ML20128D717

Forwards Written Response to Interrogatory 10a Submitted by Counsel for Minnesota Pollution Control Agency

ML20128D717
Person / Time
Site:	Monticello
Issue date:	08/19/1974
From:	Maccary R US ATOMIC ENERGY COMMISSION (AEC)
To:	Goller K US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 9212070360
Download: ML20128D717 (3)

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Karl R. Coller, Assistant Director for Operating Reactors Directorate of Licensing HONTICEL14 INTERROGATORIES - TAR ORB-2-115 Plant t allo Docket . 50-263 Project James J. Shea Branch Coder ORB-2 s e AttachedisawrittenresponsetoInterrogatoryNo.d0asubmittedbythe '

Counsel ior the Minnesota Pollution Control Agency.

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g y.D cy R. R. Maccary, Assistant Director for Engineering Directorate of Licensing Enclosures '

As Stated cc F. Schroeder, L S. _ Varga, L -

S. Lewis, 00C S. S. Pawlicki, L J. Shea, L i W. S. Rasalton, L DISTRIBUTION:

Docket File (50-263)

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Interrogatory 10a. " Provide a detailed analysis of the results of a rupture of the reactor pressure vessel at Monticello."

- Response: We have reviewed all factors contributing to the structural integrity of the reactor vessel and we conclude that the

-probability of-a disruptive failure

• of a reactor vessel is sufficiently low to make it not necessary to consider potential e

vessel failure.

. The probability of a disruptive failure event occurring in a reactor vessel is-estimated in the report WASH-1318** and is based on the following considerations

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n. Reactor vessels are designed and constructed in accordance with the rules of ASME Code,Section III.

i b.- Reactor vessels are operated in accoroance with the-

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limitations specified in AEC License Technical Specifications.

• " Disruptive failure" is'a breaching of the vessel by rupture of one of its pressure-containing components (e.g., shell, head,-or nor:le) or

. by failure of a significant fraction of closure bolts,. accompanied by

-rapid release of a large-volume of the contained pressurized fluid.

' **The Technical Report WASH-1318, " Analysis of Pressure Vessel Statistics from Fossil-Fueled Power Plant Service and Assessment of Reactor Vessel

, , Reliability in Nuclear Power Service," May 1974. ,

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c. Reactor vessels are subjceted to the preservice and inservice inspections in accordance with the rules of ,

ASME Code Section XI.

i d. Reactor vessels are provided with a higher degree of protection by virtue of design measures, overpressure.

devices, and operational control procedures from conditions that could impose, during the vessel's service lifetime, loadings and stresses in excess.of those considered in the design.

Utilizing the conservative base'of the failure probability-range derived for non-nuclear vessels, and a conservatively

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\ estimated factor of improvement resulting from the superior l quality level achieved in the design and construction of nuclear reactor vessels, and from the recurrent examinations performed during the service lifetime of nuclear reactor ,

vessels, the Regulatory staff concludes that_the upper limit (99% confidence) probability of a " disruptive failure" event occurring-in any one nuclear reactor vessel during.any service year falls within the range of 10-6 to in-7,

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