ML20235Q443
| ML20235Q443 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 02/17/1989 |
| From: | Creel G BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| RTR-NUREG-1275 GL-88-14, NUDOCS 8903020632 | |
| Download: ML20235Q443 (8) | |
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B ALTIMORE j
GAS AND ELECTRIC L
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CHARLES CENTER P.O. BOX 1475 BALTIMORE, MARYLAND 21203 February 17, 1989 l
U. S. % clear Regulatory Commission
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Washington, DC 20555 I
ATTENTION:
Document Control Desk
SUBJECT:
Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2; Docket Nos. 50-317 & 50-318 Response to NRC Generic Letter 88-14, Instrument Air Supply Problems Affectina Saf etv-Related Eauioment l
Gentlemen:
The subject generic letter requested that we review NUREG-1275, Volume 2, " Operating Experience Feedback Report - Air Systems Problems," and perform a design and operations verification of our instrument air system. The generic letter provided guidance on what this verification should address, and allowed for the delay of certain portions of the verification so as to avoid adverse systern interactions.
Our plan for performing this verification is provided for your information and review in Enclosure (1). Non-outage related portions have been completed.
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8903020632 890217 PDR ADOCK 05000,317 P
Documerit Control Desk
+ February 17, 1989 Page 2 Should you have any further questions regarding this matter, we will be pleased to discuss them with you.
Very truly yours, i
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eo e C. Creel Vice President - Nuclear Energy i
STATE OF MARYLAND ll
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TO WfT :
[ [ U x li/ 4 !. Y I hereby ert fy that on the f
d'ty of f f utWW
,19M, before me, the a Notary Public of the State of Maryland in6and for
/'_ > /n t Af supseriber j
/ / naht l.
, personally appeared George C. Creel, being dufy sworn, and states that he is()Vice President of the Baltimore Gas and Electric Company, ' a corporation of the State of Maryland; that he provides the foregoing response for the purposes therein set forth:. that the statements made are true and correct to the best of his knowledge, information, and belief; and that he was authorized to provide the response on behalf of said Corporation.
M' WITNESS my lland and Notarial Seal:
W s.
Notary Public My Commission Expires:
C > /2+ /. /Nd f
l} Dale GCC/DLS/ dim Enclosure cc:
D. A. Brune, Esquire J. E.
Silberg, Esquire R. A.Capra, NRC S. A.McNei!, NRC W. T. Russell, NRC V. L. Pritchett, NRC T. Magette, DNR
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ENCLOSURE (1)
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INSTRUMENT AIR SUPPLY SYSTEM PROBLEMS AFFECTING SAFETY-RELATED EQUIPMENT Generic Letter 88-14 requested performance of a design and operations verification of 1
the instrument air system. NRC provided guidance in three areas as to what the i
l verification should include. The generic letter also requested a ' discussion of our program for maintaining proper instrument air quality. That discussion is given below, followed by our plan for implementing the NRC guidance on verification in each of the
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three areas.
ftpRram for Maintaining Instrument Air Ouality l
l The Calvert Cliffs ! instrument air. supply system consists of two non-lubricated air l~
compressors per unit, each followed by an associated receiver. Air then passes through one of two parallel pre-filters, then one of two parallel desiccant bed air dryers, j
then finally through one of two parallel after-filters. If Plam Air must be used due to the unavailability of the Instrument Air Compressors, the air would enter between the receivers and the pre-filters. A nitrogen backup system, planned for the very near future, will enter c'ownstream of the af ter-filters.
Three quality attributes are controlled for instrument air; particle size, dewpoint, l
and oil / hydrocarbons. In accordance with ISA S7.3
- 1975, Quality Standard for l
Instrument Air, these are maintained at:
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Maximum particle size in the air stream at the instrument shall be three microns.
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Dewooint at line pressure shall be at least 18 F below the minimum local recorded ambient temperature at the plant site, o
Maximum total oil / hydrocarbon content, exclusive of non-condensables, shall be as close to zero weight basis or volume basis as possible. Under no circumstances shall it exceed one ppm weight basis or volume basis.
These levels are maintained as described below.
o Maximum Particle Size: The pre-filters have a 98% removal efficiency for particles of.04 microns or greater and 100% for particles of.6 microns or i
greater. The after-filters are rated at removal efficiency of 98% of l
particles.07 microns or greater and 100% of particles
.9 microns or greater. The manufacturer recon:.nends replacement every 12 months and 6 months for the pre-filter and after-filter, respectively, but we only l
mspect and replace annually for the following reasons:
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There are two parallel filters; flow rates are less than 30% of the filter design; Filter differential pressure is checked monthly to monitor performance.
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1 ENCLOSURE (1)
INSTRUMENT AIR SUPPLY SYSTEM PROBLEMS AFFECTING SAFETY-RELATED EQUIPMENT
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Nearly every component served by instrument air also has an associated filter or filter / regulator, providing further protection from particles.
Dewooin1: Each of our Units has one old and one new air dryer. All our air dryers 0
have humidity sensors. Electronics control the humidity to -40 F Dewpoint on the new dryers. Alarms indicate out-of-range levels. The old dryers are adjusted on startup, and will alarm if the dewpoint increases. Also, as a backup, all dryers have aduades indicators, which are blue desiccant that turns pink if numidity increases to 40% at line pressure. Preventive maintenance is performed to check the dewpoint semi-annually and to inspect the desiccant beds annually.
Oil / Hydrocarbons: The only source of oil / hydrocarbons is the air taken into the compressors, since the compressors are non-lubricated, or if the Plant Air Compressors are supplying air as a back-up. Any oil / hydrocarbons that enter the system are removed by the pre-filters and dryer dericcant beds.
NRC Qpidance #1 Verification should test that actual instrument air quality is consistent with the manufacturer's recommendations for individual components served.
Response /Results The most limiting component served by our instrument air system from the standpoint of air quality was determined to be the Ma oneilan Model 8005 I/P (current-to-pressure) converter and positioner. Air quality required is clean, dry air with particles no greater than 5 microns. The air supplied by our system was sampled and sent for laboratory analysis. Due to unforeseen circumstances, the laboratory results are not yet known. In accordance with a conversation with our NRR project manager, these results will be submitted to NRC within two weeks of the date of this letter.
1 NRC Gpidance #2
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l Verify that maintenance practices, emergency procedures, and training are adequate to ensure that safety-related equipment will function as intended on loss of instrument air.
3 Responsf Resth
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Maintenance practices were reviewed. Vendor recommendations were checked and compared to actual practices. Areas were found where frequencies for preventive maintenance are less conservative than vendor recommendations.
Our evaluation of these discrepancies is as follows: _-__-__
i ENCLOSURE (1) l INSTRUMENT AIR SUPPLY SYSTEM PROBLEMS l
AFFECTING SAFETY-RELATED EQUIPMENT
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The vendor recommends measuring the purge rate on the old dryers monthly.
We measure semi-annually. This purge rate is set each time the dryer start-up procedure is performed.
Also, alarms will give warning if dewpoint increases. Many years of operating experience have proven this to be an acceptable method. Consequently, we do not intend to change. the purge rate measurement frequency.
2.
The vendor recommends checking the dewpoint of the old dryers quarterly.
We check semi-annually. The flowrate through these dryers is very low, approximately 60% of design. Also, alarms for increasing dewpoint provide on-line monitoring. Again, a great deal of operating experience exists that supports this frequency, and ' therefore, we do not intend to adjust it.
3.
The dryer vendor recommends checking dryer solenoid valves annually. These valves have been replaced by valves from a different vendor. The new vendor will be contacted for a recommendation.
4.
Freventive Maintenance Procedures for the new air dryers have been written.
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The compressor vendor recommends inspecting intake filters and draining oil l
filter sediment monthly. We perform these quarterly. We have an alarmed differential prcssure switch across the intake filters.
Run time on compressors is generally balanced, so each compressor runs approximately half the time.
Operating experience has also shown 'that quarterly performance of this maintenance is adequate.
Plant management has increased the emphasis on instrument air system maintenance, particularly in the area of air dryers, by initiating an effort to establish a reliability-centered preventive maintenance program.
With regard to emergency procedures, we have an. Abnormal Operating Procedure covering a loss of instrument air which addresses: anticipated automatic actions in the event of an air piping rupture, indications of a loss of instrument air, and detailed response actiens specific to certain operating modes. Valves that use instrument air directly, and would therefore be 'immediately affected by lowering supply pressure, are listed.
The system recovery instruction is referenced. A test will ' be performed to verify that air-operated safety-related components perform as expected. If the test reveals areas that need heightened ' consideration during a loss of instrument air event, enhancement of our Abnormal Operating Procedure will be considered.
Comprehensive training is given to both Plant Operators and. Licensed Operators on the Loss of Instrument Air procedure and on the effects of a loss of instrument air on camponents supplied. This is incorporated into plant simulator training. Licensed Operator training reinforces understanding of equipment failure positions as lesson ob.iectives. _ _ _ - - _.
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ENCLOSURE (1)
INSTRUMENT AIR SUPPLY SYSTEM PROBLEMS AFFECTING SAFETY-RELATED EQUIPMENT NRC Guidance #3 Verify 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 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.
Resoonse/Results An initial verification of the design of the instrument air system is complete. The design failure positions of valves that' fait safe on loss of instrument air have been i
verified to be correct.
Verification by test that air-operated safety-related components will perform as expected has not been completed. Tests will' be performed at the next scheduled outage for each unit. More etails are given later in this I
enclosure.
The design verification concluded that sizing, configuration, and failure positions are adequate for assuring required safety functions. Areas of potential concern and areas where system reliability might be enhanced were identified:
s o
Emergency backup air compressor air quality improvement, operation improvement, and piping configuration improvement.
o Effect of air-regulator air usage on components with accumulators when isolated on a loss of instrument air.
o Effect on low-pressure sections of the instrument air system when air-regulators fail and allow full system pressure.
Each of these areas has been evaluated to some degree already. After system testing, further evaluation will be conducted.
Enhancements to the instrument air system recently accomplished or for which firm plans
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exist include:
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A nitrogen backup system.
o An upgrade kit, developed by our dryer manufacturer, to replace the dryer actuators.
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Improvements in monitoring and maintenance of instrument air compressors and dryers.
I ENCI.OSURE (O 1
INSTRUMENT AIR SUPPLY SYSTEM PROBLEMS AFFECTING SAFETY-RELATED EQUIPMENT l
l Testing to be completed during the next outages includes; i
l Capacity check of the en'ergency backup air compressors to ensure they are able to meet the required load.
i Testing of valves with accumulators to verify the accumulates' capacity will satisfy the minimum number of valve cycles needed.
1 Testing of check valves that isolate the safety-rela:ed headers from the j
non-safety related header.
l Verification that the Auxiliary Feedwater System accumulators supply j
sufficient air for the required two hours of operation.
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February 17, 1989 i
ff
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n TO:
Mr. G. C. Cre< 1g/
.J FROM:
D. L. Shaw
(
W. J. Lippolk i
VIA:
p
- 3. S. Montgomery C l
1
SUBJECT:
Calvert Cliffs' Response to Generic Letter 88-14 Instrument Air Supply System Problems Affecting Safety-Related Equipment The final proposed response to the subject. generic letter is forwarded for your signature. It must be notarized. The due date is February 18. Monday is a holiday for both BG&E and NRC. By NRC guidelines, the letter could be signed Tuesday and still meet the due date.
1 The final differs from the draft sent for management review in the following areas:
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The results of our air quality test could not be cbtained on time from the.
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testing laboratory. Our NRC project manager has concurred with a two-week delay in submittal of the results (page 2 of Erm,mure 1).
o Inim an of a reliability-based maintenance pros, ram for the instrument i
air system is mentioned (page 3 of Enclosure 1).
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o Design Engineering's comments carried a lot of weight since this is mamly a d3 sign verification. Their comments came in very late in the game, so l
there is really no time for another review cycle through management.
Design wanted to remove all the details about the potential concerns identified and the enhancements being considered that we could not commit to actually doing, perhaps ever. It is always a judgment call as to just how much detail to have put on our docket and how much to hold for the follow-up NRC inspection.
I I decidad to edit as Design suggested. Major potential concerns and l
enhancements are still listed, but not detailed.
I will be out of the plant from i1:00 a.m. until approximately 3:30 p.m.
I will be l
available by phone during that time, either via Donna McCready (x-4979), or directly at 326-6341. I will have a copy.
Thank you.
Un Engineer i-Licensing Unit l
DLS/ dim NRC 89-09.C Attachment l
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