ML20032B721

Suppl to Technical Evaluation of Susceptibility of safety- Related Sys to Flooding Caused by Failure of non-Category 1 Sys.Info Supports Conclusion That Facility Has Capacity to Manage Single Incident

ML20032B721
Person / Time
Site:	Maine Yankee
Issue date:	10/19/1981
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20032B716	List: ML20032B715 ML20032B721
References
NUDOCS 8111060200
Download: ML20032B721 (3)

Text

g...

s t

SUPPLEMENT TO TECHNICAL EVALUATION OF THE SUSCEPTIBILITY OF -

~

. SAFETY-RELATED SYSTEMS TO FLOODING CAUSED BY THE FAILURE OF'NON-CATEGORY I SYSTEMS FOR THE MAINE YANKEE ATOMIC POWER STATION Docket No. 50-309

~

t I INTRODUCTION By letter to the Maine Yankee Atomic Power Company (MYAPC) dated September 27, 1972, the U.S. Nuclear Regulatory Cmunission (NRC) requested that MYAPC review the Maine Yankee Atomic Power Station to determine whether the failure of any non-Class I (seisnic) equipment could result in a condition such as flooding.

that might adversely affect the safe shutdown of the facility.

MYACP responded by letters on October 20, 1972 and June 3, 1973. On December 17, 1974 NRC transmitted to MYACP a set of guidelines for protection from ficoding of equipment important to safety which expandeo on the orignal requirements of the September 1972 letter. MYAPC responded by letters of January 23, 1975 and February 19, 1975.

In February 1981, the Lawrence Livermore National Laboratory (LLNL) evaulateo the above information and NRC issued a Safety Evaluation Report on April 13, 1981, with a request that MYACP submit an analysis of flooding of safety-related equipment in the Turbine Building resulting from a failure of the circulating water piping in th'is area.

MYACP responded by letter dated July 31, 1981 with their analysis as requesteo.

This report gives LLNL's conclusions on the evaluation of MYAPC's proposed' alterations to the Turbine Building to mitigate the effects of a failure of the circulating water piping or a break in the expansion joint, kP[)d 306 ADO g

03y 3 pfg osv.-

m_m

w_.

.e

&i II EVALUATION

... The circulating water system at MYAPS utilizes a vacuum priming system which enables the circulating water pump discharge to reach the full elevation of the' condenser in addition to removing disolved gases. Any significant leakage

'_from the circulatin~g wate'r piping should result in a loss of system vacuum.

IThe alarms associated with the vacuu11 piping system when coupled with other alarms associated with the con' denser and circulating water pump, would provide, the control r_com operators with prompt indication of the f ailura.

'MYAPC engineers postulate a. leak rat'e of 10,000 gallons per minute"in 'the

~

• ' discharge 'porticn of the system. This leads to a. rise in wateri le've1,of- 0.5

~

~

~

linches per minute.'ip ' th'e' Trobine' B'uilding, assuming a zero ' leak rat'e through the many openings in the building. The only safety related equipment in the

~-lTar' bin'e' Building whi[ch'~w[ould'biivulneVabid'to flooding 'of' the Yltior,70uld be

~

~

~

f e Component Cooliny P' umps.' T'hese unit's are mounted 22 inch'es, above the th

' floor and it would take 45 minutes with no corrective action before the water would reach these pumps. MYAPC states that failure to detect and correct such

" a situation is not considered credible.

The second scenario considered by MYPAC engineers was a catastrophic open-ended break of the circulating water inlet line with a flooding rite of 110,000 gellons per minute.

S break of this magnitude is over 10 times that

~

of the outlet line and would result in a flooding rate of a little over 5 l

inches per minute. Even though this would yield a little over 4 minutes before the Component Cooling Pumps would be affected, it is felt that further steps are required to :.11tigate the' possibility th'at this condition could develope before corrective action was initiated.

i MYdPCintheirletterofJuly 31, 1981 and in conversations with the staff, have committed to install within the next twelve months, passive Openings in l

i l

the Turbine Building wall. opposite the circulating water inlet piping which would prnvide amp!e openings to relieve the consequences of a complete

~

severence of a circulating water pipe.

.. t e

m m

-,m

,e a 6

'm

~

III CONCLUSIONS

..c.

Based on our review of the information supplied by the licensee we find that

., after installation of the proposed passive openings in the side'of the Turbine

~

~

'B ilding, the Maine Yankee Atomic Power Station has the capacity and u

, capability' to manage and mitigate any single incident, such as flooding from a non-Class I system component or pipe, so that flooding will not prevent the

' safe shutdown of the plant.

~

~

~

~

,. ee

=

am g ge

=

• O 4h 4

• 8 m.

g w

.e a

4

~

1 1:

h e

m m

h 13:_-

r 9

?

~

3

.