ML20235N458

Safety Evaluation Supporting Util 810707,820623,0730 & 831215 Submittals Re Valve Operability Info for 24-inch Isolation Valves in Purge & Vent Sys.Nrc Conclusion Subj to Valves Being Modified to Have Torque Readjustments

ML20235N458
Person / Time
Site:	Cooper
Issue date:	07/10/1987
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20235N440	List: ML20235N458
References
NUDOCS 8707200080
Download: ML20235N458 (6)

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ENCLOSURE.

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION l l

RE MTING TO DEMONSTRATION OF CONTAINMENT-PURGE AND VENT OPERABILITY NEBRASKA PUBLIC POWER DISTRICT t COOPER NUCLEAR STATION DOCKET NO. 50-298 l l

1.0 . Requirement Demonstrate operability of the containment purge and vent valves, partic-ularly, the ability of these valves to close during a design basis acci-dent, 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 Description of Purge and Vent Valves The valves identified as the containment isolation valves in the Purge System are as follows:

Valve Size Operator Valve Location Valve Tag No. (Ir.ches) Type (Outside Containment)

PC-232-MV 24 Motor Drywell PC-238-AV 24 Air-Spring Drywell PC-230-MV 24 Motor Wetwell PC-245-AV 24 Air-Spring Wetwell PC-233-MV 24 Motor Wetwell PC-237-AV 24 Air-Spring Wetwell PC-231-MV 24 Motor Drywell PC-246-AV 24 Air-Spring Drywell These valves are butterfly type Model 125 FR manufactured by Allis Chalmers.

Valves 238AV and 246AV are equipped with Bettis Model T-420B-SRI operators, valves 237AV, 245AV with Bettis model 744A-1SR operators, and valves 230MV, 231MV, 232MV, 233MV with Limitorque Model SMB00 operators. Accumulators are not used on any of the air operated valves.

3.0 Demonstration of Operability

( Nebraska Public Power District (NPPD) has provided valve operability informa-l tion for the 24-inch isolation valves in Cooper Nuclear Station's purge and vent system in their submittals dated July 30,1982, ~ June 23,1982, July 7, 1981, and December 15, 1983.

8707200000 870710 PDR ADOCK 05000298 p PDRy

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NPPD's approach to the operability demonstration is based on the following:  ;

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a. Single valve operation, i.e., redundant in-series valve is failed open. i i

b. Load calculations stemming from use of a LOCA containment pressure profile, delay time and valve closure time. f

c. Pressure losses due to inlet piping are considered.

Dynamic torque predictions are based on dynamic torque coefficients developed by Allis Chalmers bench tests on 6-inch model valves. Analytical techniques involving scaling are used to determine the torque predictions. Details of the model valve test program and scaling analyses are documented in Allis Chalmer's report VER-0209.

NPPD's torque load predictions are based on the following:

a. Containment pressure response resulting from a design basis accident baset!

on the updated safety analysis report (USAR) Figure XIV-6-18 dated July 22, 1983.

b. Identification of each valves's installation configuration and application of appropriate dynamic torque coefficients from the model tests.

4.0 Evaluation 4.1 NPPD uses a ramp-rise in establishing dynamic loads for the purge and vent valves. Containment response curves for the wetwell and drywell are pro- j vided illustrating the relationship between pressure and time for a design '

basis accident. The closing times for the vent and purge valves vary as indicated by the following table.

j Tech. Spec. Time Used Actual Closure Time Valve Limit (Sec.) in Analysis (Sec.) Approximate (Sec.) l 230 15 14 4 J 245 15 14 9 233 15 14 4 237 15 34 9 231 15 4 and 14 4 246 15 9 and 14 9 232 15 4 and 14 4 236 15 6,9 and 14 9 4.2 The installation configuration descriptions provided by NPPD in relation to the information available in Allis Chalmer's report VER-0209 have been reviewed. The following qualitative evaluation of the Allis Chalmer's test data used for each of the valve installations is based on the report's general conclusion, ... test results indicate that the worst case (highest l applied shaft torque under any given pressure drop) would be when the valve

o is mounted closely to an upstream elbow at right angles to the plane of the elbow (90 out of plane) and installed with the curved side of the j disc facing upstream (seat downstream).. l

a. Valve 233MV: the installation configuration is described as 90 elbow upstream - shaft 72 out of plane. NPPD's assessment showing adequate torque niargin in is based on use of test data from Tests 31 and 32.

Test 31 (Figure 12 in VER-0209) is configured with a 90 elbow upstream - shaft 90 out of plane - seat downstream. The operator torque limit.will be 1,300 ft-lbs, pending adjustment of the torques

. switch setting. The shaft torque limit is 2,200 ft-lbs, while the maximum dynamic and bearing load is 754 ft-lbs. Based on Allis Chalmer's general ~ conclusion, it is concluded that Test. 31 is conser- li vative, relative to torque prediction, for the 233 MV configuration j blocked at 60 . When the adjustment to the torque switch setting is )

completed,. operability has been demonstrated.

b. Valve 237AV: . the installation configuration is described as being the same as 233MV's, with the exception being the presence of 233MV upstream.'Again, conservative torque predictions tend to result from )

Test 31 data. Additional conservatism results from the fact that no I credit is taken for pressure drop across 233MV which is limited to 60' open (90 = full open). The submittal discussed a 159% minimum, as installed, torque margin. Operability has been demonstrated.

c. Valve 230MV: the installation configuration is described as 45 elbow '

upstream - shaft 90 out of plane preceded by 90 elbow - shaft in plane. The seat is upstream, NPPD's assessment showing adequate torque margin is based on use of test data from Tests 29 and 32. .The operator i torque limit will be 1,300 ft-lbs, pending adjustment of the torque i switch setting. The shaft torque limit is 2,200 ft-lbs, while the maximum dynamic and bearing load is 754 ft-lbs. Based on Allis Chalmer's general conclusion, it is concluded that Tests 29 and 32 data is considered conservative, relative to torque predictions, for the 230MV configuration blocked at 60 . When the adjustment to the torque switch setting is completed, operability has been demon-strated.  !

1 L d. Valve 245AV: the installation configuration is described as 230MV l l upstream preceded by the elbows described for 230MV. 245AV's valve I shaft is described as being oriented 18 out of plane with the 45 .

elbow and 72 out of plane with the 90 elbow. The seat is downstream. J NPPD's assessment showing adequate torque margin is based on the use of test data from Tests 31 and 30. Based on Allis Chalmer's general l conclusion, it is concluded that Test 31 data is considered conser- i vative.

The minimum operator spring to close capability is 1,200 ft-lbs at approximately 35* (90 = full open), with a maximum dynamic torque 1

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1 apposing closure of 446 f t-lbt at 10 ; resulting in an excess -spring torque at 10 of 954 ft-lbs. Structurally the valve shaft is capable  ;

of absorbing a 2,200 ft-lb torque, while the operator maximum torque l aosorption capability is 1,300 ft-lbs. The staff concludes that NPPD has demonstrated operability of this valve under DBA/LOCA conditions. {

e. Valve 232MV: the installation configuration is described as straight pipe upstream (no elbows) - flow direction unknown. NPPD's assessment showing adequate torque margin is based on use of test data from  ;

Tests 29 and 30. Based on Allis Chalmer's general conclusion, the  !

staff concludes that Test 30 (Figure 11 in VER-0209) i:: conservative, relative to torque prediction for the 232MV configuration when blocked  ;

at 60 . The operator torque limit will be 1,300 ft-lbs, pending  ;

adjustment of the torque switch setting, the shaft torque limit is 1 2,200 ft-lbs while the maximum dynamic and bearing load is 946 ft-lbs.

When the adjustment to the torque switch setting is completed, opera-bility has been demonstrated.

f. Valve 238AV: the installation configuration of valve 238 is not l clearly defined. Previous submittals defined it as having a 35 elbow l upstream shaft 90 out of plane, preceding by valve 232MV and straight i pipe with the flow direction being unknown. The latest submittal indicates a proposed orientation that corresponds to Figure 11 and test 30 of the Allis Chalmer's report VER-0209. It was this orienta-tion and configuration that was considered in the analysis.

The maximum dynamic torque plus bearing torque ranges from a plus 1,011 ft-lbs, valve tends to close, to a minus 903 ft-lbs, valve tends {

to open (valve closing time of 14 seconds considered resulting in l larger loads). The minimum operator output is 3,300 ft-lbs while the shaft torque limit is 2,200 ft-lbs. The torque absorption capability of the operator is determined by the shaft torque, when the valve disc tends to close, to the operator spring closing torque. A 7%

minimum margin exists based on operator torque absorption capability I

at 90 , and not on the ability of the operator to close the valve.

When the installation configuration corresponds to Figure 11, test 30 of Allis Chalmer's report VER-0209, operability has been demonstrated.

I g. Valve 231MV: the installation configuration of valve 231 is not clearly defined in the submittal. Previous submittals describe the installa-tion configuration as having a 45 elbow upstream, shaft 90 out of plane, preceded by a 90 elbow, shaft in plane, with disc orientation being undefined. The latest submittal, indicates Figures 9 and 10, test configurations 29 and 32, respectively of the Allis Chalmer's report as being the proposed installation configuration, acknowledge that operability cannot be demonstrated with the present, as-installed, orientation,

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Figure 9 defines the test valve orientation as being flat face upstream - shaft in plane with elbow which corresponds to Allis  !

Chalmer's test configuration 29. Figure 10 defines the test valve orientation as being flat' face upstream shaft out of plane with elbow,'

this corresponds to Allis Chalmer's. Test 32.

Test data from configurations with shaft out of plane orientations 1 should be used to predict torques. Based on this, the results of - '

Tests 29 and 32, Figures 9 and 10, were reviewed, -The maximum dynamic

torque, which tends to keep the valve open is reported to be

1. 947 f t-lbs. , the minimum operator. torque limit is-1,300 ft-lbs, and shaft torque limit of 2,200 ft-lbs. When the valve orientation corresponds to either Figure 9 or 10 test orientation and test con-figuration 29 or 32, operability has been demonstrated with the valve restricted to 60 . l

h. Valve 246AV: the installation c' configuration of valve 246 is not clearly defined. Previous submittals describe it as having valve 231, blocked at 60 open, upstream preceded by the 45 elbow,. shaft 90' out of plane, and the 90 elbow, shaft in plane,' flow direction unknown.

The latest submittal indicates that the proposed installation con-figuration will reflect Figures 9 and 10 and test configuration 29 and 32 of the Allis Chalmer's report.-

The analysis presentett has considered valve orientations illustrated in Figures 9 and 10 and test 29 and 32 of the Allis Chalmer's report.

(In addition to a valve closing time of'9 and 14 seconds.) The minimum l operator output is 3,300 ft-lb while shaft torque . limit is 2,200 f t-lbs.

For the four conditions analyzed by NPPD, the maximum torque, dynamic l plus bearing, is 680 ft-1bs. When the installed valve orientation corresponds to one of the two analyzed and submitted, operability has been demonstrated.

4.3 A stress analysis was provided and is defined as representing a worst case condition of LOCA torques imposed on critical valve parts. The LOCA load imposed a load of 1,239 ft-lbs on Bettis Operator Model 744A-15R. Coupling the results of this analysis with the torque absorptien ratings of the valve operators, the staff concludes that the structural integrity of the critical valve and actuator parts has been demonstrated.

4.4 NPPD reports that a stress calculation of a result of seismic loads was submitted for these valves in the form of Allis Chalmer Report VER-0993  ;

in 1972. J 5.0 Summary We have completed our review of the operability of containment purge and vent valves for Cooper Nuclear Station. Sections 4.1, 4.2, 4.3, and 4.4 of the evaluation are the basis for the conclusion. We find that the information as I

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c 6-described in the submittals demonstrates the ability of the valves to close a0ainst the buildup of containment pressure in the event of a LOCA. This con-clusion is subject to the valves being modified to have the necessary torque switch readjustments, limit stops, and flow orientations as necessary to conform to the analyses.

Principal Contributor: R. Wright Dated: July 10,1981 1

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