ML17156A585
| ML17156A585 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 04/22/1988 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17156A583 | List: |
| References | |
| NUDOCS 8805130096 | |
| Download: ML17156A585 (8) | |
Text
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION INDEFINITE OPERATION IN SINGLE LOOP OPERATION MODE PENNSYLVANIA POWER AND LIGHT COMPANY SUS UEHANNA STEAM ELECTRIC STATION,UNIT 2 DOCKET NO. 50-388
1.0 INTRODUCTION
By letter dated June 30, 1987 (Ref-1) Pennsylvania Power and Light Company (PP8L), the licensee for Susauehanna Steam Electric Station (SSES) Unit 2, proposed to amend Appendix A of facility operating license No. NPF-22.
The application furnished information to support authorization for Single Loop Operation (SLO) with 9x9 fuel supplied by Advanced Nuclear Fuels Corporation (ANF) during Cycle 2 operation.
PPSL submitted additional information and clarification in letters dated October 30 and December 15, 1987 (Ref-2,3).
In support of the proposed amendments, the licensee submitted ANF Topical Reports XN-NF-86-146, (Ref-4)
SSES Unit 2 Cycle 2
SLO analysis and XN-NF-86-125, Susquehanna LOCA analysis for SLO (Ref-5).
The present SSES Unit 2, Cycle 2 core consist of 324 unirradiated 9x9 ANF fuel bundles and 440 irradiated General Electric P 8xGR fuel bundles.
In the interim, the PPFL submitted Unit 2 Cycle 3 reload report on December 23, 1987 requesting authorization to operate Unit 2 with Cycle 3 reload.
The SSES Unit 2 Cycle 3 {Ref-6) core will comprise a total of 764 fuel assemblies, including 236 unirradiated ANF XN-2 9x9 fuel assemblies, 324 irradiated ANF XN-1 9x9 assemblies and 204 irradiated GE 8x8R fuel assemblies.
Since the SSES Unit 2, Cycle 2 operation has already been completed, and the unit is in a refueling outage, the requested amendment for Cycle 2 operation is no longer needed.
This safety evaluation is provided to support Unit 2 SLO for Cycle 3 operations as requested in your March 24, 1988 letter.
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2.0 EVALUATION Abnormal 0 eratin Transients The licensee provided ANF report titled "SSES Unit 2, Cycle-2 SLO Analysis" (Ref-4), which evaluates the transients and accidents during SLO.
The transients were analyzed using the staff approved code COTRANSA (Ref-7) and ANF methodology (Ref-8).
The delta CPRs were calculated using XCOBRA-T (Ref-9).
The transients analyzed were:
M-G set trip, recirculation pump trip and idle loop startup.
The results confirmed that these transients are not the limiting transients considered for determining OLMCPR.
The limiting anticipated system transient is the Load Rejection Without Bypass (LRWB) pressurization event.
The reduced power and flow analyses unde~
two loop operation show that the resulting power excursion and associated delta CPR are smaller than those of the full power/full flow case.
Thus, for SSES Unit 2, the MCPR limits based on LRWB analyses at full power are conservatively applicable to the lower flow associated with single loop operating conditions.
Furthermore, LRWB analyses by ANF at reduced power and flow conditions in other BWRs with sinqle loop operation confirm this trend.
Pump Seizure Accident Pump seizure is a postulated accident where the operating recirculation pump suddenly stops rotating.
This causes a rapid decrease in core flow, a decrease in the rate at which heat can be transferred from the fuel rods and a
decrease in the critical power ratio.
Analyses with COTRANSA and XCOBRA-T show that for Cycle-3 the CPR for ANF fuel would decrease by 0.30 du~ing a
pump seizure for single loop operation.
The GE PSxSR fuel reached a maximum of delta CPR of 0.29 for Cycle-3.
Minimum Critical Power Ratio MCPR) Safet Limit For single loop operation, GE found that an increase of 0.01 in the MCPR safety limit was needed to account for the increased flow measurement uncertainties and increased TIP uncertainties associated with single pump operation.
ANF has evaluated the effects of the increased flow measurement uncertainties on the safety limit MCPR and found that the GE determined increase in the allowed safety limit MCPR is also applicable to ANF fuel during single loop operation.
Thus, increasing the safety limit MCPR by 0.01 for single loop operation (1.07) with ANF fuel is sufficiently conservative to also bound the incr eased flow measurement uncertainties for single loop operation.
MCPR 0 eratin Limit for Cycle-3 The MCPR operating limit <or single loop operation for Cycle-3 is conservatively set usina the limiting pump seizure accident delta CPR 0.30 plus the single loop operation MCPR safety limit.
This limit together with the MCPRf curve for two loop operation plus 0.01 and the MCPR
> curve for two pY loop operation plus
.01 conservatively bound all transients.
The proposed changes to Technical Specification 3.4. 1. 1.2 (a)(3) are therefore acceptable to Cycle 3 operation.
Loss of Coolant Accident (LOCA) Anal sis The licensee provided ANF report entitled "Susquehanna LOCA Analysis for Single Loop Operation" (Ref-5), which evaluates LOCA during SLO.
The approved EXEM/BWR ECCS Evaluation Model (Ref-12) was used for the analysis.
A mechanistic jet jump model was developed and included in RELAX as part of the approved EXEM/BWR model.
The RELAX model characterizes flow through the jet pump under all flow conditions including sinale loop operating conditions.
The licensee stated that the approved two loop evaluation model (Ref-12) is also valid for SLO conditions.
The staff concurs with the licensee's approach.
The limiting LOCA break calculations were performed for SSES Unit 2 based on ANF 9x9 fuel parameters.
The most limiting break for SLO is the 0.4 double ended guillotine (DEG) discharge break (same as for the two-loop operation).
The resulting peak clad temperature (PCT) is 2096'F.
This is about 50'F less
than the limiting PCT for two-loop operation and 104'F less than the 2200'F limit specified in 10CFR50.46, Appendix K.
Therefore, the calculated PCT margin is acceptable.
Since this analysis was performed at the most limiting exposure with the same Maximum Average Planar Linear Heat Generation Rate (MAPLHGR) as was used in the two loop analysis (Ref-ll), it is reasonable to expect that calculation for SLO at other exposures using the two loop MAPLHGR limit would also result in a lower PCT.
Therefore, the ANF 9x9 MAPLHGR curve for two-loop operation is acceptable for SLO.
The multiplier of 1.0 proposed for MAPLHGR in Technical Specification 3.4. 1.2(a)(3) is, therefore, acceptable for Cycle 3 operation.
2.6 Stabilit Anal sis PPSL has performed a stability startup test in SSES Unit 2 during initial startup of Cycle 2 to demonstrate stable reactor operation with ANF-9x9 fuel.
The test results showed very low decay ratio (0.30) with a core containing 324 ANF 9x9 fuel assemblies.
It is our understanding that PPSL is planning to perform a stability startup test in SSES Unit 2 during initial startup of Cycle-3 to demonstrate stahle reactor operation and to obtain baseline data for final approval of 9x9 fuel.
To further assure protection against thermal hydraulic instabilities, the PP8L has adopted SSES Unit 2 Technical Specifications, which implement survei llances for detecting and suppressing power osci llations.
One of the stability tests performed during the startup of SSES Unit 2 Cycle-2 was performed under SLO conditions.
The measured decay ratio was 0.30 at 55K power/44K flow.
The ANF performed an analysis of these tests with their COTRAN computer code and calculated a decay ratio of 0.29, which compares well with the measured decay ratio.
The above stability 'considerations based on Cycle-3 star tup tests, planned Cycle-3 tests, and the Cycle-3 Technical Specification stability surveillance requirement support approval of SLO during Cycle-3 operation.
Therefore, plant operation (SLO and two loop operation) is acceptable with regard to stability for Cycle-3 only.
The thermal hydraulic stability of cores with 9x9 ANF fuel is not yet approved on a generic basis.
- Hence, Generic Letter 86-02 "Thermal-Hydraulic Stability" is not applicable for 9x9 ANF fuel.
When SSES Unit 2 core is loaded with full 9x9 ANF fuel, the licensee must justify the stability for future reloads.
Therefore, the proposed Technical Specification changes in Section 3/4.4. 1 and Figure 3.4. 1. 1. 1.-1 are acceptable for Cycle-3 operation only.
Recirculation Pump Speed The revision to recirculation pump speed from 905 to 80K is a restriction due to gaps discovered on the jet pump restrainer bracket.
The new limit is based on a
GE jet pump vibration analysis.
The proposed change in Technical Specification 3.4. 1. 1.2 changing the pump speed is acceptable for Cycle-3 operations.
Summary on Sin le Loo 0 eration Based on the above analyses, the staff finds that with the provisions summarized below, the transients'nd accidents'ounds will not be exceeded for SSES Unit 2 during'SLO operation.
1.
Minimum Critical Power Ratio (MCPR) Safet Limit will be Increased b
0.01 to 1.07 The MCPR Safety Limit will be increased by 0.01 to account for increased uncertainties in (TIP) readings.
The licensee has determined that the change conservatively bounds the uncertainties introduced by single loop operation.
' 2.
Minimum Critical Power Ratio (MCPR) Limitin Condition for 0 eration (LCO)
The staff requires that the operating limit MCPR be greater than or equal to (a) 1.37 for Cycle-3 (b)
The MCPR determined from MCPR curve p
(c)
The MCPR determined from MCPRf curve 3.
The Maximum Average Planar Linear Heat Generation Rate MAPLHGR) Limits will be Reduced bv A ro riate Multi liers The licensee proposed to reduce the flow dependent MAPLHGR by a factor of 0.81 for GE fuel and factor of 1.0 for ENC 9x9 fuel operation.
MAPLHGR reduction factor of 0.81 for GE fuel was approved in Amendment No. 26.
4.
The Recirculation Control will be in Manual Control The licensee wi 11 continue to operate the recirculation system in the manual mode to eliminate. the need for control system analyses and to reduce the effects of potential flow instabilities.
4
3.0 CONCLUSION
Based on the above evaluation, we conclude that SLO of SSES Unit 2 in accordance with the proposed Technical Specifications will not exceed the accident and transient bounds previously found acceptable by the staff.
Therefore, indefinite operation in SLO mode for Cycle-3 operation is acceptable.
3.0 REFERENCES
1.
Letter No. PLA-2885, H.
W. Keiser (PPLCo) to Director (ONRR, NRR),
Susquehanna Steam Electric Station proposed Amendment 52 to License No.
NPF-22, dated June 30, 1987, (with attachments).
2.
Letter No. PLA-2935, H.
W. Keiser (PPLCo) to Director (ONRR, NRR),
Susquehanna Steam Electric Station, additional information on proposed Amendment 52 to License No. NPF-22, dated October 30, 1987.
3.
Letter No. PLA-2952, H.
W. Keiser (PPLCo) to Director (ONRR, NRC),
Susquehanna Steam Electric Station, response to NRC request for additional information regarding Unit-2, Cycle 2 SLO.
4.
XN-NF-86-146, "Susquehanna Unit 2 Cycle 2, Single Loop Operation Analysis,"
Exxon Nuclear
- Company, November 13, 1986.
5.
XN-NF-86-125, "Susquehanna LOCA Analysis for Single Loop Operation,"
Exxon Nuclear
- Company, November 13, 1986.
6.
Letter PLA-2953, B.
D.
Kenyon (PPLCo) to Director (ONRR, NRR),
"Susquehanna Steam Electric Station, proposed Amendment 58 to License No.
NPF-22, Unit 2 Cycle 3 Reload Submittal," dated December 23, 1987.
7.
- Letter, H.
N. Berkow (NRC) to J.
C. Chandler (ENC), "Acceptance for Referencing of Licensing Topical Report XN-NF-79-71, Rev 2, Supplements 1
through 3, Exxon Nuclear Plant Transient Methodology for Roiling Water Reactor,"
December 16, 1985.
8.
- Letter, Gus C. Lainas (NRC) to G.
N. Ward (FNC), "Acceptance for Referencing of Licensing Topical Report XN-NF-80-19(P), Yol 3, Rev 2,"
Exxon Nuclear Methodology for Boiling Water Reactors THFRMEX:
Thermal Limits Methodology Summarv Descriptions,"
November 10, 1986.
9.
- Letters, Gus C. Lainas (NRC) to G.
N. Ward (ENC), "Acceptance for Referencing of Licensing Topical Report XN-NF-84-105(P)
"XCOBRA-T:
A Computer Code for BWR Transient Thermal Hydraulic Core Analysis,"
October 27, 1986.
10.
- Letter, C. 0.
Thomas (NRC) to J.
C. Chandler (ENC) October 31,
- 1983, "Acceptance for Referencing of Licensing Topical Report XN-NF-524(P)".
11.
Memorandum dated September 22,
- 1986, from Gus C. Lainas (NRC) to E.
Adensam (NRC)
"SER for Susquehanna 2 Cycle 2".
12.
- Letter, James R. Miller (NRC) to G.
F. Owsley (ENC) January 27, 1982 "Acceptance for Referencing of Topical Report XN-NF-80-19(P),
Volume 2, 2a, 2b, 2c and Topical Report XN-NF-81-71(P)".