ML19326D890
| ML19326D890 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 07/15/1980 |
| From: | Dircks W NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Baucus M SENATE |
| Shared Package | |
| ML19326D891 | List: |
| References | |
| NUDOCS 8007250062 | |
| Download: ML19326D890 (2) | |
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JUL 151333 The Honorable Max Baucus United States Senator 320 Securities Building 2708-1/2 First Avenue North Billings, Montana 59101
Dear Senator Baucus:
We are pleased to respond to your letter of June 23, 1980, which has been re-ferred to this office for reply.
In your letter, you requested assistance in responding to two questions raised by a Mr. Ed Dobson concerning the Three Mile Island nuclear incident. We would respond as follows.
Question: Was there a pressure spike or explosion within the containment chamber anytime during the accident? If so, was the stress factor 30 psi? Was hydrogen involved in the explosion?
Answer:
Yes, the reactor containment building experienced a pressure pulse at approximately 1:50 p.m. on Wednesday, March 28.
This was 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> and 50 minutes after anset of the accident.
For the first 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> and 50 minutes after onset of the accident at Three Mile Island, Unit 2 (TMI-2), the pressure in the reactor containment remained around four pounds per square inch gauge (psig). Then, within c half hour period, the reactor contain-ment building pressure increased from about 4 psig to a peak pressure of about 28 psig and then back to below 4 psig.
The pressure pulse is believed to have been caused by the combus-tion of hydrogen. The principal source of this hydrogen was the metal-steam reaction of the zirconium in the reactor core.
The metal-steam reaction is believed to have occurred during the period from 1-1/2 hours to about 3-1/2 hours after onset of the accident when portions of the fuel cladding (zirconium) reached temperatures which were high enough to allow the clad-ding to react with steam and produce the hydrogen.
Question: What is the design strength of the containment? 60 psi has been given as a measurement; is that common to most other re-actors?
Answer:
The reactor containment building for TMI-2 is designed for an internal pressure of 60 pounds per square inch gauge (psig).
However, internal pressure is just one of several design
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The Honorable Max Baucus factors used in load combination equations to ensure that the as-built containment structure maintains an adequate margin of safety.
Based on our analysis of similar containment structures, we con-clude that the TMI-2 containment should be able to withstand at least twice the internal design pressure without failure.
The reactor containment building for TMI-2 is classified as a dry containment and the reactor is a pressurized water reactor (PWR).
For PWR's with a dry containment, the design pressure is typically about 60 psig.
For other types of reactor containment buildings and reactors, the design pressure will be different. The table below summarizes the various reactor containment building design pressures.
Typical Design Pressure of Various Containments (Typical 1200 MWe Plants)
Containment Type Reactor Type
- DesignPressure(psigl Mart I BWR 62 Mark II BWR 45 Mark III BWR 15 Ice Condenser PWR 12 Subatmospheric PWR 45 Dry PWR 60 BWR: Boiling Water Reactor PWR: Pressurizer Water Reactor I hope the above response provides you with the information you require.
Sincerely, (Signed) T. A, NM William Dircks
,u Acting Executive Director i
for Operations
.