ML20004A965
| ML20004A965 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 05/21/1981 |
| From: | Marsolais L VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | Ippolito T NRC |
| References | |
| FVY-81-83, NUDOCS 8105270053 | |
| Download: ML20004A965 (6) | |
Text
l ' VERMONT Y AN KEE NUCLEAR POWER CORPOR ATION C, '7 SEVENTY sEVEN GROVE STRECT RUTLAND, VEIO10NT 0r701 REPLY 70 ENGINEERING OFFICE
'6 ?? WORCESTER WMD FR AMINGH AM. M ASS ACH U 47Y S 01701 TELEPHONE 817 872 8100 FVY-81-83 Esy 21, 1981 P
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Mr. T. A. Ippolito
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2 0 I98I sh. 79 l
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United States Nuclear Regulatoiy Commission Washington, D. C.
20555 1,
- '88 8DN w/
Ref ere nc es :
(a) Docket 50-271
>).,/
(b) USNRC letter of March 3, 1981 N
63
Subject:
Additional Information on Containment Purge and Vent Valves
Dear Sir:
Enclosed please find a copy of your questionnaire with responses inserted as applicable.
We trust this information is satisfactory; however, should you have any questions, please contact us.
Very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATION 19 aw 4
HCS/jgh Enclosure F
I 052700 $$
va REQUEST FOR ADDITIONAL INFORMATION VERMONT YANKEE NUCLEAR POWER STATION CONTAINMENT PURCING DIF.ING NORMAL PLANT OPERATION MECHANICAL OPERABILITY DEMONSTRATION Question 1.
a.
Was the Allis Chalmer's (AC) test report A-C, VER-0209 used as the basis for predicting valve loading results f rom the DBA-LOCA postulated?
Answer:
Yes.
Question b.
What test numbers in the AC report apply to these valves?
Answer:
The AC test numbers that correspond to specific valves are:
Valve SB-6, #21; SB-16-19-7A #29; SB-7, #32; SB-16-19-7B,8,10, #30; SB-16-19-9; #31, SB-16-19-23, #22.
Question c.
Was the peak containment pressure resulting from the DBA-LOCA used for the " Initial Upstream Pressure" (as used in the AC report)?
If not, provide the rationale used to allow use of a lower " Initial Upstream Pressure." Discuss inst rument lag times used, actual valve closure times or Tech. Spec. allowable times as they apply.
Answer:
The " Initial Upstream Pressure" used in the A.C. report was taken from the Mark I containment Load Definition Report (LEL). The peak containment pressure given the LDR report was used for the torque calculations.
150 psi was used for the stress calculations.
Question 2.
What were identified as the critical parts in these valves (shaft, disc to shaft pins, other)? What were the stresses calculated? Do they include simultaneous seismic loading?
What are the design allowable stresses? What code or standards are the valves designed to?
Answer:
The requested information is tabulated below. The calculated stresses include simultaneous seismic loading, calculated using the original VY seismic analysis and static valve conditions. The values in parenthesis indicate the fraction of stress due to scismic loading.
Stresses are calculated using normal static forces at 150 psi rated pressure.
Calculated Stress Valve Critical Part Pressure & Seismic Design Allowable 8" SB-6 Shaft 461 psi (seismic.15%)
30,000 psi Di sc-be nding 5,500 psi (seismic.01%)
22,500 psi Beari ngs 362 psi (seismic.15%)
20,000 psi Operator Mounting Bolts 793 psi (seismic 27%)
54,000 psi Flange-clamping force 203 lb. seismic 1,870 lb. by bolts
18L SB-7, SB-16-19-7A B,8,9 5 10 Disc-bend ing 6,690 psi (seismic.1%)
27,500 psi Shaft 4,250 psi (seismic.1%)
30,000 psi Bearings 3,200 psi (seismic
.1%) 20,000 psi Operator Mounting Bolts 271 psi (seismic 22%)
54,000 psi Flange-clamping force 363 lb. seismic 8,810 by bolts 6" SB-16-19-23 Information will be supplied at a later date when received from the ve nd or.
Since this valve was manufactured to the same specifications criteria as the valves identified above, and supplied by the same vendor, it la reasonable to assume it will be satisfactory also.
- 21 shows the maximum torque f'r SB-6 to As an example of torque induced stress, test be 175 ft-lb., resulting in a stress of 3,700 psi. Total shaft aljouable stress is 30,000 psi.
It can similarly be shown for the other valves that the torque induced stresses are well within the design margin.
These valves are designed to the following codes and standards:
AWWA Standard C504-66 USASI Std. for ASA B16.1 150 cast iron flange, for end flange dimensions USASI B16.5 for hydrostatic test Manufacturers Standardization Society Standard Practice SP-61, 1961 Edition for Seat Leakage Test Question 3.
De the operators have maximum torque rating (s) as established by the manufacturer? How does it compare to the maximum torque developed during the accident postulated? Does combined loading of spring and dynamic torque af fect any parts of the operator to the extent that they become the limiting factor?
Answer:
Yes, the operators have a rated torque. No parts of the operator become the limiting factor.
See answer to Question 4 for torque margin information.
Question 4.
Is there sufficient torque margin available from the operator to overcome the torques developed that tend to oppose valve closure as the valve strokes from its initial open position to the fully seated position. What is the minimum margin available and at what disc angle does this minimum exist?
Answer:
Sufficient torque margin is available for the situation de sc ribe d. The requested information is tabulated below.
Disc Angle at Margin (available torqua-Valve Minimum Margin opposing torque)
SB-6 20 open 302.2 ft.-lb SB-7 50 open 443 ft.-lb SB-16-19-7A 400 open 461.8 ft.-lb S B-16-19-8,10 1C0 455 ft.-lb open F3-16-19-9 200 open 459 ft.-lb A-16-19-23 250 open 41 ft.-lb dB-16-19-7B (Information to be supplied later)
Question 5.
For those valve assemblies (with air operators) inside containment, has the containment pressure rise (backpressure) been considered as to its affect on torque margins available (to close and seat the valve) from the actuator? During the closure pe 'od, air must be vented from the actuators opening side throub.. the solenoid valve into this backpressure.
Discuss the installed actuator bleed configuration and provide basis for not considering this backpressure affect a problem on torque margin. Valve assembly using 4-way rolenoid valve should especially be reviewed.
Answer:
The valves in question are outside containment.
Question 6.
Describe the extent to which the valve assembly (valve and operator) is seismically qualified?
Answer:
These valves are designed for a horizontal seismic coefficient of.14g.
As the calculations show, seismic stresses are a small percentage of normal stresses. These in turn are a small percentage of allowed stresses. These valves are considered to be fully qualified.
See note under Item 2.
Question 7.
Describe the extent to which the pilot solenoid valves are seismically qualified and environmentally qualified for long-term exposure to the normal plant environment.
If the purge valves are to be operative post-LOCA, describe the extent to which the solenoid valves are environmentally qualified for the LOCA environment. Do the elastomeric parts, solenoids, etc. have a qualified design life where periodic replacement of parts is required?
Answer:
The pilot solenoid valves in question are being evaluated j
under IE Bulletin 79-Olb.
Question 8.
Describe the extent to which the operators are seismically qualified and environmentally qualified for long-term exposure to the normal plant environment?
If the purge valves are to be operative post-LOCA, describe the extent to which the operators are environmentally qualified for the LOCA environment. Do the clastomeric parts in the operator have a qualified design life where periodic replacement is required?
Answer:
See answer to question 7. !
Qusstion 9.
Do tha clastom2ric pirts in the valva body h va a qunlified design life? Are they required to be replaced periddically?
- ~
Answer:
The seats of the subject valves are made of Nordel.
These seats are replaced as dictated by the results of periodic type "C" leak rate testing performed on these valves as required by Vermont Yankee's ISl program.
Question 10.
Have the manuf.acturer's recommended preventive maintenance instructions (lubrication, etc.) been reviewed for the valve, operator i vi solenoids and are they being followed?
Answer :
Manufacturers preventative maintenance instructions are being reviewed and they will be followed as applicable to our installation. Valves have been under surveillance test and containment leakage test programs.
Question 11.
Where air operated valve assemblies use accumulators as the fail-safe feature, describe the accumulator air system configuration and its operation.
Provide necessary faformation to show the adequacy of the accumulator to stroke the valve i.e., sizing and operation starting from lower limits of initial air pressure charge. Discuss active electrical components in the accumulator system, and the basis used to determine their qualification.for the environmental conditions experienced. Is this system seismically designed?
Answer Accumulators are not used. Valve operator is air to open, spring to close.
Question 12.
Provide an assessment of the structural capability of any ducting or piping in the purge system which is upstream or downstream of the valves and is exposed to the flow condition associated with the LOCA and the seismic event. The staff is particularly interested in the ef fects that loose debris from the pipe or duct system may have on the closure capability of these valve s.
Answer:
The piping system downstream of the containment isolation valves leading to the Standby Cas Treatment System (SBCT) is constructed of pipe, fittings, and valves designed to 100 psi.
This exceeds the containment design pressure or 56 PSI.
The Primary Containment Atmosphere Control Piping penetrations are designed with a tail piece that projects into the containment.
The drywell connection is high up, far from any inside equipment. The torus connection is on top of the toru s. No additional provisions were made in the original design to prevent entrance of debris.
In addition, in the small BWR containments, there is not much that could generate debris; therefore, it is not likely that debris would be carried into the piping. The redundant back-up valves are located far from the containment, further reducing the probability of debris preventing containment isolation. -
e V;rn:nt Yankea cencludas that th:re io little er no possibility of debris entering the piping from the containment atmostphe're, or being generated in t'he piping.
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