ML20044H054
| ML20044H054 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 06/01/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20044H052 | List: |
| References | |
| NUDOCS 9306070309 | |
| Download: ML20044H054 (5) | |
Text
-.
/,.
2-S UNITED STATES 5
i NUCLEAR REGULATORY COMMISSION k.....,/
WASHINGTON, D.C. 20555 0001 SAFETY EVALUATION BY THE OFFICE 3F NUCLEAR REACTOR REGULATION i
RELATED T0 AMENDMENT NO.172TO FACILITY OPERATING LICENSE NO. DPR-66 AMENDMENT N0. 51 TO FACILITY OPERATING LICENSE NO. NPF-73 i
e DUOVESNE LIGHT COMPANY l
OHIO EDIS0N COMPANY PENNSYLVANIA POWER COMPANY...
THE CLEVELAND ELECTRIC ILLUMINATING COMPANY-THE TOLED0 EDISON COMPANY BEAVER VALLEY POWER STATION.' UNIT N05. 1 AND'2 i
DOCKET NOS. 50-334 AND 50-412 l
1.
INTRODUCTION By letter dated February 19, 1993, Duquesne Light Company (the' licensee)
)
submitted proposed revisions'to the Technical Specifications (TS) for Beaver-Valley Units 1 and 2 to support.a 1.5 percent reduction in minimum Reactor l
Coolant System (RCS) total flow rate. Additional proposed revisions of an administrative nature were also submitted. A conference. call with the licensee was held on March 17, 1993, and' a request for additional information.
dated March 19, 1993 was subsequently transmitted. ;The licensee responded to this request by letter dated March 31, 1993. A subsequent' conference call was held-on April 12, 1993. The licensee responded to open. items discussed in the call by letter dated April 19,1993. The March 31, and April 19, 1993, submittals provided additional information.that did not change the initial no significant hazards consideration determination.
i The licensee's request to reduce minimum RCS total flow rate is in i
anticipation of the need to plug or. sleeve defective steam generator tubes,
~
the extent of which will be determined for Unit I'during the current refueling / steam generator inspection outage. The proposed 1.5 percent C
reduction is expected to accommodate future levels of' steam generator tube plugging / sleeving predicted by the licensee for both units.
To reflect the proposed reduction in flow for Units 1 and 2,_ the design flow per loop specified in TS Table 2.2-1 is changed from 88,500 gpm to 87,200 gpm.
Additionally, the allowable value associated with Table item 12 (" loss of flow") is changed from 88.9% to 89.0% for-Unit 1, and from 88.8% to 88.9% for Unit 2.
In Table 3.2-1 for Unit 1, total' flow rate is changed-from 265,500 gpm to 261,600 gpm, while for Unit 2, this change-is from 270,850 gpm to 261,600 gpm. The difference reflects the fact;that the current Unit 2 value includes a 2.0% flow uncertainty whereas the' Unit I value.does~ not. The-footnote in Table 3.2-1 (Unit 2) that refers to the inclusion of flow uncertainty will be deleted to maintain consistency with Unit 1.
Flow uncertainty for Unit 2 will be accounted for administratively, as it currently 9306070309 930601 PDR ADOCK 05000334 P
.a. -
. is for Unit 1, through the operating procedures.
Further, the proposed addition of footnote (1) to TS 3.2.5. for Units 1 and 2 clarifies that the values in Table 3.2-1 are intended to be analysis limits and not indicated values.
To support the proposed reduction in flow, the exit boiling portion of the core thermal limits i.11ustrated in Figure 2.1-1 required revision for Units:1 1
and 2.
Additionally, Figures 2.1-2 and 2.1-3 (and all references to them) have been deleted for-Unit 1.
These figures, which provide core thermal limits for two-loop operation, are extraneous because plant operation with less than three loops is not permitted under the current license.
Similarly, the limits pertaining to two-loop operation in Table 3.2-1 for Unit I have been deleted. The Unit 2 TS do not address two-loop' operation.
A proposed revision to TS 3.2.5 for Unit I has been made to allow entry into.
Mode 1 in the event the surveillance interval for RCS total flow rate extends beyond the required 18-month interval specified in TS 4.2.5.2.
The flow rate must be determined by measurement at a reactor power of at least 90 percent..
With the plant shut down, current limiting condition for operation (LCO) 3.2.5 would prevent (through TS 4.0.4) commencement of power operation and thus the execution of the -surveillance. Therefore,-an exclusion to TS 4.0.4 for this I
case has been added in the form of a footnote to TS 3.2.5'.
A similar change is made for Unit 2.
Finally, the limit on Tavg specified in Table 3.2-1 has been reduced from s581 F to s580.7 F for Unit 1, and from 5580.3 F to 5580.2 F for Unit 2.
2.0 EVALUATION Minimum RCS total flow rate is a critical input parameter to the analyses presented in Chapters 14 and 15 of the licensee's Updated Final Safety Analysis Reports (UFSAR). Accordingly, to support operation of Units.1 and 2 under the proposed reduction in flow, the impact of this reduction on these analyses must be evaluated. The licensee's above-referenced submittals provide a summary of these evaluations and assessments of the following:
1) whether all acceptance criteria continue to be met, 2') whether the current core thermal limits remain bounding, 3) whether current setpoints set forth in the TS continue to provide adequate protection, and 4) whether the performance of key components and rystems remains acceptable.
l l
For the non-loss 'of coolant accident (LOCA) transients, the current licensing basis supports a maximum tube plugging level of 20 percent.. The l
re-evaluations consider only the effects of a 1.5 percent. reduction in RCS total flow rate and continue to support a 20 percent plugging level.
For those transients with departure from nucleate boiling (DNB) acceptance l
criteria,Lthe licensee has determined through sensitivity studies that the.
l proposed reduction in~ flow will reduce the departure from nucleate boiling ratio (DNBR) by 2.4 percent or less. The current. retained DNBR margin for i
Units 1 and 2 is 9.9 percent (based on a safety analysis DNBR limit of 1.33 and a design limit DNBR of 1.21). To account for the adverse impact off flow-reduction on DNBR, the licensee has taken a 2.4 percent penalty against this -
4 l
- j retained margin for all relevant non-LOCA transients. : Any. resulting analysis l
margins for the specific events (i.e., based on the difference between the minimum DNBR for an event and the safety analysis limit) were not credited.
With regard to the impact of the proposed flow reduction 'on core thermal:
limits, the licensee's' evaluation indicates that the DNBR-limited segmentzof l
each thermal limit line in the current -TS remains bounding. As noted above, the retained DNBR margin.is large enough to accommodate the penalty assessed-against it due -to flow reduction.. The vessel exit boiling segment of each
-l thermal limit line was revised, however, to reflect the J.5 percent reduction
+
in flow. The effect is less than a.1*F decrease in exit boiling limits.
Additionally, the licensee confirmed that the current OT delta-T and OP delta-T setpoint equations continue to provide protection for.the revised core thermal limits.
i For those non-LOCA transients which are not DNB related or for which other acceptance criteria in addition to DNB are relevant, the licensee has examined the effects of the proposed reduction -in flow. To determine if the design basis continues to be met, existing sensitivity data as well as sensitivity analyses performed to support the proposed reduction in flow were employed.
The licensee has presented, for each of the relevant transients,.results which indicate that adequate margin to the applicable acceptance criteria currently.
l exists to accommodate the effect of reduced flow.
l
~
t The large and small break LOCA events (LBLOCA and SBLOCA) and steam generator tube rupture (SGTR) event were re-evaluated to determine if the relevant :
acceptance criteria continue to be met under the proposed flow reduction. The SGTR re-evaluation (at a tube plugging level of'20 percent for each unit) indicated a slight increase in break flow and calculated radiation dose.
However, based on conservative assumptions made in the FSAR analyses of record regarding coolant activity-(which is unaffected by the proposed flow
. reduction) the licensee has stated that the FSAR results remain bounding.
1 For Unit 1, the analysis of record for the LBLOCA limiting break case indicates a calculated peak cladding temperature (PCT). of 2149 F.
This is based on a BASH re-analysis at a 20 percent tube plugging level. A total penalty of 4 *F has been assessed against this value to account for fuel rod backfill initial pressure uncertainty and, as specified.in the present '
amendment request, a revised RCS Tavg uncertainty. This results in a cumulative PCT of 2153 *F.
The analysis of record for the limitirig break SBLOCA. indicates a PCT of 1802 F and is based on a NOTRUMP analysis at a 10 percent plugging level.
Excluding penalties associated with the present amendment ' request, a net penalty of 380 F (consisting of various permanent and interim penalties and j
benefits) has been assessed against this value to date. The penalties associated with the proposed amendment total 15 F and are due to a revised RCS'Tavg uncertainty (5 F) and a' corresponding Burst / Blockage SPIKE interim penalty (10 F). The result is a cumulative PCT' of 2197 *F.. For Unit 1, the licensee reports that no change in RCS Tavg is predicted as a direct result of
,.,.. J
. ~
. ~
t i
' the proposed flow reduction and, therefore, no corresponding PCT penalty or benefit is incurred for either the LBLOCA or SBLOCA case.
The Unit 2 analysis of record for the LBLOCA limiting break case is based on a BART analysis at a 5 percent plugging level and indicates a PCT of 2120 F.
)
Including penalties assessed against this value prior to the present amendment J
request, the most recent cumulative PCT is 2191 F.
The licensee's April 19, 1993 submittal identifies a 25 'F PCT benefit related to the WREFLOOD structural heat model, which reduces the cumulative PCT to 2166 F.
The licensee reports that, for Unit 2, the proposed flow redyction results in a small decrease in RCS Tavg for both the LBLOCA and SBLOCA cases.
Because existing BART data indicates that higher values of RCS Tavg are limiting for the LBLOCA, a PCT benefit would thus result. The licensee, however, has not quantified or credited this benefit.
For the Unit 2 SBLOCA, the analysis of record for the limiting break case is based on a NOTRUMP analysis at a 5 percent plugging level and indicates a PCT of 1399 F.
Including penalties assessed against this value prior to the present amendment request, the most recent cumulative PCT is 2119 F.
Existing NOTRUMP sensitivity data indicates that either direction (i.e., an i
increase or decrease) can be limiting for RCS Tavg.
For the proposed flow reduction and resulting small decrease in RCS Tavg, these data show that a j
1 F change in PCT could result. The licensee has conservatively taken this 1 F change as a penalty. Additionally, the licensee has discovered discrepancies between the RCS Tavg input values to the LBLOCA and SBLOCA analyses, and the current values. These discrepancies, due to error and to evolutionary changes in the plant, are such that the analyses values exceed the current values. This would have a beneficial effect on the LBLOCA PCT since a higher RCS Tavg is limiting. However, this benefit was not quantified or credited. For the SBLOCA, on the other hand, a PCT penalty of 20 F was assessed for conservatism. A corresponding 36 F Burst / Blockage SPIKE interim penalty was then taken, bringing the cuuulative PCT to 2176 F.
The above results for LBLOCA and SBLOCA indicate that Units 1 and 2 may be small break limited.
Further, the SBLOCA results for;both units and the LBLOCA results for Unit 2 reflect significant changes / from the analyses of record, in the context of 10 CFR 50.46.
In all cases, however, the above results indicate that the acceptance criterion of a cumulative PCT of less j
than 2200 F has been met. The licensee has also examined the effect of the proposed flow reduction on the LOCA mass and energy release calculations and has concluded that the current FSAR analyses remain bounding.
The effect of the proposed flow reduction on key NSSS components, the steam generator, key heat exchangers, valves and pumps, and fluid systems has been evaluated by the licensee to confirm that their operation continues to remain in compliance with the applicable acceptance criteria, codes, and standards.
In all cases for Units 1 and 2, the results of these evaluations indicated continued acceptable performance under reduced flow conditions.
i
c 4 On the basis of the above evaluation, we find that with regard to the proposed TS revisions, the licensee has provided adequate supporting evaluations to demonstrate that-1)
For all non-LOCA and LOCA events addressed in Chapters 14/15 of the UFSARs for Units 1 and 2, the relevant acceptance criteria continue to be met for operation at the proposed reduced RCS total flow rate.
2)
The core thermal. limits have been revised to bound operation of Units 1 and 2 at the reduced flow rate.
3)
The current OT delta-T and OP delta-T setpoints provide adequate plant protection at the reduced flow rate.
4)
Performance of key systems and components continues to remain acceptable at the reduced flow conditions.
Therefore, we find the proposed TS revisions to be acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Pennsylvania State official was notified of the proposed issuance of the amendments. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendments change a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The NRC staff has determined that the amendments 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 amendments involve no significant hazards consideration, and there has been no public comment on such finding (58 FR 16224). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact a
statement or environmental assessment need be prepared in connection with the issuance of the amendments.
5.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, i
l that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor: H Abelson Date:
June 1, 1993 1
I