ML20195H879
| ML20195H879 | |
| Person / Time | |
|---|---|
| Site: | 05000083 |
| Issue date: | 06/09/1988 |
| From: | Vernetson W FLORIDA, UNIV. OF, GAINESVILLE, FL |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| NUDOCS 8806290012 | |
| Download: ML20195H879 (11) | |
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NUCLEAR ENGINEERING SCIENCES DEPARTMENT Nuclear Reactor Facility ,
University of Florida >
1 W.G.Yemetson Dwector a
- i NUCUAR 21 ACTOR BULDING * ,
Goinev0s,Horido 32411
- ass
- June 9, 1988 Final Report Safety Channel 1 Circuit Failure ua Nuclear Regulatory Commission Suite 2900 -
101 Marietta Street, N.W. O Atlar:ta , Georgia 30323 .
U Attention: J. Nelson Grace -
Regional Administrator, Region II rc W
Re: University of Florida Training Reactor Facility License: R-56, Docket No. 50-83 Gentlemen:
Pursuant to the reporting requirements of paragraph 6.6.2(3)(c) of the UFTR Technical Specifications, a description of a potential abnorm 1 occurrence as defined in the UFTR Technical Specifications, Chapter 1 was previously de-scribed in an interim 14-day report dated April 25, 1988 to include NRC noti-fication, occurrence scenaric, corrective action and evaluation as well as current status of the system. This transmittal is intended to constitute a final report or the occurrence. The potential promptly reportable occurrence involved the recurrence of failure of the Safety Channel #1 circuit to provide proper power indica tion for several seconds on April 9, 1988 af ter the return to normal operations on April 1, 1988 following the previous failures on March 15 and 16, 1988 ( the la tter during a test prior to return to nonral opera-tions) per previous report dated March 28, 1988.
NRC Notification The Executive Committee of the Reactor Safety Review Subcommittee reviewed this latest occurrence on April 11, 1988 and concluded that it is a potential abnormal occurrence as defined in UFTR Technical Specifications, Chapter 1 following NRC notification as per Section 6.6.2 of the UFTR Tech Specs earlier on the same da y. This notification was carried out by both telephone to Mr.
Paul Burnett and a following telecopy on April 11, 1988. In addition to sev-eral discussions to update Mr. Burnett on 11 April 1988, later conversations with Mr. Robert Carroll and Mr. Paul Frederickson of Projects have kept Region II apprised of reactor status including staged restart with extra monitors in-stalled which occurred on April 25-27 and subsequent UFTR return to norml op-erations with an extra staff member monitoring Safety Channels for all opera-tions until registering 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> compensated operr "on above 50 kw and finally a return to norml monitoring conditions on May ' rolemented on May 23, 1988) with a caution memorandum issued to operat.v - mke them aware that no root cause has been found for the Safety Channel is_ .are ( Attachment I).
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9 Nuclear Regulatory Commission June 9, 1988 Page Two Initial Event Scenario At 1209 on April 9, 1988, with a Reactor Operations Laboratory class (ENU-5176L) in progress with power increasing at ~75% power, safety Channel 1 failed to the bottom meter stop. G.W. Fogle, reactor operator at the controls, noted that the indications on Safety Channel 2, the log pen recorder, the wide range indicator and other indicators were all normal and commenced a reactor shutdown while notif ying the SRO on call who concurred. As power reduction be-gan, Safety Channel 1 returned to normal indication as with the previous fail-ures on March 15 and March 16, 1988. Again the subjective evaluation was that the return was not instantaneous, but the meter returned to normal indication relatively slowly over several seconds ( i.e. , not as if switched on, but rather as if recovering from an electrical transient). The shutdown was com-pleted with all instruments responding normally at 1210 with the reactor secured at 1214 Corrective Action Plan For the first occurrence the reactor had been put on administrative shutdown and the full RSRS had met on March 22, 1988 with this event as one item on its agenda. All agreed the situation was being addressed properly although the exact cause of the event had not yet been identified. Via a series cf trouble-shooting and corrective maintenance activities, the problem was isolated to involve the fission chamber, preamp or connections shown in Attachment II which is Figure 1-8 of the UFTR Safety Analysis Report. There was a strong possibility that cleaning connectors on these components had corrected the problem per conversations with one vendor and concurred with by two UPTR per-sonnel familiar with such instrumentation behavior. As a result, the UFTR was returned to normal operation on 1 April 1988 following completion of an ap-proved special test procedure. It should be noted that failed noise suppres-sion feedback capacitors have been replaced in both Safety Channels (original-ly thought to be the cause of SC-1 failure) but these were not at fault for the current failure and, in failed state, have negligible impact on circuit operations because this is a DC amplifier where the feedback coef ficient is set by a precision resistor. Such a failure could have occurred anytime since console ins ta lla tion.
The immediate indications this time were the same as for the previous occur-rences - namely, that an intermittent fault had developed in the circuitry for Safety Channel 1 (part of the wide range drawer) but not in any other section of the wide range drawer. With the reactor secured, Maintenance Log Page #88-14 was initiated to investigate and control correction of this failure recur-rence. Although another series of checks was performed, again no root cause could be identified.
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Nuclear Regulatory Commission June 9, 1988 Page Three The recurrence of the Safety Channel 1 failure on April 9, 1988, following about a week of normal operation including 9.65 hours7.523148e-4 days <br />0.0181 hours <br />1.074735e-4 weeks <br />2.47325e-5 months <br /> of operation above 50 kw indicates that the Safety Channel 1 fault is intermittent and not isolatable by the usual test methods of investigation. Therefore, a new program was de-velopeG to isolate and correct the cause of the failure; each potential prob-lem is to be dealt with in a systematic manner followed by a retest and spe-cial monitoring period prior to restoring the reactor to normal unrestricted ope ra tion. Corrective actiona as well as actions to expedite fault isolation are to be taken during each of three possible major steps in the maintenance program. Therefore, the following program was implemented (per isolation of the fault to the connections, preamplifier or fission chamber shown in Attach-ment II, Figure 1-8 of UFTR SAR) to isola te and correct the fault in Safety Channel 1 with the reactor to be restored to normal opera tions whenever the test program is successful for each of the following three (3) steps:
1 Attempt to isolate the intermittent failure as external to the console by interchanging SC-1 and SC-2 linear amplifier c.ccuits and change out con-nectors on the wide range drawer and on the preamplifer cables to the wide range drawer. A crimp type connector will be used to replace one clamp type connector; this modification is considered a possible fix for the failure while the interchange of amplifiers is only considered an aid to fault isolation should the failure recur.
- 2. Replace the preamplifier with one equivalent to that presently in use at the UFTR according to the vendor except that the replacement item uses one cable connection for the pulsed and the current instruments while the currently installed preamplifier uses two. This will require a 10 CFR 50.59 evaluation to bring both signal lines to a single connec tor, but is not expected to present any significant dif ficulties technically or ad-mi ni s t ra tivel y.
- 3. Replace the fission chamber and its caoles/ cable connections. The fission chamber (previously, model RSN-314-L2552) is a s tandard item, but not stocked by the current vendor General Electric which requires 30 to 60 da ys lead time. Ef forts are currently underway to obtain a detector from another source within the Department of Energy.
Eva lua tion Except during the transient, the functions of indication and trip were not in-hibited or changed- tha t i s , there was only a temporary loss of indication and trip function in bafety Channel #1 The impact of this failure on system op-eration is minimized because t occurs for only a few seconds.
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Nuclear Regulatory Conmission June 9, 1988 Page Four This safety Channel #1 Circuit failure le potentially a promptly reportable occurrence per UFTR Technica.' Specifications, Section 6.6.2 celineating rc-quirements for Special Reports where Paragraph (3)(c) states certain safety system failures are promptly reportable. Specifically, a special report is needed for a "reactor safety systs.4 malfunction that renders the reactor safety sy9 tem incapable of performing its intended safety function, unless the malfunction or condition is discovered during maintenance tests or periods of reactor shutdowns" or involves components or systems in addition to these re-quired by Tech Soecs.
Similarly one definition of Abnormal Occurrences for the UFTR in Tech Specs Section 1.0 is "a malfuncticn of a safety system component or other component or system malfunction that could, or threatens to, render tha (safety) s ys tem incapable of performing its intended safety function." Since Reactor Safety System is also defined in Tech Speca section 1.0 to be "a combination of mea-suring channels and associated circuitry that forms the automatic protective action to be initiated, or provides information which requires the initiation of manual protective action," the initial and later occurre .ces of this event may not be strictly required 'o be promptly reported.
Ba s ica ll y, this event was considered to heve no direct impact on safety and not to impact the health and safety of the public. However, the ovent was re-posted promptly on April 11, 1986 and later support ed by the RSRS recommenda-tic 7 on the same day since there was at least a partial failure of the safety b >s tem. Nevertheless, safety implications are negligible since Safety Channel
- 2 was always operable and Safety Channel #1 was only lost for a few seconds.
Correct ive Action - Currer.t S ta tus The special test procrdure contained in the April 25 Interim Report was used to control restart in March following the first occurrence. Except for an oc-casion when a monitoring connector slipped o:1 necessitating a shutdown to re-cor.nec t 'e devies, the original monitored restart on 31 March 1988 was un-eventful with all systems responding properly with no recurrence of the Safety Channel circuit failure. Af ter removing the monitoring instrumantation and performing a daily checkout during which a spurious noise-induced period trip signal due to wirea laying on the preamp was corrected by securing the wires, a final run at full power with no special monitoring instrumentation was con-ducted as the final requirement prior to the first return to normal opera-tions. All systems functioned normally for this run also so with concurrer.ce by the RSRS (previously granted per the test procedure but reverified) and with NRC Region II verbal notification via telephone conversation with Paul Bur nett, the UPTR was returned to normal operations with the problem con-sidered corrected by the various maintenance activities to check and clean all connections. The recurrence on April 9 negated this declaration as the UFTR was returned to administr tive shutdown to correct the cause of thi Safety Cnannel failure recurrence.
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Nuclear Regule tory Commission June 9, 1988 Page Five For this recurrence, a modified form of the previous special test procedure was used to support again a staged restart to normal operation begun on 25 April 1988 with delayed completion on 27 April 1988 af ter replacement of a failed motor on an Air Particulate Detector. To date only the first of the ,
three program steps listed above under Corrective Action Plan has been found necessary. As indicated in the April 25 interim report, this Special Test Pro- i cedure was prepared for RSRS review and approval to allow declaring the UPTR operable pending successful completion of all normal checks and again per-mitted restart in steps following corrective and diagnostic mainterance ac-tivities as a test to verif y proper operation of Safety Channel #1 by provid-ing for continuous visual monitoring of voltage levels in the linear channel section of the preamplifier with respect to ground, the current drawn by de-tector operation from high voltage supply and the high voltage power supply output voltage. This procedure again provided compensation for possible recur-rence of the Safety Channel failure by having a second competent staff member present in the control room to monitor both safety channels continuously dur-ing the entire restart program wh'eh included holds at 1 kw for 10 minutes, 10 kw for 10 minutes, 50 kw for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, 75 kw for 10 minutes and 100 kw for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> with monitoring d.? vices in place. This time the return to normal opera-tions usage of the UFTR was accompanied by the requirement that the second competent individual be maintained for all operations until 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> operation above 50 kw was logged.
Af ter successful completion of the staged restart begun on April 25 and com-pleted on April 27, 1988, a memorandum ( Attachment III) authorizing UFTR Re-turn to Norral Operations Except for the Extra Staf f Person Monitoring Safety Channels for all operations was then issued on April 28, 1988 as the UFTR was declared ready to return to normal operations with only the requirement that a second competent staf f person be in the control room to monitor the Safety Channel meters for all operations until 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> operation above 50 kw had been completed. During the operations to get 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> above 50 kw with an ex-tra monitoring individual, normal experimental and training usages of the UFTR were approved and conducted with no recurrence of safety channel failure. This ten hours of operation above 50 kw was completed as of May 19, 1988 as indi-cated in a memorandum (see Attachment IV) dated May 20, 1988 from the Facility Director to Acting Reactor Manager P.M. Whaley documenting having met the power requirement and approving the return to uncompensated operations; tha t is, no extra person monitoring the Safety Channels. The record of operations above 50 kw af ter May 20 through June 8 is contained in Table 1 as Attachment V. At this puint the corrective action was considered successful and the reac-tor declared ready fcr return to normal operations with normal personnel re-quirements sufficient for t'urther operations but with a caution to operations staf f that no root c ause had yet been found. This return to uncompensated op-erations was completed on May 23, 1988 and documented on that date for all operators via a memorandum ( Attachment I) f rom P.M. Whaley acknowledging the return to uncompensated opera tions but with a caution to operations staff that no root cause has been identified for the Safety Channel failure.
Nuclear Regulator Commission June 9, 1988 Page Six Since May 23 the UPTR has been conducting normal operations, with no recur-rence of the Safety Channel failure. Since May 20, 1988 the UPTR has operated above 50 kw for nearly (9) additional hot.rs ( see Attachment V). Based on the successful results of the staged test restart with special monitoring instru-mentation installed, the operations with an extra individual monitoring until completing 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> operation above 50 kw and the subsequent operations with no additional monitoring, the corrective action taken is considered to have corrected the failure problems though admittedly no root cause has been found.
At this time the Safety Channel failure incident is considered closed. Further infornution will be supplied and Region II will be kept updated should this event recur whereupon another step in the Special Test Procedure will be con-sidered necessary.
If further information is needed please advise.
Sincerely, W - p William G. Vernetson Director of Nuclear Facilities WGV/ps Atta chments cc: P.M. Wha ley Reactor Safety Review Subcommittee h-}0-
[ Nota ry Date Note Puh5c, $ tate of flodde My Commission Espires Oct. 5,199T a ,
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ATTACHMENT I NUCLEAR ENGINEERING SCIENCES DEPARTMENT Nuclear Reactor Facility ,
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- Phone (904)3921429.' Asa 64330 May 23, 1988 MEMORANDy T0: All UFTR Operators and Staf f FROM: P.M. Whaley 8'
SUBJECT:
Saf ety Channel 1 Tes t Program Status As of May 20, 1988 the fits t e tep of the proposed tes t procedure has been completed with the accumulation of 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> 23 minutes of run time above 50 kw with no f allure of Saf ety Channel 1.
Since this 10 hour1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> ic*erval wcs based on the longes t time above 50 kw between f allures f or Saf ety Channel 1, the successf ul com-pletion of greater than 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> is evidence that the cable re-terminction has repaired the Saf ety Channel 1 f ault; n eve r t he-less , the root cause has not been definitely determined except by b the absence of a f ailure. Theref ore, all UFTR reactor operators and reactor operator trainees are cautioned to be particularly vigilant of the perf ormance of Saf ety Channel 1 and Saf e ty Chan-nel 2 during reactor operations in the power range.
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ATTACID1ENT III
. NUCLEAR ENGINEERING SCIENCES DEPARTMENT Nuclear Reactor Facility ,,
University of Florida .!! 1 w o.v.,awm. o =ter .
NVCttAt H. ACTOR BMNG , ,
Coinevke,Fiorida 12611 rw.c,v4 set.1429.r.'.asataa April 28, 1988 MEMORANDUM TO: P.M. Whaley
- 'b FROM: W.G. Vernetson
SUBJECT:
UFTR Return to Normal Operations Based upon the successful completion of the special test pro-cedure with the monitoring equipment in place at 1617 hours0.0187 days <br />0.449 hours <br />0.00267 weeks <br />6.152685e-4 months <br /> on April 27 and subsequent removal of the equipment on April 28, 1988 to address the UPTR Safety Channel #1 Circuit Failure and prior concurrences by the RSRS Executive and Full Committees as well as NRC Region II (Paul Frederickson) , the UFTR is hereby w authorized to commence normal experimental operations as of 9:00 a.m. toda y, April 28, 1988.
Remember that the second individual as a member of our staf f must be monitoring the safety channel indications for all operations until at least 10 more hours of norrral operation above 50 kw have been completed and until I authorize otherwise. Only upon such successful completion will the UTTR be cleared for return to nor-Tal operation with no extra rnonitoring. .)
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ATTACIG1ENT IV
. NUCLEAR ENGINEERING SCIENCES DEPARTMENT Nuclear Reactor Facility o c.c.v.,. . omw University of Florida gh,,
weumtActonueino May 20, 1988
- cu.:r re aan aas Phon 3 (904) 3921429.Teka 64333 MEMORANDUM T0: P.M. Whaley FROM: W. G. Ve e ne ts on
SUBJECT:
Approval f or Return to Normal Control Room Operations Staffing Requirements Since the successf ul conclusion of the UFTR res tart on April 27, 1988, with special monitors ins talled per the Special Tes t Procedure approved on April 11, 1988, the UFTR has conducted power operations above 50 kw for the time in-tervals and on the dates s hown as f ollows :
Date Time Total Time (hr-min) 28 April 1009 - 1014 0-5 1102 - 1241 1 - 39 1331 - 1431 1 - 00
) 29 April 1645 - 1700 0 - 15 3 May 1214 - 1233 0 - 19 5 May 1220 - 1302 0 - 42 10 May 1538 - 1545 0-7 1628 - 1659 0 - 31 11 May 1608 - 1626 0 - 18 12 May 1500 - 1703 2 - 03 13 May 1613 - 1622 0 - 09 1655 - 1755 1 - 00 16 May 1402 - 1602 2 - 00 If May 1612 - 1627 0 - 15 Total Time Above 50 kw: 10 hr. 23 min.
An extra monitoring s taf f member has been on duty to monitor the two saf ety channels during all of these ope ra tions . Since the saf ety channel f ailure loss of indication and signal has not recurred and since this 10< 38 hours4.398148e-4 days <br />0.0106 hours <br />6.283069e-5 weeks <br />1.4459e-5 months <br /> of opera- l tion above 50 kw meets the condition se t in the Special Tes t Procedure per NRC !
and RSRS commitments of greater than 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> above 50 kw with no fallure, the l UFTR is now approved to continue normal operations with the usual control room l
and other s taf f requirements . The requirement f or the separate individual to j monitor the saf ety channels is hereby ended. '
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ATTACHMENT V TABLE 1 UFTR POWER (> 50 KW) OPERATIONS SINCE 20 MAY 1988 THK0 UGH 8 JUNE 1988 Date Time Total Time (hr-min) 21 May 1734 - 1812 0 - 38 23 May 1044 - 1120 0 - 36 1632 - 1700 0 - 28 25 May 1133 - 1322 1 - 49 26 May 0915 - 0930 0 - 15 1228 - 1428 2 - 00 ,
27 May 1507 - 1522 0 - 15 31 May 1214 - 1224 0 - 10 2 June 1737 - 1752 0 - 15 3 June 1439 - 1443 0-4 1638 - 1642 0-4 6 June 1244 - 1256 0 - 12 1316 - 1331 0 - 15 1858 - 1930 0 - 32 8 June 1433 - 1438 0-5 1717 - 1838 1 - 21 T0TAL............................. 8 - 59
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Facility Director V hY D'a te
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