ML20236U380
| ML20236U380 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 11/24/1987 |
| From: | Zimmerman S CAROLINA POWER & LIGHT CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| 87TSB18, NLS-87-267, NUDOCS 8712020456 | |
| Download: ML20236U380 (4) | |
Text
,
gpgg Carolina Power & Light Company NOV 2 4 $87 SERIAL:
NLS-87-267 10CFR50.90 87TSB18
-United States Nuclear Regulatory Commission ATTENTION: Document Control Desk Washington, DC 20555 BRUNSWICK STEAM ELECTRIC PLANT, UNIT NO. 2 DOCKET NO.-50-324/ LICENSE NO. DPR-62 SUPPLEMENT TO REQUEST FOR LICENSE AMENDMENT MSIV WATER LEVEL Gentlemen:
Based on conversations with members of your staff on November 5, 1987, Carolina Power &' Light Company hereby submits a revised significant hazards analysis for the MSIV Water Level Setpoint Change amendment. request submitted on September 29, 1987 for the Brunswick Steam Electric Plant, Unit No.
- 2. details the basis for the Company's determination that the proposed changes do not involve a significant hazards consideration.
Please refer any questions regarding this submittal to Mr.. Stephen D.
Floyd at (919) 836-6901.
Yours very truly, MW S.
R.
immerman anager Nuclear Licensing Section BAB/bab
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Enclosures:
1.
10CFR50.92 Evaluation cc:
Mr. Dayne H.
Brown Dr. J.
Nelson Grace Mr. W. H. Ruland Mr. E.
D.
Sylvester k
neie,gh N c 27602 411 reyettevote street. p o. so,
- " " "*'"# " N M E N " " C" 8712O20456 871124 l)
i ENCLOSURE 1 BRUNSWICK STEAM ELECTRIC PLANT, UNIT 2 NRC DOCKET 50-324 OPERATING LICENSE DPR-62 SUPPLEMENT TO REQUEST FOR LICENSE AMENDMENT 10CFR50.92 EVALUATION The Commission has provided standards in 10CFR50.92(c) for determining whether a significant hazards consideration exists.
A proposed amendment to an operating license for a facility involves no significant hazards consideration if operation of the facility in accordance with the proposed amendment would not:
(1) involve a significant increase in the probability or consequences of an accident previously evaluated, (2) create the possibility of a new or different kind of accident from any accident previously evaluated, or (3) involve a significant reduction in a margin of safety.
Carolina Power & Light Company has reviewed this proposed license amendment request and determined that its adoption would not involve a significant hazards consideration.
Under the current Technical Specification requirements, main steam isolation valve (MSIV) closure leads to a loss of feedwater flow to the vessel due to the isolation of supply steam to the feedwater system pumps (turbine driven).
Since the feedwater system is not available for vessel level control, the high pressure coolant injection (HPCI) and reactor core isolation cooling (RCIC) systems and the safety / relief valves are needed to maintain vessel level control.
The reduction of MSIV closures during routine scrams would reduce the need to rely on HPCI and RCIC for vessel level control, thereby reducing unnecessary challenges to these two safety systems.
Furthermore, the use of HPCI without the benefit of feedwater induces possible thermal stress on the vessel feedwater sparger.
Avoiding use of HPCI without the benefit of feedwater may also increase the life expectancy of the vessel feedwater sparger.
Main steam isolation valve closure also results in loss of the main condenser as a P sat sink.
As a result, the suppression pool must be used as a heat sink via the safety / relief valves.
The reduction of MSIV closures during routine reactor scrams will l
also reduce number of safety / relief valve challenges.
By avoiding use of the suppression pool as a heat sink, containment duty may also be reduced.
Carolina Power & Light Company has reviewed the proposed amendment and determined the request does not involve a significant hazards consideration for the following reasons:
l El-1 l
l
L 1.
The proposed amendment does not involve a significant increase in the probability or consequences of an accident previously evaluated.
The setpoint change was evaluated with respect to several operating. parameters, including the minimum critical power ratio (MCPR), peak vessel pressure, radiation release, and shutdown capability during abnormal operational transients.
Fuel cladding integrity during a loss of coolant' accident (LOCA) and the reactor response during an ATWS event were also evaluated.
Results of this evaluation are provided in the GE Topical Report NEDC-30601-P, " Safety Review of Water Level Setpoint Change for Brunswick Steam Electric Plant, Units 1 and 2."
As stated in Sections 4.2.3 and 4.2.4 of that report, the change will.not cause a reduction in MCPR, an increase in the peak pressure, an increase in radiation release, equipment damage, a reduction in plant shutdown capability, or a decrease in core cooling capability.
The MSIV level setpoint change has no impact on LOCA events previously evaluated, nor does it cause consequences of accidents previously evaluated to be increased.
2.
The proposed amendment does not create the possibility of a new or different kind of accident from any accident previously evaluated.
Several operating parameters, including MCPR, peak vessel pressure, radiation release, and i
shutdown capability during abnormal operational transients were evaluated with respect to this change.
Fuel ~ cladding integrity during a LOCA and reactor response during an ATWS event were also evaluated, and the results provided in NEDC-30601-P.
None of these evaluations indicated that any new or different type of accident would be created by the change..In addition, the present function and structure of the Group 1 isolation valves remains unchanged, thereby i
eliminating possible operator confusion and training problems that could lead to a new or different type of accident.
3.
The effects of the setpoint change for LOCA events has been reviewed, and it has been determined that the change has no impact.
As stated in NEDC-30601-P, large and intermediate LOCA events will not be affected because the rapid depressurization and rapid inventory loss will cause the l
MSIV to close almost immediately after the accident, before i
any fuel failure could occur.
Thus, the lower MSIV trip will not increase inventory loss from the reactor core or radiation release to the environment.
For a small break LOCA, the highest peak cladding temperature for the worst case single failure (i.e., failure of the HPCI system) is l
considerably less than the 2200 F peak clad temperature l
limit.
Therefore, the setpoint change will have no effect on the limiting maximum average planar linear heat generation rate (MAPLHGR).
El-2
[
4 For-a loss of feedwater flow event under the proposed amendment, tho' reactor would not be. isolated while HPCI and RCIC aro operating.
Reactor core isolation cooling system flow would compensate for steam flow through the turbine control valves to the main condenser, thereby maintaining water level above Low Level 3, keeping the MSIVs open, and.
preventing the safety / relief valves from opening.
Thus, the MSIV setpoint change _will not compromise core cooling capability for the loss of feedwater flow event.
Furthermore, it reduces suppression pocl heatup for this event because the main condenser is available for a longer time.
The Low Level 3 reactor water level setpoint for the Group 1 primary containment isolation system valves still " ensures-the effectiveness of the instrumentation used to mitigate the consequences of accidents" as demonstrated by the evaluation in Sections 4 and 5 of NEDC-30601-P.
Thus, for the reasons. described above, the margin of safety is not reduced'and'may actually be increased.
d El-3
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