05000309/LER-1987-001, :on 870504,two Component Cooling Trains Became Interconnected While Instrument Air Sys Depressurized.Caused by Design Review Mod to Diesel Cooling Sys.Alternate Diesel Cooling Supply Valve Mechanically Closed
| ML20214T875 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 06/03/1987 |
| From: | Mcgrath R Maine Yankee |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| GDW-87-136, LER-87-001, LER-87-1, MN-87-66, NUDOCS 8706100461 | |
| Download: ML20214T875 (3) | |
| 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)(1) 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii) 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(x) |
| 3091987001R00 - NRC Website | |
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MAINE YANKEE ATOMIC POWER COMPANY T
lNRCForm366 U.S. Nuclear Regulatory Connission l l(9-83)
Approved OMB No. 3150-0104 l
l LICENSEE EVENT REPORT (LER)
Expires: 8/31/85 l
l l
lFacilityName(l) l Docket Number (2) l Paoe(3) l l
Maine Yankee Atomic Power Company l
l l
l 10151010101310191llofl012l i
l Title (4) l l
Comoonent Coolina Svstem Redundanev Lost with NNS Air System Deoressurization l
l Event Date(5) l LER Number (6)l l Reoort Date(7) i Other Facilities Involved (8) l l Month l Day l Year l Year l l Sequential l l Revision l Month l Day l Year l Facility Names lDocketNumber(s)l l
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I l l Number l I Number l l
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1 1I II I
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I l 01 51 01 418I7 1817 l-l 0 1 0 11 1-1 0 1 0 1 01 61 01 3181 71 1IIIIIII l l
l l This Report is Submitted Pursuant to the Requirements of 10 CFR $
l l Operating l l (Check one or more of the followina) (11) l l Mode (9) 11 l l20.402(b) l_l20.405(c) l_l50.73(a)(2)(iv) l_l73.71(b) l l Power l l_l20.405(a)(1)(1) l_j50.36(c)(1) jXl50.73(a)(2)(v) l_l73.71(c) l l Level l l l l_l20.405(a)(1)(ii)ll50.36(c)(2) l_l50.73(a)(2)(vii) l_l0ther (Specify in]
l(10) l01010l120.405(a)(1)(iii)l_l50.73(a)(2)(1) l_l50.73(a)(2)(viii)(A)l Abstract below l
l l_l/0.405(a)(1)(iv) lKl50.73(a)(2)(ii) l_l50.73(a)(2)(viii)(B)l andinText,NRCl l
l l'20.405(a)(1)(v) I 150.73(a)(2)(iiiil 150.73(a)(2)(x)
I Form 366A) l l
LICENSEE CONTACT FOR THIS LER (12) l lNAME l
Telephone Number l
l l Area Code l l
l l Richard S. McGrath. Nuclear Safety Enaineeer 12101718181216131211l l
COMPLETE ONE LINE FOR EACH COMP 0flENT FAILURE DESCRIBED IN THIS REPORT (13) l l
l l Con-lManufac-l Reportable l l
l l Com-lManufac-l Reportable l l
lCauselSvsteml conenti turer i to NPRDS 1 lCauselSysteml ponenti turer i to NPRDS l j
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Suoplemental Report Expected (141 l Expected l Month l Day l Year l t
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l Submission l l
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(If yes, complete Expected l__
l Date(15)l l
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l l Yes Submission Date)
IX l No l
l i l l I l l l ABSTRACT (Limit to 1400 spaces, i.e., approximately fif teen single-space typewritten lines) (16) l l
l i
l On May 4,1987, while shut down for refueling, a deficiency in the component cooling water, l
lCCW,systemwasidentified. The two component cooling trains became interconnected while the l
l instrument air system was depressurized.
l 1
l 1
l The cross-connection of CCW trains occurred at a single header supplying alternate fire main l
l cooling to both emergency diesel generators. When the instrument air system was removed from l
l service for maintenance, two air operated valves on the header opened, interconnecting the l
l diesel coolers and CCW trains.
l l
l l The potential to cross-tie these trains resulted when the diesel cooling system was modified l
lin1981.
l l
l l
l To correct this condition the diesel's alternate cooling supply valves, not required for l
ldesignbasis,havebeentalockedshut. A diesel cooling system design evaluation to develop l
lapermanentmodificationandtoreviewsystemredundancyisinprogress.
l i
l k't
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l 0706100461 870603 PDR ADOCK 0500 9
i 8758L-SDE
M AINE YANKEE ATOMIC POWER COMPANY lNRCForm366A U.S. Nuclear Regulatory Commission l l(9-83)
Approved OMB No. 3150-0104 l
l Expires: 8/31/85 l
l LICENSEE EVENT REPORT (LER) TEXT CONTINUATION l
l 1
lFacilityName(l) lDocketNumber(2)l LER Number (6) 1 Paae(3) l l
l l Year l l Sequential l l Revision l l l l
lMaineYankeeAtomicPowerCompany l
l l l Number ll Number l l l l
l 1
1 II II I
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l 1015!01010131019l817l-l0l011 l-l 0 10 1 2fofl 21 l l TEXT (If more space is required, use additional NRC Form 366A's) (17) l l
1 l On Monday, May 4,1987, while shutdown for refueling, a design deficiency in the component l
l cooling water system (CC) was identified. The two trains of compenent cooling water, CCW, l
l became cross-connected when a non-nuclear safety class system, instrument air (LF) was l
l depressurized for maintenance. The CCW trains are designed to be independent.
l 1
l l The interconnection between the primary and seccndary cor.ponent coolips systems occurred at a l
I l header supplying alternate fire main cooling to the emergency diesel generators (EK). Each l
l diesel is normally cooled by a separate CCW train. Both diesels have an alternate cooling l
l supply f rom the fire water system (KP). When the instrument air system was depressurized, the l
l air operated valves (TCV) that supply fire water to the diesel coolers opened. This resulted l
l in a common header being aligned to both diesel coolers and interconnecting the two CCW trains. l l
l l The original diesel generator, DG, cooling system at Maine Yankee consisted of a Secondary l
l Component Cooling supply to both DG's with an alternate supply to both DG's from the plant l
lfiremain. In 1981, to improve the independence of the two DG's, Secondary Component Cooling l
l was removed from the "A" train diesel and replaced with Primary Component Cooling. However, l
l the backup supply to both DG's from the fire main was lef t intact. This created a condition l
l whereby a simultaneous loss of instrument air to both of the fire main supply valves could l
l provide a cross-connect path between the otherwise independent CCW trains.
l l
l l The root cause of this condition was an oversight in the design review of the modification l
l to the diesel cooling system. The review was extensive but failed to reveal this particular l
lsysteminteraction. This does not appear to be due to a fault in the review process.
l 1
l l A break in the Secondary Component Cooling Water system, SCCW, would eventually result in l
l loss of instrument air pressure, because instrument air compressors are cooled by SCCW. The l
l alternate cooling vahes would open on loss of air supply and allow the break in the SCCW l
l system to affect the Primary Component Cooling Water system, PCCW. The safety consequences of l
l this event were not significant for the following reasons: The instrument air system has a l
l history of high reliability; the instrument air compressors have an alternate cooling supply; l
l a break in seismically qualified CCW piping is unlikely; the portion of the SCCW piping that l
l Is not seismically qualified has automatic isolation valves that would close and isolate a l
l break; more than enough time would exist for operator action to easily prevent the effects of l
l CCW train cross-connection.
l l
l l To prevent potential for cross-connecting the CCW trains, the alternate diesel cooling supply l
l valves have been mechanically blocked closed. The alternate cooling is not part of the l
l emergency diesel generator design basis and is normally isolated manually. In the event l
l alternate cooling is needed it can be manually aligned to one diesel without impacting CCW l
ltrainredundancy. A diesel cooling system design evaluation to develop a permanent l
lmodificationandtoreviewsystemredundancyisinprogress.
l 1
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8758L-50E
1 MAME 9ARHEE M0Ml0 POWER 00MPA09e avaug7,y,?u"gW,'s (207) 623-3521 e
June 3, 1987 10CFR50.73 MN-87-66 GDH-87-136 United States Nuclear Regulatory Commission Attention: Document Control Desk Hashington, D. C.
20555
References:
(a) License No. DPR-36 (Docket No. 50-309)
Subject: Maine Yankee Licensee Event Report 87-001 Component Cooling System Redundancy lost with NNS Air System Depressurization Gentlemen:
Please find enclosed Maine Yankee Licensee Event Report 87-001-00.
This report is sut'mitted in accordance with the requirements of 10 CFR 50.73(a)(2)(ii) and (a)(2)(v).
Very truly yours, MAINE YANKEE ATOMIC POWER COMPANY b
$It G. D. Whittier, Manager Nuclear Engineering and Licensing GDH/bjp Enclosure cc: Mr. Victor Nerses Mr. H1111am T. Russell Mr. Pat Sears Mr. Cornelius F. Holden American Nuclear Insurers 8758L-SDE h