ML20028B803
| ML20028B803 | |
| Person / Time | |
|---|---|
| Issue date: | 10/25/1982 |
| From: | Catton I Advisory Committee on Reactor Safeguards |
| To: | Kerr W, Shewmon P Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-CT-1520, NUDOCS 8212060323 | |
| Download: ML20028B803 (1) | |
Text
A H 26-FL a
e C7- /SJo MEMORANDUM 25 October 1982 j/.'
T0:
Paul Shewmon andf511 Ker
/
t n n_
FROM:
Ivan Catton,/
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SUBJ: Primary System Failure Mechanism During a High Pressure Transient l
A study carried out by a European group arrived at some conclusions about the TLMB transient for 2-loop PWR of 1400 MWth that you may find interesting. To put them in perspective, the present procedures or ideas i
about how the vessel fails are more the result of group discussion that actual analysis.
The primary system was divided into three main parts:
-components with a thick wall (vessel - low alloy carbon steel A508)
-piping of the primary system (low alloy carbon steel A508)
-U tubes of the steam generator (Incoloy 800).
Temperatures and pressures were calculated through out the sytem using a typical thermal hydraulic code. They then calculated loop stress in the various parts of the system.
The conclusion reached as a result of this analysis was that failure of the primary system occurs by failure of the hot leg piping. This occured at a temperature that was low enough that steam-zircaloy reactions were not yet very important (probably before failure of the fuel rods).
The resulting depressurization allows injection of ECC water. A slight modification to the sequence, failure of the steam generator SRV lead to early failure of the steam generator tubes.
Both of these failure paths, if followed, could lead to much less serious consequences than the usual core melt path. To study them requires a more interdisciplinary view. A number of other hypothetical sequences that lead to high risk may also result in early failure of the primary system. The consequences would, I think, be significantly reduced by the early failure. The probability of core melt could be significantly reduced.
For both reasons I think these ideas should be pursued.
J kaAAAKED ORIGINAL 8212060323 821025 ID N
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5 CT-1520 PDR
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