ML20212N695
| ML20212N695 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 03/03/1987 |
| From: | Chi L, Griffith K, Tran P GENERAL ELECTRIC CO. |
| To: | |
| Shared Package | |
| ML20212N681 | List: |
| References | |
| DRF-A-2948, DRF-A00-02948, NUDOCS 8703130121 | |
| Download: ML20212N695 (4) | |
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SUMMARY
EVALUATION FOR CHANCING THE MSIV WATER LEVEL ISOLATION SETPOINT FOR THE LASALLE COUNTY STATION UNIT 2 March 3, 1987 DRF A00-02948
- 1. INTRODUCTION Loss-of-Coolant Accident (LOCA) analyses were performed to justify changing the water level isolation setpoint of the Main Steam Isolation Valves (MSIV) for the LaSalle County Station Unit 2.
The MSIV water level isolation setpoint is lowered from Level 2 to level 1.
The impact of the setpoint change on the Peak Cladding Temperature (PCT) over the entire break spectrum (large, intermediate, and small breaks) was evalunted.
The results of the calculations indicate that lowering the MSIV level isolation setpoint has no significant impact on the PCT and will not change the Maximum Average Planar Linear Heat Ceneration Rate (MAPLHCR) for LaSalle Unit 2.
2 LIMITING RRRAlt SIZES AND SINGLE FAILURE Presented in Table 1 are the systems available for the various limiting break sizes (large, intermediate, and small breaks) and the corresponding single failures for the LaSalle County Station Unit 2 (Referonce 1).
Figure 1 shows the present break spectr.nn and singla failures for LaSalle Unit 2.
The most limiting IDCA break that results in the highest PCT and determinos the MAPLHCR limit at the LaSalle County Station Unit 2 is the recirculation suction design basis accident (DBA) with an assumed failure of the LPCS Diesel Generator (point 1 in Figure 1).
To justify changing the MSIV water level trip from Level 2 to Level 1, the LOCA analyses were reanalyzed over the break spectrum for the large to small break with the assumed limiting single failuro combinations as annotated in Figure 1.
- 3. ANALYSES RESULTS_
The LOCA calculations were performed with GE codes (SAFE, REFLOOD, and CHASTE) approved for the 100FR50.46 and 10CFR50 Appondix K applications.
The standard Appendix K assumptions were used in the analysos.
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.9 The analyses results show that the large and intermediate LOCA events are not affected by the setpoint change.
This is.because the rapid l
depressurization and the rapid inventory loss will cause the MSIVs to closo almost immediately after the accident, before any appreciable fuel heatup occurs.
Consequently, lowering the MSIV level trip will not increase the inventory loss from the reactor core, the total core uncovery time or subsequent fuel heatup, or the radiation release to the environment.
Small break accidents are not limitin5 events (as shown in Figure 1) for the LaSalle County Station Unit 2.
However, since there is potential for the MSIVs to remain open longer durin5 a small break LOCA, lowering the MSIV level trip might cause an increase in the PCT for small break LOCA.
With the MSIV isolation level setpoint lowered from Level 2 to Level 1, the analyses results show that the increase in PCT for the most limiting small break is less than 30'F.
The small break PCT with the MSIV level trip setpoint change is substantially less than the lar5e break PCT and the 2200 F limit.
The seepoint change will not adversely affect the LOCA ovents over the entire break spectrum; therefore the limiting MAPLHGR will not be changed.
- 4. REFERENCES 4.1 Chapter 6 and 15 FSAR for LaSalle County Station Unit 2.
Prepared by:
h/
Prepared by: M. O.
/-// k,
P.T7 Tran,' Engineer K. A. GriffitT17 Engineer Application Engineering Application Engineering Services Services l
Verified by:
L.L. Chi, Senior Engineer Application Engineering Services e
Approved by:
G/L. Sozdi, dtfager Application Engineering Services 2
i
Table 1 PCT Impact On MSIV Setpoint Change for the LaSalle County Station Unit 2 Point Break Size PCT *
(Fin 11 (ft i Sinele Failure Systems Romaining Imnact ( F) 1 3.1 LPCS DC HPCS, 2 LPCI, ADS None 2
1.0 HPCS LPCS, 3 LPCI, ADS None 3
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HPCS FAILURE 1
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,3, BREAK AREA (FT')
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l Figure 1.
Paak Cladding Temperature Vs. Break Area for the LaSa ne County Station Unit 2 l
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