ML19269C441

in Compliance w/10CFR50.55E,forwards Rept Description of Neutron Suppl Shield, Describing Collar/Saddle Shield & Radiation Analysis Performed to Determine Adequacy of Suppl Shield

ML19269C441
Person / Time
Site:	North Anna
Issue date:	01/31/1979
From:	Brwon S VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19269C443	List: ML19269C441 ML19269C444
References
300A, NUDOCS 7902020241
Download: ML19269C441 (2)

Text

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v Ro:NI A ELECTRIC AND POWER COMP ANY, RICHMOND, VIRGIN 4 A 23261 \

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January 31,~1979

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Mr. James P.'0'Reilly Serial No. 300A

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~0ffice of Inspection -&' Enforcement PSE&C/ft.M:adw

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U. S. . Nuclear Regulatory Comission

Region II'

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Docket No. 50-339 101 Marietta Street, Suite 3100 '

Atlanta, Georgia .30303,

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Dear Mr. O'Reilly:

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Lin compliance with.10CFR50.55(e), NRC Region'II was notified on April 28, 1978 that the maximum dose rates on the operating vivor of North

• Anna Unit 2 could exceed the values presented in the FSAR, resulting in excess

exposure.to operating personnel. A detailed radiation survey was performed within selected areas of the. reactor containment building at North Anna Unit 1 on June 27 and 28,1978. , The <results of the survey indicated that the higher than expected neutron dose rates experienced in the Unit _1 contain-

' ment were a result of neutron streaming from the reactor cavity. Also, the principal contribution to the gama dose rate was determined to be .from -

neutron capture in_ the concrete and liner of the containment.

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An interim report was submitted to NRC Region ~ II on May 25, 1978

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(Serial No.c300) stating that we were investigating several methods of re-ducing the higher than anticipated radiation levels. Stone & Webster Engineering Corporation as the architect engineer for Vepco has designed a collar / saddle _ shield for North Anna Unit 2 to reduce the dose rates on the operating floor of the reactor containment. The location of the supplemental shield is-somewhat different from shielding solutions proposed at other plants.

" The " usual" solution-to this shielding problem has been the design of an annular shield above' the reactor vessel head. The novel design for the

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shield which we propose has a substantial advantage over previous designs.

in that removal of the shield is not required during refueling operations.

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Attached you will find Description of Neutron Supplementary Shield which 'y

? describes in detail the collar / saddle shield and the radiation analysis per- i fomed to determine 'the adequacy of the supplemental shield. Also, a-

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comprehensive reevaluation of the.RPV support system was conducted in a manner similar to that described.in Appendix 5A, Section 5A.4.4 of the FSAR. Details of this analysis are presented in the attached document.

• Vepco will obtain experimental confirmation of the adequacy of the' shield

. design for North Anna Unit 2 following startup of Unit 2.

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zMr. James P. 0'Reillyi

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We consider'this to-be the final report under the proVis' ions of'. '

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.10CFR50.55 e . Please contact me-if'further infonnation is required.

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.Ve7'truly. urs,: / '

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l$hVicePresident/%f h$a Serfio

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' -Attachment

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cc: Mr. John G. Davis,' Acting Director

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. Mr. Harold R. ' Denton, Director: .

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Office of Nuclear Reactor Regulation'

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