ML20128H297

Topical Rept Evaluation of Addendum 1 to NEDO-10466A, Power Generation Control Complex Design Criteria & Safety Evaluation. Rept Acceptable for Referencing in License Applications,Subj to Listed Conditions

ML20128H297
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Issue date:	05/17/1985
From:	NRC
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ML20128H254	List: ML20128H297
References
NUDOCS 8505300487
Download: ML20128H297 (2)

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ENCIDSURE s

Safety Evaluation Report GE Tcpicai Report, NE00-10466A Adddender i Fower Generation Control Ccrplex Introduction-In Revision 2 of NED0-10466A dated March 1978, General Electric reccmmended that a Halon 1301 fire extinguishing system would be required to protect the PGCC.

The system would provide a 20 percent concentration cf Halen 1301 for a soak time for 20 minutes for deep seated fires.

The staff found it acceptable.

By letter dated Februtry 28, 1986, General Electric submitted Addendum 1 to NEDO-10466A.

General Electric requested deviations that wculd reduce the Halon 1301 concentration to be prov.ided to protect the PGCC and the amount of soak time required.

For PGCC's with 80 percent or greater Tefzel cable, General Electric requested that the concentration and soak time of Halon 1301 be changed to be surface burning fire concentration and soak time, i.e., 6

ercent for 10 minutes.

Discussion / Evaluation s -

Based on testing anc research performed on cable insulation since 1978, Genera 1 Electric.has reevaluated deep seated fires occurring in the PGCC.

General Electric indicates that Figure 4.2 of NEDO-10466,' Revision 2, Appendix F, shows that the rate and degree of burning of the Tefzel cable used in the PGCC essentially corresponds with that of the ignition source.

Because of this, the key to limiting the severity of burning of Tefzel is in the capability of-extinguishing the ignition source.

If the ignition source is extinguished, the fire in the Tefzel will self-extinguish, almost simulta-neously. Tefzel is a thermoplastic material, which reans that as its temper-ature is raised it will melt before it burns, that is, the auto ignition temperature is higher than-its melting temperature.

This characteristic of melting.before it burns ensures that burning can occur only at its surface as a liquic.

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2 Tne st'rface burning cFaracteristic of Tefzel have been substantiated in every fire' test. conducted by General Electric.

V Afte? reviewing the' test results in Appendix F of NEDO-10466A, we agree with General Electric that Tefzel cable will exhibit surface burning characteristics and not deep seated. -Therefore, the amount of Halon 1301 required to extinguish Tefzel cable fires should be base'd on surface burning fires in accordance with NFPA 12A~, i.e., 6. percent for 10 minutes.

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Based on the burning characteristics..of Tefzel cable, fire test results in

non-Tefzel cables, anc NFPA for acceptance, for non-Tefzel cable we find

'that an automatic 'Halon 1301 extinguishing system with an adequate amount of Halon 1301 to achieve a 6 percent concentration'for a 10 minute' soak time will extingu'ish cable fires in PGCC's enclosures'which contain 80 percent Lor greater by weight Tefzel cabling, n

Conclusion Based on our evaluation, we conclude.that an automatic Halon 1301 extinguishing

, system with an adequate amount of Halon 1301 to achieve a 6 percent concentra-tion for a 10 minute soak time will be acceptable for PGCC's which contain

-80 peretnt or greater by weight Tefzel cabling. Therefore, we find General Electric's request for deviation from NED0-10466A acceptable.

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