ML19221A839

Reg Guide 1.5, Assumptions Used for Evaluating Potential Radiological Consequences of Steam Line Break Accident for Bwrs

ML19221A839
Person / Time
Issue date:	03/10/1971
From:	NRC OFFICE OF STANDARDS DEVELOPMENT
To:
References
REGGD-01.005, REGGD-1.005, NUDOCS 7907100059
Download: ML19221A839 (4)

Text

{{#Wiki_filter:. 3/10/71 SAFETY GUIDE 5 ASSUMPTIONS USED FOR EVALUATING THE POTENTIAL RADIOLOGICAL CONSEQUENCES OF A STEAM LINE BREAK ACCIDENT FOR BOILING WATER REACTORS A. Introduction

1. The steam line breaks with tre reador at fun pov er ' and the reactor scrams Section 50.34 of 10 CFR Part 50 requires that

2. The steam line isolation valve,1.. -e i n each applicant for a construction permit or op.

the maximum time incorpm aini or to erating license provide an analysis and evalua-be inccrporated in the technxai 3peci. tion of the design and perfcrmance of struc-fications. This closure time v. Q be seri-tures, systems, and components of the facility fied by suitabie pericdic testing with the objective of assessing the risk to pub _

3. The total mass of coolant re.e d ec 14 lic health and safety resulting from operation that amount in the steam lir.e and o n-of the facility. The steam line break accident is one of the postulated accidents used to evaluate necting linn at the time of the break the adequacy of these structures, systems, and plus the amount that passes throurn tne valves prior to closure.

( Rupt ares components with respect to the public health within the turbine complex are not con-and safety. This safety guide gives acceptable sidered in this guide.) assumptions that may be used in evaluating the radiological consequences of this accident for a

4. The radioactivity in the coolant is as-aumed to be the maximum amount in-boiling water reactor, corporated or to be incorporatec. in the B. Discussion technical specifications, provided that no further fuel f:.ilures are aerned to In the process of reviewing a large number of occur as a result of delays in valve applications for construction permits and op-erating licenses, the regulatory staff has de-

5. All of the iodine :no credit for plateout veloped, based on engineering judgment and on is allowed) and noble gases from the applicable expecimental results from safety re-released coolant are released ty the search programs conducted by the AEC and atmosphere with,n 2 hours at a neight i

the nuclear industry, a number of appropriately f 30 meters with a fumigation condi-conservative assumptions which are used by the .tion. regulatory staff to evaluate the applicant's esti-

6. The assumptions for dose i o n ver-ion mate of the radiological consequences of various and atmospheric dilTusion are:

postulated accidents. This safety guide lists the (a) No correction is made for deple; aMumptions ' used by the regulatory staff to tion from the eMuent plume of evaluate the steam line break accident for a radioactive iodine due to deposition Lciling water reactor. on the ground, or for the radio-logical decay of loc.ine 131 in C. Regulatory Position transit The assumptions related to the release of radioactive ma:erial are: ' For purposes of this guide a steam line treak is defined as a complete severance of the pipe ar.d the pipe centerline is ofset by at least the pipe diameter. ' In some cases, plant design conditions may exist

• For certain design, cther operating modes (ie.. het w hich require special consideration and different as-standby) may represent c. worse condition. Ti.ese de-O.

signs will be evaluated on an indsvidual case baals. sum ptions-125 031 5.1 "i9071000 9/'

(b) The breathing rate of persons off. special meteoro:ogical, topo-site is asaumed to be 3.47 x 10" graphical,.ind other ch. rac-cubic meters per second. (This teristics which may a !ect the value is developed frem the aver. maximum plume concen t r.i-age daily breathing rate [2 x 10' tion. These site related char-cm'/ day) assumed in the report of acteristics must be e s.d n.ited ICRP, Committee II-1959.) on an individual case bau in (c) The iodine dose conversion factors the case of beta radiattou. the are given in ICRP Publica*ioa 2, receptor is assumed to be ex. Report of Committee II, "Permis. posed to an infimte cloud at sible Dose for Internal Radiation," the maximum ground Ms e; 1959. concentration at that distance (d) External whole body doses are from the reactor. In the t ase calculated using " Infinite Cloud" of gamma radiation, the re-assumptions, i.e., the dimensions ceptor is assumed to be ex-of the cloud are assumed to be posed to only one-half the large compared to the distance that cloud owing to the presence of the gamma rays and beta parjeles the ground. The maximum travel. "Such a cloud would be con-cloud concentration is always sidered an infinite cloud for a re-assumed to be at ground leves. ceptor at the center because any (2) The appropriate average beta additional [ gamma and) beta emit. and gamma energies emitted ting material beyond the cloud di-per disintegration, an given in mera.ons would not alter the flux the Table of Isotopes; Sixth of [ gamma rays and) beta parti. Edition ; by C. M. Lederer, J. cles to the receptor" (Meteorology M. Hollander. I. Perlman; and Atomic Energy, Section 7.4.1.1 University of California. --editorial additions made so that Berkdey ; Lawrence Radiation gamma and beta emitting material Laboratory should be used. could be considered). Under these (e) (1) The equatior, used to deter. conditions the rate of energy ab. mine the atmospheric dif. sorption per unit volume is equal fusion from an elevated re-to the rate of energy released per lease at 30 meters, uniform unit volume.' wind direction with a fumiga-The following snecific assun:ptions tion condition existing is: are used: 0.0133 XQ~ / (1) The dose at any distance frvm e,u the reactor is calculated based Where: on the maximum concentra. x = the short term aver-tion in the plume at that dis-age centerline value tanca taking into account of the ground level

• Meteorology and Atomic Energy-1968, Chapter 7, From a senminfinite cloud, the ga mnea i.n,e "Itadioactive Cloud-dose Calculations," hsta the follow-rate in air in: s D' = OSik mg equations:

Where : A.,For an infirite uniform cloud enntsa nin g x ,Di beta done rate from an infin.tc c:oua c u ries of beta radioactivity per cubic meter ( rad /itec) the leta dose rate in air at the cloud center is: ,D'. = gamma dose rate fenm an inf. :te ,1 V = 0.457 R,x cinud (rad, se< > The urface 1,ody none rate fiam beta emitte s F5 -- ave rage beta energy par & vreera. m the inhnite cloud can be apprnxirnated as tion (Mev/dM tring une-h.tlf this amount (i e.. sD'. " 0 23 Esi l-K, - average ga rr rr a energy per d s nte-R For gammn emitt mg material i.. dose rate i. gration (Mes %s) t air at the cloud center n: x - concentrat n.n of beta or gamrr a emit-lT =0, } h ting ISolbpe in Ihe ChLd ( C u r# 'm' 5.2

logical Observations @~ concentration (cur. for Estnnating At-ies/ meter') m spheric Ihsper-Q = amount of material sion,, F. A. GitTord, ,j Jr.) ,,) u - wind speed (meters ,, - the horizontal /***) standard deviation of the plume (2) Figum 1 gives eleva.ted release (rneters) [See Fig > atmospheric diffusion factors assuming a release at thirty ure V-1, Page 48, meters, and atmospheric con-Nucleer

Safety, dition.s assamed to be Pas.

June 1961, Volume 2, Number 4, "Use Wil F, windspeed 1 meter / sec. ct Routine Metacro-g 125 033 5.3

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