ML082321198

Application to Use Weighting Factors for External Exposure

ML082321198
Person / Time
Site:	Millstone, Kewaunee, Surry, North Anna
Issue date:	08/18/2008
From:	Hartz L Dominion Energy Kewaunee, Dominion Nuclear Connecticut, Dominion Resources Services, Virginia Electric & Power Co (VEPCO)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
08-0430
Download: ML082321198 (9)

Text

.~

~,

" Domlnlon~

• c Dominion Resources Services, Inc.

~I)O() Dominion Boulevard, Glen Allen. VA )'11(,(

Weh *\ddress: www.dom.com August 18, 2008 U.S. Nuclear Regulatory Commission Serial No. 08-0430 Attention: Document Control Desk NL&OS/GAW RO One White Flint North Docket Nos. 50-305 11555 Rockville Pike 50-336/423 Rockville, MD 20852-2738 50-338/339 50-280/281 License Nos. DPR-43 DPR-65/NPF-49 NPF-4/7 DPR-32/37 DOMINION ENERGY KEWAUNEE, INC. (DEK)

DOMINION NUCLEAR CONNECTICUT, INC. (DNC)

VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)

KEWAUNEE POWER STATION MILLSTONE POWER STATION UNITS 2 AND 3 NORTH ANNA AND SURRY POWER STATIONS UNITS 1 AND 2 APPLICATION TO USE WEIGHTING FACTORS FOR EXTERNAL EXPOSURE Pursuant to footnote 2 to the "Organ Dose Weighting Factors" table in 10 CFR Part 20.1003, DEK, DNC and Dominion request approval to use weighting factors for calculating external whole body dose. The application is provided as an attachment to this letter.

Specifically, DEK, DNC and Dominion request approval to apply the weighting factors specified in the consensus technical standard, American National Standards Institute, HPS N13.41-1997, "Criteria for Performing Multiple Dosimetry," to assign total effective dose equivalent (TEDE) from external sources of radiation.

As described in the application, the approved use of weighting factors would improve the assessment of occupational dose to individuals from exposure to highly non-uniform radiation fields.

The technical basis for this application is the consensus technical standard approved by the American National Standards Institute - Accredited HPS N13 Committee. The standard is practical and consistent with the organ or tissue weighting factors in 10 CFR Part 20.1003.

The NRC previously approved use of weighting factors for Florida Power & Light Company plants (St. Lucie Units 1 and 2, Turkey Point Units 3 and 4, Seabrook Station and the Duane Arnold Energy Center) in a letter dated February 28, 2007 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML00530387).

Serial Number 08-0430 Docket Nos. 50-305/336/423/338/339/280/281 Application to Use Weighting Factors for External Exposure Page 2 of 3 If you have any questions or require additional information, please contact Mr. Geoffrey Wertz at (804) 273-3572.

Sincerely, e::tY?~

Leslie N. Hartz~

Vice President - Nuclear Support Services Dominion Resource Services, Inc., for Dominion Energy Kewaneee, Inc.

Dominion Nuclear Connecticut, Inc.

Virginia Electric and Power Company

Attachment:

Application to Use Weighting Factors for External Exposure Commitments made by this letter: None cc: U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, Pennsylvania 19406-1415 U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW Suite 23T85 Atlanta, Georgia 30303 U.S. Nuclear Regulatory Commission Region III 2443 Warrenville Road Suite 210 Lisle, Illinois 60532-4352 NRC Senior Resident Inspector Kewaunee Power Station NRC Senior Resident Inspector Millstone Power Station NRC Senior Resident Inspector North Anna Power Station

Serial Number 08-0430 Docket Nos. 50-305/336/423/338/339/280/281 Application to Use Weighting Factors for External Exposure Page 3 of 3 cc: (continued)

NRC Senior Resident Inspector Surry Power Station Mr. P. S. Tam NRC Project Manager - Kewaunee U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 0-8 H4A 11555 Rockville Pike Rockville, Maryland 20852-2738 Ms. C. J. Sanders NRC Project Manager - Millstone Units 2 and 3 U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 0-8 83 11555 Rockville Pike Rockville, Maryland 20852-2738 Mr. S. P. Lingam NRC Project Manager - Surry and North Anna U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 0-8 G9A 11555 Rockville Pike Rockville, Maryland 20852-2738

Serial No. 08-0430 Docket Nos. 50-305/336/423/338/339/280/281 ATTACHMENT APPLICATION TO USE WEIGHTING FACTORS FOR EXTERNAL EXPOSURE DOMINION ENERGY KEWAUNEE, INC. (DEK)

DOMINION NUCLEAR CONNECTICUT, INC. (DNC)

VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)

KEWAUNEE POWER STATION MILLSTONE POWER STATION UNITS 2 AND 3 NORTH ANNA AND SURRY POWER STATION UNITS 1 AND 2

Serial No. 08-0430 Docket Nos. 50-305/336/423/338/339/280/281 APPLICATION TO USE WEIGHTING FACTORS FOR EXTERNAL EXPOSURE

1.0 INTRODUCTION

1 1.1 PURPOSE 1

1.2 REGULATORY EVALUATION

1 2.0 TECHNICAL JUSTIFICATION 1 2.1 IMPROVED ASSESSMENT OF DOSE 1 2.2 COMPARTMENT FACTORS 2 2.3 CHEST COMPARTMENT 3 2.4 DOSIMETER SELECTION AND PLACEMENT 3 2.5 DOSE ASSIGNMENT 3

2.6 CONCLUSION

3

Serial Number 08-0430 Docket Nos. 50-305/336/423/338/339/280/281 Attachment Page 1 of 4

1.0 INTRODUCTION

1.1 PURPOSE Pursuant to 10 CFR Part 20.1003, "Weighting factor WT," Dominion Energy Kewaunee, Inc. (DEK), Dominion Nuclear Connecticut, Inc. (DNC), and Virginia Electric and Power Company (Dominion), request approval to use weighting factors for calculating external whole body dose.

Specifically, DEK, DNC and Dominion request approval to use weighting factors specified in HPS N13.41 (HPS N13.41-1997, "Criteria for Performing Multiple Dosimetry," approved December 1996, American National Standards Institute, Inc.) for assessing effective dose equivalent (EDE) based on direct measurement of external exposures using personnel dosimeters. The assigned EDE is the sum of each dosimeter measurement modified by its appropriate weighting factor.

The assigned EDE will be used as a component part in the calculation of total effective dose equivalent (TEDE).

This application is not intended to seek approval to use other methods or standards that are outlined in HPS/ANSI N13.41.

1.2 REGULATORY EVALUATION

Dose limits in 10 CFR Part 20 are specified in the dose quantity TEDE. TEDE is defined in 10 CFR 20.1003 as the sum of the effective dose equivalent (for external exposures) and the committed effective dose equivalent (for internal exposures).

Footnote 2, in the "Organ Dose Weighting Factors" table in 10 CFR 20.1003, permits the use of weighting factors for external exposure with prior NRC approval. DEK, DNC and Dominion seek NRC approval to use weighting factors to calculate the external exposure quantity EDE and to use in the calculation of TEDE.

2.0 TECHNICAL JUSTIFICATION 2.1 IMPROVED ASSESSMENT OF DOSE In uniform radiation fields, the dosimeter used to measure whole body dose is worn on the chest. The dosimeter measures radiation exposure using an operational dose quantity called deep dose equivalent (ODE).

When the radiation field is highly non-uniform, either the chest dosimeter is moved to the part of the whole body expected to receive the highest dose or additional dosimeters are worn so that the highest whole body dose can be measured.

Serial Number 08-0430 Docket Nos. 50-305/336/423/338/339/280/281 Attachment Page 2 of 4 Difficulties arise because the annual occupational dose limit is based on the stochastic risk from whole body exposure, which is related to the dose quantity EDE. While the use of DOE as a surrogate quantity to approximate EDE works well in uniform radiation fields, in highly non-uniform radiation fields, a more accurate estimate of EDE is needed to improve the assessment of occupational dose.

2.2 COMPARTMENT FACTORS HPS N13.41 provides a method for assessing EDE based on measurements of DOE at specific areas of the body called "compartments" and applying appropriate weighting factors called "compartment factors." A compartment factor "relates the fractional risk to the organs underlying the measurement location to the total risk from uniform irradiation of the whole body."

HPS N13.41, Appendix A describes how the 10 CFR Part 20 organ or tissue weighting factors are apportioned to each "compartment" based on the associated underlying organs and tissues. The resulting compartment factors used to calculate EDE are listed below:

HPS N13.41 COMPARTMENT FACTORS Compartment Name Compartment Factor Head and neck 0.10 Thorax, above the diaphragm 0.38 Abdomen, including the pelvis 0.50 Upper right arm 0.005 Upper left arm 0.005 Right thigh 0.005 Left thigh 0.005

Serial Number 08-0430 Docket Nos. 50-305/336/423/338/339/280/281 Attachment Page 3 of 4 2.3 CHEST COMPARTMENT Consistent with DEK, DNC and Dominion's current practice, a single chest dosimeter will measure the dose to both the thorax and abdomen compartments. The combined compartments will be called the chest compartment. To ensure that the calculation of EDE (external) is conservative, DEK, DNC and Dominion will measure the dose to the highest portion of the thorax and abdomen and place the dosimeter at that location.

2.4 DOSIMETER SELECTION AND PLACEMENT A national voluntary laboratory accreditation program (NVLAP) accredited dosimeter will be worn at each compartment or composite compartment at the highest exposed area.

The dosimeter will be the same as previously used for multiple badge locations in dose gradients and, therefore, not pose any new challenges concerning angular dependence.

The criteria for the use of multiple whole body dosimetry will remain the same as defined in station procedures. The criteria are consistent with the guidance found in INPO 05-008, "Guidelines for Radiological Protection at Nuclear Power Stations."

2.5 DOSE ASSIGNMENT The DOE for each compartment will be determined from dosimeters worn at that location. When no dosimeter is worn at a particular compartment, DOE will be determined from the dosimeter positioned where the exposure is similar. The assigned EDE will be the sum of each DOE measurement multiplied by its appropriate compartment factor.

The assigned lens dose equivalent (LDE) will be the higher of the head or chest dosimeters. The assigned shallow dose equivalent (SDE) will be the highest of any whole body dosimeter.

2.6 CONCLUSION

Accurate assessment of occupational dose from external sources of radiation in highly non-uniform radiation fields requires a method for assessing EDE. NRC approval of this application will improve the accuracy of licensee assessment of occupational dose.

DEK, DNC and Dominion will assess EDE based on the consensus technical standard, HPS N13.41. This standard was approved by the American National Standards Institute - Accredited HPS N13 Committee on 20 June 1996. At the time of balloting, the HPS N13 Committee membership included representatives from the Nuclear

Serial Number 08-0430 Docket Nos. 50-305/336/423/338/339/280/281 Attachment Page 4 of 4 Regulatory Commission and the National Council on Radiation Protection and Measurements.

The HPS N13.41 consensus technical standard has previously been approved for use by the NRC for evaluating occupational dose to medical personnel wearing lead aprons in Regulatory Issue Summary 2002-06, "Evaluation Occupational Dose for Individuals Exposed to NRC-Licensed Material and Medical X-Rays," dated April 16, 2002.

The proposed method will monitor the part of the whole body expected to receive the highest dose using the criteria for dosimeter selection and placement found in current station procedures.