vermont Yankee has two types of safety-related check valve accumulator l
systems.
These systems are for the main steam safety-relief valves and the j
Each of the four main steam safety-relief i
valves and each of the eight main steam isolation valves (inboard and out-l board) is provided with a separate accumulator assembly.
Main Steam Safety Relief Valves t
The accumulator capacity for this system was verified during impleme-l nation of a 1980 design change when new soft-seated check valves were installed.
Presently, this Accumulator System is tested each refueling outage to verify satisfactory check valve operation.
This testing includes a gradual reduction in air pressure.
Based upon operational experience, Vermont Yankee will install filters upstream of the check valves to decrease the possibility of fouling from corro-sion and enhance system operation by installing larger accumulators (Enclosure 2, Item (10)].
Main Steam Isolation Valves The accumulator capacity was recently analytically verified to meet the FSAR design requirements.
Presently, the accumulator systems of the inboard and outboard main steam isolation valves are not tested to verify that the check valves do not leak.
During the 1990 refueling l
outage, the inboard and outboard main steam isolation valve accumula-
)
tor assemblies will be tested to verify leakage is within acceptable I
limits (Enclosure 2, Item (7)].
Further testing will be determined j
based on the results of this initial testing.
This test will include a gradual loss of air test.
Instrument air lines upstream of the main steam isolation valve check valves are already equipped with two filters in series which are periodically replaced.
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l The safety-related accumulator systems at Vermont Yankee are adequately 1
designed to perform their intended function.
The improvements mentioned j
above are expected to enhance the availability of the accumulator systems.
l D.
VERMONT YANKEE'S PROGRAM FOR MAINTAINING PROPER INSTRUMENT AIR QUALITY Vermont Yankee's method for maintaining proper instrument air quality con-sists of the performance of maintenance on air supply systems including instrument, containment, and diesel generator air start.
Maintenance programs consist of surveillance and preventive and corrective main-tenance.
Preventive maintenance programs include such items as filters, compressors, desiccants, dryers, and moisture traps.
This program will be expanded to include the inspection of additional filters (Enclosure 2, Item (8)].
In addition, the Air Supply System will be periodically blown down to remove any moisture or particulate [ Enclosure 2, Item (9)].
The air quality monitoring and maintenance programs described above, in combination with enhanced procedural guidance and training, previously discussed, will provide cor.tinued and enhanced assurance that the proper instrument air quality is maintained. Vermont Yankee will continue to i
monitor indications of developing problems in accordance with existing pro-cedures and make corrections as necessary.
In addition, Vermont Yankee will thoroughly investigate air system-related problems to obtain root causes. Accordingly, Air Supply System improvements or modifications will be implemented as dictated by evaluation of performance.
E.
RESULTS Vermont Yankee has completed the design and operations verification of the Instrument Air System required by Generic Letter 88-14.
To date, no com-ponents, other than Reactor Building door seals described in Enclosure 3, have been identified which may not accomplish its required safety function.
Actions which were taken or that are planned to be taken as a result of the verification are listed in Enclosures 2 and 3.
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PREPARER
/
Date REVIEWER
/
Date FIGURE 1 AIR-OPERATED COMPONENT WORKSHEET COMPONENT SAFETY CLASS SYSTEM ASSOCIATED AIR COMPONENT AIR SUPPLY (Instrument Air or Containment Air)
SERVICE NORMAL POSITION (opened or Closed)
FAILURE POSITION ON LOSS OF AIR SUPP'.Y (0pened, Closed, or As Is)
FAILURE POSITION ANALYSIS EXPECTED SYSTEM (S)
RESPONSE UPON LOSS OF AIR l
I CONSEQUENCES OF WRONG FAILURE POSITION REFERENCES
____-__-______A
s FIOURE 2
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AIR QUALITY WORKSHEET FOR AIR-OPERATED COMPONENTS COMPONENT 1
HANDWHEEL (Yes or No)
LIMIT SWITCHES (Yes or No)
A1.
ACTUATOR:
A2.
AIR QUALITY REQUIREMENTS:
- MANUFACTURER:
- MOISTURE:
- MODEL:
- OIL:
- PARTICLE SIZE:
61.
SOLEN 0ID:
B2.
AIR QUALITY REQUIREMENTS:
- MANUFACTURER:
- MOISTURE:
- MODEL:
- OIL:
- PARTICLE SIZE:
C1.
POSITIONER:
C2.
AIR QUALITY REQUIREMENTS:
- MANUFACTURER:
- MOISTURE:
- MODEL:
- OIL:
- PARTICLE SIZE:
D1.
CONTROLLER:
D2.
AIR QUAILITY REQUIREMENTS:
- MANUFACTURER:
- MOISTURE:
- MODEL:
- OIL:
- PARTICLE SIZE:
E1.
AIR FILTER REGULATOR:
E2.
MOST RESTRICTIVE PARTICLE:
- MANUFACTURER:
- SIZE:
- MODdL:
- FILTER SIZE:
F1.
ADDITIONAL FILTERS:
F2.
MOST RESTRICTIVE PARTICLE:
- SIZE:
- SIZE:
ENCLOSURE 2 IMPLEMENTATION SCHEDULE APPLICABLE TO
__ GENERIC LETTER NO. 88-14 RESPONSE SCHEDULE FOR ITEM EXPECTED COMPLETION DATE 1.
Review and evaluation of air quality
. June 1, 1989 testing results.
- 2.. Completion of procedure revision to June 1, 1989 assist operators concerning loss-of-air events.
3.
Completion of all training for September 1, 1989 operators.
4 Evaluation of the adequacy of the September 1, 1989 existing Air Quality Testing Program.
' 5.
Permanent fix for the Reactor Building As soon as practical, following equipment access doors.
receipt of materials required for design modification.
6.
Testing of all components which were Before startup from the next determined to require testing to scheduled refueling outage (1990).
verify correct position on venting of air.
7.
Testing of MSIV Accumulator Systems.
Before startup from the next scheduled refueling outage (1990).
8.
Incorporation of a program to Before startup from the next periodically inspect and clean filter scheduled refueling outage (1990).
regulators on the air supply lines to safety-related components.
9.
Incorporation of a program to Before startup from the next periodically blowdown the Instrument scheduled refueling outage (1990).
Air System.
- 10. Installation of filters and larger Before startup from the next accumulators on the four safety scheduled refueling outage (1990).
relief valve accumulator assemblies.
- 11. Written notification to the NRC that Sixty days following startup from all requirements of Generic Letter the 1990 refueling outage.
88-14 have been completed.
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ENCLOSURE 3 OPEN ITEMS 1.
Inflatable Door Seals for Reactor Buildina Equipment Atcqss Doors These door seals are currently required to be inflated with instrument air when closed in order to maintain secondary containment integrity. On loss of air, there is the possibility that air seals would deflate since instru-ment air components are non-nuclear safety.
In order to provide assurance that secondary containment integrity will be maintained in the unlikely event of loss of air, Vermont Yankee installed, as a temporary measure, an additional passive-type seal. A permanent fix will be designed and installed as soon as practical following receipt of materials required to implement the design modification (Enclosure 2, Item (5)).
2.
Reactor Building to Torus Vacuum Breakers During the review of Generic Letter 88-14, a concern was raised in regard to the Reactor Building to torus vacuum breakers.
The concern is that upon loss of instrument air, the air-operated vacuum breakers would open, leaving only a check valve in each of two vent paths closed to maintain primary containment iso 17 tion.
Vermont Yankee performed an investigation into the requirements of the Reactor Building to torus vacuum breakers and concluded that the current operation and design is in compliance with the original design basis and Vermont Yankee's current licensing basis.
However, Vermont Yankee is pursuing this issue further on a generic basis, through the BWR Owner's Group, as it applies to other BWR's which are simi-lar in design to Vermont Yankee.
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