ML20211K535

Forwards Draft Seabrook Station Steam Generator Tube Rupture During Severe Accidents. Study of Generator Tube Rupture Difficult Due to Complexity of Phenomena & Developmental Nature of Techniques.Further Work Necessary

ML20211K535
Person / Time
Site:	Seabrook
Issue date:	12/08/1986
From:	Rossi C Office of Nuclear Reactor Regulation
To:	Noonan V Office of Nuclear Reactor Regulation
Shared Package
ML19310H511	List: ML20211K535 ML20211K545
References
NUDOCS 8612110095
Download: ML20211K535 (2)

Text

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MEMORANDUM FOR: Vincent A. Noonan, Project Director Project Directorate #5 Division of PWR Licensing-A FROM: Charles E. Rossi, Assistant Director Division of PWR Licensing-A

SUBJECT:

STEAM GENERATOR TUBE RUPTURE DURING SEVERE ACCIDENTS AT SEABROOK STATION - DRAFT INTERIM REPORT Plant Name: Seabrook Station, Unit 1 pcg Docket Number: 50-443 Resp. Directorate: PWR Directorate #5 A',d Project Manager: Victor Nerses Review Branch: Facilities Operations Branch, DPL-A Review Status: Ongoing An accident sequence with the potential to impact risk at pressurized water reactor plants under some conditions is the loss of steam generator tube integrity due to generation of high temperatures at hioh pressure during a core melt accident. The potential concern involves movement of high tempera-ture fluid from the region of the melting reactor core into the steam genera-tor tubes with a resultant overheating of the tubes which leads to steam generator tube rupture (SGTR). High pressure fluid containing radioactive material from the melting core would thereby be released to the secondary side of the steam generators, from where it could be released to the environment via the steam generator relief valves, thereby bypassing containment.

Public Service of New HampsMre (PSNH) has investigated the possibility of encountering conditions in the reactor coolant system under which SGT of concern, and has determined the likelihood to be less than 4 X 10 g can per be reactor year. This is sufficiently high, and the potential consequences of SGTR under severe accident conditions are sufficiently great under some circumstances, that PSNH initiated an investigation of this topic.

The enclosed report is a draft copy of an interim document prepared by Warren Lyon (F0B/DPL-A) which addresses the state of knowledge pertaining to Steam Generator Tube Rupture during postulated severe accidents, and the application of this knowledge to the Seabrook Station nuclear power plant.

This report is prepared with the assumption that the work and assessment will continue. The report does not cover all material received from PSNH and its j contractors, and PSNH and their contractors have offered to discuss the issue further. It also has not been subjected to comprehensive peer evaluation i within the NRC.  :

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Contact:

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.o DEC 8 1986 Vincent Noonan The major conclusions provided in the draft report are as follows:

1. Study of SGTR due to severe accident conditions is difficult due to the complexity of the phenomena and the developmental nature of analysis techniques.

P. Further work is necessary to conclude that SGTR is unlikely under conditions associated with a severe accident.

3. SGTR due to severe accident conditions can be shown not to be a problem if the reactor coolant system is depressurized.

Originalsignedit, Charles E. Rossi, Assistant Director Division of PWR Licensing-A

Enclosure:

As stated cc: T. Novak S. Long F. Coffman Distribution J. Han Docket File V. Leung F08-A r/f V. Benaroya F08-A p/f kR B PWR-A:F0B WLyon:bjp SNewberry VPenaroya CERossi 12/f/86 12/8/86 12/$/86 I?/7/86

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