05000213/LER-1990-001, :on 900202,engineering Evaluation Revealed That Failure of Svc Water Filters May Occur Rendering Containment Air Recirculation Fans Inoperable.Caused by Design Error. Bypass Lines Installed Around Both Filters

:on 900202,engineering Evaluation Revealed That Failure of Svc Water Filters May Occur Rendering Containment Air Recirculation Fans Inoperable.Caused by Design Error. Bypass Lines Installed Around Both Filters

ML20033E180
Person / Time
Site:	Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png
Issue date:	03/02/1990
From:	Kasuga R, Miller D CONNECTICUT YANKEE ATOMIC POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-001, LER-90-1, NUDOCS 9003090255
Download: ML20033E180 (4)

LER-1990-001, on 900202,engineering Evaluation Revealed That Failure of Svc Water Filters May Occur Rendering Containment Air Recirculation Fans Inoperable.Caused by Design Error. Bypass Lines Installed Around Both Filters

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v), Loss of Safety Function
2131990001R00 - NRC Website

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CONNECTICUT YANKEE ATOMIC POWER' COMPANY HADDAM NECK PLANT-Ei RRN1

• BOX 127E

• EAST HAMPTON,CT 06424-9341 f

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March 2, 1990 Re: 10CFR50.73 (a) (2) (v) (D) e t

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- U.

S. Nuclear Regulatory Commission l Document Control Desk-Washington, D. C. 20555 4

Reference:

Facility Operating License No. DPR-61 Docket No. 50-213

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Reportable-Occurrence LER 50-213/90-001-00 Gentlemen:

This letter forwards the Licensee Event Report 90-001-00,-required

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.to be-submitted, pursuant to the requirements of Connecticut 1

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Yankee Technical Specifications.

l Very.truly yo s,

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fr Donald B.

Miller, Jr.

E Station Superintendent DBM:/dl 4

Attachment:

LER 50-213/90-001-00 l-cc:

- Mr.

William T.

Russell

' Regional Administrator, Region I 475 Alienable Road King of Prussia, PA 19406 J. T.

Shedlosky l,

Sr. Resident' Inspector Haddam Neck t.

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PAWW (31 HaMam Neck 0 l 5 l 0 l 0 l 01211 13 1l0Fl013 18148 tes rocian Deficiency Identified In Service Water Filters IVENT DATI tEl LER NUMBER tel REPORT DATI (7i OTHth F ActLITil8 INVOLVED 05)

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r ABSTRACT On February 2, 1990 at approximately 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> with the plant shutdown in Mode 6 (refueling) an engineering evaluation revealed that it would be possible for a failure (i.e.,

clogging or breaking) of the Service Water filters to render the Containment Air Recirculation Fans inoperable following a Design Basis Loss-of-Coolant accident.

The root cause of this event is a design error which occurred during the original construction of the plant.

Corrective Action consists of installing bypass lines around both filters, which will have the capability of remote operation prior to plant startup.

This event is being reported under 10CFR50.73 (a) (2) (v) (D) since this condition alone could have prevented the fulfillment of a safety function of a system needed to mitigate the consequences of an accident.

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BACKGROUND INFORMATION

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'The two Service Water filters (EIIS Code: FLT) are part of the Containment Air Recirculation (CAR) Fan Cooling System (EIIS Code:

BK) which is required to reduce Reactor Containment pressure after a-design basis accident (DBA).

During normal operations one

~ filter is inservice and the other in standby, These filters remove particulate matter from the cooling water to the CAR fan cooling coils, motor coolers and spent fuel pit cooling system.

'The filters also have a backwash system which runs continuously to extend the time between filter plugging.

During normal operations-j when the in service filter becomes clogged, as evidenced by a low-flow alarm in the CAR fan coolers, an operator is dispatched to manually switchover to the standby unit thus isolating the clogged filter for cleaning,- The existing backwash system is not safety-related, and therefore it is not credited as being available post-i accident.

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EVENT DESCRIPTION

On February 2, 1990, at approximately 1416 with the plant shutdown

'in Mode 6 (refueling), an engineering evaluation of a suspected 4

design deficiency of the Service Water Adam-Filters revealed that i

it would be possible for a failure (i.e.,

clogging or breaking) of the inservice filter to render the CAR fans inoperable following a Design Basis Loss-of-Coolant accident -(LOCA).

The identified failure mode results from the use of:a non-safety grade backwash filter cleaning system, and the inability of an~ operator to access

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the filter area to perform a manual switchover to the clean filter i

due to excessive radiation levels following a LOCA.

Based on historical information the plugging of the inservice filter might-occur before the CAR fans are able to remove sufficient heat from the containment atmosphere.

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CAUSE OF THE EVENT

The root cause of this condition is a design error which occurred during the original construction of the Haddam Neck Plant.

The failure mode described within was not recognized when the plant was originally designed.

The discovery of this design deficiency was part of the continuing investigation of the service water system to ensure that single failure conditions do not exist

'elsewhere.

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W 9ese M U.S NUCLE A% G_lOULATORY COMMIN60N

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SAFETY ASSESSMENT

This event is being reported under 10CFR50.73 (a) (2) (v) (D) since this condition alone could have prevented the fulfillment of a safety function of a system needed to mitigate the consequences of an accident.

Without an operable backwash system, the filters will continue to clog at an increasing rate.

Discussions with the manufacturer-have indicated that the filters can clog fully.

Clogging of the filters will result in a continuous decrease in the cooling. water flow to the CAR fans, with a corresponding decrease in the CAR fan heat removal rate.

Insufficient heat removal from containment, following a LOCA, could result in the i

temperature and pressure limits of the equipment qualification to t

be exceeded.

In addition,-with severe cloggage, the integrity of the containment structure could be challenged.

CORRECTIVE ACTION

The installation of safety grade bypass lines around each filter is planned' prior to startup.

The bypasses will utilize remote operated valves to allow for manual bypassing of the filters without having to accees the area.

ADD.'.TIONAL INFORMATION None

SIMILAR EVENTS

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