ML18030A287

Advises That GE Analysis of BWR Performance Following Small Break LOCA & LOCA Mitigation Under Degraded Conditions Is Acceptable.Analysis Completes Util Response to Close Out SER Outstanding Issue 37

ML18030A287
Person / Time
Site:	Susquehanna
Issue date:	05/14/1981
From:	Curtis N PENNSYLVANIA POWER & LIGHT CO.
To:	Youngblood B Office of Nuclear Reactor Regulation
References
PLA-761, NUDOCS 8105190277
Download: ML18030A287 (4)

Text

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DOCKET 050003 SUUJECI: Aavises that GE analysis of BWH performance following smal 1

Oreak LOCA 5

LOCA mitigatiOn under degraded COnditiOnS iS acceptaole

~ Analysis completes util response to close out SEH Outstanding Issue 37.

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18101 PHONE:

(2 IS) 82 1-S IS I NORMAN W. CURTIS vice President. Engineering 8 construction 821-5381 May 14, 1981 Mr. B. J. Youngblood, Chief Licensing Branch No.

1 U.S. Nuclear Regulatory Commission Washington, D.C.

20555 Docket: Nos.

50-387 50-388 SUSQUEHANNA STEAM ELECTRIC STATION SER OUTSTANDING ISSUE 37 ER 100450 FILE 841-2 PLA-761

Dear Mr. Youngblood:

The Susquehanna SER states that "if low pressure coolant injection di-version prior to 10 minutes is allowed by design, then procedural re-strictions alone are not sufficient unless analyses are submitted which show compliance with 10CFR50.46 for diversion earlier than 10 minutes."

Analyses of BWR performance following a small break LOCA and LOCA, mitigation under degraded conditions have-been performed by General Electric as a part of the BWR Owners'roup program.

Analyses bases, assumptions and conclusions are discussed in GE report NEDO-24708A, Revision 1, December 1980 entitled, "Additional Information Required For NRC Staff Generic Report On Boiling Water Reactors".

Reference is made to Section 3.1.1 (small break LOCA) and 3.5.2 (inadequate core cooling).

It should be noted that these analyses were performed utilizing "realistic" assumptions as defined in Sections 3.1.1.3 and 3.5.2.4.

The conclusion in Section 3.5.2.1.8 summarizes the capability of the BWR to maintain adequate core cooling, even under severely degraded conditions resulting from multiple failures and operator errors, following a loss of inventory either through a pipe break or through the safety relief valve.

nor Based on the first group of analyses presented it was concluded that for s

any plant and any loss of inventory event, the availability of ADS and one low pressure ECC system provides adequate core cooling if no high I/o pressure injection is available.

These analyses covered the case of multiple mechanical or electrical failures and operator errors that might have caused the failure of the systems, assumed to be unavailable.

8~05>90 PENNSYLVANIA POWER rL LIGHT COMPANY

Mr. B. J. Youngblood Page 2

May 14, 1981 The second set of analyses addressed the condition of the vessel being at high pressure with a low water level. It was shown that operator actions, either to initiate high pressure systems or to depressurize the vessel and initiate at least one low pressure

system, terminate this condition and assure adequate core cooling.

The analyses showed that even for such severely degraded transients there is sufficient time for operator action to mitigate the consequences.

The third set of analyses address the condition of the vessel being at low pressure with a low water level but with the low pressure systems not injecting. It was shown that operator actions either to start the low pressure systems injecting into the vessel or to initiate the high pressure

systems, terminate this condition and assure adequate core cooling.

For all analyses, it was shown that the process variable information available to the operator in the control room is sufficient to adequately warn of an inventory threatening event and to present the information the operator needs to assure that appropriate actions are taken to maintain adequate core cooling.

The control room indications will not mislead the operator when taking corrective actions.

Even under the extremely degraded conditions considered in these

analyses, the BWR requires only the most basic operator actions to mitigate the consequences of an inventory threatening event.

If the operator were to divert LPCI prior to 10 minutes post-LOCA, such an action would be considered an operator error.

Since the current ECCS performance evaluation already assumes the accident, a loss of offsite power and a worst active single failure, an additional operator error is considered to be an additional Appendix K assumption.

It is therefore appropriate that the "realistic" assumption analysis be considered for this situation as stated in the conclusions in NEDO-24708A "for any plant and any loss of inventory event, the adequate availability of ADS and onelow pressure ECC system provides adequate core cooling..."

This analysis is deemed acceptable to provide satisfactory assurance of acceptable event consequences, in consideration of the equipment failures and operator errors assumed.

This response completes our action to close SER Outstanding Issue 37.

Very truly yours, N.

W. Curtis Vice President-Engineering

& Construction-Nuclear CTC/mks cc:

R.

M. Stark - NRC