05000285/LER-1981-002-01, /01T-0:on 810413,during Normal Operation at 65% Power,Notification Received of Defect in Certain Foxboro Transmitters.Transmitters Have Capacitor Amplifier Which May Fail Due to Heat During Operation or After LOCA
| ML19343D422 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 04/14/1981 |
| From: | Core M, Mehaffey R OMAHA PUBLIC POWER DISTRICT |
| To: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| Shared Package | |
| ML19343D418 | List: |
| References | |
| LER-81-002-01T, LER-81-2-1T, NUDOCS 8105040450 | |
| Download: ML19343D422 (10) | |
| Event date: | |
|---|---|
| Report date: | |
| 2851981002R01 - NRC Website | |
text
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60 61 COCKET NUMBER 68 69 EVENT oATE 74 15 REPORT oATE 80 EVENT DESCalPTION AND PROBABLE CONSEQUENCES h
'I o f 2 l l-During normal power operation at a nominal 65% power. notification was received fromI g g lthe Foxboro Company that a potential defect may exist in certain transmitters manu-I l0l4l lfactured by Foxboro. The transmitters in question may have had a capacitor instn11ed l
.in the amplifier that could fail due to heat either during operation or af ter a LOCl..
ll o l 3, I Further, some of the transmitters mcy have had insulation installed that could beccme 1
- 10 t o I @rittle af ter exposure to hish radiation which may occur af ter a LOCA.
See attached l
ll o l 7 l l letter (Foxboro #120381 date612 March 1981) for further clarification. Technical l
lUia1l Specification 5.9.2(9) applies.
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3J 34 32 36 31 40 41 42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS liitil The transmitters in cuestion are those mnnufnctured by vnyhnro en ufchernna n T ara I
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g,,jg These transmitters have been installed at Fort Calhoun Station to measurp y processes that are critical to plant operation and those processes necessary to mitigate an accident. Failure of the capacitor or insula. tion could cause the trans-g l
mitter to fail. See Attachment 2 for corrective action.
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Foxboro MA02035U.SA The Foxboro Company (sm sa-87so 12 March 1981 Omaha Public Power Dist.
Attention: Purchasing Agent Fort Calhoun, NB 68023
Subject:
Potential Deficiency Affecting Foxboro Transmitters Model Nos. N-Ell, N-E13, or Ell, E13 with Suffix Codes /MCA, /MCA/RRE, or /MCA/RR -- Listing Attached Gentlemen:
Our records indicate that you have received one or more of the Foxboro model nu=bered transmitters listed above. This letter is to notify you that two deficiencies have been discovered in some of these transmitters which may exist in the units shipped to you.
The transmitters in question operate at a signal level of 10-50mA. Similar model numbered units opemting at 4-20mA are not affected.
The first issue involves the possible use of incorrect insulating sleeving on transistor and zener diode lead vires in the amplifier.
The second issue involves the use of a specific vendor's capacitor which is not hermetically sealed (although claimed to be so). As a result, the capacitor electrolyte an leak under adverse service conditions, specifically heat and time.
The failure mode is a decrease in resistance across the capacitor resulting in electrical leakage. The transmitter operation can be affected by limiting the output to something less than full value which, in time, can degrade to no output at all.
Insulating Sleeving - Radiation resistant sleeving consisting of a silicone coated glass fiber braid has been substituted by a teflon sleeving in some transmitters.
Tests have shown that teflon will become brittle and deteriorate with a substantial integrated radiation dose. Foxboro testing has demonstrated that the teflon sleeving used in these devices vill withstand an integrated dose of 10 megarads with no noticeable deterioration.
Tests to 200 megarads produce the brittle conditions which can result in the teflon flaking from the wires.
Based on these tests, operating plants not expected to exceed an integrated dose of 10 megarads have no potential problem and no action is required.
Where the integrated dose rate could exceed 10 megarads, then units in service should be inspected to determine if the proper insulating matarial has been used. This can be accomplished by opening the transmitter in accordance with Foxboro Master Instruction MI 20-145.
The amplifier cover must be removed exposing the amplifier assembly. At one end of the assembly, a transistor and a zener diode are mounted in the base casting which serves as a heat sink.
The l
insulating material in question is a sleeving slipped over the lead wires #-a-these two components.
The proper material is white and heavy looking.
Positive t
fOXBORO ammmmmmmmr
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Page 2 12 March.1981
Subject:
Potential deficiency affecting Foxboro transmitters identification can be made by inspecting one end of the material to establish that the outer material covers an inner braid. Teflon, if used, will be a single layer material and could be either clear or white.
If improper insulation is present, then the corrective action is to replace the amplifier (Foxboro P/N N0148PW).
Replacement amplifiers can be purchased from your local Foxboro Sales or Service Representatives.
If you prefer to have Foxboro Service Personnel inspect the equipment and, if necessary, replace the amplifier, this can be arranged at standard service races.
Capacitor - The capacitor degradation problem was discovered over time through tracking failure situations. Internal corrective action has been taker to remove the vendor involved'from the qualified vendor list and to purge 11 stock of capacitors from this vendor. Degradation of this espacitor is a function of time and service conditions with heat being a primary contributor. This phenomenon was observed in recent tests of transmitters using these capacitors.
The capacitor in question is manufactured by Cornell-Duebilier and can be specifically identified by a type number in the form TX-o5-XXIX as well as a usonogram in a box followed by a date code, e.g.lCDR 0874 l It is assigned Eagboro part number N0141MF.
To determine if this capacitor is present requires a visual inspection of the amplifier which can be accomplished as described above for the insulating sleeving inspection. The recommended corrective action should the above described capacitor be present is to replace the amplifier (Foxboro P/N N0148PV) although is is possible to replace the capacitor with a foxboro.provided substitute. Use of Foxboro Service personnel to perform the inspection and replacement, if necessary, can be arranged at standard service rates as described above.
Due to lack of knowledge of specific application, redundancy, and the like, Foxboro cannot determine if the NRC reporting requirements of 10CFR Part 21 are applicable.
This determination is the responsibility of the user and any such reporting would be made by them after completing their evaluation of the situation.
If you have any questions regarding the above, please contact the undersigned directly.
Very truly yours, THE FOIBORO COMPANY William Calder, Manager Corporate Quality Assurance l
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Enclosure MI 20-145 POXBORG anum =rzm
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Omahn Public Pow;r, Ft. Calhsun, NB i..
The following list reptesents all 10-50mA N-E10 and E10... -/MCA, -MCA/RR,
-/MCA/RR7 transmitters or Part No. N0148PW amplifiers which we have been able to identify as being shipped to you either directly or through an agent.-
It should be noted that any Foxboro part number N0148PV a:Plifiers you may hmes as spares should also be chetkad per the letter for potential deficicacica.
Serial No./Part No.
Tag No.
.N0148PW (Amplifier) none 4201579 FT-1109
- - 4201580 FT-1110 4201580 PT-105 4201581 PT-115 4201582 LT-901A 4201583 LT-901B 4201584 LT-901C 4201585 LT-901D 4201586 LT-904A 4201587 LT-904B 4201588 LT-904C 4201589 LT-904D 4203969 LT-101T 4205440 Blank EOXBORG w
I LER 81-002.
- - Omaha Public Power District F rt.Calhoun Station Unit No.~ l Docket No.: 05000285
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Safety Analysis
The following table represents the results of the inspection of the safety related Foxboro transmitters which could have potentially been exposed to a degrading environment.
Channel Defective Teflon No Problem l
No.
Function Capacitor Insulation Found LT10lX Pressurizer Level Control X
LT10lY Pressurizer Level Control X
LT103X Pressurizer Pressure Control X
LT103Y Pressurizer Pressure Control X
FT313 HPSI Flow X
FT316 HPSI Flow X
FT319 HPSI Flow X
l FT322 HPSI Flow X
LT901A Steam Generator A Level: Reactor Pro-tective X
LT9018 Same as above X
LT901C
$ame as above X
LT901D Same as above X
l PT902A Steam Generator A Pressure: Reactor Protective, ESF X
l PT902B Same as above X
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PT902C-Same as above X
- - PT902D Same as above X
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LT904A.'
.'SteamGeneratorBI t-Level: Reactor Pro-tective X
LT904B Same as above X
LT904C Same as-above X-LT904D Same as above X
PT905A Steam Generator B i
. Pressure:: Reactor.
Protective, ESF X
1 PT905B-
~Same as above X
PT905C Same as above X
PT905D lSame as above X
i
.PT102A-Pressurizer Pressure Narrow Range: Reactor i
Protective, ESF X
.PT102B Same as above X
I
- - PT102C.
Lame as above X
PT1020' Same as above X
l FT1109 Auxiliary Feedwater Flow to SGA X
FT1110 Auxiliary Feedwater Flow to SGB X
1.
LT384 Post Accident Sump Level X
PT105 Pressurizer Pressure l
Wide Range X
1 j
PTil5
'Same as above X
Total 8
17 8
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As;is pointed out in the above table, two potential problems were identi-fied by Foxboro to the District.
The first being a defective output ca-5
'pacitor which may degrade over time (and is accelerated by temperature and humidity);resulting in a transmitter which may.not drive to full output if required to, by the process input.
This failure may be dramatically accelerated 'if the transmitters were environmentally stressed by an acci-
. dent condition. The second problem area was that of teflon insulation
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- - on an amplifier'zener diode and output transistor.
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It should be noted that the District has noted no abnormal operational problems over the history of the station.
In no case have the trans-mitters, when considered as a group, failed to initiate a required safety function (random failures have occurred and were within the de-sign criteria of the station).
~
The only area of concern during normal operation would be a capacitor failure which would impede an increasing signal.
Of the safety parame-ters which had defective capacitors the only automatic safety function required on an increasing signal was that of a high pressurizer pressure reactor trip.
In this case, 3 of 4 channels would be operable.
This exceeds the minimum Technical Specification requirements. The remaining potentially defective transmitters are provided with redundant unaffected readouts and/or any failure would have been in the conservative direction.
Redundant readouts would have permitted operator identification of a pro-blem.
It is the District's opinion that during the period of time when poten-tially defective transmitters were installed, the plant cN1d have been safely shut down and maintained in a safe shutdown should an accident have occurred.
The teflon insulation was not considered to be a safety hazard.
Foxboro recommended that the exposure be limited to 107 rads to insure insulation integrity. Actual failure occurred after an exposure of greater than 108 rads at one test facility, followed by mechanical shock during shipment to a different test facility. The expected 1000 hour0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> exposure of the transmitters in a post accident situation is 1.36 x 107 rads with the ex-ception of the HPSI flows which will receive approximately a 3 x 107 rad dose. Since no mechanical inputs are expected and the dose is approxi-mately of the same magnitude, no failure would have been expected.
It should be noted that the failure of the insulation would not necessarily cause transmitter failure. The insulation must crack and cause a short which would be difficult since the circuit is a low voltage instrument circuit.
The capacitor time to failure in a post accident situation is an unknown quantity. For the purposes of the analysis it was assumed that the trans-mitters failed with some low output signal.
Please note that the trans-mitters were expected to be operable for some period of time.
In the case of pressurizer level, one channel would have remained operable.
For a large break, pressurizer level is not required.
For a small break, if level was needed, both channels were likely available (due to reduced environmental stress).
If failure of one channel resulted in confusion to the operator, the HPSI pumps could remain in-service assuring cool-ing with no detrimental effect.
For pressurizer pressure all 8 channels must be considered as a system.
If both wide ranges had failed, the narrow range, 1500 to 2500 psia, could have been used in conjunction with HPSI pump flow indication to insure ade-quate cooling.
The steam generator levels were provided as a back up to auxiliary feedwater flow to insure flow to the steam generators.
Even with capacitor failure, adequate information was available to insure flow.
- - The single ' capacitor on the PT9028 channel would not effect the overall re--
liability of that parameter indication during a post LOCA situation.
The affected transmitter amplifiers have been replaced.
No further analy-sis of this concern is planned.
1 i
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LER 81-002 Omaha Public Power Listrict Fort Calhoun Station Unit No. 1 Docket No.- 05000285 Attachment No. 2
Corrective Action
Upon receipt of Foxboro letter 120381 of 12 March 1981, an evalu-ation was initiated to determine if an unsafe condition could exist at the Fort Calhoun Station. Additionally, the Commission was notified that the District had received the letter and that an evaluation of Foxbora transmitters had begun. Plant staff immediately checked all spare parts in the storeroom and two transmitters installed in the Auxiliary Feedwater (AFW) flow loops for the potential defect. The investigation showed that 4 of 10 spare amplifiers had the potential defect and the transmitters installed in the AFW flow loops had no problem.
During the time period between receipt of the Foxboro letter and subsequent plant shutdown, many telephone conversations were held be-tween the District and Corporate Quality Assurance at Foxboro. During one of the conversations, it was discovered that the potential defect could. exist in transmitters not listed in the Foxboro letter of 12 March 1981.
At that time, a decision was made to place the plant in hot shutdown to inspect all Foxboro transmitters installed in critical loops in the containment.
Each transmitter of the LOCA/RR, MCA or N-E10 series was opened and the amplifier checked for components that could produce the possible l
defect (i.e., capacitor or insulation) that was the subject of Foxboro letter 120381 of 12 March 1981, attached.* If either the capacitor or insulation was found to be of the incorrect type in any of the trans-l mitters, the entire amplifier was replaced with an exact replacement ampitfier that had previously been inspected for proper components.
After the amplifier was replaced, the transmitters were recalibrated using the appropriate calibration procedures.
The instruments were returned to service and channel checks were made of all the instruments affected.
No further corrective action ie anticipated.
- Attachment 1 providas a summary list of the results of this inspection.
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LER 81-002 10maha Public Power' District
[
Fort'Calhoun Station Unit No.'1
~
' Docket No. 05000285.
Attachment No. 3 l
' Failure Data L
This is'the.first instance of possible degradation'of Foxboro l
transmitters at Fort Calhoun Station.
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