Text

LER 90-003-00:on 900319,inadvertent Primary Containment Isolation Sys Actuation Occurred.Caused by Lack of Coordination Between Monitor Downscale Setpoint & Monitor Reading.Proper Coordination established.W/900412 Ltr
	ML20042E169
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	04/12/1990
From:	Pelletier J; VERMONT YANKEE NUCLEAR POWER CORP.
To:	; NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
	LER-90-003, LER-90-3, VYV-90-125, NUDOCS 9004200320
	Download: ML20042E169 (5)
	v • d • e

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VERMONT YANKEE NUCLEAR POWER CORPOR ATION P, o. nox 157 GOVI2NOR HUNT ROAD l

VERNON, VERMONT 05354 April 12, 1990 VYV# 90-125 U.S. Nuclear Regulatory Commission Document Control Desk ,

Washington, D.C. 20555

REFERENCE:

Operating License DPR-28 Docket No. 50-271 Reportable Occurrence No. LER 90-03

Dear Sirs:

As defined by 10CFR50.73, we are reporting the attached Reportable Occurrence as LER 90-03.

Very truly yours,

-i VERMONT YANKEE NUCLEAR POWER CORPORATION M James P. Pelletier Plant Manager cc: Regional Administrator i USNRC i Region I '

475 Allendale Road King of Prussia, PA 19406

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90042003209004h2ADOCK

["DR PDC 0500 271 I

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[ NRC Form 366 U.S.. NUCLEAR REGULATORY COMMISSION

' ~

. APPROVED OMS NO.3150-OLO4~

a-

~', (6-89) a,. . -EXPIRES 4/30/92-

,. ESTIMATED BURDEN PER RESPONSE TO COMPLY:

. WITH THIS INFORMATION COLLECTION REQUEST::

50.0 HRS. FORWARD COMMENTS REGARDING-LICENSEE EVENT REPORT (LER) ' BURDEN ESTIMATE TO.THE RECORDS AND REPORTS '

MANA0EMENT BRANCH (P-530),.U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC ,

.20555. AND TO THE PAPERWORK REDUCTION, PROJECT (3160-0104),.0FFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20603; FACILITY NAME ('). =PAGE (a)

VERMONT YANK [E_ NUCLEAR POWER STATION DOCKET NO.

Ol5l0l0l0 (*bl0l110Fl0l4 2l7l1 ,

TITLE (*) INADVERTENT PRIMARY CONTAINMENT ISOLATION SYSTEM ACTUATION DUE,TO RADIxTION' MONITOR DOWNSCALE TRIPS.

EVENT ~DATE'(*) LER NUMBER (*) REPORT DATE_(') OTHER FACILITIES INVOLVED (*)

1 MONTH DAY YEAR YEAR SEO. # REV# MONTH DAY YEAR FACILITY NAMES DOCKET NO.(S)

N/A 0 5 0 0 0 0l3 1l9 9l0 9 l 0' - 01013 - 010 '0l'4 1' l 2 9l0 N/A 0 5 0 0 0 OPERATING THIS REPORT'IS SUBMITTED PURSUANT TO RE0'MTS OF 10CFR 6 ( ONE OR MORE (11)

MODE (')- N _.

20.402(b) _ 20.405(c) .

X 50.73(a)(2)(iv) _ 73.71(h)

POWER _ 20.405(a)(1)(I)- _ 50.36(c)(1)- _ 50.73(a)(2)(v) _ 73.T1(c)

LEVEL ($*) 0l010_ 20.405(a)(1)(II) _ 50.36(c)(2) _ _ 50.73(a)(2)(vii) _. _

OTHER:

............... _ 20.405(a)(1)(III) _ 50.73(a)(2)(I): _ 50.73(a)(2)(viii)(A)

............... _ 20.405(a)(1)(iv)- _ 50.73(a)(2)(II) _ 50.73(a)(2)(viii)(B)

.c............. 20.405(a)Q)(v) 50,73(a)(2)(III) 50.73(a)(2)(x)

LICENSEE CONTACT FOR THIS LER (ia)

NAME TELEPHONE NO.

AREA CODE -

JAMES P. PELLETIER, PLANT MANAGER 8lOl2 21Sl71-l71.7111.1 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE _ DESCRIBED IN THIS REPORT ('*)

CAUSE SYST COMPNT MFR REPORTABLE ..... CAUSE SYST- COMPNT. MFR- REPORTABLE ......

TO NPRDS a... TO NPRDS ......

N/A -------------------------------- ..... N/A --------------------------------

l l l ...... l l l ......

N/A -------------------------------- ..... N/A' --------------------------------

SUPPLEMENTAL REPORT EXPECTED ('*)' EXPECTED. M0 DA _YR SUBMISSION

~~l YES (If ves, complete EXPECTED SUBMISSION DATE) X l NO DATE (SS) l l l _.

ABSTRACT (Limit to 1400 spaces, i.e., approx. fifteen single-space' typewritten lines)-()

At approximately 1048 hours0.0121 days 0.291 hours 0.00173 weeks 3.98764e-4 months on 03-19-90, with the reactor shutdown for a scheduled-

-taintenance outage, a Primary Containment Isolation ~ System.(PCIS) Group III and subsequent Standby Gas' Treatment System (SBGTS) initiation occurred.- The PCIS isolation, initiated as a result of downscale trips of both Refuel Floor radiatio _n monitors (EIIS= MON)-due to de-creasing area radiation levels as a result of the reactor shutdown.-

. The events were caused by a lack of coordination between the monitor's downscale setpoint

and the monitor reading produced by the sensor / converter's internal radioactive source.

Corrective actions are to consist of establishing proper coordination of the setpoint and a mechanism to verify that proper coordination exists in the future when~ sensor / converter units are replaced.

~

'.NRC Form 366_(6-89)

mm ,

m 7

'stC' Form $66A

. U.S. NUCLEAR REGULATORY _COMMISSIONf , APPROVED OMS.NO.3150-0104:

g (6-89) 3 -'

EXPIRES 4/30/92 '

i ESTIMATED BURDEN PER RESPONSE TO COMPLYE y WITH THIS-INFORMATION COLLECTION REQUEST:

[ 50.0 HRS.-FORWARD COMMENTS REGARDING LICENSEE EVENT REPORT (LER) BURDEN ESTIMATE TO THE RECORDS AND REPORTS TEXT CONTINUATION MANAGEMENT BRANCH (P-530), U.S. NUCLEAR-REGULATORY COMMISSION, WASHINGTON, DC ,

L 20555;'AND'TO THE PAPERWORK' REDUCTION PROJECT (3160-0104), OFFICE OF MMAGEMENT AND BUDGET, WASHINGTONJ DC 20603.

UTILITY NAME:(?) DOCKET NO. (*)_ LER NUMBER (*) PAGE-(*)-

YEAR SEO. - # REV#

~_ VERMONT YANKEE NUCLEAR POWER STATIO4 01Slbl010121711- 9l0 -

0l0l3 -

0-l 0 0l2 0F 0l4 TEXT (If more space.is required, use additional'NRC Form 366A) ()

DESCRIPTION OF EVENT At approximately 2048 hours0.0237 days 0.569 hours 0.00339 weeks 7.79264e-4 months on 03-19-90, with the reactor' shutdown for a scheduled mainte-

-n:nce outage, a Primary Containment Isolation System (PCIS)' Group-III and subsequent Standby G:s Treatment System (SBOTS) initiation. occurred. The PCIS isolation, which; isolates the-primary and secondary containment ventilation, initiated when the East Refuel Floor

.rtdiation monitor _"17-453B" went downscale'due to decreasing area radiation levels as an result of the reactor shutdown.-

.At approximately 1128 hours0.0131 days 0.313 hours 0.00187 weeks 4.29204e-4 months , after verification.of normal area radiation levels, Control Room peruonnel reset the isolation and_ returned the ventilation systems to normal operation.

Prior.to the 03-19-90 event, at approximately 1950 hours0.0226 days 0.542 hours 0.00322 weeks 7.41975e-4 months on 03-16-90, the West-Refuel Floor radiation monitor "17-453A" had also experienced a downscale trip, was declared in-operable, and bypassed. This trip was due to reduced area radiation levels __resulting froni-the reactor shutdown.

There are two r.adiation monitors for the Refuel Floor area and two-for Reactor Building _

v:ntilation. A downscale signal from both of the. Refuel floor or both of the Reactor

. Building ventilation units will cause the system to trip, generating a PCIS Group III iso-1ction signal. An upscale trip from any one of the four units Will also cause~a PCIS Group III isolation.

The Instrument and Control Department-(I & C) investigated the occurrence and_ determined that the monitors were functioning properly. The'downscale trips were caused'by decreasing radiation levels during shutdown and.a lack of coordination between the' monitor downscale catpoint and the monitor reading produced by the sensor / converter's internal radioactive cource.

Both of the Refuel Floor sensor / converter units were recently replaced during power operation because of service life considerations discussed in LER 89-26. These-sensor /

converters were rebuilt and recertified by GE/Reuter Stokes prior to their installation this year.

The "A" Refuel Floor radiation monitor was-removed from bypass and declared operable at-0745 hours on 3-20-90.-

Both monitors functioned normally as area radiation levels came back up during.the reactor startup and power ascension which began at 0304 hours0.00352 days 0.0844 hours 5.026455e-4 weeks 1.15672e-4 months on 03-21-90.

4 :

NRC Form 366A (6-89)

R

o i

^

NRC F,orm 3b6A. U.S. NUCLEAR REGULATORY C'OMMISSION APPROVED 0MS NO.3150-0104:

(6-89) . EXPIRES 4/30/92.

ESTIMATED BURDEN PER RESPONSE TO COMPLY-WITH THIS INFORMATION COLLECTION REQUEST:

50.0 HRS. FORWARD COMMENTS REGARDING LICENSEE EVENT REPORT.(LER)' _ BURDEN ESTIMATE TO THE RECORDS AND. REPORTS TEXT CONTINUATION. MANAGEMENT BRANCH (P-530), U.S. NUCLEAR, REGULATORY COMMISSION, WASHINGTON, OC.

20555, AND'T01 THE PAPERWORK REDUCTION PROJECT (3160-0104), OFFICE OF. MANAGEMENT AND BUDGET, WASHINGTON, DC 20603.

UTILITY NAME (') DOCKET _NO. (*) LER NUMBER _(5) PAGE (*)

YEAR SEQ. # REV#

VERMONT YANKEE NUCLEAR POWER STATION dddddd711 910 -

0l0l3 --

0l0 d3 '0F d4 TEXT (If more space is required, use additional NRC Form 366A) . ( 7) s CAUSE OF EVENT The downscale trips and the PCIG Group III isolation were caused by a lack of coordina-Ltitn between the monitor downscale aetpoint and the monitor reading produced by.the sensor /-

.ctnv;rter internal radioactive source. The reduced area radiation levels associated with, the reactor shutdown, resulted in the monitor readings falling below the downscale setpoint.

The I & C Department has reviewed the calibration certification-data for the Refuel Floor sensor / converter units when they were returned from GE/Reuter Stokes. TheLreview chows that the radioactive sources internal to the units are within the manufacturer's rcquired specification values, however, they are at the low end of 'theLacceptance range.

l ~Thic resulted-in sensor / converter units that would drop below the downscale setpoint of I cillirem per hour when there is reduced background radiation.

ROOT CAUSE The root cause of this event is that there was no established mechanism to verify the

' coordination between the monitor downscale setpoint and the radiation level produced by the-s:nsor/convarter's internal sources. This relationship was therefore not' verified when the sin:or/ converters were recently replaced.

L ANALYSIS OF EVENT The event did not have adverse safety implications to plant equipment or the'public.

l-The PCIS_ Group III and_SBGTS operated as designed and successfully isolated the primary =

and'tecondary containment ventilation. A PCIS Group III isolation and SBGTS initiation are L ' thy txpected result of downscale trips of both Refuel Floor, radiation monitors.

5

_NRC' Form?366A (6-89)

RRC((rw366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMS NO.3150-0104 (6-89) EXPIRES 4/30/92 ESTIMATED BURDEN PER RESPONSE;TO COMPLY.

1WITH THIS-INFORMATION COLLECTION REQUEST:

'50.0 HRS. FORWARD COMMENTS REGARDING LICENSEE EVENT REPORT (LER) DURDEN ESTIMATE TO THELRECORDS AND REPORTS TEXT' CONTINUATION. MANAGEMENT BRANCH (P-530), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC.

20555, AND TO THE PAPERWORK REDUCTION PROJECT (3160-0104), OFFICE OF MANAGEMENT AND BUDGET,-WASHINGTON, DC 20603.

UTILITY NAME ($)- DOCKET NO. (8). LER NUMBER (*) PAGE (*)

YEAR SEQ. # REV#

VERMONT YANKEE NUCLEAR POWER STATION d d d d 'Ol 2l 7l 1 9l0 -

0 l 0 l 3- -

0l0 d4 0F dA TEXT (If more space is required, use additional NRC Form 366A) ( ?)

CORRECTIVE ACTIONS

-1. The Refuel Floor and Reactor Building ventilation radiation monitor sensor / converter units will be evaluated.and appropriate changes made-to the downscale setpoint or in-tornal source. location such that the downscale setpoint will be below the level produced by the internal source. GE/Reuter Stokes has stated that the internal sources can be moved closer to the Geiger-Mueller-tube for a higher output.

2. A mechanism will be established to verify the proper coordination between the downscale estpoint and the internal source configuration for future sensor / converter replacements.

' ADDITIONAL INFORMATION NoLother incidents involving Group III isolations resulting from downscale trips of-the

.r:diation monitors have occurred during the last five years, 1

NRC-Form:366A1(6-89)-

ML20042E169

Text

REFERENCE:

Dear Sirs:

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