ML20151T639
| ML20151T639 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 08/05/1988 |
| From: | Bradham O SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| NUDOCS 8808160426 | |
| Download: ML20151T639 (7) | |
Text
e So th Car fina Electric & Gas Company o
S Bradham Jsnkinsv% SC N Nuchar Operations (803) 34 9 040 SCE&G August 5, 1988 Document Control Desk U. S. Nuclear Regulatory Comission Washington, DC 20555 i
Subject:
Virgil C. Summer Nuclear Station Docket No. 50/395 Operating License No. NPF-12 Technical Specification Change VANTAGE 5 Reload lentlemen:
The Nuclear Regulatory Commission issued a S2fety Evaluation Report (SER) to WCAP 10444, "Westinghouse Reference Core Report VANTAGE 5 Fuel Assembly."
In this SER the Staff identified 13 plant specific concerns which must be addressed in a Licensee submittal. The attachment to this letter provides the South Carolina Electric & Gas Company responses to the 13 concerns.
L This letter supplements the May 20, 1988, June 20, 1988 and July 8, 1988 letters which requested a revision to the Virgil C. Summer Nuclear Station Technical Specifications in support of the transition to the VANTAGE 5 improved fuel design. Should you have any rdditional questions concerning this matter, please call at your convenience.
Very truly yours, D&w.5&
4
- 0. S. Bradham MOB /OSB: led Attachment pc:
- 0. A. Nauman/J. G. Connelly, Jr./0. W. Dixon, Jr.iT. C. Nichols, Jr.
E. C. Roberts W. A. Williams, Jr.
R. L. Prevatte J. N. Grace J. B. Knotts, Jr.
J. J. Hayes, Jr.
H. G. Shealy General Managers M. D. Blue C. A. Price /R. M. Campbell, Jr.
L. R. Cart h R. B. Clary NSRC K. E. Nodland RTS (TSP 880013) j J. C. Snelson NPCF i
l G. O. Percival File (813.20) 8800460426 000005 PDH ADOCK 05000395 P
PNV i
g i
9 Viroil C. Summer Nuclear Station Coments on Plant SDecific ADDlication of WCAP-10444 The Nuclear Regulatory Commisssion (NRC) stat / reviewed WCAP-10444, "Reference Core Report VANTAGE 5 Fuel Assemulf ar.d concluded that the Westinghouse topical report was an acceptable reference to support plant specific applications of VANTAGE 5 provided certain conditions were addressed. These conditions are listed below with comments addressing their relevance to the recent South Carolina Electric & Gas Company (SCE&G) licensing submittals (References 1-3).
1.
The statistical convolution inethod described in WCAP-10125 for the evaluation of initial fuel rod to nozzle grevth gap has not been approved. This method should not be used in VANTAGE 5.
Comment:
The worst case fabrication tolerances were used to determine the initial fuel rod to nozzle growth gaps in the evaluation of fuel rod performance summarized in Reference 1. Attachment 1, Section 3.0.
This is in compliance with condition 1 of the VANTAGE 5 NRC Safety Evaluation Report (SER).
2.
For each plant application, it must be demonstrated that the LOCA/ seismic loads considered in WCAP-9401 bound the plant in question; otherwise additional analysis will be required to demonstrate the fuel assembly structural integrity.
Comment:
4 An evaluation of VANTAGE 5 fuel assembly structural integrity considering the lateral effects of a LOCA and a seismic accident has been performed. The safe shutdown earthquake and LOCA comparative analyses indicated that the flow mixers will share some grid load among the structural grids. The grid load comparison study results show that the VANTAGE 5 fuel assembly has more margin in withstanding the faulted condition transient load than the low parasitic (LOPAR) fuel assembly.
Virgil C. Summer Nuclear Station (VCSNS) is not bounded by the LOCA/ seismic loads considered in WCAP-9401. Thus, in accordance with
.i condition 2 of the VANTAGE 5 NRC SER, additional analyses have been performed to demonstrate fuel assembly structural integrity.
Since VANTAGE 5 has been shown to have inore margin than the LOPAR fuel used in previous cycles, the evaluation of the VANTAGE 5 fuel assembly in accordance with NRC requirements as given in Standard Review Plan, 4
Section 4.2, Appendix A, shows that the VANTAGE 5 fuel is structurally acceptable for an all VANTAGE 5 core; the grids will not buckle due to combined impact forces of a LOCA/ seismic event.
The same conclusion is 1
true for a transition core composed of both VANTAGE 5 and LOPAR assemblies. Thus, the core coolable geometry is maintained since the 1
stresses in the fuel assembly components resulting from seismic and LOCA induced deflections are well within acceptable limits. The reactor can be safely shutdown under the combined faulted condition loads.
1
-,-,,,_,-..w..
,---.--w,,
,e~,..
..-w
Attachment to Document Control Desk Letter August 5, 1988 Page 2 of 6
, 3.
An irradiaticn demonstration program should be performed to provide i
early confirmation performance data for the VANTAGE 5 design.
Coment:
l The VANTAGE 5 Demonstration Program is addressed in Reference 1. Page 3.
1 4.
For those plants using the ITDP, the restrictions enumerated in Section
{
4.1 of this report must be addressed and information regarding measurement uncertainties must be provided.
Coment:
Westinghouse has addressed (Reference 7) the restrictions enumerated in Section 4.1 of the VANTAGE 5 NRC SER. The ITDP instrument uncertainty methodology used for VCSNS with VANTAGE 5 fuel is presented in WCAP-11656 (Reference 8), which was provided to the NRC in Reference 1.
5.
The WRB-2 correlation with a DNBR limit of 1.17 is acceptable for application to 17x17 VANTA3E 5 fuel. Additional data and analysis are required when applied to 1444 or 15x15 fuel with an appropriate DNBR limit. The applicability range of WRB-2 is specified in Section 4.2.
Coment:
17x17 VANTAGE 5 fuel will be utilized at VCSNS. As described in Reference 1 Attachment 1. Section 5.0, the WRB-2 correlation with a DNBR limit of 1.17 is used for the VANTAGE 5 fuel with the ITDP methodology. The WRB-2 correlation is supported by the DNB test data contained in Appendix A to WCAP-10444-P-A (Reference 4) and is applied within its approved range of applicability on VCSNS.
6.
For 14x14 and 15x15 VANTAGE 5 fuel designs, separate analyses will be required to determine a transitionel mixed core penalty. The mixed core penalty and plant specific safety margin to compensate for the penalty should be addressed in the plant Technical Specifications Bases.
Coment:
17x17 VANTAGE 5 fuel will be utilized at VCSNS. The Westinghouse transition core DNB methodology as applied to VCSNS is discussed in Reference 1, Attachment 1 Section 5.0.
The VCSNS application incorpcrates the recent change to the generic VANTAGE 5 transition core penalty discussed in Reference 6.
Table 1 of this attachment provides a sumary of the DNBR margins.
The transition core and rod bow penalties are covered by margin maintained between the design and safety limit I
CNBR.
This margin is addressed in the proposed changes to Section 2.1.1 of the VCSNS Technical Specifications, reactor core safety limits bases (Reference 1. Attachment 2). Numerical values, as specified in Table 1, are not included in the proposed Technical Specifications since significant changes would be required after the transition period.
Maintenance of adequate DNBR margin to cover DNBR penalties is confirmed on a cycle specific basis during the reload safety evaluation process.
Attachment to Document Control Desk Letter August 5, 1988 Page 3 of 6
, 7.
Picot specific analysis should be performed to show that the DNBR limit will net be violated with the higher value of FAH.
Comment:
The core DNB methodology as applied to VCSNS with VANTAGE 5 fuel is presented in Reference 1 Attachment 1 Section 5.0.
The VANTAGE 5 licensing submittals (Reference 1 and 2) contain VCSNS specific analyses which support the use of a FaH of 1.62 during the transition period and with a full core of VANTAGE 5 fuel. All safety criteria are met with a FAH of 1.62.
8.
1he plant-specific safety analysis for the steam system piping failure event should be performed with the assumption of loss of offsite power if that is the most conservative case.
Comment:
VCSNS sp?cific safety analyses for major secondary steam system pipe ruptures were performed in support of the transition to VANTAGE 5 fuel.
These analyses included cases with and without offsite power available and are described in Reference 1, Attachment 3, Section 15.4.2.1 and Reference 2 Page 17 9.
With regard to the RCS pump shaft seizure accident, the fuel failure criterion should be the 95/95 DNBR limit. The mechanistic method mentioned in WCAP-10444 is not acceptable.
Comment:
The mechanistic method was not used with regard to the RCS pump shaft seizure (locked rotor) accident addressed in either Reference 1,, Section 15.4.4 or Reference 2. Page 18. Any rods which violated the 95/95 DNBR limit were assumed to fail.
Results of this evaluation show that fuel failure is less than 15%.
10.
If a positive MTC is intended for VANTAGE 5, the same positive MTC consistent with the plant Techntcal Specifications should be used in the plant specific safety analysis.
Comment:
In conjunction with the transition to VANTAGE 5 fuel, a positive MTC is proposed for VCSNS as described in Reference 1. Attachment 1, Section 7.5.
The supporting VCSNS safety analyses have utilized MTC assumptions which are consistent with or conservative with respect to the proposed l
Technical Specifications.
Specific discussion of MTC assumptions within the VANTAGE 5 safety analysis is presented in Reference 1. Attachment 1, Section 6.1 (page 29). All non-LOCA accidents reanalyzed demonstrate that the appropriate safety criteria are met.
I
Attachment to Document Control Desk Letter August 5, 1988 Page 4 of 6
- 11. The LOCA analysis performed for the reference plant with higher FQ of 2.55 has shown that the PCT limit of 2200'F is violated during transitional mixed core. Plant specific LOCA analysis must be done to show that with the appropriate value of FQ, the 2200T criteria can be met during use of transitional mixed core.
Comment:
In accordance with Condition 11 of the VANTAGE 5 NRC SER, VCSNS specific LOCA analysis were performed with consideration of transitional core effects. The large Break LOCA analysis is summarized in Reference 1, Section 6.2, and the detailed results are provided in Reference 1 Attachment 4. Section 15.4.1.
As described therein, the ECCS acceptance criteria of 2200'F is met for VCSNS with a LOCA FQ of 2.45.
The worst case peak clad temperature is 21917; it includes a conservative transition core penalty of 507.
- 12. Our SER on Westinghousc's extended burnup topical report WCAP-10125 is not yet complete; the approval of the VANTAGE 5 oesign for operation to extended burnup levels is contingent on NRC approval of WCAP-10125.
However, VANTAGE 5 fuel may be used to those burnups to which WesC aghouse fuel is presently operating. Our review of the Westinghouse extended burnup topical report has not identified any safety issues with operation to the burnup value given in the extended burnup report.
Comment:
WCAP.~10125 (Reference 5) has been approved.
The extended burnup methodology contained in this topical has been applied and is addressed in Reference 1, Attachment 1. Section 3.0.
- 13. Recently, a vibration problem has been reported in a French reactor having 14-foot fuel assemblies; vibration below the fuel assemblies in the lower portion of the reactor vessel is damaging the movable incore instrumentation probe thimbles. The staff is currently evaluating the i
implications of this problem to other cores having 14 foot long fuel bundle assemblies. Any limitations to the 14 foot core design resulting from the staff evaluation must be addressed in plant specific evaluations, j
Comment:
VCSNS has 12 foot long fuel assembly bundles, and therefore, the above condition is not applicable.
1 i
Attachment to Document Control Desk Letter o
August 5, 1988 Page 5 of 6
, References 1.
0.A. Nauman to USNRC, "Technical Specification Change - VANTAGE 5 Reload" May 20, 1988.
2.
0.A. Nauman to USNRC, "Technical Spectfication Addendum - VANTAGE 5 Reload" June 20, 1988.
3.
0.S. Bradham to USNRC, "Technical Specification Change - VANTAGE 5 Reload, July 8, 1988.
4.
"Reference Core Report - VANTAGE 5 Fuel Assembly", WCAP-10444-P-A, September 1985.
5.
"Extended Burnup Evaluation of Westinghouse Fuel", WCAP-10125-P-A, December 1985.
6.
Westinghouse Letter, W.J. Johnson to M.W. Hodges (NRC), NS-NRC-87-3208, "VANTAGE 5 DNB Transition Core Effects", October 2, 1987.
7.
Westinghouse Letter, E.P. Rahe, Jr. to C.O. Thomas (NRC), "Response to Request Number 1 for Additional Information on WCAP-10444 entitled,
' VANTAGE-5 Fuel Assembly'" (Proprietary) NS-NRC-85-3014, dated March 1, 1985.
8.
"Westinghouse Improved Thermal Design Procedure Instrument Uncertainty Methodology". WCAP-11656, December, 1987, i
)
Attachment to Document Control Desk Letter August 5. 1988 l
u Page 6 of 6
)
TABLE 1 DNBR MARGIN
SUMMARY
LOPAR VANTAGE 5 Correlation Limit 1.17 1.17 Design Limit Typical Cell 1.36 1.33 Thimble Cell 1.35 1.32 Safety Limit Typical Cell 1.48 1.68 Thimble Cell 1.44 1.60 DNBR Margin (Between Design and Safety Limit DNBR's)
Typical Cell 8.1%
20.8%
Thimble Cell 6.3 17.5%
3NBR Penalties Typical Cell
<1.3%
<1.3%
Thimble Cell 0.0%
12.5%
.