NUREG-1026, Intervenor Exhibit I-1,consisting of Table 5.11 & App F to NUREG-1026, Fes Related to Operation of Braidwood Station, Units 1 & 2, June 1984

Intervenor Exhibit I-1,consisting of Table 5.11 & App F to NUREG-1026, Fes Related to Operation of Braidwood Station, Units 1 & 2, June 1984

ML20154S663
Person / Time
Site:	Braidwood
Issue date:	03/11/1986
From:	Office of Nuclear Reactor Regulation
To:
References
RTR-NUREG-1026 OL-I-001, OL-I-1, NUDOCS 8604070166
Download: ML20154S663 (7)

Text

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$NRC 86 APR -3 A9 :21 Final Envhmental Statement related to the 6peration of Braidwood Station, Units 1 and 2 Docket Nos. STN 50-456 and STN 50-457 Commonwealth Edison Company U.S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation June 1984 p age, kWLielt n.4.i.La f 0 A T GGair.414.ic n Jadet No. - "A _._ ffklat Erh. No.

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. Table 5.11 Summary of environmental impacts and probabilities 3

Population Cost of

& exposure, Latert* offsite 8

a Probability Persons Persons millions of person- canc(rs, mitigating A of impact per exposed exposed Early rees, 80-km (50-mi)/ 80-km (50-mi)/ actions,

• reactor yr over 200 rems over 25 rems fatalities total total $ millions 10 4 0 0 0 0/<0.003 0/0 <5 10 5 0 0 0 0.35/0.81 71/220 7 5 x 10 s 0 3,400 0 1.3/12 220/730 470 10 s 480 87,000 3 19/51 1,400/3,100 2,600 10 7 3,200 730,000 1,000 47/88 3,600/6,400 7,100

, 10.a 10,100 730,000 1,500 67/88 -

8,100/9,000 16,000 h Related figure 5.9 5.9 5.11 5.10 5.12 5.13

• Includes cancers of all organs. Genetic effects would be approximately twice the number of latent cancers.

NOTE: Please refer to Section 5.9.4.5(7) for a discussion of uncertainties in risk estimates.

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1, APPENDIX F CONSEQUENCE MODELING CONSIDERATIONS 9

F.1 Evacuation Model

" Evacuation," used in the context of offsite emergency response in the event of substantial amount of radioactivity release to the atmosphere in a reactor acci-dent, denotes an early and expeditious movement of people to avoid exposure to the passing radioactive cloud and/or to acute ground contamination in the wake of the cloud passage. It should be distinguished from " relocation " which denotes a postaccident response to reduce exposure from Icng-term ground con-tamination after plume passage. The Reactor Safety Study (RSS) (NUREG-75/014, formerly WASH-1400) consequence model contains provisions for incorporating radiological consequence reduction benefits of public evacuation. The benefits of a properly planned and expeditiously executed public evacuation would be manifested in a reduction of early health effects associated with early expo-sure; namely, in the number of cases of early fatality (see Section F.2) and acute radiation sickness that would require hospitalization. The evacuation model originally used in the RSS consequence model is described in WASH-1400 as well as in NUREG-0340 and NUREG/CR-2300. The evacuation model that has been used herein is a modified version of the RSS model (Sandia, 1978) and is, to a certain extent, site emergency planning oriented. The modified version is briefly outlined below.

The model uses a circular area with a specified radius (the 16-km (10-mi) plume exposure pathway emergency planning zone (EPZ)), with the reactor at the center It is assumed that people living within portions of this area would evacuate if an accident should occur involving imminent or actual release of significant quantities of radioactivity to the atmosphere.

Significant atmospheric releases of radioactivity would in general be preceded by one or more hours of warning time (postulated as the time interval between the awareness of impending core melt and the beginning of the release of radioactivity from the containment building). For the purpose of calculation of radiological exposure, the model assumes that all people who live in a fan-shaped area (fanning out from the reactor) within the circular zone with the downwind direction as its median--that is, those people who would potentially be urc'er the radioactive cloud that would develop following the release--would leave t. heir residences af ter lapse of a specified amount of delay time

• and tb* evacuate. The delay time is calculated from the beginning of the warning time and is recognized as the sum of the time required by the reactor operators to notify the responsible authorities; the time required by the authorities to interpret the data, decide to evacuate, and direct the people to evacuate; and the time required for the people to mobilize and get under way.

• Assumed to be a constant value, I hour, that would be the same for all evacuees.

Braidwood FES F-1

The model assumes that each evacuee would move radially outward

• away from the reactor with an average effective speed ** (obtained by dividing the zone radius l by the average time taken to cicar the zone after the delay time) over a fixed I

distance from the evacuee's starting point. This distance is selected to be 24 km (15 mi) (which is 8 km or 5 mi more than the 16-km (10-mi) plume exposure i pathway EPZ radius). After reaching the end of the travel distance, the evacuee j is assumed to receive no further radiation exposure.

A q The model incorporates a finite length of the radioactive cloud in the downwind y direction that would be determined by the product of the duration over which 3

v the atmospheric release would take place and the average wind speed during the release. It is assumed that the front and the back of the cloud would move with I an equal speed which would be the same as the prevailing wind speed; therefore, its length would remain constant at its initial value. At any time after the release, the concentration of radioactivity is assumed to be uniform over the length of the cloud. If the delay time were less than the warning time, then

, all evacuees would have a head start; that is, the cloud would be trailing

$ behind the evacuees initially. On the other hand, if the delay time were more j than the warning time, then, depending on ire!tial locations of the evacuees, p it is possible that (1) an evacuee would still have a head start, or (2) the 5

cloud would be already overhead when an evacuee starts to leave, or (3) an

[ evacuee would be initially trailing behind the cloud. However, this initial

{ picture of cloud / people disposition would change as the evacuees travel, depend-ing on the relative speed and positions between the cloud and people. The cloud

and an evacuee might overtake one another ene or more times before the evacuee 4 would reach his/her destination. In the model, the radial position of an evacuating person, either stationary or in transit, is compared to the front p( and the back of the cloud as a function of time to determine a realistic period q of exposure to airborne radionuclides. The model calculates the time periods during which people are exposed to iudionuclides on the ground while they are stationary and while they are evacuating. Because radionuclides would be depos-ited continually from the cloud as it passed a given location, a person under the cloud would be exposed to ground contamination less concentrated than if the cloud had completely passed. To account for this, at least in part, the

' revised model assumes that persons are (1) exposed to the total ground contam-ination concentration that is calculated to exist after complete passage of the cloud, after they are completely passed by the cloud; (2) exposed to one-half the calculated concentration when anywhere under the cloud; and (3) not exposed when they are in front of the cloud. Different values of the shielding protection factors for exposures from airborne radioactivity and ground contam-ination have been used.

Results shown in Section 5.9.4.5 of the main body of this report for accidents involving significant release of radioactivity to the ..tmosphere were based on the assumption that all people within the 16-km (10-mi) plume exposure path-way EPZ would evacuate according to the evacuation scenario described above.

• In the RSS consequence model, the radioactive cloud is assumed to travel radially outward only, spreading out as it moves away.

• • Assumed to be a constant value, 1.1 mi (1.8 km) per hour, that would be the same for all evacuees.

Braidwood FES F-2

8 Because sheltering can be a mitigative feature, it is not expected that detailed inclusion of any facility (see Section S.9.4.5(2)) near a specific plant site,

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where not all persons would be quickly evacuated, would significantly alter the '

conclusions. For the delay time before evacuation, a value of 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> was used.

The staff believes that such a value appropriately reflects the Commission's emergency planning requirements. The applicant has provided estimates of the time required to clear the 16-km (10-mi) zone. .

From these estimates, the staff has conservatively estimated the effective j evacuation speed to be 0.5 m per second (1.1 mph). It is realistic to expect that the authorities would aid and encourage evacuation at distances from the site where exposures above the threshold for causing early fatalities could be reached regardless of the EPZ distance. As an additional emergency measure for the Braidwood site, it was also assumed that all people beyond the evacua-l tion distance who would be exposed to the contaminated ground would be relocated 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> after passage of the plume.

A modification of the RSS consequence model was used, which incorporates the assumption that if the calculated ground dose to the total marrow over a 7-day i period were to exceed 200 rems, then this high dose rate would be detected by l actual field measurements following plume passage, and people from these region's

would be relocated immediately. For this situation the model limits the period of ground dose calculation to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />; otherwise, the period of ground exposure l is limited to 7 days for calculation of early dose.

I Figure F.1 shows the early fatalities for (1) a pessimistic case for which no

early evacuation is assumed and all persons are assumed to be enposed for the l first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> following plume passage and are then conditionally relocated on

the basis of projected dose as described above and (2) a less pessimistic case, j the same as (1) except relocation occurs 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> after plume passage. ,

l The model has the same provision for calculation of the economic cost associated i

with implementation of evacuation as the original RSS model. For this purpose, i the model assumes that for atmospheric releases of durations 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> or less, l all people living within a circular area of 8-km (5-mi) radius centered at the reactor plus all people within a 45' angular sector within the plume exposure pathway EPZ and centered on the downwind direction will be evacuated and tempo-1 rarily relocated. However, if the duration of release would exceed 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />, the l cost of evacuation is based on the assumption that all people within the entire

plume exposure pathway EPZ would be evacuated and temporarily relocated. For

! either of these situations, the cost of evacuation and relocation is assumed to

! be $225 (1980 dollars) per person, which includes cost of food and temporary

sheltering for a period of 1 week.

F.2 Early Health Effects Model The medical advisors to the Reactor Safety Study (WASH-1400, Appendix IV, '

Section 9.2.2, and Appendix F) proposed three alternative dose-mortality rela-i tionships that can be used to estimate the number of early fatalities in an exposed population. These alternatives characterize different degrees of postexposure medical treatment, from " minimal" to " supportive" to " heroic";

they are more fully described in NUREG-0340. There is uncertainty associated with the mortality relationships (NUREG/CR-3185) and the availability and effectiveness of different classes of medical treatment (Andrulls, 1982).

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The calculated estimates of the early fatality risks presented in Sec-tion 5.9.4.5(3) of the main body of this report and in Section F.1 of this appendix used the dose-mortality relationship that is based on the supportive treatment alternative. This implies the availability of medical care facilities and services that are designed for radiation victims exposed in excess of 170 rems, the approximate level above which the medical advisors to the Reactor Safety Study recommended more than minimum medical care to reduce, early fatality risks. At the extreme low probability end of the spectrum (i.e., at the 3 chances in 100 million per reactor year level). the number of persons involved might exceed the capacity of facilities that provide the best such services, in which case the number of early fatalities might have been underestimated. How-ever, this number may riot have been greatly underestimated, because the hospitals now in the United States are likely to be able to supply considerably better care to radiation victims than the medical care that the sometimes assumed minimal medical treatment relationship is based on. Further, a major reactor accident at Braidwood would certainly cause a mobilization of the best available medical services with a high national priority to save the lives of radiation victims. Therefore, the staff expects that the mortality risks would be less than those indicated by the RSS description of minimal treatment (and much less, of course, for those who will be given the type of treatment defined as

" supportive"). For these reasons, the staff has concluded that the early fatal-ity risk estimates are bounded by the range of uncertainties discussed in Sec-tion 5.9.4.5(7).

F.3 References

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l Andrulis Research Corp. , Task 5 letter report from Dr. D. A. Elliot to A. Chu, l NRC Project Officer, on Technical Assistance Contract No. NRC-03-82-128, l December 13, 1982.

Sandia Laboratories, "A Model of Public Evacuation for Atmospheric Radiological l Releases," SAND 78-0092, June 1978.

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U.S. Nuclear Regulatory Commission, NUREG-75/014 (formerly WASH-1430), " Reactor Safety Study," October 1975.

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-- , NUREG-0340, " Overview of the Reactor Safety Study Consequences Model," l October 1977.

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-- , NUREG/CR-2300, "Draf t: PRA Procedure Guide. A Guide to the Performance of Probabilistic Risk Assessments for Nuclear Power Plants," Vol.1, Revision 1, ,

April 1982. '

-- , NUREG/CR-3185, " Critical Review of the Reactor Safety Study Radiological' >

Health Effects Model," March 1983. o l

Braidwood FES F-5 I