Regulatory Guide 1.3

Assumptions Used for Evaluating the Potential Radiological Consequences of a Loss of Coolant Accident for Boiling Water Reactors

ML003739601
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Issue date:	06/30/1974
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RG-1.3, Rev 2
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Revision 2 June 1974 U.S. ATOMIC ENERGY COMMISSION

REGULATORY GUIDE

DIRECTORATE OF REGULATORY STANDARDS

REGULATORY GUIDE 1.3 CONSEQUENCES

ASSUMPTIONS USED FOR EVALUATING THE POTENTIAL RADIOLOGICAL WATER REACTORS

OF A LOSS OF COOLANT ACCIDENT FOR BOILING

A. INTRODUCTION

review, guideline, exposures of 20 rem whole the body and values

150 rem thyroid should be used rather than Section 50.34 of 10 CFR Part 50 requires that each given in § 100.11 in order to allow for (a) uncertainties in final design details and meteorology or (b) new data applicant for a construction permit or operating license and calculational techniques that might influence the provide an analysis and evaluation of the design and final design of engineered safety features or the dose performance of structures, systems, and components of reduction factors allowed for these features.)

the facility with the objective of assessing the risk to public health and safety resulting from operation of the facility. The design basis loss of coolant accident

C. REGULATORY POSITION

(LOCA) is one of the postulated accidents used to evaluate the adequacy of these structures, systems, and 1. The assumptions related to the release of radioactive components with respect to the public health and safety. material from the fuel and containment are as follows:

This guide gives acceptable assumptions that may be a. Twenty-five percent of the equilibrium used in evaluating the radiological consequences of this radioactive iodine inventory developed from maximum accident for a boiling water reactor. In some cases, full power operation of the core should be assumed to unusual site characteristics, plant design features, or be immediately available for leakage from the primary other factors may require different assumptions which reactor containment. Ninety-one percent of this 25 will be considered on an individual case basis. The percent is to be assumed to be in the form of elemental Advisory Committee on Reactor Safeguards has been iodine, 5 percent of this 25 percent in the form of consulted concerning this guide and has concurred in the particulate iodine, and 4 percent of this 25 percent in regulatory position. the form of organic iodides.

B. DISCUSSION

b. One hundred percent of the equilibrium radioactive noble gas inventory developed from After reviewing a number of applications for maximum full power operation of the core should be construction permits and operating licenses for boiling assumed to be immediately available for leakage from the reactor containment.

water power reactors, the AEC Regulatory staff has c. The effects of radiological decay during holdup developed a number of appropriately conservative assumptions, based on engineering judgment and on in the containment or other buildings should be taken into account.

applicable experimental results from safety research d. The reduction in the amount of radioactive programs conducted by the AEC and the nuclear industry, that are used to evaluate calculations of the material available for leakage to the environment by diological consequences of various postulated containment sprays, recirculating filter systems, or other accidents. engineered safety features may be taken into account, but the amount of reduction in concentration of radioactive materials should be evaluated on an This guide lists acceptable assumptions that may be individual case basis.

used to evaluate the design basis LOCA of a Boiling e. The primary containment should be assumed to Water Reactor (BWR). It should be shown that the leak at the leak rate incorporated or to be incorporated offsite dose consequences will be within the guidelines in the technical specifications for the duration of the of 10 CFR Part 100. (During the construction permit USAEC REGULATORY GUIDES Copies of published the divisions s nay be obtained by request Indicating D.C.

Washington, 20645, desired to the US. Atomic Energy Commission, Public Attention: Director of Regulatory Standrds. Comments and suggestions for Regulatory Guides are issued to descobe and mal available to theparts of Improvements In thes guides we encouraged and should be sent to the Secretary methods acceptable to the AEC Regulatory staff of implementing specific staff in of the Commission, US. Atomic Energy Commission, Washington, D.C. 20645, ths Commission's regulations, to delineate techniques used by the guidance to Attention: Chief, Public Proceedings Staff.

eveluating specific problems or postulatediaccidents, or to provide applicants. Regulatory Guides are not substitutes for regulations end compliance set out in The auides are issued in the following ten broad divisions:

with them is not required. Methods end solutions different from thorn the guldes will be acceptableof Ifathey provide a basis for the findings requisite to 1. Power Reactors 6. Products the issuance or continuance permit or license by the Commissio

7. Transportation

2. Research and Test Reactors

3. Fuels and Materials Facilities

8. Occupational Health

4. Environmental and Siting 9. Antitrust Review Published guide will be revised periodically, asappropriate, to accommodate 5. Materials and Plant Protection 10. General comments to reflect new information or experience.

accident. 1 The leakage should be assumed to pass developed from the average daily breathing rate [2 x 107 directly to the emergency exhaust system without cm3 /day] assumed in the report of ICRP, Committee mixing_2 in the surrounding reactor building atmosphere 11-1959.).

and should then be assumed to be released as an elevated d. The iodine dose conversion factors are given in plume for those facilities with stacks. ' ICRP Publication 2, Report of Committee II,

f. No credit should be given for retention of "Permissible Dose for Internal Radiation," 1959.

iodine in the suppression pool. e. External whole body doses should be calculated using "Infinite Cloud" assumptions, i.e., the dimensions

2. Acceptable assumptions for atmospheric diffusion of the cloud are assumed to be large compared to the and dose conversion are: distance that the gamma rays and beta particles travel.

a. Elevated releases should be considered to be at "Such a cloud would be considered an infinite cloud for a height equal to no more than the actual stack height. a receptor at the center because any additional [gamma Certain site dependent conditions may exist, such as and] beta emitting material beyond the cloud surrounding elevated topography or nearby structures dimensions would not alter the flux of [gamma rays which will have the effect of reducing the actual stack and] beta particles to the receptor" (Meteorology and height. The degree of stack height reduction should be Atomic Energy, Section 7.4.1.1-editorial additions evaluated on an individual case basis. Also, special made so that gamma and beta emitting material could be meteorological and geographical conditions may exist considered). Under these conditions the rate of energy which can contribute to greater ground level absorption per unit volume is equal to the rate of energy concentrations in the immediate neighborhood of a released per unit volume. For an infinite uniform cloud stack. For example, fumigation should always be containing X curies of beta radioactivity per cubic meter assumed to occur; however, the length of time that a the beta dose in air at the cloud center is:

fumigation condition exists is strongly dependent on geographical and seasonal factors and should be SD4g = 0.457 EX

evaluated on a case-by-case basis.4 (See Figures IA

through 1D for atmospheric diffusion factors for an The surface body dose rate from beta emitters in the elevated release with fumigation.) infinite cloud can be approximated as being one-half this b. No correction should be made for depletion of amount (i.e., 0D+/- = 0.23 ETX).

the effluent plume of radioactive iodine due to deposition on the ground, or for the radiological decay of iodine in transit. For gamma emitting material the dose rate in air at the c. For the first 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />, the breathing rate of cloud center is:

persons offsite should be assumed to be 3.47x 104 cubic meters per second. From 8 to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> following D 0.507 .EX

the accident, the breathing rate should be assumed to be From a semi-infinite cloud, the gamma dose rate in air

1.75 x 10"4 cubic meters per second. After that until the end of the accident, the rate should be assumed to be is:

2.32 x 10-4 cubic meters per second. (These values were S= 0.25 E~x

1The effect on containment leakage under accident Where conditions of 1 features provided to reduce the leakage of radioactive materials from the containment will be evaluated on = beta dose rate from an infinite cloud (rad/sec)

an individual case basis. gamma dose rate from an infinite cloud

"2In some cases, credit for mixing will be allowed; however, (rad/sec)

the amount of credit allowed will be evaluated on an individual Eg = average beta energy per disintegration case basis. (Mev/dis)

' Credit for an elevated release should be given only if the EB = average gamma energy per disintegration point of release is (1) more than two and one-half times the "(Mev/dis)

height of any structure close enough to affect the dispersion of X = concentration of beta or gamma emitting the plume, or (2) located far enough from any structure which isotope in the cloud (curie/m 3 )

could have an effect on the dispersion of the plume. For those BWR's without stacks the atmospheric diffusion factors assuming ground level release given in section 2.h. should be used f. The following specific assumptions are to determine site acceptability. acceptable with respect to the radioactive cloud dose calculations:

4 For sites located more than 2 miles from large bodies of (1) The dose at any distance fronthe reactor water such as oceans or one of the Great Lakes, a fumigation should be calculated based on the maximum condition should be assumed to exist at the time of the accident and continue for one-half hour. For sites located less than 2 concentration in the plume at that distance taking into miles from large bodies of water, a fumigation condition should account specific meteorological, topographical, and be assumed to exist at the time of the accident and continue for other characteristics which may affect the maximum

4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. plume concentration. These site related characteristics

1.3-2

must be evaluated on an individual case basis. In the case (3) The atmospheric diffusion model s for an of beta radiation, the receptor is assumed to be exposed elevated release as a function of the distance from the to an infinite cloud at the maximum ground level reactor, is based on the information in the table below.

concentration at that distance from the reactor. In the case of gamma radiation, the receptor is assumed to be Time Following exposed to only one-half the cloud owing to the Accident Atmospheric Conditions presence of the ground. The maximum cloud concentration always should be assumed to be at ground 0-8 hours See Figure I(A) Envelope of Pasquill level. diffusion categories based on Figure A7

(2) The appropriate average beta and gamma Meteorology and Atomic Energy-1968, energies emitted per disintegration, as given in the Table assuming various stack heights; windspeed 1 of Isotopes, Sixth Edition, by C. M. Lederer, J. M. meter/sec; uniform direction.

Hollander, I. Perlman; University of California, Berkeley;

Lawrence Radiation Laboratory; should be used. 8-24 hours See Figure I(B) Envelope of Pasquill g. For BWR's with stacks the atmospheric diffusion categories; windspeed 1 meter/sec;

diffusion model should be as follows: variable direction within a 22.50 sector.

(1) The basic equation for atmospheric diffusion from an elevated release is: 14 days See Figure 1(C) Envelope of Pasquill

2) diffusion categories with the following exp(-h 2 I2oz relationship used to represent maximum X/Q a iu Sy~z plume concentrations as a function of distance:

Where Atmospheric Condition Case 1 X = the short term average centerline value of the 40% Pasquill A

ground level concentration (curie/meter 3 ) 60% Pasquill C

Q = amount of material released (curie/sec) Atmospheric Condition Case 2 u = windspeed (meter/sec) 50%Pasquill C

y= the horizontal standard deviation of the 50% Pasquill D

plume (meters) [See Figure V-l, Page 48, Atmospheric Condition Case 3 Nuclear Safety, June 1961, Volume 2, 33.3% Pasquill C

Number 4, "Use of Routine Meteorological 33.3% Pasquill D

Observations for Estimating Atmospheric 33.3% Pasquill E

Dispersion," F. A. Gifford, Jr.] Atmospheric Condition Case 4 oz= the vertical standard deviation of the plume 33.3% Pasquill D

(meters) [See Figure V-2, Page 48, Nuclear 33.3% Pasquill E

Safety, June 1961, Volume 2, Number 4, 33.3% Pasquill F

"Use of Routine Meteorological Atmospheric Condition Case 5 Observations for Estimating Atmospheric 50% Pasquill D

Dispersion," F. A. Gifford, Jr.] 50% Pasquill F

h = effective height of release (meters)

wind speed variable (Pasquill Types A, B, E,

(2) For time periods of greater than 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> and F windspeed 2 meter/sec; Pasquill the plume from an elevated release should be assumed to Types C and D windspeed 3 meter/sec);

variable direction within a 22.50 sector.

meander and spread uniformly over a 22.50 sector. The resultant equation is:

4-30 days See Figure I(D) Same diffusion relations as given above; windspeed variable dependent

2.032 exp(-h 2/2az 2) on Pasquill Type used; wind direction 33.3%

x/Q a=ux frequency in a 22.50 sector.

Where This model should be used until adequate site meteorological data are obtained. In some cases, available information, such as meteorology, topography and geographical x = distance from the release point (meters); location, may dictate the use of a more restrictive model to other variables are as given in g(l). insure a conservative estimate of potential offsite exposures.

1.3-3

h. For BWR's without stacks the atmospheric (4) The atmospheric diffusion model for diffusion model 6 should be as follows: ground level releases is based on the information in the

(1) The 0-8 hour ground level release table below.

concentrations may be reduced by a factor ranging from one to a maximum of three (see Figure 2) for additional Time dispersion produced by the turbulent wake of the Following reactor building in calculating potential exposures. The Accident Atmospheric Conditions volumetric building wake correction factor, as defined in section 3-3.5.2 of Meteorology and Atomic Energy 0-8 hours Pasquill Type F, windspeed 1 meter/sec,

1968, should be used only in the 0-8 hour period; it is uniform direction used with a shape factor of 1/2 and the minimum cross-sectional area of the reactor building only. 8-24 hours Pasquill Type F, windspeed 1 meter/sec,

(2) The basic equation for atmospheric variable direction within a 22.50 sector diffusion from a ground level point source is:

14 days (a) 40% Pasquill Type D, windspeed 3

1 meter/sec x/Q = 7rUOryc"Z (b) 60% Pasquill Type F, windspeed 2 meter/sec (c) wind direction variable within a 22.50

Where sector x = the short term average centerline value of the 4-30 days (a) 33.3% Pasquill Type C, windspeed 3 ground level concentration (curie/meter 3) meter/sec Q = amount of material released (curie/sec) (b) 33.3% Pasquill Type D, windspeed 3 u = windspeed (meter/sec) meter/sec ay = the horizontal standard deviation of the (c) 33.3% Pasquill Type F, windspeed 2 plume (meters) [See Figure V-1, Page 48, meter/sec Nuclear Safety, June 1961, Volume 2, (d) Wind direction 33.3% frequency in a Number 4, "Use of Routine Meteorological 22.50 sector Observations for Estimating Atmospheric Dispersion," F. A. Gifford, Jr.] (5) Figures 3A and 3B give the ground level z= the vertical standard deviation of the plume release atmospheric diffusion factors based on the (meters) [See Figure V-2, Page 48, Nuclear parameters given in h(4).

Safety, June 1961, Volume 2, Number 4,

"Use of Routine Meteorological

D. IMPLEMENTATION

Observations for Estimating Atmospheric Dispersion," F. A. Gifford, Jr.]

The purpose of the revision (indicated by a line in the margin) to this guide is to reflect current Regulatory

(3) For time periods of greater than 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> staff practice in the review of construction permit appli the plume should be assumed to meander and spread cations, and the revised guide, therefore, is effective unikormly over a 22.50 sector. The resultant equation is: immediately.

2.032 X/Q =-

Where x = distance from point of release to the receptor;

other variables are as given in h(2).

1.3-4

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