NRC-91-0055, LER 91-006-00:on 910410,balance of Plant Breaker Opened Causing Reactor Bldg HVAC Isolation.Caused by Component Failures.Nprds Search Conducted for Similiar Problems. W/910510 Ltr

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LER 91-006-00:on 910410,balance of Plant Breaker Opened Causing Reactor Bldg HVAC Isolation.Caused by Component Failures.Nprds Search Conducted for Similiar Problems. W/910510 Ltr
ML20024H088
Person / Time
Site: Fermi DTE Energy icon.png
Issue date: 05/10/1991
From: Orser W, Pendergast J
DETROIT EDISON CO.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
CON-NRC-91-0055, CON-NRC-91-55 LER-91-006, LER-91-6, NUDOCS 9105210213
Download: ML20024H088 (5)
v • d • e


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op+rauan May 10, 1991 NRC-91-0055 U. S. Nuclear Regulatory-Commission Attention: Document Control Desk Washington, D.C. 20555

Reference:

Fermi 2 NRC Docket No. 50-341 NRC License No. NPF-43

Subject:

Licensee Event Report (LER) No.91-006 Please find enclosed LER No.91-006, dated May 10, 1991, for a reportable event that occurred on April 10, 1991. A copy of this LER is also being sent to the Regional Administrator, USNRC Region III.

If you have any questions, please contact Joseph Pendergast, Compliance Engineer, at (313) 586-1682.

Sincerely, f

6 6eut

Enclosure:

NRC Forms 366, 366A cc: A. B. Davis J. R. Eckert R. W. DeFayette W. G. Rogers J. F. Stang Wayne County Emergency Management Division i

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, tlCEUSEE EVENT REPORi (LER) '"a'*'

FQCitl1V N AME 01 DOCRt1 hum 8tM RI f AUE i3' Fermi 2 0 lb 1010101314 l_1 l lod 014 Balance of Plant Breaker Opened Causing Reactor Building Heating Ventilation and Air Conditioning Isolatitn EVENT DATI 161 Lt R NUM6( A 44: REPORY DATE 47i OrHE R 9 ACILifit s INv0LVt D 181 MUNTH DAY vtAq SEai

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Navi TE LEPHONE Nuv8Ep A H L a (~4 6 Joseph Pendergast, Compliance Engineer 3 ,1 i 3 5,8, 6 i l i i 6i 8:2 COMPLETE ONE LINE FOm E ACH COMPONINT F AILLARE DESCplSIC IN THis REPopf H36

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vo o - o., u An wow ssics s 65 (19 ges, comotore i MotCTIO SuB%*'S$10N DA b No l l aca,e AC, wa n ~x a., u a..-.e u . e, . no an..~n. un.u ve, At 0754 hours0.00873 days <br />0.209 hours <br />0.00125 weeks <br />2.86897e-4 months <br /> on April 10, 1991, a " Balance Of Plaut" breaker which provides 120/208 VAC feed to distribution panel 72B-4C-1 opened.

Division I of the Reactor Building Heating Ventilation and Air Conditioning (RBHVAC) system isolated, and Standby Gas Treatment System (SGTS) automatically started. The Control Center Heating Ventilation and Air Conditioning System (CCHVAC) received an isolation signal, however, it was already in the recirculation mode for surveillance testing.

The isolation / actuation signals were caused by component failure.

Initial troubleshooting identified the main feed breaker in distribution panel 72B-4C-1 as the cause for the loss of power. The breaker was removed and electrically tested by simulating overload conditions; the X and 2, phases tripped as expected. However, the Y ,

phase indicated an open circuit. The breaker was opened for inspection. Contact degradation was determined to be the apparent cause for the Y phase opening. The breaker 72B-4C-1 was replaced.

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LICENSEE EVENT REPORT (LER) ' 5,'s','#,0M M'"J' AM'i/ ,Jf*n' ,*o',".'.#

TEXT CONTINUATION TAT 7,O'o',"/'o^2dOU'.'luM'"'/l2 L"i E"fA W,,'M's?*:W%*??W',NG Of M AN40( M( N1 AND thub0(i, W A&MTON. DC /fWU)nRdC Ma" fACILif v hAML Hi DOC a tl NUM.L .12 g g g ,ygga 4 pagg a "a" " M'; P. W.E Fermi 2 0 l5 t o l 0 l 0131411 91 1 010l6 -

0 10 0 12 0' 014 im m - . -< weio,,,, m uHn Initial Plant Conditions:

Operational Condition: 5 (Refueling)

Reactor Power: O Percent Reactor Pressure: O psig Reactor Temperature: 82 degrees Fahrenheit Description of Event:

At 0754 hours0.00873 days <br />0.209 hours <br />0.00125 weeks <br />2.86897e-4 months <br /> on April 10, 1991, the main feed >reaker (BKR) in

" Balance Of Plant" 120/208 VAC distribution parel (Pl.) 72B-4C-1 opened. This caused a loss of power to the Post Accident Sampling System (IP), the Reactor Building (NG) Stationary Particulate lodine and Noble Gas (SPING) radiation monitor (MON) and various Fire Detection / Suppression CO2 control circuits (DET). Ultimately, the Reactor Building ventilation exhaust, the Control Center make-up air, and the Standby Gas Treatment System (SGTS) (BH) SPING radiation monitors became inoperable. Division I of the Reactor Building Ileating Ventilation and Air Conditioning (RBilVAC) (VI) system isolated, and Standoy Gas Treatment System (SGTS) (Bil) automatically started. The Control Center lleating Ventilation and Air Conditioning System (CCllVAC) (VI) received an isolation signal, however, it was already in the recirculation mode for surveillance testing. The isolation / actuation of these systems occurred in response to the loss of power to the radiation monitors.

The opening of this breaker also removed power from several fire detection panels (PL). In accordance with section 9A.6 of the Updated Final Safety Analysis Report fire watches were established until power was restored.

The main feed breaker is a Square D FA type molded case circuit breaker, rated at 100 amps. This type of breaker has a permanent trip unit containing individual thermal and magnetic trip elements in each pole. When the breaker trips the operating handle assumes a center position. The operating handle of the breaker was found in the full "on" position. No voltage was present on the load side of the breaker. The breaker was reset and operated properly. At 1248 hours0.0144 days <br />0.347 hours <br />0.00206 weeks <br />4.74864e-4 months <br />, RBHVAC and SGTS were returned to normal line-up to allow for proper Reactor Building atmospheric conditions during outage activities.

Subsequently, the breaker was replaced.

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TEXT CONTINUATION 2"J*R,','o',l;', u."ntj 00',i!"l*^,',',,'? ',",' "M."f' PAPf WO tt f& T er N i if 0 0 i Of M AN AGE ME NT AND BuDG4 T. W A&NINGl eN. DC 3%01 f ACILIT V N Aut ut DW a t t Nuun R m LtR NUM8tht$i FAG 3 (r "a t'etm O.*,n

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0 10 01 3 0F 0l4 Cause of Event:

The isolation / actuation signals were caused by component failure.

Initial troubleshooting identified the main feed breaker in distribution panel 72B-4C-1 as the source for the loss of power. It was difficult to place the breaker's operating handle in the "off" position anu then move to the "on" position during trouble shooting.

However, after being reset the breaker functioned nornally.

The breaker w1s removed and electrically tested by simulating overload conditions; the X and Z phases tripptd as expected. However, the Y phase indicated an open circuit. The breaker was opened for inspection. Contact degradation was determined to be the apparent cause for the

  • phase opening. The cause of contact degradation could not be determined. It appears that the Y phase contacts nay have been welded together thus accounting for the initial difficulty in resetting the breaker. The welded contacts would also explain why the breaker was found in the full closed position, but was still "open".

Analysis of Event:

The RBHVAC, CCHVAC and SGTS Engineered Safety Feature responses were consistent with the design basis of these systems. Had this occurred

during plant operation these systems would have appropriately

! pert'ormed their safety related functions. Thus, this event did not decrease the ability of these systems to perform their safety design functions. As a result, this event had no impact on plant safety.

Therefore, the health and safety of the public and plant employees was protected.

l Corrective Actions; t

A Nuclear Plant Reliability Data System (NPRDS) search was conducted for similar problems (i.e., contact degradation as described above) with molded case breakers. No similar problems were identified. The main feed breaker in distribution panel 72B-4C-1 was replaced.

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0l0 0l4 OF 0 l4 nx, w w. m .m uc + m im, Previous Similar Events:

This is the first Licensee Event Report at Fermi 2 where this type of breaker failure caused an Engineered Safety Feature isolation signal.

Failed Component Data:

The failed breaker was a 100 amp, Square D FA type molded case circuit breaker, part number FA36100. This particular breaker has no previous failure history.

r NRC Form 3664 (649

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