ML20076G391
| ML20076G391 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 06/07/1983 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8306140656 | |
| Download: ML20076G391 (9) | |
Text
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TENNESSEE VALLEY AUTHORITY CH ATTANOOGA. TENNESSEE 374ol 400 Chestnut Street Tower II June 7, 1983 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 20555
Dear Mr. Denton:
In the Matter of the
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Docket Nos. 50-259 Tennessee Valley Authority
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50-260 50-296 By letter from D. B. Vassallo to H. G. Parris dated May 19, 1983, we received a request for information regarding the containment purge and vent valves at the Browns Ferry Nuclear Plant. The information was requested pursuant to 10 CFR Part 50.54(f). We have reviewed the Safety Evaluation enclosed with the May 19 letter. Enclosed is our response to the items listed in Section 4.0, Evaluation, of the SER.
Based on the information provided in our previous submittals and the enclosed response, we believe that we have demonstrated the ability of the valves to adequately perform their intended function in the event of a Loss of Coolant Accident. We intend to continue containment purge operations in accordance with our current technical specification limits.
Based on the enclosed information, we believe that continued operation of the Browns Ferry Nuclear Plant is justified and that there is no need to modify, suspend, or revoke the Browns Ferry licenses.
Very truly yours, TENN SSEE VALLEY AUTHORITY L.
M'. Mills, anager Nuclear Licensing Subscribed 3nd sworn to before me this 7 H day of O2 M 1983 Notary Public Q
My Commission Expires /
Enclosure cc: See Page 2 I
T F306140656 830607 PDR ADOCK 05000259 P
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An Equal Opportunity Employer
. Mr. Harold R. Denton June 7, 1983 cc (Enclosure):
U.S. Nuclear Regulatory Commission Region II ATTN: James P. O'Reilly, Regional Administrator 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30303 N'. R. J. Clark r
Browns Ferry Project Manager U.S. Nuclear Regulatory Commission 7920 Norfolk Avenue Bethesda, Maryland 20814
ENCLOSURE RESPONSE TO D. B. VASSALLO'S LETTER TO H. G. PARRIS DATED MAY 19, 1983 CONTAINMEhT PURGE VALVE OPERABILITY BROWNS FERRY NUCLEAR PLANT General Comment We believe that the NRC Staff evaluation should give further consideration to the safety concerns (i.e., personnel hazards) raised by the total restriction on purging with the reactor in a hot condition. We identified in our previous submittals and discussions with the NRC Staff that inspection requirements make personnel e.ntry into the drywell with the reactor in hot standby necessary. Without purge capability the probability of severe injury or death to one or more plant personnel over the life of the plant would be high when compared to the low probability of a LOCA severe enough to seriously challenge the purge valves occurring during purge operations.
We believe that the health and safety of plant personnel must be emphasized. Based on this comparison, we believe that the continued operation of the purge and vent valves is justified.
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1 Specific Comments 4.1 NRC Comment TVA's analysis applied torque and flow coefficients applicable to valves other than Rockwell when determining valve loading.
Historically, butterfly manufacturers establish these coefficients for their individual designs since they are known to be shape sensitive. The potential problem of misuse of flow and torque coefficients is a concern of the butterfly valve industry and is flagged in one of the industry standards, i.e.,
ANSI /AWWA C504-80.
Response
The sensitivity of disc shape to flow torque coefficient is a strong function of disc type. Offset disc flow coefficients can be very sensitive to shape, moment arm, and flow direction. However, symmetric disc flow coefficients are much less sensitive to perturbations in such parameters.
The discs in TVA's Rockwell-Edwards purge valves are symmetric discs of the Pratt anvil design. As discussed in our earlier submittals, Rockwell-Edwards closed their butterfly valve plant a number of years ago and in the process, data of flow coefficients was also lost. TVA, from drawings and inplant measurements, obtained critical valve dimensions. These dimensions were used in discussion with personnel from the Henry Pratt Valve Company to determine that the disc shape and the seat arrangement was very similar to a Henry Pratt valve design. These discussions also indicated the flow coefficients for the Pratt valve were appropriate for use with the Browns Ferry valves.
Industry standard ANSI /AWWA C504-80 was one reference source used in our operability evaluation. The note in appendix A, ANSI /AWWA C504-80, stating "The values of these coefficients should not be applied indiscriminately when calculating torque requirements for operation of valves produced by another manufacturer" was certainly applied in our evaluation. Considerable time and effort were spent to ensure torque coefficients used were appropriate and not applied indiscriminately.
O-4.2 NRC Comment TVA has not aus,essed the subject of installatian
-configuration, such as upstream fittings, shaft orientation relative to upstream elbows, disc closure direction, separation distance, etc., and the affects on torque coefficient values.
Available data shows these considerations to be a major factor affecting the dynamic torque required for valve closure.
Response
The configuration of the piping system on the fluid mixture as it relates to valve disc and shaft orientetion has been addressed. The final paragraph before the concluding remarks of our June 2,1981, submittal delineates those valves which required rotation have been rotated such that the valve shaft is in the plane of the source causing the flow change. Table 1 of the same submittal lists the pipe diameters between the purge valves and the nearest flow change. The effects of flow direction on torque coefficients and valve closure were addressed in the hydrodynamic torque section of the June 2, 1981, response.
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4.3 NRC Comment Results of the valve assembly stress analysis, analysis of the valve-operator extended structure and associated interfacing hardware under combined operating and seismic loads was not performed.
Response.
TVA's structural evaluation of the purge valves, the operators, the internals, and appurtenances was based on the combination of the LOCA loads imposed simultaneously with seismic. This evaluation showed the valve / operator assemblies to be totally qualified structurally for the load combination imposed.
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4.4 NRC Comment Operator spring torque curves were not presented for all operator models. The one curve presented should be re-evaluated with respect to the dynamic torque as discussed in 4.1 above.
This should demonstrate that each operator is capable of stroking the valve to its closed position without exceeding the torque rating (structural limitation) of the operator at any disc position.
Response
Table 1 of our June 2, 1981, submittal included the spring torques for each of the valve operators. Per our response to 4.1 above, no new analysis is necessary as hydrodynamic torques were properly considered.
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l 4.5 NRC Comment Modifications have been made to the valves to improve the closing time from approximately 15 seconds to less than 2.5 seconds. The basis for the 2.5 seconds should be justified.
Response
The purge valve closure times were reduced from 15 seconds to 2.5 seconds to ensure the standby gas treatment system would not be damaged due to pressurization. A reduction in the offsite dose was an additional benefit from this change. The change was not made as a result of our. valve operability analysis.
The valves are stroke time tested periodically as specified by the Browns Ferry Surveillance Instruction 4.7.D as requried by Technical Specification 3 7.D. i i
4.6 NRC Comment Fisher has developed torque coefficients for these valve designs based on straight pipe configured (uniform approach flow) bench tests on model valves. Coefficient values for the 10" Fisher valve for dynamic torque predictions were not used.
Response
As a result of the NRC Staff comment, we contacted Fisher Controls Company. They indicated that based on test data, they could calculate the total dynamic torque on our 9100 series valve. They did not have torque coefficient data for the Browns Ferry valve. We are entering into negotiations with Fisher to obtain the data.
There is no basis at this time for concluding our operability analysis is not totally adequate.
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