ML20070K967
| ML20070K967 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 03/12/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20070K950 | List: |
| References | |
| NUDOCS 9103190224 | |
| Download: ML20070K967 (4) | |
Text
_
gl.9 AICc
'o, UNITED sT ATEs l'
NUCLE AR REGULATORY COMMISSION
.#c
{
,E n AsHWGTON, D, C. 20555
\\....+f' SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 60 TO FACILITY OPERATING LICENSE NO. DPR-80 AND AMENDMENT 110. 59 TO FACILITY OPERATING LICENSE 110.___DPR-82 PACIFIC GAS AND ELECTRIC COMPANY DI ABLO CANYON NUCLEAR POWER PLANT, UNIT NOS.1 AND 2 DOCKET NOS. 50-275 AND 50-323
1.0 INTRODUCTION
By letter dated Decenter 21, 1990, Pacific Gas and Electric Company (PG&E or the licensee) requested amendments to the Technical Specifications appended to Facility Operating License flos. DPR-80 and DPR-82 for operation of Diablo Canyon fluclear Power Plant, Unit tios. I and 2.
The amendments revise the conbined Technical Spccifications (TS) for the Diablo Canyon Power Plant (DCPP) Unit Nos. I and 2 to implement power-dependent Reactor Coolant System (RCS) flow rate limits.
The amendments also delete selected unit-dependent and cycle-dependent parameters that are no longer applicable.
The specific TS charges proposed are as follows:
A.
Changes to TS 2.1 (1) A note regarding operation in the expanded regions of proposed Figures 3.2-3a and 3.2-3b would be added to Fi Safety Limit (Units 1 and 2 Cycle 4 and After)gure 2.1-la, " Reactor Core TS 2.1 requires that the conbination of percent rated thermal power (RTP), pressuri:er pressure and highest locp T not exceed the limits shown in Figure 2.1-la.
The margin between actual plant conditions and the appropriate safety limit curve is the nargin existing to either the safety analysis departure from nucleate boiling ratio (DNBR) limit or saturation conditions at the reactor vessel exit.
The DNBR limits are based upon a nuclear enthalpy rise hot channel factor equal to the 100 percent RTP TS limit and an RCS flow rate equal to the TS minimum acceptable value.
The note would require using 100 percent RTP to determine margin if operation in the expanded regions were to become necessary.
Using 100 percent RTP when power is restricted to less than 100 percent RTP would account for any downward shif ting of the safety limit curves resulting from operation at reduced RCS flow rates.
Proposed TS Figures 3.2-3a and 3.3-3b would also contain an appropriate note referencing the safety limit figure.
(2) The TS references to " Units 1 and 2 Cycle 4 and af ter" and " Unit 2 Cycle 3" would be deleted since these dependencies are no longer required.
(3) Figure 2.1-lb, " Reactor Core Safety Limit (Unit 2 Cycle 3)," would be deleted since this figure is no longer required.
Figure 2.1-la would become Figure 2.1-1 as a result of this deletion.
9103190224 910312 PDR ADOCK 05000275 P
~.
.. - _. _ _ ~ _ _ _. _ _ _ _ _ _.. _
-2 (4) The TS Bases would be revised to delete references to " Unit 2 Cycle 3" and " Cycle 4 and af ter," since these dependencies are no longer required.
B.
Changes to TS 3/4.2.3 (1) The acceptable operation regions of Figures 3.2-3a and 3.2-3c, "RCS Total Flow Rate Versus R," would be expanded to require a 2 percent rated thermal power (RTP) reduction for a 1 percent reduction in RCS flow rate.
This tradeoff between percent RTP and flow could be applied to flow rate reductions of up to 5 peicent, corresponding to a limitation on power of 90 percent RTP.
(2) The Unit 2 Cycle 3 TS requirements and the TS references to " Cycle 4 and after," would be deleted since these dependencies are no longer required.
(3) Figure 3.2-3b, "RCS Flow Rate Versus R (Unit 2 Cycle 3)," would be deleted since this figure is no longer required.
Figure 3.2-3c would become L
Figure 3.2-3b as a result of this deletion.
l (4) The TS Bases would be revised to reflect the power-dependent RCS flow rate limits and to delete references to " Unit 2 Cycle 3" and " Cycle 4 and af ter," since these dependencies are no longer required.
TS 3/4.2.3 requires power reduction to less than 50 percent RTp when the measured RCS flow rate falls below the acceptable operation regions of TS i
Figures 3.2-3a and 3.2-3c for Units 1 and 2, respectively.
A further reduction to less than 5 percent RTP is required if the flow rate is not restored within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
The expanded acceptable operation regions of 2
proposed Figures 3.2 30 and 3.2-3b would prevent plant unavailability by providing flexibility in meeting the TS requirements on measured RCS flow rate.
j 2.0 EVALUATION l
In its letter of December 21, 1990, the licensee presented information to i
justify operation at a reduced RCS flow rate, provided that the reactor power is reduced by 2 percent for each I percent-reduction in RCS flow. The 1
proposed change would limit the allowed RCS flow reduction to S percent, and the corresponding power reduction would be limited to 10 percent. The licensee evaluated the effects of reduced RCS flow /rsduced power on all the relevant safety analyses. These included loss of coolant accident (LOCA) and LOCA-related accidents, licensee evaluated the effects of these accidents onnon-LOC (SGTR) accidents. The key safety parameters such as departure from nucleate boiling ratio (DNBR),
LOCA hydraulic forces, post-LOCA long-term cooling flow and criticality effects, post-LOCA hot leg switchover time, and the response of the containment and RCS mechanical equipment / components to accident forces.
In each case, the licensee showed that the proposed 2 percent power reduction for each I percent reduction in RCS flow.is conservative, and that all potentially affected safety limits will be met.
i 4
3-i.
1 i
Tht licensee states that the non LOCA analyses indicate that the steady state margin to MER wovie te maintained by reducing Rip by 0.6 percent for each I percent reduction in RC$ flow.
Therefore, the licensee concluded that the oroposed 2 percent reduction in power for each I percent reduction in RCS flow is conservative for steady state operation.
The licensee also concluded that i
the previous small brent LOCA and lerge break LOCA analyses continue to be bounding, including tht> eff ects of reduced RC$ flow / reduced power on hot leg switchover tire.
The licensee also states that the results of the $GIR analysis will be unaf fected by the proposed TS change, as will the containnent integrity anciysis end the performance of all RCS components.
Based on this analyses, the licensee concludes that the proposed power-dependent RC$ flow rate limits will not adversely affect plant safety.
The NRC staff has i
rev4ewed the licenste's evaluation and finds it acceptable.
The licerset also proposed, in its letter of December 21, 1990, to delete f rom the TS e numttr of references to unit specific, cycle specific parameters that no 1coger are relevant because the cycle for which these parameters are i
applicetle has t een completed.
Specifically, all references to Unit I, Cycle 4 and eer11er are no longer applicable because Cycle 4 for l' nit I was completec in early February 1991.
Similarly, all references to Unit 2, Cycle ? er.d Earlier are no longer epplicable beccuse Unit 2 is currently in Cy c le a.
As e result, deletion of limits applicable to past cycles represents en cdmiristrative change, and is of benefit because it removes extraneous and potentially confusing information from the TS.
The NRC staff has reviewed the prop 0std celttion of previous cycle material and finds the deletion 4
acceptabit on the basis that the changes are purely administrative.
In summary, the NRC staff has reviewed the licttsee's basis for the proposed chcnges to the tombinec Ttchnical Specifications for Diablo Canyon Units I and 2 and finds them acceptable, 3.0 D"m0N" ENTAL C0h51 DERAT 10N These archdnents involve chtnges with respect to the installation or use of a f acility component located within the restricted area as defined in 10 CFR part 20 or change a surveillance requirement.. The st6f f has determined that the amendrents involve no significant increase in the amounts, and no significant change in the types, of any effluents' that may'be released offsite and that there is no significant increase in individual or cumulative occupational radiation exposure.
The Commission has previously issued a proposed finding that the amendrents involve no significant h5Zards consideration and there has been no public comment on such finding. Accordingly, these amendments meet the 1
eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
l Pursuant to 10 CFR 51.22(b) no environmental impact statement or environrental assessment need be prepared in connection with the issuance of these amendments.
l j
_ _. _ -. ~. ~, _.,, ~
u
l 1
4.
i
4.0 CONCLUSION
l The Connission has proposed to determine that these amendrents involve no significant hazards consideration.
The proposed determination was published
}
in the Federal Register on Janvery 23,1991 at 56 FR 2553.
No public comments or requests for hearing were received.
The fMC steff has concluded, based on the considerations discussed above, that (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) such t
activities will be conducted in complionce with the Commission's regulations, and the issuance of these amendments will not be inimical to the comnon defense and security or to the health and safety of the puLlic.
J Dated: March 12, 1991 2
1 5
i
[
I i
i l
i 1
i i
J
.