ML19263E179
| ML19263E179 | |
| Person / Time | |
|---|---|
| Site: | 05000580, 05000581 |
| Issue date: | 04/05/1979 |
| From: | Barth C NRC OFFICE OF THE EXECUTIVE LEGAL DIRECTOR (OELD) |
| To: | Bowers E, Cowan F, Shon F AFFILIATION NOT ASSIGNED, Atomic Safety and Licensing Board Panel |
| References | |
| NUDOCS 7906040376 | |
| Download: ML19263E179 (1) | |
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u UNITED STATES 3 *s..
A fJUCLEAR REGULATORY COMMisSIOfJ f,
WASHINGTON, D. C. 20555
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April 5, 1979 E
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- WRC Pugtic 990Ugg Elizabeth S. Bowers, Esq., Chairman Dr. Frederick P. Cowan Atomic Safety and Licensing Board Apt. B-125 U.S. Nuclear Regulatory Commission 6152 N. Verde Trail Washington, D.C.
20555 Boca Raton, Florida 33433 Mr. Frederick J. Shon
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In the Matter of p
Ohio Edison Company, et al.
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(Erie Nuclear Plant, Units 1 ant :)
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3i g&TIW, Docket Nos. STN 50-580 and STN 50-581 f
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Dear Members of the Board:
Enclosed for the information of the Board is a mercorandum which discusses certain information concerning behavior of iodine during postulated steam generator tube rupture accidents.
Sincerely, Charles A. Barth Counsel for NRC Staff
Enclosure:
As Stated cc:
(w/ enclosure)
Thomas A. Kayuah, Esq.
Jay Silberg, Esq.
Mr. Robert W. Tufts Atomic Safety and Licensing Board Panelgg }jg Atomic Safety and Licensing Appeal Board Docketing and Service Section 40060403%
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WA0ntr.G l OT.. D. C. /0E 'f.lfI'... r'l ) ,,[,, # 11,.. A ( Il0TE T0: Domenic 3. Vassallo, Assistant Director for Light Water Reactors, DPt FROM: Richard 11. Vollmer, Assistant Director for Site Analysis, DSE
SUBJECT:
C0tlSul.lA!!T REPORT REGARDI!!G N0:1-CO:ISERVATISM Ill STAFF MODEL As a result of a technical as istance contract with a staff consultant, a technical report (Utr.EG-0409) on " Iodine Dehavior in a PUR Cooling System Follouing ; rostulate1 Steam Generator Tube Rupture Accident," ~ by A. K. Pos tm and P. S.1.na, was published in January 1978. The report is a t>oretical study of the. iodine behavior in the primary and secondary c;;olunt systems of a Pk.'R following a postulated steam generator tube rupture. The recort concludes that, as a result of such a rupture, prmary coolant. tater containing iodine would be atomized by . hydrodynamic forces as it flashed through the leal; path into the stean system. The removal of ierline by the secondary water was predicted to be highly dependent upon the prir.ory-to-secondary pressure difference and upon the m ter depth. Calculatir;ns made in the report, and unich the report emphni::cd uero designed to yicld conservative predictions, O indicated that in the early part of the accident less than 503 f the iodine might lie rt"oved by the sccendary water, whereas in the. later phases of the accident, about 00~. of the iodine v:oulc be removed. Although the re!.' ort att emptcd to exscss t; c iodine recoval by steam separa tors i t did not exar..in.? possible iodine rer.; oval due to the pr>x-imity of neighboring tubes and other subr.:erged structures.in the steam generator. The present staf f mndel, as outlined in Stcodard Review Plan 15.6.3, assumes that a constant valur of 20% of the icdiac transferred to the secondary water is rer.oved and retainc<i in it. Therefore, HUREG-0409 implies that the present,'af f r.;odel way be non-conservative in the early phases of the accident, but may be overly conservative in the later phases. ~ i' The overall degree of can'.erntism or non-conservatism of the staff's present :udel cannot easily W sssessed witnout a truch more detailed examina tion. However, sci.:e perspective regarding the implications may }}gg ;}Q g _a 9 % 1.16 m I O 14WIR*
s-FEU 2 4 kg.3 Don.enic B. Vassallo 2 be gained by observiiig that the present staff codel predicts the radio- \\ logical conscquenses of a stcara nencrator tube rupture coincident with a large iodine spil:e tn be about 75 ren to the thyroid for a typical PWP. at a site uith rnor (X/g ' 1 x 10-3 sec/m3) meteorology. We can conclude frou thi; tiwt even if the staff's n:odel was less conservative throughout the a".cident by as auch as a factor of four, that our con-clusions regarding the acceptability of this event,would not likely change. The staf f. is currently tabinq action in this matter in two ways.
- First, the staff is preparino and evaluating a more detailed rodel to be incor-porated in its revised Standard Revicu Plan in this area which will allow for a time-dcpend'at iodine retention fraction in the secondary water.
Second, the staf f is planning to have experiraents perfor,cd, as suggested by !!Ui!EG-0409, that will confirra or refute the values i
- cated by the report.
He believe, in view of the possibility of a non-conservative staff model in this regard, that the licensing boards currently in progress for all PUR plants should be duly informed. -'( ../b<YJ Richard H. Vollmer, Assistant Director for Site Analysis O Division of Site Safety and Environr.: ental Analysis Ujij 9 $ h nbi J 2288 .>21 .n. ' i.-
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