05000368/LER-1985-001, :on 850102,during Monthly Surveillance Testing of Plant Protection Sys Channel A,Inadvertent Actuation of Recirculation Actuation Sys Occurred.Caused by Spurious Matrix Logic Signal

:on 850102,during Monthly Surveillance Testing of Plant Protection Sys Channel A,Inadvertent Actuation of Recirculation Actuation Sys Occurred.Caused by Spurious Matrix Logic Signal

ML20107B436
Person / Time
Site:	Arkansas Nuclear
Issue date:	02/06/1985
From:	Enos J, Dante Johnson ARKANSAS POWER & LIGHT CO.
To:	NRC OFFICE OF ADMINISTRATION (ADM)
References
2CAN028502, 2CAN28502, LER-85-001, LER-85-1, NUDOCS 8502200392
Download: ML20107B436 (3)

LER-1985-001, on 850102,during Monthly Surveillance Testing of Plant Protection Sys Channel A,Inadvertent Actuation of Recirculation Actuation Sys Occurred.Caused by Spurious Matrix Logic Signal

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv), System Actuation 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(1) 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(i)
3681985001R00 - NRC Website

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NRC Form 366 (9-83)

U.S. Nuclear Regulatory Commission Approved OMB No. 3150-0104 Expires: 8/31/85 LICENSEE EVENT REPORT (L E R)

FACILITY NAME (1) Arkansas Nuclear One, Unit Two l DOCKET NUM8ER (2) lPAGE (3) 1015101010f 31618tif 0F10f 2 TITLE (4)

Inadvertent Recirculation Actuation Signal During Plant Protection System Testing EVENT DATE (5)

LER NUMBER (6)

REPORT DATE (7) i OTHER FACILITIES INVOLVED (8) i i

i 15equentiall IRevision l

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l Monthi Day lYear lYear i i Number I l Number IMonthi Day lYear l Facility Names Docket Number (s) i i

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l 015 010 0 01 11 Of 21 81 51 81 51--I 0 I Of 1 t--! O I O IOf2101618151 045 010 0 OPERATING j IIHIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR 5:

MODE (9) 1 11 (Check one or more of the following) (11)

POWERI l~1 20.402(b) i i 20.405(c) l_xl 50.73(a)(2)(iv)

I j 73.71(b)

LEVEL l l l'20.405(a)(1)(1) l_t 50.36(c)(1) l_t 50.73(a)(2)(v) l _l 73.11(c)

(10) 1110101 1 20.405(a)(1)(ii) l_l 50.36(c)(2) l_l 50.73(a)(2)(vii) l l 50.73(a)(2)(viii)(A)l _ l Other (Specify in l l 20.405(a)(1)(iii)

I J1 50.73(a)(2)(1) l Abstract below and l _1 20.405(a)(1)(iv) l _1 50.73(a)(2)(11) l _I 50.73(a)(2)(viii)(B)l in Text, NRC Form f_I 20.405(a)(1)(v) l l 50.73(a)(2)(fii) l_l 50.73(a)(2)(x) l 366A)

LICENSEE CONTACT FOR THIS LER (12)

Name l Telephone Number Dwight J. Johnson, Licensing Engineer IArea l l Code l 1510111916141-13111010 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

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is SUPPLEMENT REPORT EXPECTED (14) l EXPECTED i Month Day Year i SUBMISSION l

_l~l Yes (If yes, complete Expected Submission Date) TV) No l DATE (15) l I I I I I ABSTRACT (Limit to 14G0 spaces, i.e., approximately fif teen single space typewritten lines) (16)

On 1/2/85, during monthly surveillance testing of Plant Protection System channel ' A', with the unit at 100% full power, an inadvertent actuation of the Recirculation Actuation System (RAS) occurred. The RAS automatically caused the suction for the safety injection pumps to be shif ted from the Refueling Water Tank (RWT) to the Containment Sump resulting in gravity draining of s50,000 gallons of borated water from the RWT to the reactor building sump.

The caus? of the event was attributed to a spurious RAS signal generated within the matrix logic circuit in Engineered Safety Features Actuation System (ESFAS) trip path i'4 while trip path #2 was in the tripped condition during required surveillance testing. This resulted in a "2 out-of 4" trip logic sequence and subsequent RAS actuation. RWT level was restored in s3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> and normal processing of the borated water in the Containment Sump commenced. Subsequent testing of the ESFAS trip path #4 logic matrix relays did not identify a relay degradation or failure, however, the matrix relay card which is suspected to have caused the actuation was replaced.

8502200392 850206 PDR ADOCK 05000368 S

PDR MA

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.,U'.S. Nuclear'Regulatorv Commission

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Approved OMB No. 3150-0104 Expires: 8/31/85 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILITY NAME (1) l DOCKET NUMBER (2) l LER NUMBER (6) l PAGE (3)

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Arkansas Nuclear One, Unit Two l

l i 15equentiall IRevisionl j

l l Year. ! Number-l l Number l l

10l51010101 31 61 81~8TT --l 0 1 0l l--l 0 l 0 101210Fl012

' TEXT (If more space is required, use additional NRC Form 366A's) (17)

On 1/2/85, ~at s0838 hours0.0097 days <br />0.233 hours <br />0.00139 weeks <br />3.18859e-4 months <br /> with the unit at 100% full power Instrumentation and Control (I&C) technicians were -

performing the Plant Protection System (PPS) channel 'A' A8 logic matrix actuation test for the Recirculation Actuation System (RAS) portion of the Engineered Safety Features Actuation System (ESFAS) as part of normal monthly PPS surveillance testing. Per procedure, the anticipated result of this testing was the de-energization of the 4AB-1 logic matrix relay (ESFAS RAS trip path #1) with annunciation, status panel indication and

" half-leg" actuation of the ESFAS RAS. However, due to a spurious signal within the logix matrix relaying of the PPS, a coincident RAS logic matrix relay de-energized resulting in a "2 out-of 4" RAS actuation logic.. The inadvertent RAS actuation resulted in the gravity draining of $50,000 gallons of borated water from the Refueling -

Water Tank to the Containment Sump.

The RAS transfers suction of the Emergency Core Cooling System safety injection pumps from -

RWT to the Containment Sump on iow RWT-level. Upon RAS actuation containment sump suction valves opi

.h a normal open s

stroke time of s22 seconds. The RWT outlet valves begin to close as soon as containment i suction valves reach full open with a normal close stroke time of s80 seconds. During this suction path i I!greent period, the RWT level decreased from s98% to s88%. At $0840 hours, during the resetting of the RAS, plant operators noted that control room PPS status lights indicated channel ' A' (trip path #1) and channel 'D' (trip path #4) generated the inadvertent RAS.

The system was realigned to the non-actuated condition. Makeup to the RWT was commenced at s0848 hours0.00981 days <br />0.236 hours <br />0.0014 weeks <br />3.22664e-4 months <br /> and Technical Specification required level was restored at $1100 hours. At $0855 hours draining of the containment sump and processing of the borated water commenced. The draining of the reactor building sump was completed on 1/5/85, at s0400 hours0.00463 days <br />0.111 hours <br />6.613757e-4 weeks <br />1.522e-4 months <br />. A reactor building entry was made on 1/7/85, to inspect the containment floor area.

Inspection of the containment sump screen revealed the west side door to be open. Apoarently the door was forced open by the reverse flow from the RWT gravity drain to the containment sump. This door is normally closed to prevent debris from entering the sump during sump recirculation. Controls have been implemented to verify the sump doors are closed and secured when the plant is above cold shutdown.

At 1430 hours0.0166 days <br />0.397 hours <br />0.00236 weeks <br />5.44115e-4 months <br /> on 1/2/85, 1&C technicians recommenced 'A' PPS monthly testing at the RAS procedure section.

A temporary procedure change was made requiring closure of RWT outlet valves as a precaution to prevent recurrence of RWT draining should another inadvertent actuation occur. The 'A' PPS channel monthly. functional test was completed with no further incidents.

Subsequent bench testing of each ESFAS trip path #4 logic matrix relay did not identify a relay degradation or failure. Replacement of the AB logic matrix relay card containing the relay being tested at the time of the inadvertent RAS has been performed as a precautionary measure.

f ARKANSAS POWER & LIGHT COMPANY l

POST OFFICE BOX 551 UTTLE ROCK. ARKANSAS 72203 (501) 371-4000 February 6, 1985

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2CAN028502 U. S. Nuclear Regulatory Commission Document Control Desk Washington, D.C.

20555

Subject:

Arkansas Nuclear One - Unit 2 Docket No. 50-368 License No. NPF-6 Licensee Event Report No. 85-001-00 Gentlemen:

In accordance with 10CFR50.73 (a)(2)(i) and 10CFR50.73 (a)(2)(iv), attached is the subject report concerning an inadvertent recirculation actuation signal during plant protection system testing.

Very truly yours,

(

J. Ted Enos Manager, Licensing JTE:RJS:ds Attachment cc:

Mr. Richard C. DeYoung Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission Waihington, DC 20555 Mr. Norman M. Haller, Director Office of Management & Program Analysis i

U. S. Nuclear Regulatory Commission I

i Washington, DC 20555 j

/',

p MEMBEA MtOOLE SOUTH UTsuTIES SYSTEM