ML17216A378
| ML17216A378 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 12/12/1985 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17216A377 | List: |
| References | |
| NUDOCS 8512230255 | |
| Download: ML17216A378 (7) | |
Text
~
pe RECy
~ ~
(,i Cg Cy
+o t
UNITED STATES t
NUCLEAR REGULATORYCOMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.
70 TO FACILITY OPERATING LICENSE NO.
DPR-67 FLORIDA P014ER 8 LIGHT COMPANY ST LUCIE PLANT UNIT NO I
DOCKET NO. 50-335 INTRODUCTION The licensee notified the
- NRC, on August 27, 1985, that an input data error had been found in the Exxon Nuclear Company (Et'IC) large break LOCA-ECCS Evaluation Model and administratively restricted the Linear Heat Generation Rate (LHGR) limit to 14.0 Kw/ft from 15.0 Kw/ft for the remainder of Cycle 6
(Reference I).
Because of this error, a revised large break LOCA-ECCS study
~
~
~
XN-NF-85-117) was performed by ENC in support of the Cycle 7 safety analysis Reference 2).
As a result of the re-analysis, it was determined that Technical Specifications changes are needed to assure continued compliance with 10 CFR 50.46 criteria.
On October 17, 1985, the licensee submitted a
proposed license amendment for the LHGR Limiting Condition for Operation (LCO)
(Reference 3).
The proposed changes will change the LHGR LCO from the constant value of 15 Kw/ft to an axially dependent LHGR limit.
The allowable local power density limits for operation when incore detectors are out of service will also be lowered.
The third change will be removal of the LHGR uncertainty factor for axial fuel densification and thermal expansion.
The final change requested will not require the LCO on LHGR to be met during Moderator Temperature Coefficent testing.
Ilhile not specifically mentioned in the proposed amendment, the large break LOCA re-analysis (XN-NF-85-117) also pertains to an increased limit on the allowable steam generator tube plugging, from 5l to 15% uniform plugging.
The Cycle 7 safety analysis for non-LOCA transients and accidents is found in XN-NF-85-73 Revision 2 (Reference 4).
The scope of this safety evaluation is limited to the large break LOCA -
ECCS re-analysis in support of the proposed license amendment for the LHGR LCO Technical Specifications changes.
The proposed increase in plugging is not encompassed in this licensing action.
In addition to the review of the proposed amendment and XN-NF-85-117, the NRC has also reviewed the licensee's responses (Reference
- 5) to our request for additional information covering the large break LOCA -
ECCS re-analysis.
8512230255 851212 PDR ADOCK 05000335 PDR
A
~'
)
~
~
~ EYALUATION The revised large break LOCA -
ECSS performance analysis was made using an NRC-approved evaluation model (EH) which satisfies the requirements of 10 CFR 50.46 and Appendix K to Part 50.
The methods for accounting for steam generator. tube plugging are based on ENC's experience with the EM model and chosen as being representative of the worst case for the level of steam generator tube plugging, 15% uniform average plugging with as much as 4X asymmetry betwee'n the two steam generators.
The current (as of November 26, 1985) fraction of plugged tubes are 4X and 3.6X.
The effects of the increased plugging (from 5C to 15%),
and asymmetric plugging, on non-LOCA transients and accidents is not addressed in this safety evaluation.
The identification of the limiting large break LOCA in XN-NF-85-117 is based on results which are preliminary insofar as the increase to 15Ã plugging is concerned.
A supplement to XN-NF-85-117 containing the large break LOCA spectrum results and exposure study results is currently in preparation.
This supplement will contain the final break spectrum results using the 15 Kw/ft power profile peaked at 0.6 x/l.
The break spectrum results provided in XN-NF-85-ll7 show that the double-ended ouillotine cold leg break with a discharge coefficient of 0.8 (0.80ECLG) has the highest fuel and cladding temperature at,the end of the b'lowdown portion of the LOCA.
ENC analyses using REFLEX and
- TOODEE2, NRC-approved evaluation model computer programs, have consistently shown that the refill and reflood behavior differs little between breaks in a large break LOCA spectrum.
Therefore, the LOCA with the highest temperature at the end of blowdown will also yield the highest peak cladding temperature during reflood.
Since the 0.8 DECLG break is the most limiting, this break size was used to establish the Linear Heat Generation Rate (LHGR) limits for St, Lucie I Cycle 7, and beyond.
The bounding power distribution was determined from the 0.8 DECLG break system bounding conditions.
Two points were determined.
At 0.6 of the active core length (0.6x/1) the peak LHGR was found to be 15 Kw/ft.
A peak LHGR of 13.4
"'w/ft was found at the 0.8lx/1 elevation.
These power distributions meet the criteria of 10 CFR 50.46 and are the basis for the proposed license amendment, Item I of Reference 3.
Based on the large break LOCA spectrum results provided in XN-NF-85-117, the limiting large break LOCA was found to be a 0.8 DEGCL break.
The Limiting Heat Generation Rate (LHGR) was found to be 15 Kw/ft at 0.6 of the 'active core height (0.6x/1).
The peak cladding temperature is calculated to be 2188'F.
The total core hydrogen generation is less than l~ and the local cladding oxidation is 9.47% for the limiting break.
These values are within the required limits as specified in 10 CFR 50.46.
The staff finds the revised analysis is acceptable for the determination of the LHGR LCO Technical Specifications limits.
0 h
The acceptability of the proposed license amendment includes a condition requiring the submittal of the supplement to XN-NF-85-117 which will provide the complete large break LOCA spectrum r suits.
These results are required to demonstrate full compliance with the criteria of 10 CFR 50.46 and Appendix K
to Part 50 with 155 tube plugging.
The staff expects that the limiting break size and location will not change as a result of the supplemental analyses.
The change to the LHGR LCO, Technical Specification 3.2. 1, results in a more restrictive limit for the allowable peak linear heat generation rate.
The limitation on LHGR ensures that in the event of a Loss of Coolant Accident (LOCA), the peak temperature of the fuel cladding will not exceed 2200'F.
A review of the results as presented in XN-NF-85-117 (St. Lucie 1 Revised LOCA-ECCS analysis with 15% Steam Generator Tube Plugging) indicates the following.
(a)
The calculated peak fuel element clad temperature does not exceed the 2200'F limit.
(b)
The amount of fuel element cladding that reacts chemically with water or steam does not exceed 1/ of the total amount of zircalloy in the reactor.
(c)
The cladding temperature transient is terminated at a time when the core geometry is still amenable to cooling.
The hot fuel rod cladding oxidation limits of 17'. are not exceeded during or after quenching.
(d)
The system lonq term cooling capability provided for previous cores remains applicable for ENC fuel.
The allowable local power density limits for operation when in-core detectors are out of service (Technical Specification 4.2. 1.3, Figure 3.2-2) has been narrowed to reflect the charges to the linear heat generation rate limit.
ENC statistical methodology was used to determine the allowed power versus Axial Shape Index incorporating appropriate uncertainties.
The ENC safety analyses include the fuel densification and thermal expansion uncertainty factor in the engineering factor.
Thus, it is not necessary to apply the 1.01 fuel densification and thermal expansion uncertainty factor to adjust the alarm setpoint.
Therefore, the fuel densification and thermal expansion uncertainty factor is deleted from Technical Specification 4;-2. 1.4 and the Bases 3/4.2. 1.
The licensee has requested that the LHGR LCO be footnoted to allow"for exceeding the limits of Figure 3.2-1 during performance of Specification 4. 1. 1.4.2, Noderator Temperature Coefficient (MTC) testing.
This is necessary because during full power NTC testing, the measured linear heat rate typically increases due to a CEA insertion.
4 The highest axial linear heat rate is expected during the beginning of Cycle 7 ETC testing.
The predicted LHGR is not expected to exceed the limit of Technical Specification Figure 3;2-1.
However, the alarm setpoint for the incore detectors that are used to ensure compliance with the linear heat rate Technical Specifications are subject to radial peaking and could alarm prematurely during NTC testing.
Because of this incore detector response during the HTC test, the special test exception was requested.
The staff has elected to defe~ action on this request until the licensee can positively demonstrate that the LHGR limit will not be exceeded if an incore detector alarm should occur during NTC testing.
The staff has reviewed the material submitted by the licensee in the October 17, 1985 submittal and the additional clarifying information submitted in the letter dated December 2, 1985.
Based on the review of this material and the above discussi'on, the staff finds the proposed
- changes, with the exception of the request to exceed LHGR limits during ETC testing, to the St. Lucie 1 Technical Specifications acceptable.
ENVIROJJJ iENTAL CONSIDERATION This amendment involves a change in the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
The staff has determined that the amendment involves 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 published a proposed finding that the amendment involves no significant hazards consideration and there has been no public comment on such finding.
Accordingly, the amendment meets the eliaibility criteria for categorical exclusion set forth in 10 CFR
$51.22(c)(9f.
Pursuant to 10 CFR 551.22(b),
no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
CONCLUSION Me have 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 activities will be conducted in compliance with the Commission's regulations,'nd the issuance of the amendment will not be inimical to the common defense and security or-to the health and safety of the public.
Date:
December 12, 1985 Principal Contributors:
E. Throm H. Chatterton D. Sells
REFERENCES 1.
Docket No. 50-335, Florida Power and Light letter L-85-331, J.
W. Williams, Jr, (FPL) to H. L. Thompson (NRC), dated August 27, 1985.
2.
XN-NF-85-117, "St. Lucie Unit 1 Revised LOCA-ECCS Analysis with 15K Steam Generator Tube Plugging,"
Exxon Nuclear Company, Inc.,
November 5, 1985.
3.
Docket No.
50-335, Florida Power and Light letter L-85-3967, J.
W. Williams, Jr.
(FPL) to H. L. Thompson (NRC), dated October 17, 1985.
4.
XN-NF-85-73, Revision 2, "St. Lucie Unit 1 Cycle 7 Safety Analysis Report,"
Exxon Nuclear Company, Inc., October 28, 1985.
5.
Docket No. 50-335, Florida Power and Light letter L-85-447, J.
W. Williams, Jr.
(FPL) to H. L. Thompson (NRC), dated December 2, 1985.