ML20050D350
| ML20050D350 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 04/06/1982 |
| From: | Vincent R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| TASK-02-02.C, TASK-2-2.C, TASK-RR NUDOCS 8204120143 | |
| Download: ML20050D350 (5) | |
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O Consumers Power Company General Offices: 1946 West Pernell Road, Jock eon, MI 49201 * (517) 788-0550 rs April 6, 1982 p
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Dennis M Crutchfield, Chief Operating Reactors Branch No 5 Nuclear Reactor Regulation US Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PLANT - SEP TOPIC II-2.C, ATMSOPIIERIC TRANSPORT AND DIFFUSION CilARACTERISTICS FOR ACCIDENT ANALYSIS Attached is the Consumers Power Company evaluation of SEP Topic II-2.C for the Big Rock Point Plant.
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Robert A Vincent Staff Licensing Engineer CC Administrator, Region III, USNRC NRC Resident Inspector-Big Rock Point Attaciunent - 3 pages
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SEP TOPIC II-2.C ATMOSPHERIC TRANSPORT AND DIFFUSION CHARACTERISTICS FOR ACCIDENT ANALYSIS Big Rock Point Plant i
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Big Rock Point Plant SEP TOPIC II-2.C, ATMOSPHERIC TRANSPORT AND DIFFUSION CHARACTERISTICS FOR ACCIDENT ANALYSIS 1.
Introduction The objective of this topic is to review atmospheric transport and diffusion characteristics utilized to demonstrate compliance with 10 CFR 100 guidelines with respect to plant design, control room habitability and doses to the public during and following a postulated design basis accident.
2.
Criteria 10 CFR 100 requires that as an aid in evaluating a proposed site, the applicant should hypothesize a fission product release (generally assumed to be a result of a substantial meltdown of the core with subsequent release of appreciable quantities of fission products) from the core, the maximum expected leak rate from the containment and the meteorological conditions pertinent to the site.
The total dose to an individual at the boundary of the exclusion area over the first two hours after this hypothesized event must be less than 25 rem to the whole body or 300 rem to the thyroid. Also, SRP 2.2.1 and 2.2.2 request that the potential hazard from industrial, military and transportation facilities be evalu-ated, SRP 2.2.3 requests that analysis of the consequences to the plant personnel of accidents involving these facilities be evaluated, and SRP 2.3.4 requests that the meteorological data and models used to determine these consequences be presented.
Other pertinent guidance is provided in Regulatory Guides 1.3, Assumptions Used for Evaluating the Potential Radiological Consequences of a LOCA for Boiling Water Reactors and 1.145, Atmospheric Dispersion Models for Potential Accident Consequence Assessments at Nuclear Power Plants.
3.
Summary of Previous Analysis Methods Transport of airborne radioactivity from the Big Rock Point site has been calculated by several different means over the past 20 years of plant operation.
Briefly, the techniques and reference documentation for each are as follows:
1.
Siting criteria calculations - Atmospheric diffusion based on Sutton's method for analyses of onsite preoperational meteorology data.
Documented in Sections 13 and 14 of the Big Rock Point Final Hazards Summary Report, November 14, 1961.
2.
Current safety analyses, including Emergency Plan and Emergency Implementing Procedure calculations - Atmospheric diffusion parameters from Regulatory Guide 1.3, assuming ground level or elevated release, dependent upon observed release mode.
nu0482-0010c142
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SEP Topic II-2.C 3.
Environmental dose calculations for 10 CFR 50, Appendix I - Regulatory Guides 1.109 and 1.111 were utlized for computation of doses from elevated releases, based on onsite meteorology data collected February 9,1961 through February 8,1962.
Bases and results of these calcula-tions are presented in Consumers Power Compnay (CP Co) letter dated June 4, 1976.
4.
Offsite consequences of accidents, Probabilistic Risk Assessment -
Preoperational meteorology data was utilized in accordance with the methods of WASH-1400. Results of the consequence analyses were submitted by CP Co letter dated March 31, 1981.
4.
Discussion An evaluation of x/Q values at the Big Rock Point Plant was presented in Section 14 of the Big Rock Point Final Hazards Summary Report (FHSR). As described in Section 14, a meteorological tower was constructed on a point of land at the shore of Lake Michigan about 2,000 feet to the WNW of the stack. Trees in the surrounding area were removed. The area was chosen so that the measured data would be most accurate for winds blowing toward the Harbor Springs - Petoskey and Charlevoix areas.
Hourly data was taken from November 1960 to February 1962.
Wind direction was obtained from 36 points (0 to 360). Wind direction and speed were obtained from sensors located at 32 ft, 64 ft, 128 ft and 256 ft.
Temperature data was obtained at 3 ft below the surface of the water, 10 f t, 50 f t, 100 ft,150 ft, 200 ft and 250 ft above the surface. The data was analyzed using a computer program and hourly valves of x/Q were obtained.
The data has since been used in three ways. First, Section 13 of the FHSR (Maximum Credible Accident) used four selected points in the atmospheric diffusion spectrum which encompass the conditions encountered at the site.
Atmospheric diffusion methods of Sutton were used for the neutral and unstable cases and Hanford diffusion results (Report HW-54128) were used for inversion cases. These were compared with site data and found to be conservative. Radiation doses at the site boundary and beyond were calculated using the stated diffusion methods. The worst case x/Q at 3
site boundary for a ground level release was found to bg 4 E-04 sec/m.
This compares with Reg Guide 1.3 values of 6 E-04 sec/m for 0-8 hours, 2.2 E-04 for 8-24 hours, 8 E-05 for 1-4 days and 1.7 E-05 for 4-30 days.
Since the radiation doses at the site boundary are very much below the limits given in 10 CFR 100 the actual difference between 4 E-04 and 6 E-04 is not significant with respect to meeting 10 CFR 100 limits.
The second use of the meteorological data was in the Big Rock Point Probabilistic Risk Assessment (PRA), submitted to NRC by CP Co letter of March 31, 1981. Doses to the public from dominant sequences were calculated using a variety of meteorological conditions with the CRAC code (same methodology as WASH-1400). The conditions were chosen using the sampling technique of WASH-1400. The values for x/Q were not listed in the output of the CRAC code. However, previous analyses of the meteoro-logical tower data show that the worst case x/Q (worst 2-hour interval calculated in accordance with Regulatory Guide 1.145) at the site nu0482-0010c142
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boundary, 7.5 E-04 sec/m is almost the same as that used in the FHSR.
Control Room Habitability with regards to external events was also presented in the PRA. Habitability was demonstrated by showing that the operatf or could isolate the control room ventiliation system prior to intake of excessive quantities of toxic gases, smoke, etc. Also, the probabilityoftheseeventsoccurringalongwithtg/yr).
e proper meteorological conditions and ventilation failure was small (<10 The third use of the meteorological tower data was in the CP Co submittal of June 4, 1976 concerning 10 CFR 50, Appendix 1.
The meteorological data was used to obtain x/Q and D/Q values, wind roses, monthly and yearly joint frequency distributions, and an annual average x/Q. The Methodology used was in accordance with Regulatory Guide 1.111.
This data was then input into the GASPAR computer code for radiation dose calculations.
The maximug annual average x/Q for an elevated release was found to be 2.5 E-07 sec/m. This occurred in the East sector at 2414 m from the stack.
Additional data may be found in Table 3.1 of the Appendix I submittal dated June 4, 1976.
5.
Conclusion Because the radiation doses calculated at the site boundary are small, the demonstration of compliance with 10 CFR 100 limits is not particularly sensitive to the x/Q values used.
Consumers Power Company's intent is to continue with the use of onsite preoperational data for realistic analyses performed for PRA and environmental dose purposes. For all other calculations, Regulatory Guide 1.3 values will be used. Assuming a ground level release for all unknown accident conditions, the following values of x/Q are applicable at 0.5 miles (EAB and LPZ):
0-8 hours 6.0 E-04 8-24 hours 2.2 E-04 1-4 days 7 4 E-05 4-30 days 1.8 E-05 nu0482-0010c142
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