ML17139B670
| ML17139B670 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 07/26/1983 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML17139B669 | List: |
| References | |
| NUDOCS 8308080808 | |
| Download: ML17139B670 (5) | |
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Sus uehanna Steam Electric Station Units 1 and 2
Docket Numbers 50- 387/398 Demonstration of Containment Pur e
and Vent Valve 0 erability Demonstration of operability of the containment purge and vent valves, particu-larly the ability of these valves to close during a design basis
- accident, is necessary to assure containment isolation.
This demonstration of operability is required by BTP CSB 6-4 and SRP 3.10 for containment purge and vent valves which are not sealed closed during operational conditions 1, 2, 3,
and 4.
2.0 Descri tion of Pur e and Vent Valves The valves identified as the containment isolation valves in the purge and vent system in which operability has not previously been demonstrated are as fol 1 ows:
Valve PAID Number HV-1,2 25703 HV-1,2 25704 HV-1,2 25724 HV-1,2 25725 HV-1,2 25713 HV-1,2 25714 HV-1,2 25722 HV-1,2 25723 Valve Size Inches 18 18 18 18 24 24 24 24
~Ty e Butterfly Butterfly Butterfly Butterfly Butterfly Butterfly Butterfly Butterfly Location Outside containment Outside containment Outside containment Outside containment Outside containment Outside containment Outside containment Outside containment The 18 and 24-inch valves are Pratt valves Model 1200 150 lbs with an offset asymmetric disc.
The 18-inch valves are equipped with Bettis Operators, Model T312-SR3, air open-spring close.
The.24-inch valves are equipped with Bettis Operators, Model T416-SR3.
Pennsylvania Power and Light's (PPEL) assess-ment is that the valves are capable of closing from the full open (90') posi-tion under the accident case postulated.
PP8L has previously demonstrated operability for the 6-inch valves installed in the purge and vent system.
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- 3. 0 Demonstration of Operabi 1 it Pennsylvania Power and Light has provided information demonstrating operability for the purge and vent system isolation valves for Susquehanna Steam Electric Station Units in the following submittal s:
A.
Pratt gualification Analysis Report for the 18-inch valves HBB-BF-A0-5703, 5704,
- 5724, 5725 dated 1/ll/83.
B.
Pratt gualification Analysis Report for the 24-inch valves HBB-BF-A0-5713, 5714,
- 5722, 5723 dated 1/28/83.
PPKLs approach to operability demonstration is based on the following considerations:
a.
The maximum dynamic torque occurs when initial sonic flow occurs.
This corresponds with an open angle of 68'or an asymm'etric disc.
b.
Closure plus delay time equalled 11 seconds.
c.
Closure time under LOCA conditions is less than no-load stroke times.
d.
Flow di rection through the valve is toward the hub side (asymmetric disc), which is the worst case dynamic torque developed.
- e. 'ingle valve closure is assumed.
f.
All valves are air operated and are located outside containment.
Containment back pressure effect is not applicable.
g.
Accumulators are not part of any valve assembly.
h.
The analysis of the structural integrity and operational adequacy of the valve assembly is based principally upon containment pressure vs time data, system response (delay) time, piping geometry upstream of the valve, back pressure due to ventilation components downstream of the valve, valve orientation, and di rection of valve closure.
- 4. 0 Eva,1uati on 4.1 Revised pressure response and temperature response curves for a recircula-tion line break are presented.
A peak Wetwell pressure of 41 psia and a peak dry well pressure of 58.2 psia were used in the analysis.
The FSAR (Section 6.2.1.1,3.1) states that. the calculated accident parameter is 43.8 psig and 29 psig for the dry well and suppression
- chamber, respectively.
The staff bases their review on the latest submittal or the
'41 psia and
- 58. 2 psia values.
4.2 The analysis presented states that the maximum dynamic torque occurs when intial sonic flow occurs.
This corresponds with an open angle of 68'or an asymmetric disc.
Downstream pressure was selected by considering the valve
closure time and pressure time curves such that the downstream pressure at 68'ould yield the critical ratio for the air stream mixture.
This was con-.
- sidered, by Pratt and the staff, based on the information submitted, to be the worst case approach in determining valve loading.
4.3 Pratt's approach to determining dyamic torque--T0 for the subject valves is based in part on the fact that they have determined from the model valve tests that the maximum value of Tp occurs when initial sonic flow occurs coincident with a disc angle of 68'or the asymmetri'c disc (90' full open).
Based on this, the TD equation for sonic flow (given in the submittal) is used with appropriate dynamic torque coefficient, media difference (steam/air mixture) and size difference factors to determine the maximum value of T0 possible in the subject valves.
Coefficient of friction used for the bronze beari ngs is 0.25.
Seating Torques (TS) are calculated by an equation in AWWA C504-80.
Seating factor or coefficient of seating (CS) is said to be determined by Pratt lab tests.
T8 defined as "maximum operati ng torque for valve" is used in the applicable areas of the stress analysis as the torque load.
T8 is shown to be the higher value of the algebraically combined TD and TB or TB plus TS.
For the 18.0-inch valves, T8 is 20551 i nche -lbs or basically equal to TD, which is more conservative then T0 -TB.
-For the 24.0-inch valves, T8 is 69617 inche -lbs or basically equal to TD, which again is more conservative than Tp -TB, to which the staff agrees.
4.4 In their analysis reports, H. Pratt has indicated that the stress'nalysis is structured to comply wth paragraph NB-3550 of Section 'III of the ASNE BPVC and that design rules for Class I valves are used (exceeds rules for Class 2
and 3).
Pratt states that valve components are. analyzed under the assumption that the valve is either at maximum fluid dynamic torque or seati ng against the maximum design pressure.
An analysis temperature of 300'F is used along with 5g seis-mic accelerations statically applied simultaneously in each of three mutually perpendicular directions.
Stress summary tables were provided for both the 18 and 24-i nch isolation
~ valves.
As requested by the NRC, Pratt has revised the shear stress allowable to 0.4Sy.
Utilizing the revised peak post-LOCA 'Wetwell pressure in combination with the shear stress allowable of 0.4Sy and with the addition of new materials in the top disc pin and redesign of the bonnet for the 24-'inch valve the stress levels for the 18 and 24-inch valves were found to be below the. code allowables and acceptable.
4.5 Closing time, including delay time, is said to be 11 seconds.
- However, this is not an issue since the analysis has considered a constent peak con-tainment pressure throughout the analysis.
- 5. 0
~Summa r We have completed our review of the information submitted to date concerning.
operability of 18 and 24-inch containment purge and vent valves for the Susquehanna Steam Electric Station.
We find the information submitted demonstrates the ability of the 18 and 24-inch purge,Sand vent valves to close against the buildup of containment pressure in the event of a LOCA.