ML20209E639
| ML20209E639 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 07/03/1985 |
| From: | Fay C WISCONSIN ELECTRIC POWER CO. |
| To: | Butcher E, Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NRC-85-10, TAC-56844, TAC-56845, VPNPD-85-37, NUDOCS 8507120050 | |
| Download: ML20209E639 (2) | |
Text
,
O Wisconsin Electnc eom come 231 W. MICHIGAN, P.O. BOX 2046. MILWAUKEE, WI 53201 July 3, 1985 VPNPD 37 NRC 85-10 Mr.
H.
R. Denton, Director Office of Nuclear Reactor Regulation U. S. NUCLEAR REGULATORY COMMISSION Washington, D.
C.
20555 Att:
Mr. Edward Butcher, Acting Chief Operating Reactors, Branch 3 Gentlemen:
DOCKET NOS. 50-266 AND 50-301 REQUEST FOR ADDITIONAL INFORMATION TECHNICAL SPECIFICATION CHANGE REQUEST NO. 101 UNDERFREQUENCY. TRIP SETPOINT POINT BEACH NUCLEAR PLANT, UNITS 1 AND 2 In response to your request, the following additional information is provided for clarification relative to our proposed change to the Technical Specifications, dated January 30, 1985, which would reduce the underfrequency trip setpoint for the reactor coolant pumps from 57.5 Hz to 55.0 Hz.
As previously stated, Westinghouse Electric Corporation performed a reanalysis of the complete loss-of-flow transient utilizing the same methodology as was used for the FSAR loss-of-flow analysis with the following assumptions:
1.
Reactor trip occurs on a RCP underfrequency signal at a setpoint of 54.5 Hz.
Consistent with previous loss-of-flow analysis, 0.5 Hz allodance was included in the technical specification value to allow'for uncertainty.
2.
Reactor trip delay time was assumed to be 0.6 seconds.
This value is the same as assumed for the low reactor coolant flow trip outlined in Section 14.1.8 of the FSAR and is comprised of 0.3 second for underfrequency trip circuitry response including delay to prevent spurious trip during fast bus transfer, 0.15 second for trip breaker opening and 0.15 second for RCCA release.
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R. Denton July 3, 1985 3.
Reactor coolant system (RCS) flow was assumed to decay linearly in response to a frequency decay at a constant rate' of 5 Hz per second. ' Analysis of the Wisconsin Electric transmission system shows that. realistic maximum frequency decay rates would be approximately 2 Hz per second.
. Additionally, Westinghouse sensitivity studies show that a resultant DNBR is inversely proportional to the decay.
rate.
Therefore, the assumed decay rate of 5 Hz per second, which is greater than the maximum expected for the Wisconsin Electric system,-is conservative and results in a DNBR of
-approximately 1".65 at approximately 3.4 seconds.
(Attachment 1 to our January ~ 30, 1985 request.)
The analysis bounds standard fuel cores, cores consisting entirely of OFA fuel, and transition cores-containing both fuel types and operation at either 2000 psia or 2500 psia with either the Model.44-or Model 44F steam generator.
Our' reasoning.and conclusion that the proposed amendment tx) the. Point. Beach Technical Specifications will not constitute a significant hazards consideration remain unchanged.
It is recognized that operating with a reactor coolant pump.under-frequency. trip setpoint of 55 Hz instead of the current setpoint of 57.5 Hz would be more limiting with respect to the minimum DNBR reached during a complete loss-of-flow transient.
- However, the resultant minimum DNBR of approximately 1.65 is acceptable in. comparison to the design DNBR of 1.3.
Therefore, our no significant hazards consideration evaluation for the proposed change falls within the scope of ' example vi. of 48 Federal Register'14870, "A change which either may result in some increase to the probability'or consequences of a previously analyzed accident or may reduce in some way a safety margin, but where the results.of.the change are clearly within all acceptable criteria...".
We hope this information clarifies our previous submittal.
If you have any questions, please contact us.
Very truly yours, exc/
Vice President-Nuclear Power C. W. Fay Copies to.NRC Resident Inspector Mr. R. S. Cullen, PSCW