REGULATORY GUIDE ASSUMPTIONS USED CONSEQUENCES

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
REACTORS
WATER
OF A LOSS OF COOLANT ACCIDENT FOR BOILING
A. INTRODUCTION
Section 50.34 of 10 CFR Part 50 requires that each
applicant for a construction permit or operating license
provide an analysis and evaluation of the design and
performance of structures, systems, and components of
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
(LOCA) is one of the postulated accidents used to
evaluate the adequacy of these structures, systems, and
components with respect to the public health and safety.
This guide gives acceptable assumptions that may be
used in evaluating the radiological consequences of this
accident for a boiling water reactor. In some cases,
unusual site characteristics, plant design features, or
other factors may require different assumptions which
will be considered on an individual case basis. The
Advisory Committee on Reactor Safeguards has been
consulted concerning this guide and has concurred in the
regulatory position.
B. DISCUSSION
After reviewing a number of applications for
construction permits and operating licenses for boiling
water power reactors, the AEC Regulatory staff has
developed a number of appropriately conservative
assumptions, based on engineering judgment and on
applicable experimental results from safety research
programs conducted by the AEC and the nuclear
industry, that are used to evaluate calculations of the
diological consequences of various postulated
accidents.
This guide lists acceptable assumptions that may be
used to evaluate the design basis LOCA of a Boiling
Water Reactor (BWR). It should be shown that the
offsite dose consequences will be within the guidelines
of 10 CFR Part 100. (During the construction permit
USAEC REGULATORY GUIDES
Public
Regulatory Guides are issued to descobe and mal available to theparts
of
methods acceptable to the AEC Regulatory staff of implementing specific
in
staff
the
by
used
techniques
delineate
to
regulations,
ths Commission's
to
guidance
eveluating specific problems or postulatediaccidents, or to provide
compliance
end
regulations
for
substitutes
applicants. Regulatory Guides are not
set out in
with them is not required. Methods end solutions different from thorn
for the findings requisite to
provide a basis
acceptableof Ifathey
be
will
guldes
the
permit or license by the Commission.
the issuance or continuance
Published guide will be revised periodically, asappropriate, to accommodate
to reflect new information or experience.
comments
review, guideline, exposures of 20 rem whole the
body
and
values
150 rem thyroid should be used rather than
given in § 100.11 in order to allow for (a) uncertainties
in final design details and meteorology or (b) new data
and calculational techniques that might influence the
final design of engineered safety features or the dose
reduction factors allowed for these features.)
C. REGULATORY POSITION
1. The assumptions related to the release of radioactive
material from the fuel and containment are as follows:
a. Twenty-five percent of the equilibrium
radioactive iodine inventory developed from maximum
full power operation of the core should be assumed to
be immediately available for leakage from the primary
reactor containment. Ninety-one percent of this 25
percent is to be assumed to be in the form of elemental
iodine, 5 percent of this 25 percent in the form of
particulate iodine, and 4 percent of this 25 percent in
the form of organic iodides.
b. One hundred percent of the equilibrium
radioactive noble gas inventory developed from
maximum full power operation of the core should be
assumed to be immediately available for leakage from
the reactor containment.
c. The effects of radiological decay during holdup
in the containment or other buildings should be taken
into account.
d. The reduction in the amount of radioactive
material available for leakage to the environment by
containment sprays, recirculating filter systems, or other
engineered safety features may be taken into account,
but the amount of reduction in concentration of
radioactive materials should be evaluated on an
individual case basis.
e. The primary containment should be assumed to
leak at the leak rate incorporated or to be incorporated
in the technical specifications for the duration of the
the divisions
s nay be obtained by request Indicating D.C.
Copies of published
20645,
Washington,
desired to the US. Atomic Energy Commission,
for
suggestions
and
Comments
Standrds.
Regulatory
of
Attention: Director
Secretary
Improvements In thes guides we encouraged and should be sent to the
20645,
D.C.
Washington,
Commission,
Energy
Atomic
US.
of the Commission,
Attention: Chief, Public Proceedings Staff.
are issued in the following ten broad divisions:
The auides
6. Products
1. Power Reactors
7. Transportation
2. Research and Test Reactors
8. Occupational Health
3. Fuels and Materials Facilities
9. Antitrust Review
4. Environmental and Siting
10. General
5. Materials and Plant Protection
accident. 1 The leakage should be assumed to pass
directly to the emergency exhaust system without
mixing_2 in the surrounding reactor building atmosphere
and should then be assumed to be released as an elevated
plume for those facilities with stacks. '
f. No credit should be given for retention of
iodine in the suppression pool.
2. Acceptable assumptions for atmospheric diffusion
and dose conversion are:
a. Elevated releases should be considered to be at
a height equal to no more than the actual stack height.
Certain site dependent conditions may exist, such as
surrounding elevated topography or nearby structures
which will have the effect of reducing the actual stack
height. The degree of stack height reduction should be
evaluated on an individual case basis. Also, special
meteorological and geographical conditions may exist
which can contribute to greater ground level
concentrations in the immediate neighborhood of a
stack. For example, fumigation should always be
assumed to occur; however, the length of time that a
fumigation condition exists is strongly dependent on
geographical and seasonal factors and should be
evaluated on a case-by-case basis.4 (See Figures IA
through 1D for atmospheric diffusion factors for an
elevated release with fumigation.)
b. No correction should be made for depletion of
the effluent plume of radioactive iodine due to
deposition on the ground, or for the radiological decay
of iodine in transit.
c. For the first 8 hours, the breathing rate of
persons offsite should be assumed to be 3.47x 104
cubic meters per second. From 8 to 24 hours following
the accident, the breathing rate should be assumed to be
1.75 x 10"4 cubic meters per second. After that until the
end of the accident, the rate should be assumed to be
2.32 x 10-4 cubic meters per second. (These values were
developed from the average daily breathing rate [2 x 107
cm3 /day] assumed in the report of ICRP, Committee
11-1959.).
d. The iodine dose conversion factors are given in
ICRP Publication 2, Report of Committee II,
"Permissible Dose for Internal Radiation," 1959.
e. External whole body doses should be calculated
using "Infinite Cloud" assumptions, i.e., the dimensions
of the cloud are assumed to be large compared to the
distance that the gamma rays and beta particles travel.
"Such a cloud would be considered an infinite cloud for
a receptor at the center because any additional [gamma
and] beta emitting material beyond the cloud
dimensions would not alter the flux of [gamma rays
and] beta particles to the receptor" (Meteorology and
Atomic Energy, Section 7.4.1.1-editorial additions
made so that gamma and beta emitting material could be
considered). Under these conditions the rate of energy
absorption per unit volume is equal to the rate of energy
released per unit volume. For an infinite uniform cloud
containing X curies of beta radioactivity per cubic meter
the beta dose in air at the cloud center is:
SD4g = 0.457 EX
The surface body dose rate from beta emitters in the
infinite cloud can be approximated as being one-half this
amount (i.e., 0D± = 0.23 ETX).
For gamma emitting material the dose rate in air at the
cloud center is:
D
0.507 .EX
From a semi-infinite cloud, the gamma dose rate in air
is:
S=
0.25 E~x
Where
1The effect on containment leakage under accident
conditions of 1 features provided to reduce the leakage of
radioactive materials from the containment will be evaluated on
an individual case basis.
beta dose rate from an infinite cloud (rad/sec)
gamma dose rate from an infinite cloud
(rad/sec)
Eg = average beta energy per disintegration
(Mev/dis)
EB = average gamma energy per disintegration
=
"2
In some cases, credit for mixing will be allowed; however,
the amount of credit allowed will be evaluated on an individual
case basis.
' Credit for an elevated release should be given only if the
point of release is (1) more than two and one-half times the
height of any structure close enough to affect the dispersion of
the plume, or (2) located far enough from any structure which
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
to determine site acceptability.
"(Mev/dis)
X
= concentration of beta or gamma emitting
isotope in the cloud (curie/m 3 )
f. The following specific assumptions are
acceptable with respect to the radioactive cloud dose
calculations:
(1) The dose at any distance fronthe reactor
should be calculated based on the maximum
concentration in the plume at that distance taking into
account specific meteorological, topographical, and
other characteristics which may affect the maximum
plume concentration. These site related characteristics
4 For sites located more than 2 miles from large bodies of
water such as oceans or one of the Great Lakes, a fumigation
condition should be assumed to exist at the time of the accident
and continue for one-half hour. For sites located less than 2
miles from large bodies of water, a fumigation condition should
be assumed to exist at the time of the accident and continue for
4 hours.
1.3-2
(3) The atmospheric diffusion model s for an
elevated release as a function of the distance from the
reactor, is based on the information in the table below.
must be evaluated on an individual case basis. In the case
of beta radiation, the receptor is assumed to be exposed
to an infinite cloud at the maximum ground level
concentration at that distance from the reactor. In the
case of gamma radiation, the receptor is assumed to be
exposed to only one-half the cloud owing to the
presence of the ground. The maximum cloud
concentration always should be assumed to be at ground
level.
(2) The appropriate average beta and gamma
energies emitted per disintegration, as given in the Table
of Isotopes, Sixth Edition, by C. M. Lederer, J. M.
Hollander, I. Perlman; University of California, Berkeley;
Lawrence Radiation Laboratory; should be used.
g. For BWR's with stacks the atmospheric
diffusion model should be as follows:
(1) The basic equation for atmospheric
diffusion from an elevated release is:
Time
Following
Accident
0-8 hours
14 days
exp(-h 2 I2oz
a
iu Sy~z
Where
=
wind speed variable (Pasquill Types A, B, E,
and F windspeed 2 meter/sec; Pasquill
Types C and D windspeed 3 meter/sec);
variable direction within a 22.50 sector.
(2) For time periods of greater than 8 hours
the plume from an elevated release should be assumed to
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
on Pasquill Type used; wind direction 33.3%
frequency in a 22.50 sector.
2.032 exp(-h 2/2az 2)
x/Q
a=ux
This model should be used until adequate site
meteorological data are obtained. In some cases, available
Where
x
See Figure 1(C) Envelope of Pasquill
diffusion categories with the following
relationship used to represent maximum
plume concentrations as a function of
distance:
Atmospheric Condition Case 1
40% Pasquill A
60% Pasquill C
Atmospheric Condition Case 2
50%Pasquill C
50% Pasquill D
Atmospheric Condition Case 3
33.3% Pasquill C
33.3% Pasquill D
33.3% Pasquill E
Atmospheric Condition Case 4
33.3% Pasquill D
33.3% Pasquill E
33.3% Pasquill F
Atmospheric Condition Case 5
50% Pasquill D
50% Pasquill F
the short term average centerline value of the
ground level concentration (curie/meter 3 )
Q = amount of material released (curie/sec)
u = windspeed (meter/sec)
y= the horizontal standard deviation of the
plume (meters) [See Figure V-l, Page 48,
Nuclear Safety, June 1961, Volume 2,
Number 4, "Use of Routine Meteorological
Observations for Estimating Atmospheric
Dispersion," F. A. Gifford, Jr.]
oz= the vertical standard deviation of the plume
(meters) [See Figure V-2, Page 48, Nuclear
Safety, June 1961, Volume 2, Number 4,
"Use of Routine Meteorological
Observations for Estimating Atmospheric
Dispersion," F. A. Gifford, Jr.]
h = effective height of release (meters)
X
See Figure I(A) Envelope of Pasquill
diffusion categories based on Figure A7
Meteorology and Atomic Energy-1968,
assuming various stack heights; windspeed 1
meter/sec; uniform direction.
8-24 hours See Figure I(B) Envelope of Pasquill
diffusion categories; windspeed 1 meter/sec;
variable direction within a 22.50 sector.
2)
X/Q
Atmospheric Conditions
information, such as meteorology, topography and geographical
location, may dictate the use of a more restrictive model to
= distance from the release point (meters);
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
diffusion model 6 should be as follows:
(1) The 0-8 hour ground level release
concentrations may be reduced by a factor ranging from
one to a maximum of three (see Figure 2) for additional
dispersion produced by the turbulent wake of the
reactor building in calculating potential exposures. The
volumetric building wake correction factor, as defined in
section 3-3.5.2 of Meteorology and Atomic Energy
1968, should be used only in the 0-8 hour period; it is
used with a shape factor of 1/2 and the minimum
cross-sectional area of the reactor building only.
(2) The basic equation for atmospheric
diffusion from a ground level point source is:
(4) The atmospheric diffusion model for
ground level releases is based on the information in the
table below.
Time
Following
Accident
0-8 hours Pasquill Type F, windspeed
uniform direction
14 days
x/Q = 7rUOryc"Z
Where
(a) 40% Pasquill Type D, windspeed 3
meter/sec
(b) 60% Pasquill Type F, windspeed 2
meter/sec
(c) wind direction variable within a 22.50
sector
4-30 days (a) 33.3% Pasquill
meter/sec
(b) 33.3% Pasquill
meter/sec
(c) 33.3% Pasquill
meter/sec
(d) Wind direction
the short term average centerline value of the
ground level concentration (curie/meter 3)
Q = amount of material released (curie/sec)
u = windspeed (meter/sec)
ay = the horizontal standard deviation of the
plume (meters) [See Figure V-1, Page 48,
Nuclear Safety, June 1961, Volume 2,
Number 4, "Use of Routine Meteorological
Observations for Estimating Atmospheric
Dispersion," F. A. Gifford, Jr.]
z= the vertical standard deviation of the plume
(meters) [See Figure V-2, Page 48, Nuclear
Safety, June 1961, Volume 2, Number 4,
"Use of Routine Meteorological
Observations for Estimating Atmospheric
Dispersion," F. A. Gifford, Jr.]
=
Type C, windspeed
3
Type D, windspeed 3
Type F, windspeed 2
33.3% frequency in a
22.50 sector
(5) Figures 3A and 3B give the ground level
release atmospheric diffusion factors based on the
parameters given in h(4).
D. IMPLEMENTATION
The purpose of the revision (indicated by a line in
the margin) to this guide is to reflect current Regulatory
staff practice in the review of construction permit appli
cations, and the revised guide, therefore, is effective
immediately.
(3) For time periods of greater than 8 hours
the plume should be assumed to meander and spread
unikormly over a 22.50 sector. The resultant equation is:
2.032
X/Q =Where
x
1 meter/sec,
8-24 hours Pasquill Type F, windspeed 1 meter/sec,
variable direction within a 22.50 sector
1
x
Atmospheric Conditions
= distance from point of release to the receptor;
other variables are as given in h(2).
1.3-4
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