ML19256D295
| ML19256D295 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 05/10/1971 |
| From: | Ross D US ATOMIC ENERGY COMMISSION (AEC) |
| To: | Deyoung R US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 7910170804 | |
| Download: ML19256D295 (2) | |
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c May 10,1971 R. C. DeYoung, Assistant Director for Pressurized Water Reactors, DEL THRU:
C. G. Long, C2ief, PWR Project Branch No. 2, DRL ROD EJECTION ACCIDENT ANALYSIS FOR THREE MILE ISLAND NUCLEAR UNIT 1 (DOCKET NO. 50-289)
Our draft ACES Report on Three Mile Island 1, now under review, presents a calculation of 1383 Ram for the 2-hour thyroid dose at the site boundary.
In addition to the obvious difficulty of this analysis, the fact that the dose is well above rather thon well below Part 100, there are several other problems. Dese are:
1.
The assumed release fractions were 10% of the iodines, 20% of the noble gases. No justification for these values is available.
2.
The accident analysis was revised by Met-Ed in March 1971 to account for a 0.65% AK/K ejected rod, rather than the 0.46% rod used in Oconee.
There is additional kinetics work to be done, both by the applicant and by us, if this higher value is to be accepted. Fuel cycle calculations by the applicant do not indicate a need for a value higher than 0.46%,
although the FSAR is somewhat misleading in this respect.
__ 3.
There are two mechanisms for calculating dose to the public for this event. They ares a.
Assume the released fission products are dissolved uniformly in the primary coolant system, and released to the environs via a steam generator laak and the secondary safety valves.
b.
Assume the fission products are released to the containment and are released to the environe at the stipulated containment leak rate.
We calculated both mechanisms on Oconee getting about eight times the dose 10 rad on model (a) as on model (b). For model (a) we assumed 68 4 x 10 (equivalent) of 1 dine released to the coolant; 1.36 x 10~ fraction of coolant (10 gpa fc
- 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />) carried over to the secondary; a factor of 10 reduction for ri lease from OTSG and sjfsty valves; breathing rate of 3.47 x 10-4 3
m /sec; sad I/Q = 1.16 x 10. The calculated dose was about 40 Ram *.
(We have.c justification for the reduction for the release path through the safety "alves).
- 0n Oconee we assumed a partition factor of 100 in the main condenser, which has auriliary cooling provisione by gravity drain from the nearby lake. his effectively reduces the rod ejection dose to about 5 Res.
The 40 Rem value corresponds to the release through safety Valves.
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R. C. DeYoung 2
May 6,1971 The release via containment (model b) would be about 5 Rem.
We have calculated model (a) for TMI-1 using similar assumotions and arrive at 1383 Rem.
This increase is due to the X/Q values (factor of 9 higher on TMI-1) and more failed rods (factor of 4.3 higher on TMI-1).
We need DRL management concurrence on the following proposed position:
1.
The accident analysis should be based on a realistic combina-tion of models (a) and (b). The time rate of release to the containment (via the postulated broken rod drive mechanism) should be calculated. Technical Specification leak rate for primary-secondary leakage will be used.
2.
Credit for sprays will be allowed, if the pressure in the containment is high enough to turn them on.
3.
The applicant will be told about oor difficulty with the kinetics analyses;' release fractions from the fuel; and with seccmdary reduction factors (or plateout). We will require additional information. We will also work independently on our evaluation model..
4.
The calculated does will be brought below 200 Ram thyroid, using the proper, conservative blend of the above numbers.
Control rod insertion limita can be adopted if necessary.
Denwood F. Ross PWR Project Branch No. 2 DISTRIBUTION:
Division of Reactor Licensing PWR-2 Reading W. Nischan G. Burley H. Denton P. A. Mor: 3 F. Schroeder T. R. Wilson 45() 254 PWR Branch Chiefs D. Ross (3)
H. Richings M.
Rosen PWR-2/DRL PWA..-2 / DaL
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