ML19338C404
| ML19338C404 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 08/11/1980 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8008150363 | |
| Download: ML19338C404 (3) | |
Text
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400 Chestnut Street Tower II August 11, 1980 Director of Nuclear Reactor Regulation Attenticn:
Mr. A. Schwencer, Chief Licensing Branch No. 2 Divisien of Licensing U. S. Nuclear Regulatory Ccemissien Washingten, DC 20555
Dear Mr. Schwencer:
In the Matter of the Applicatien of
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Docket Nes. 50-327 Tennessee Valley Authcrity
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50-328
References:
1.
R&D Associates letter, H. W. Hubbard to V. Gilinsky dated July 25, 1980 2.
R&D Associates letter, H. W. Hubbard to V. Gilinsky dated August 4,1980 In response to R. L. Tedesco's letter to H. G. Parris dated July 29, 1960, TVA provided cc=ents en the R&D Associates Report, Reference 1, in =y letter to you dated August 5,1980. Enclosure 1 responds to t'he request in Mr. Tedesec's letter fer information en TVA's review cf the R&D Associates Report, Reference 2. responds to a request by NRC during the teeting en July 29, 1980, for TVA to calculate the result of a 600 kg burn of hydrogen unifer=ly distributed in the Sequcyah Nuclear Plant contain=ent.
If you have any questiens, please get in touch with D. L. Lambert at FT! c57-2581.
Very truly yours, TEN'iESSEE VALLEY AUTHORITY c 3s n
J f L, L. M. Mills, Manager Nuclear Regulatien and Safety 3
Enclosures
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s0081503 0 f
E::CLOSURI 1 o
Ccements en R&D Associates Report of August 4, 1980 1.
We agree that 300 Kg (660 pounds) to 600 Kg (1,320 pounds) of hydrogen unifer:1y_=ixed and adiabatically burned without heat re= oval would lead to contain=ent failure. We have been reporting that we can acco odate about 450 pounds of hydrogen with these assumptions. However, =uch depends en the rate of hydrogen accu:ulatien in the contain=ent, the usage of distributed controlled ignitien syste: to burn off the hydregen before it reaches a high concentration level, and heat removal syste s.
Since hydrogen is generated in the lower cc=partment, the ignition of the hydrogen rich contect there would cause a flew through the ice cendenser. It would be very conservative to ignore such an efficient passive heat sink. The containment spray syste:
would also re=ove heat since there is always =cisture dreplets in the contain=ent.
2.
The centain=ent spray syste: acts as a heat sink in the
=acroscopic sense and the water droplets (not just stea:) should have a tendency to retard burr.ing. We believe that heat receval systers are positive facters in safety.
3 We agree with R&D en the philosophy of distributed centrolled ignition. We feel that since we cannot rule cut uncontrolled ignitien (as in the case of TMI), a distributed centrolled ignition syste: would be of benefit. Also, we reason that whatever negative effect a centrolled ignition =ay have, one has to assu:e fer an uncentrolled ignition anyway.
4.
The heating and cooling calculatiens regarding the RHR heat exchangers are cnly approxicately correct. The heat removal capability (Stuh) of the heat exchangers are expected to be different frc: that in the nor=al cooldown mode due to inlet conditiens being different.
S.
The purpose of the fan-induced circulation is not to back up the e=ergency core ecoling syste: failure.
6.
The subject of inerting was studied in detail at TVA. We did not start with an assignment to justify why not to inert. Rather, we started with a design study to inert, found cut what was needed in design and =cdifications, evaluated the final product in ter:s of safety, operatien, and design, and then we concluded that nitrogen inerting was not the proper solution to the hydrogen problem. These were presented and docu=ented in the ACRS
=eetings. Further:cre, TVA is actively studying Halen as a post-accident inerting agent, using outside consultants.
7.
In general, the calculations provided by R&D are accurate.
However, cuch of the pressure calculations are based on adiabatic burn with no heatsinks. The state-of-the-art has progressed beyond that kind of si ple, scoping, and conservative calculations. We are using co:puter code with =ultincde, ice condenser heat sink, etc., to arrive at ore realistic values.
These would affect so e of the conclusions drawn by R&D
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Associates.
ENCI.CSURE 2 Ouestien on 600 Kg Hydrogen Burn During the July 29,1980, =eeting we were asked the following question: "What are the results of distributing 600 Kg of hydrogen unifor=ly within the Secuoyah contain=ent and then detonating it?"
Walt Butler of the NRC staff was asked for clarification on this questien on August 6, 1980. He suggested that we answer the following questions instead.
1.
Consider a s1=ple gec=etry, such as a sphere, having the volu=e of the Sequoyah centain=ent and deter =ine if the contain=ent could withstand the detonation loads due to 600 Kg of hydrogen unifor=1y distributed inside the contain=ent.
Response - A 68 percent =etal-water reaction would generate 600 Kg of hydrogen. If all the hydrogen is released to the centain=ent and unifor:1y distributed, it would represent about 18 percent by volu=e of hydrogen. This could be a detonable
=ixture.
We have instead considered the case of 100 percent =etal-water reaction (about 2,000 pounds of hyd:cgen and about 25 percent of hydrogen by volu=e). We considered that the contain=ent was a si=ple cylinder (which is structurally weaker than a sphere) consisting of only a 1/2-inch-thick steel shell(the =ini=u= shell thichness at Sequoyah). We used the "i= pulse" Icading infor=ation p cvided by C. K. Chan. 1 Fe have concluded that failure of the contain=ent wall due to detonation shock wave is not expected to occur; hcwever, even though the contitin=ent can withstand the detonation leading, due to it's short ddration, the resulting.
relatively lcng tett pressure due to thc oxidatien of a *arge a=ount of hydrogen would exceed the ulti= ate capability of the contain=ent. This would be true for 600 Kg of hydrogen unifor=17 distributed and ce=pletely burned in one short period.
2.
Consider whether or not the lower ce=part=ent of the containment can withstand the effects of detonation and resulting long ter=
pressure frc= the adiabatic burn if 18 percent hydrogen is distributed unifor=1y in the icwer ce=part=ent.
nescense - The detonation case here is bounded by questien 1 above. Therefore, the contain=ent shell can withstand the j
detonation load.
l We have also found that in this case the contain=ent can withstand, within the ulti= ate capability of the containment, the relatively long ter= peak pressure due to the adiabatic burn.
l
- 1. C. K. Chan, "On the Failure Medes of Alternate Containment Designs l
Following Postulated Core Meltdown," UCLA-ENG-7661, June 1976, Principal Investigater D. Okrent, pp. 58, 59, 60, and 93.
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