ML20024G553

Submits Response to 721218 Request for Documentation & Analysis of Consequences of Postulated Pipe Failures Outside of Containment Structure Including Rupture of Main Steam or Feedwater Line

ML20024G553
Person / Time
Site:	Monticello
Issue date:	01/05/1973
From:	Ward E NORTHERN STATES POWER CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 9102120651
Download: ML20024G553 (3)

Text

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January 5, 1973 -_ s

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,* Yk Docket No. 50-263 /

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Mr A Giambusso, Deputy Director # 8 for Reactor Projects Directorate of Licencing 4 $c0t;#$4

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Dear Mr Giambussor MONTICELLO NUCLEAR GENERATING PLANT E-5979 Postulated Pipe Failures Outside Containnent Your letter of December 18 requested documentation and analysis of the consequences of postulated pipe failures outside of the containment structure, including the rupture cf a main steam or feedvater line.

Attached to your letter was a list of information that you vill require, where applicable, for our Monticello facility. If the results of our analysis indicate the need for plant modifications, you have requested a description of such modifications and a schedule estimate for implementing the proposed changes.

Based on investigations to date, we do not see that the postulated type failures vill interfere with safe shutdown of the reactor. The following describes the original design general approach taken regarding failures of high energy process lines external to primary containment:

Reactor building pipe tunnel area - This area was analyzed

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for the it.rgest possible pipe break, a main steam line break, for possible damage to Class I structural members. As a result a protective panel was provided to allow relief of the pressure into the turbine building. No equipment located in the tunnel which is required to function to mitigate the consequences of the break would be adversely affected by the atmosphere within the tunnel following the break.

Suppression pool area - Analysis of a rupture of the largest high pressure line, the HPCI steam line, showed no damage to the structure or containment that would interfere with safe plant shutdown. Further the equipment items required to mitigate the consequences of this accident are not located ,

in the affected area.

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Itoactor building, ground floor and above - This area was

• - analyzed for failuro of the only system normally containing high pressure, high temperaturo fluid, the reactor vator

! cleanup system. As a result, the design accommodates the pressure trannient resulting from a pipo failuro so that no atractural damage vill occur to interfero with safo plant shutdown. The equipment items required to mitigato the consequencos of this accident would not be provented from performing their functions as a result of the accident.

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Turbino building - This aron was investigated from tho l standpoint of gross structural failuro as a result of a

! main steam lino break and anfo shutdown of the plant is accured.

As va previously indicated to you, no significant problems have been identified whereby failuro of steam or feod ater lines vould provent ,

a plant shutdown. Ilovever wo are proceeding with the detailod in-vestigation in accordanco with the informational requiremento attached to your letter of December 18, 1972 and our reporting vill be submitted by June 15, 1973.

Yourn very truly, s

% 5 YLu E C Mird, Director l

Engineering Vico Presidential Staff Cc: G Clutrnoff D E Nelson 1

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AEC DIGiiLIICTION P03 PART 50 DOCXET P.tcrAL

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• I, Northern States Power Company Minneapolis, Finr.. 55401 .

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• 50-263 DEScall'210;is EliCLOSTdES: -

Ltr re our 12-18-72 ltr..... furnishing info rc6a2 ding postulated pipe failures outside ,

containment st2ucture........

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