NRC-89-0046, Forwards Response to NRC Generic Ltr 88-14, Instrument Air Supply Sys Problems Affecting Safety-Related Equipments. Encl Also Includes Discussion of Program for Maintaining Proper Instrument Air Quality
| ML20235U012 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 03/01/1989 |
| From: | Sylvia B DETROIT EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| CON-NRC-89-0046, CON-NRC-89-46 GL-88-14, NUDOCS 8903090008 | |
| Download: ML20235U012 (15) | |
Text
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f
- 3. R:lph Sylvia Senior Vice President 6400 North Dixie Highway f
Newport. Michigan 48166
%s7 (313) 586-4150 March 1, 1989 Nic-89-0046 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C.
20555
References:
- 1) Fermi 2 NIC Docket No. 50-341 NTC License No. NPF-43
- 2) NUREG-1275, Volume 2, " Operating Experience Feedback Report - Air Systems Problems" 3)
NFC Generic Letter 88-14, " Instrument Air Supply System Problems Affecting Safety-Related Equipment", dated August 8,1988
Subject:
Resoonse to N E Generic Letter 88-14 Detroit Edison has received and reviewed NUPIG-1275, Volume 2 (Reference 2) and Generic Letter 88-14 (Reference 3). In response to Generic Letter 88-14, a design and operations verification of the Fermi 2 instrument air system has been performed. Our response to Generic Letter 88-14 is provided in the enclosure of this letter, which also includes a discussion of our program for maintaining proper instrument air quality, as requested.
If you have any questions, please contact fir. Girija Shukla at (313) 586-4270.
Sincerely, Enclosure cc:
A. B. Davis R. C. Knop W. G. Rogers J. F. Stang 8903090008 890301 g
PDR ADOCK 0500(
1 L _ -- _
USimC liarch 1,1989 IEC-89-0046 Page 2 I, B. IMLPH SYLVIA, do hereby affirm that the foregoing statements are based on facts and circunctances which are true and accurate to the best of my knowledge and belief.
An Q
B. PALPff SYLVIn Senior Vice President' On this id dal day of dlar t to
, 1989, before me personally appeared B. Ralph Sylvia, being first duly sworn and says that he executed the foregoing as his free act and deed.
T w u -/9L -fb o 1 Notary Public KARELL fli. REED Nctzry Public, Monroe County, Mi:h.
My Ccari::i:n Egircs May 14.13)2 l
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Enclosura to 4
Page 1 HESPONSE 1D NRC GENERIC LETTER 88-14 o
Background
Detroit Edison's Fermi 2 has two instrument air systems which provide instrument quality air to safety-related equipment. These are the interruptible control air (IAS) and noninterruptible control air systems (NIAS). The noninterruptible control' air system is a safety-related system consisting of two independent divisions.
Its primary function is to provide instrument air to those safety-related components requiring instrument air to perform their safety-related function. The interruptible control air system is non-safety related. However, it does supply instrument air to some safety-related components requiring instrument air during normal operation. These safety-related components either fail in a safe position on loss of air or have pericdic tested, qualified accumulators adequate to provide the necessary instrument air. Therefore, they do not depend on the non-safety related air supply to fulfill their safety function.
The emergency diesel generators starting air systems are not fed from either instrument air system. Each diesel has its own compressor, dryer and accumulator tanks. The accumulators provide the assurance that air is available to start the diesels. The accumulators in these air systems are fully qualified with respect to seismic and EQ for their safety-related service.
The normal nitrogen supply to the pneumatic system outside of the primary containment isolation valves is not a qualified nitrogen supply system. The piping, valves and accumulators from the containment isolation valves to the pneumatic users is fully seismically and EQ qualified. Individual accumulators for the ADS, Low-Low Set reilof valves and main steam isolation valves provide the pneumatic supply for these valves to perform their safety-related function. As a back-up, the ADS, one Low-Low set relief valve and main steam isolation valves can be fed from Division I of the noninterruptible control air system.
Secondary containment has one railroad car air lock that requires air to pressurize the inflatable seals on the doors and operate the door latches. The seals assist in maintaining secondary containment air ar.d water leakage integrity. The air for these doors is provided by an independent compressor and piping system.
This system does not tie into any plant instrument air system.
This system is not fed from a QA1 power supply in normal service nor qualified seismically. Presently, a passive seal is installed on the outer railroad car door as a back-up to the air seal for secondary containment integrity. For ease of operating the doors and maintaining the sealing integrity, alternate methods of sealing are being investigated.
Enclo;ura to NRC-89-0046 Page 2 i
o Design and Operations Verification of the Instrument Air System
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Generic letter 88-14 requests that each licensee review NUREG 1275, Vol. 2 and perform a design and operations verification of the instrument air system.
Petroit Edison's respcase to each item of the Generic Letter 88-14 is given below:
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Generic Letter Item No. 1j Verification by test that actual instrament air quality is consistent with the manufacturers recommendations for individual components served, o
Detroit Edison Response:
A review of manufacturers' instrument air quality recommendations was performed for components using instrument air at Fermi 2.
The review indicated that ISA standard S7 3, Quality standard for instrument air, meets or is more conservative than the manufacturer's recommendations, except in the case of dew point.
ISA standard S7 3 would only require a dew point reading of -37 F based on the lowest recorded site temperature referenced in the 0
UFSAR, Section 2 3 1.2.
G.E. recommends a -40 F dew point (reference G.E. BWi plant requirements Spec. 22A1300BC14).
Both Fermi 2 instrument air systems, interruptible and noninterruptible, were designed to meet or exceed the air quality requirements specified in ISA standard S7 3 The following is a comparison between ISA standard S7.2
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requirements, Fermi 2 design and periodic checks made to assure l
the instrument air quality:
Dew point l
o Requirements:
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ISA - S7 3 - dew point at line pressure shall be < 18 F below o
the minimum ambient temperature to which any part of the i
instrument air is exposed. Per Fermi 2 UFSAR, section 2 3 1.2, U
the lowest recorded site temperature is -19 F.
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Enclo ura to 4
- NRC-89-0046 Page 3-o--Fermi 2 design basis - den point at line pressure shall'be 5
-40 F for.both interruptible and noninterruptible centrol air systems, reference UFSAR Section 9 3 o Checks performed:
o Noninterruptible control air system o Preoperational test P5002.001
-o Div I measured -50.8 F at its dryer outlet at maximum flow and pressure rate.
U o Div II measured -49 F at its dryer outlet at maximum flow and pressure rate.
o Maintenance procedure NPP 35.622.002 requiresguarterly checks with an acceptance criteria being 5 -40 F.
0 o Div I measured -47.8 C (-54 F) at last test performed, 2-8-89 l
0 o Div II measure - 49 C (-56.2 F) at last test performed, 2-16-89 In lieu of adding a continuous dew point monitor which could affect the integrity of the system, the frequency of the testing will be changed to a monthly activity under procedure NPP 35.622.002 by March 31, 1989.
In addition, the round checks made shiftly to bina down the manual drain valves on the prefilters, afterfilters and receiver tanks would detect any abnormal amount of water in the system.
o Interruptible control air system o Preoperational test P5002.001 o Measured dew point -72 F at its dryer outlet at maximum flow rate and pressure.
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o Continuous dew point monitoring o The operating dryee tower is maintained at at least a i
-50 F dew point. When the dew point rises to a -50 F in the operating tower, the controls switch to the other tower. If the dew point rises to a -35 F, an alarm is received in the main control room indicating dryer l
malfunction.
In addition, the header supplying the reactor building is continuously monitored and if the dew point should rise to a -35 F an alarm is received in the main control room.
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a Enclorura to
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NRC-89-0046 Page 4 Particle size' o ISA S7 3 - maximum particle size in the air stream shall be three (3) micrometers (micron).
o Fermi 2 design basis - maximum particle size is < 0.5 micron (normal) for both noninterruptible and interruptible control air systems, reference UFSAR, section 9 3 o
Periodic or continuous monitoring Monitoring of particulate content in the instrument air stream is not being performed. The basis for this is:
o Both the noninterruptible and interruptible control air dryers have coalescing prefilters and particulate afterfilters. The afterfilters are capable of removing all particles 1.0 micron and larger and 98% of 0.5 micron and larger.
This is extremely conservative, considering the ISA standard, S7 3, only requires a 3 micron removal capability. Assurance that the filters are performing adequately is provided by high differential pressure alarms received in the main control room and by replacing the filters on a semi-annual preventive maintenance program.
Oil Content o
ISA ST.3 - maximum total oil / hydrocarbons content, exclusive of noncondensibles, shall not exceed one (1) PPM w/w under normal operating conditions.
o Fermi 2 design - both noninterruptible and interruptible control air shall be oil free, reference UFSAR section 9 3 o
Periodic or continuous monitoring Honitoring of oil / hydrocarbons content is not being performed.
The basis for this is:
o The primary source for oil in an instrument air system is from their compressors. Fermi 2 uses non-lubricated reciprocating style compressors. Their locations provide for an oil free atmosphere for their air intake.
This eliminates all principal sources for oil / hydrocarbon contamination in the instrument air systems.
Enclc ura to 1
NRC-89-0046 Page 5, o In addition, noninterruptible control air dryers have Pall coalescing prefilters having efficiency for oil removal of 99 995 Based on a maximum flow rate and with maximum 50 PPM
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w/w of oil entrained in the air stream prior to the
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prefilter, the filtration would result in less than.0014 PPM w/w of oil entrained in the air stream.
o The interruptible control air dryer also has a coalescing prefilter. The Dollenger coalescing prefilter is capable of removing 99.97% of all dispersed liquids / oils, 0 3 micron and larger droplets and 98% of all dispersed liquids / oils, 0.02 micron and larger droplets, o Both the interruptible and noninterruptible prefilters have automatic drains and if the filters become plugged, the differential pressure alarms across the entire dryor system would alarm in the main control room indicating a dryer malfunction. The filters are also checked (including for oil), cleaned and cartridges replaced semi-annually, o Based on the above oil content discussions, the coalescing prefilters differential pres.sure alarms and maintenance performed on the filters,'which includes checking for oil on the filter cartridges, semi-annually, assures we meet the ISA standard without continuous or periodic monitoring.
c o As an additional prudent measure, a sampling program for determining the presence of an adverse trend in oil and total particulate content will be established.
Contaminants o ISA S7 3 - Compressor intake areas shall be free of all corrosive contaminants and hazardous gases, flammable or toxic, which may be drawn into the instrument air stream. Any cross connections or process connections to the instrument air piping shall be isolated to preclude contamination of the instrument air system. Regular periodic checks should be made to assure high quality instrument air.
o Fermi 2 design o Compressor area contaminants - The station air compressors, which are the primary source of air for the instrument air systems, are located in the northwest corner of the turbine building first floor. Under normal plant operation, this area is free of any significant corrosive contaminants and hazardous gases that could be drawn into the compressors.
The noninterruptible control air compressors are in their own
LEncloIura to NRC-89-0046 Page 6 I
. room,51ocated,in.the reactor auxiliary building mezzanine, elev. 551'-0".
This area is also free of corrosive.
contaminants and hazardous gases under normal plant operations.
In addition,' operations would be aware of any abnormal conditions in the area of the station or control air
' compressors as the result of operator rounds, o Cross connections or process connections to instrument air-piping - The noninterruptible control air system has two (2) process system cross connections, one (1) in each division L
which connect'to the main steam system. These connections are for the main steam isolation valve leakage control system. In.this case, isolation is provided by three'(3).
normally closed solenoid-operated valves in series, per division.1 Between the second and third isolation valve is a normally open solenoid operated drain valve. This open drain' valve prevents the third isolation valve from being pressurized by mairr steam, should the other valves leak, thus providing additional protection against contaminating the noninterruptible control air system.
The interruptible' control air system has a cross tie to the standby liquid control system through the level instrument (bubbler) on the standby liquid control storage tank.
In this case, intrusion of. contaminants (boron) into the interruptible air system is prevented by the actual bubbler tubing configuration and the fact that the storage tank is vented to the atmosphere. With the tank being vented to the
-atmosphere,.the tank cannot develop enough pressure to force the' boron into the instrument air system.' The instrument air tubing to the bubbler is routed such that if a loss of air pressure occurred, the boron.could not enter the air system via' gravity or storage tank head pressure. As a result, a check valve or. isolation valve to prevent any back contamination in this case, is not considered to be a required.
The station air compressors, their intercoolers and after coolers, and the. control air compressors and their aftercoolers all require cooling water. All of this equipment is upstream of the instrument air dryers.
Therefore, intrusion of water from any minor leaks would be eliminated by the dryers. Major leaks would either be detected by the cooling water systems loss of pressure or the overloading of the dryers resulting in a high differential pressure alarm across the dryers. For the noninterruptible control air system, the operator, during his rounds,~is; required to-blowdown the drain valves on the control air receiver tanks and dryer filters.
The presence of significant amounts of water would alert operations to the presence of possible cooling water leaks. The interruptible air dryer high dew point alarm would also alert operators to potential cooling water in the interruptible air supply, i
Enclosure to NRC-89-0046 Page 7 I
o Generic Letter Item No. 2:
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Verification that maintenance practices, emergency procedures, and training are adequate to insure that safety-related equipment will function as intended on loss of instrument air.
o Detroit Edison Response:
The following preventive maintenance is performed on the instrument air systems to maintain their operation and the instrument air quality.
o Noninterruptible control air system o Once per shift - Manual drain valves on the dryer's prefilters, afterfilters and receiver tants are blown down. This provides an indication that the filters and dryers are free of abnormal amounts of moisture. The control air compressors oil levels are also checked.
o Monthly - The quarterly activity to check the dew point at the outlet of the dryers will be changed to a monthly activity as the result of this review. The basis for this change was discussed previously in this response.
(Reference Procedure NPP 35.622.002).
o Quarterly - The drain traps on the control air compressor aftercoolers are internally inspected and cleaned.
o Semi-annual - The dryer prefilter and afterfilter assemblies are inspected, cleaned and the cartridges replaced. The dryer's desiccant and purge exhaust flow restrictors are inspected and replaced based on the results of these inspections (Reference Procedure NPP-35.622.002). Also, the control air compressor's crankcase oil is sampled every 24 weeks.
o Annually - The dryer's inlet and exhaust valve assemblies are inspected, cleaned and repaired / replaced as required.
(Reference Procedure NPP-35.622.002). The control air compressor's/ motors are cleaned and inspected.
The compressors oil and filters are changed. The oil strainers and crankcase breathers are cleaned. The motors are lubricated and their belts are checked.
o Every 2 years - The control air compressors suction and discharge valves are refurbished or replaced, based on their ",as-found" conditions..
c Enciccura to
.NRC-89-0046 Page 8' The noninterruptible control air system has the following performance and surveillance checks performed:
o NPP-24.129.01 - Station and control air system valve operability and position indication verification test.
o Valve operability test periodicity is 92 days.
o Valve position verification test periodicity is 18 months.
o NPP-27 129.01 - Control air compressor auto start tett with a required frequency of 92 days.
o Surveillance procedure will be developed, by the first refueling optage, to' test accumulators' isolation capabilities. This surveillance will also be included in the Inservice Testing program.
-o Interruptible control air system o Monthly - The dryer's four-way selector valves, two-way isolation valves and air cylinder rods are lubricated, o Quarterly - The dryer's desiccant, heaters, belts, and gaskets are checked and replaced as necessary (Reference Procedure NPP-35.622.oot).
o Semi-annual - The prefilter and afterfilter assemblies are inspected and the cartridges are replaced.
o Annually - The dryer's reactivation cooler and associated ducts are checked, refurbished and repaired based on the "as-found" conditions. (Reference Procedure NPP-35.622.oo1).
Presently a temporary heatless type desiccant dryer is installed in parallel with the permanent interruptible control air dryer. 'This allows maintenance to be performed without using wet, unfiltered station air to feed the intarruptible control air users. A permanent heatless air dryer is currently being installed under EDP 5323, which will be completed by the first refueling outage. Once installed, the new dryer will have similar preventive maintenance as the noninterruptible control air dryers, which are of the same make and design.
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Enclorure to NRC-89-0046 Page 9 o Station air systes (supply portion to control air) l o Once per shift - Compressor's oil temperature, oil
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pressure, cooling water temperature and receiver tank
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pressures are checked and recorded on the operator round sheets. These sheets are reviewed shiftly by operations management.
o Monthly - Every 4 weeks a crankcase oil sample is taken.
o Quarterly - Tightness of valve covers is checked and inlet air filters on the compressors are cleaned or replaced based on the "as-found" condition.
(Reference Procedure NPP-35.129 001).
o Semi-annual - Condensate drain traps on the intercoolers, aftercoolers and receiver tanks are inspected and cleaned.
o Annually - Compressor foundation bolts, taskmaster valve, piston rod packing, high & low pressure cylinders suction, discharge and feather valves are checked and refurbished, repaired, or replaced based on their "as-found condition".
o Every 2 years - The compressors are overhauled.
Additional PMs will be established and/or revised when the compressors, aftercoolers and receiver tanks drain improvement is currently being performed per EDP 1511 and will be completed by the first refueling outage.
A review of vendor manuals for the noninterruptible control air dryers, interruptible control air dryer, control air compressors and station air compressors indicates that the maintenance being performed, as described, is adequate to maintain the instrument air quality and reliable function of the systems. In the past, the water and contaminants in interruptible control air were due to the interruptible control air dryer and its filters being by-passed while maintenance activities were performed on them. This resulted in station air being fed directly into the interruptible control air receiver tank. The present temporary air dryer connected in parallel with the permanent dryer allows for maintenance.
1 Enc 11:ura b3 NRC-89-0046 Page 10 When.EDP 5323.is implemented, a permanent parallel interruptible control air dryer will be installed. This will provide a permanent means of performing maintenance on either dryer, thus eliminating future problems with water and contaminants in the interruptible control air system due to by-passing the dryer.
o Ope' rating, abnormal and alarm response procedures Operations revised the procedures to assist operators in the identification, control and recovery from a total loss of instrument air events. The procedures include the following:
o The current operating procedures provide a means of identifying a loss of instrument air, i.e. alarms, automatic actions, functions lost, etc.
o Procedure 20.129 01, loss of station air and/or control air and alarm response procedures 7D48, D50, D51, D52, D53, D54, D55, D56, D57, DS9, D60, D61, D66 and D69 address these items.
o The current operating procedure provides a means of identification of critical components operated by instrument air and the position in which they fail on loss of air.
o Procedure 20.129.01, loss of station and/or control air, enclosure A addresses these items.
o Expected system and plant responses to a loss of instrument air and the consequences of these responses are described in current operating procedure.
o Procedure 20.129.01, loss of station and/or control air, enclosures B and C, addresses these items.
o Manual actions the operators are expected to take are contained in the current operating procedure.
o Procedure 20.129 01, loss of station and/or control air and the previously identified alarm response procedures address this item.
o Restoration actions to be taken after instrument air is repaired are addressed by the normal start-up procedures.
0 No components were found to need special restorative l
actions when restoring control air that are not already in the normal system start-up procedures.
9 Enclecura to NRC-89-0046 Page 11 o
Training o The Fermi Control Room Simulator has been upgraded to allow for simulation of loss of instrument air event.
o Licensed operator requalification classes have been updated to include discussion and simulation of loss of instrument air scenario. Requalification classes are scheduled to be completed by April 14, 1989.
o Fermi Plant System courses have been revised. Sections were added which identify air operated equipment and failure modes.
o Initial licensed and non-licensed operator training use the Fermi Plant Systems course as described above.
o Maintenance personnel will be required to read Generic Letter 88-14 and Fermi 2's response to it in order that they have a better appreciation for the consequence of losing or contaminating instrument air by lack of or poor maintenance practices. This will be required to be completed by June 30, 1989.
o Generic Letter Item 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 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.
o Detroit Edison Response:
The noninterruptible control air system was reviewed in its entirety. Prior to the receipt of Generic Letter 88-14, Design Calculation 4931 was developed and issued to address all the current noninterruptible air users and document the capability of the air receivers to provide sufficient air until the control air compressors auto start. Also, the calculation identifies the failed position of the user on loss of air.
Be.ued on the calculation, the noninterruptible control air users list was updated. A review of the Updated Final Safety Analysis Report (UFSAR) indicates that the present noninterruptible centrol air users and the noninterruptible air system operation are in conformance with the UFSAR.
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Encitture to NRC-89-0046 Page 12 The following safety-related equipment, which use accumulators to fulfill their safety related functions, were reviewed. The capability of the accumulators to support the intended safety functions was verified.
o B2104F013E, F013H, F013J, F013P and F013R - automatic depressurization system valves (ADS).
o B2104F013A & F0130 - Low-low set relief valves (LLS) o B2103F022 A-D - Main steam inboard isolation valves (MSIV) o B2103F028 A-D - Main steam outboard isolation valves (MSIV) o P5002A001 & A002 - Noninterruptible control air receivers.
o R3000A009 thru A016 - Emergency diesel generator starting air receivers.
Result of the accumulator review is as follows:
o Design Calculation 469, REV. C provides justification of adequacy of the design for the ADS, LLS and MSIV accumulators.
The ADS accumulator adequacy is reinforced by the response to NRC questions addressed in letter NRC-87-0074, dated May 26, 1987 o Pre-op test B2100.001 verified the size of the ADS, LLS & MSIV accumulators by physically measuring each accumulator. This was done to insure that the volume installed met or exceeded the requirements of DC 469, Rev. C.
o Pre-op test B2100.001 performed a pressure drop test on each ADS & LLS accumulator to confirm that the isolation check valves provided adequate isolation upon loss of air supply.
o The MSIV accumulators did not have a pressure drop test. A functional test of the MSIVs was performed after simulating a loss of air supply event. The valves all cycled closed as required. The outboard MSl; accumulators have hard seat check
. valves. As a result, a review of the operation of the MSIVs along with a calculation was performed to insure that their accumulator design is adequate.
o Future testing of the ADS, LLS & MSIV accumulators to assure their check valve leakage rate is acceptable will be performed under surveillance procedures 43 137.02 and 43 201.01 during refueling outages. These procedures are being developed and scheduled for issuance by April 15, 1989 L
Enclecura ts-l NRC-89-0046 Page 13 o Design Calculation 4931 provides justification for the capacity of the receivers to maintain a 10 minute reserve on loss of air supply.
o Pre-op test P5002.001 verified that equipment fed by the receivers could still function for a safe shutdown if the inlet to the receivers were isolated for at least 10 minutes. The isolation of the noninterruptible control air system from the non Q, nonseismic station air system is accomplished by air operated valves that fail closed on loss of air or power and close on low header pressure. Therefore, no credit was taken for the check valves serving an isolation function.
o Colt, supplier of the diesels, sized and furnished the air start receivers. Pre-op test R3000.001 verified that the two (2) receivers per diesel generator had the capability of starting their diesel a minimum of 5 times without charging.
This is consistent with the UFSAR.
o Each diesel start air receiver tank has a low pressure alarm which is monitored in the main control room.
This, along with the diesel start surveillance, provides assurance that the system is functioning correctly.
o The diesel air start system has its own compressor for each diesel along with a refrigerant dryer to reduce the moisture and contaminants in the starting air. Colt diesels do not use starting air motors, but rather inject directly into the cylinders. Thus, the potential for cir starting failures due to contaminants and moisture is reduced.
o Fermi 2 Program for maintaining proper instrument air quality.
The testing, preventative maintenance, and training that has been described constitutes Fermi 2's program for maintaining proper instrument air quality.
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