RA-08-015, Estimated Dose Report for 2007 Maine Yankee Independent Spent Fuel Storage Installation

Estimated Dose Report for 2007 Maine Yankee Independent Spent Fuel Storage Installation

ML081140670
Person / Time
Site:	Maine Yankee, 07100465
Issue date:	04/30/2008
From:	Radiological Safety & Control Services
To:	Office of Nuclear Material Safety and Safeguards
References
MN-08-008, RA-08-015
Download: ML081140670 (7)

Text

ESTIMA TED DOSE REPORT FOR 2007 MAINE YANKEE INDEPENDENT SPENT FUEL STORA GE INSTALLA TION License No. DPR-36 Maine Yankee Atomic Power Company rS"'........ S ie a \~r .............

April 2008 Prepared by: Radiological Safety & Control Services 91 Portsmouth Avenue Stratham, Nil 03885-2468 TABLE OF CONTENTS Page TA B LE O F C O N TEN T S .........................................................................................................................

I LIST O F TAB LE S ....................................................................................................................................

2 1.0 IN TR O D U C TIO N ........................................................................................................................

3 2.0 D O SE A SSE SSM EN T ..........................................................................................................

3 3.0 RE FER EN C E S ..............................................................................................................................

4 LIST OF TABLES TABLE TITLE Page TABLE 1 Maine Yankee Atomic Power Station Maximum Annual Dose from Direct External Radiation (a) (4OCFR1 90).............................................................................

5 TABLE 2 Receptor Locations for Maine Yankee .....................................................

6 2 MAINE YANKEE ATOMIC POWER STATION ESTIMATED DOSE REPORT FOR 2007

1.0 INTRODUCTION

The Maine Yankee ISFSI is designed with the NAC-UMS Transportable Storage Containers that are stored in Vertical Concrete Cask. Per the NAC-UMS Safety Analysis Report, and the 10 CFR 72.212 Evaluation, this type of design meets the definition of a leak tight canister as defined by as defined by ANSI N 14.5. As such, there are no liquid, particulate, or gaseous effluents resulting from ISFSI operations.

The only dose to be considered from facility operations is from direct radiation.

For the purposes of demonstrating compliance with 40CFRI90, "Environmental Radiation Protection Standards for Nuclear Power Operations," radiation dose estimates must include direct radiation contributions from significant plant sources. Data from thermoluminescent dosimeters (TLDs) in the area of the western ISFSI controlled area boundary indicated a plant-related direct radiation component at the stream running from Bailey Cove (nearest off-site area to the plant) during the monitoring period. Since members of the public use the mud flats in the cove during periods of low tide, an assessment was performed to determine compliance with the 40CFRI90 dose limits. Table 2 lists the exposure results from ISFSI related sources to any member of the public at Bailey's Cove.The total dose to the most limiting member of the public due to ISFSI related direct radiation was well below the dose standards of 40CFRI90.2.0 DOSE ASSESSMENT The, annual (calendar year) total dose to any member of the public due to direct radiation from fixed sources are limited to EPA's radiation protection standards for the uranium fuel cycle (40CFR190).

The dose limits are set to less than or equal to 25 mrem per year to the total body or any organ, except the thyroid, which is limited to less than or equal to 75 mrem per year.Direct external dose from fixed sources of radioactive materials within the ISFSI controlled area was estimated from Maine Yankee's TLD data. The data from TLDs posted in the west and east sectors of the ISFSI controlled area boundary indicate above-background radiation.

However, it is not reasonable to consider that someone would spend long periods of time living in a houseboat on the Back River by the banks of the river east or southeast of the ISFSI. Therefore the dose estimate is performed to a member of the public along the west boundary where clam diggers and worm diggers occupy the area throughout the year. The maximum annual dose from fixed radiation sources to members of the public in the mudflats, as derived from TLD measurements, was estimated to be 0.37 mrem. This estimate of dose incorporates an occupancy time of 325 hours0.00376 days <br />0.0903 hours <br />5.373677e-4 weeks <br />1.236625e-4 months <br /> per year for worm diggers, as determined in the occupancy study around the Maine Yankee site for demonstrating compliance with 40CFR190.The receptor location used (containing TL-I-14) in the dose assessment was the center of the nearest portion of the pathway leading to the mud flats exposed at low tide, approximately 340 meters from the Cenlier of the ISFSI. The Maine Yankee Dry Cask Storage Array Skyshine Analysis, NAC International Calculation No. 12412-4104, Rev. 2 defines the center of the ISFSI as the point in the center of the second southernmost column of storage pads. It is noted that most of the mud flat region in Bailey Cove that is used by the public is situated further away from this selected reference point. As a result, actual exposures from direct radiation would be less than the value applied in the estimate of direct dose (0.37 mrem) to the clam and worm diggers as they move across the flats. Additionally, the dose estimate is conservative since the dose calculation makes no attempt to apply a correction factor to the onsite TLD measurement for the purpose of obtaining the exposure rate to the mudflat location.

The dose rate at the mudflat location would be much less as a function of distance.Table 1 provides the quarterly and annual dose to the maximally exposed member of the public from direct radiation associated with ISFSI operations.

3 Table 2 identifies the receptor locations, nearest resident, garden and milk locations.

Although milk and garden locations are associated with gaseous effluent releases, they were left in this report as they could provide useful information to the site.

3.0 REFERENCES

I. "Off-Site Dose Calculation Manual," Maine Yankee Atomic Power Company.2. 40CFR190, Environmental Radiation Protection For Nuclear Power Operations

5. NUREG-0133, "Preparation of Radiological Effluent Technical Specifications for Nuclear Power Plants," U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation, October 1978.6. Maine Yankee Dry Cask Storage Array Skyshine Analysis, NAC International Calculation No. 12412-4104, Rev. 2, May 31, 2001.4 TABLE 1 Maine Yankee Atomic Power Station Maximum Annual Dose from Direct External Radiation(a)

(40CFR190)

Pathway 1s Qtr. 1 2 nI tr 1 3 Year Direct External Exposure Rate (Micro-R/hr) 1.30(c) *1.30(c) 0.90(c) 1.30(c) 1.20 avg.Occupancy Hours/interval 32.5(a) 130(a) 130(a) 32.5(a) 325(a)mrem/interval

[ 4.225E-2 *1.69E-1 1.17E-1 4.225E-2 3.71E-I*NOTE: The calculated exposure rate at TL-I-14 for the 2 nd quarter was less than background after subtracting the exposure rate from the Maine Yankee control location (Wiscasset Fire Station).

Therefore, in place of a null dosimeter reading, the Ist quarter value of the TL-I-14 station was applied to the 2 nd quarter for this dose estimate.(a) The location of maximum individual doses from direct radiation corresponds to exposed mud flats at low tide in Bailey's Cove, south west of the ISFSI site. The hours per interval were proportioned to a reasonable time of clamming or worm digging for each interval due to changes in the season. The annual occupancy (325 hours0.00376 days <br />0.0903 hours <br />5.373677e-4 weeks <br />1.236625e-4 months <br /> per year) is a result of a detailed evaluation for the Maine Yankee site for demonstrating compliance with 40CFRI190.(b) For any member of the public, EPA radiation protection standards (40CFRI90) established annual dose limits of 25 mrem to the total body and any organ (except the thyroid, which has a dose limit of 75 mrem).(c) Exposure rate above the average background of the Maine Yankee offsite TLD locations (Wiscasset Fire Station).

For this dose estimate, the TLD location with the highest average exposure rate along the most likely occupied location (mudflats) was used (TL-I-I 4).5 TABLE 2 Receptor Locations for Maine Yankee Nearest Milk Nearest Receptor(a)

Nearest Resident Nearest Garden Animal Sector (Meters) (Meters) (Meters) (Meters)N 340 1260 -- --NNE 340 2230 2400 2650 (cows)NE 340 1270 1470 --ENE 340 920 1250 --E 730 900 900 --ESE 670 700 --..SE 670 700 900 --SSE 820 900 900 --S 350 1700 1700 --SSW 340 3000 5000 --SW 340 1500 4000 --WSW 340 960 1940 1880 (cows)W 340 810 2710 --WNW 340 1900 --..NW 340 1930 1930 --NNW 340 1060 1180 --(a) The nearest receptor location is taken to be the site boundary for all sectors except the E through S sectors. The actual site boundary for each of these sectors is located next to Back River (water boundary).

The receptor locations noted represent the closest dry land points beyond the site boundary where a 100% occupancy time is assumed. Other site boundaries bordered by water, and mud flats exposed at low tides, which may be worked by worm diggers, have occupancy factors applied equal to 325 hour0.00376 days <br />0.0903 hours <br />5.373677e-4 weeks <br />1.236625e-4 months <br />s/year (MY ODCM).6