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

~0ffice of Inspection -&' Enforcement PSE&C/ft.M:adw U. S. . Nuclear Regulatory Comission

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

Atlanta, Georgia .30303,

Dear Mr. O'Reilly:

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.

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

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

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-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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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,: / '

l$hVicePresident/%f h$a Serfio

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

. -' Office of Inspection .& Enforcement

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

Office of Nuclear Reactor Regulation' F

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