NRC 2008-0051, Transmittal of Application to Use Weighing Factors for External Exposure
| ML082140476 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 07/30/2008 |
| From: | Meyer L Florida Power & Light Energy Point Beach |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NRC 2008-0051 | |
| Download: ML082140476 (7) | |
Text
FPL Energy Point Beach, LLC, 6610 Nuclear Road, Two Rivers, WI 54241 FPL Energy Poiirat Beach Nuclear Piant July 30, 2008 NRC 2008-0051 10 CFR 20.1003 U.S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555-0001 Point Beach Nuclear Plant, Units 1 and 2 Dockets 50-266 and 50-301 Renewed License Nos. DPR-24 and DPR-27 Application to Use Weiahtina Factors for External Exposure References (1) Letter to NRC Dated December 11,2008, Duane Arnold Energy Center, St Lucie Nuclear Plant, Units 1 and 2, Seabrook Station, and Turkey Point Nuclear Plant, Units 3 and 4 - Application to Use Effective Dose Equivalent Weighting Factors for External Exposure (ML063480330)
Pursuant to 10 CFR 20.1003, "Weighting Factor WT," FPL Energy Point Beach, LLC, requests approval to use weighting factors for calculating external whole body dose. The application is provided in the Enclosure to this letter.
Specifically, FPL Energy Point Beach requests 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 from external sources of radiation.
As described in the application, approval 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 delineated in 10 CFR 20.1003.
An FPL Group company
Document Control Desk Page 2 Reference (I) requested approval to use weighting factors for calculating external whole body dose as described above. By letter dated February 28, 2007, the NRC staff concluded that authorization of this request was acceptable, and within the provisions of 10 CFR 20.1003.
FPL Energy Point Beach proposes to begin using weighting factors for external exposures during 2009. Therefore, FPL Energy Point Beach is requesting the proposed authorization by August 1,2009.
Please contact Mr. Carl Onesti, Health Physicist, at 19201755-6170 if there are questions associated with this application.
Very truly yours, FPL Energy Point Beach, LLC Site Vice President Enclosure cc: Regional Administrator, Region Ill USNRC Project Manager, Point Beach Nuclear Plant Senior Resident Inspector, USNRC, Point Beach Nuclear Plant PSCW
ENCLOSURE I FPL ENERGY POINT BEACH, LLC POINT BEACH NUCLEAR PLANT, UNITS 1 AND 2 APPLICATION TO USE WEIGHTING FACTORS FOR EXTERNAL EXPOSURE 1.0
SUMMARY
DESCRIPTION
- 1. I Purpose 2.0 TECHNICAL JUSTIFICATION 2.1 Improved Assessment of Dose 2.2 Compartment Factors 2.3 Chest Compartment 2.4 Dosimeter Selection and Placement 2.5 Dose Assignment 2.6 Additional Considerations
3.0 REGULATORY EVALUATION
3.1 Regulatory Evaluation 3.2 Precedents 3.3 Conclusion 4 pages follow
1.0 INTRODUCTION
1 . Purpose Pursuant to 10 CFR 20.1003, "Weighting factor WT," FPL Energy Point Beach requests approval to use weighting factors for calculating external whole body dose.
Specifically, FPL Energy Point Beach requests approval to use weighting factors specified in HPS N13.41 (HPS N13.41-1997, "Criteria for Performing Multiple Dosimetry," approved in 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.
2.0 TECHNICAL JUSTIFICATION 2.1 lm~rovedAssessment 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 DDE. 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 the highest whole body dose can be measured.
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 DDE 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 DDE 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 Area of the Body 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 2.3 Chest Compartment Consistent with FPL Energy Point Beach 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.
2.4 Dosimeter Selection and Placement NRC Inspection Procedure 71 121.01, "Access Control To Radiologically Significant Areas" issue date 03/06/02, Section 03.04(c), "Dosimeter selection and placement criteria," will be used to provide adequate criteria for monitoring the part of the body expected to receive the highest dose.
2.5 Dose Assinnment The DDE for each compartment will be determined from dosimeters worn at that location.
When no dosimeter is worn at a particular compartment, DDE will be determined from the dosimeter positioned where the exposure is judged to be similar. The assigned EDE will be the sum of each DDE 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 Additional Considerations (1) The FPL Energy Point Beach application seeks approval to calculate the external dose quantity EDE using the compartments, compartment factors, and method of summation specified in HPSIANSI N13.41. EDE will be used in place of DDE in the calculation of TEDE. This application does not seek approval to use the ANSI Standard's Section 4, "Criteria for When to Use Multiple Dosimeters," or Section 5.5 "Alternatives to the Use of Multiple Dosimeters."
(2) FPL Energy Point Beach will monitor the part of the whole body within each compartment (andlor composite compartment) that receives the highest dose. FPL Energy Point Beach will use the criteria in our current procedures addressing dosimeter selection and placement. These procedures use criteria consistent with guidance found in current NRC inspection procedures.
(3) The same NVLAP accredited dosimeters will be worn at the same whole body locations after the application is approved as they are today. Because we will continue to monitor the part of the body expected to receive the highest dose, the dosimeter orientation toward the source will not change. Therefore, there are no new challenges to the dosimeter's angular response characteristics resulting from approval of this application.
3.0 REGULATORY EVALUATION
3.1 Re~ulatorvEvaluation Dose limits in 10 CFR 20 are specified in the dose quantity total effective dose equivalent (TEDE). TEDE is defined in 10 CFR 20.1003 as the sum of the external dose quantity called deep dose equivalent (DDE) plus the internal dose quantity called committed effective dose equivalent.
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. FPL Energy Point Beach seeks NRC approval to use weighting factors to calculate the external exposure quantity EDE and to use EDE in place of DDE in the calculation of TEDE.
3.2 Precedents The proposed method is consistent with the NRC Safety Evaluation dated February 28, 2007, (ML070530387) for Duane Arnold Energy Center, St. Lucie Nuclear Plant, Units 1 and 2, Seabrook Station, and Turkey Point Nuclear Plant, Units 3 and 4, for application to use effective dose equivalent weighting factors for external exposure. The NRC staff concluded that authorization of this request was acceptable, and within the provisions of 10 CFR 20.
3.3 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.
FPL Energy Point Beach 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 June 20, 1996. At the time of balloting, the HPS N13 Committee membership included representatives from the Nuclear 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, "Evaluating 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 NRC inspection procedures.