ML13331A232
| ML13331A232 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 10/23/1987 |
| From: | Medford M SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| IEB-85-003, IEB-85-3, NUDOCS 8710290131 | |
| Download: ML13331A232 (6) | |
Text
IEB 85-03 Southern California Edison Company P. 0. BOX BOO 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 M. 0.
MEDFORD TELEPHONE MANAGER OF NUCLEAR ENGINEERING (818) 302-1749 AND LICENSING October 23, 1987 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555 Gentlemen:
Subject:
Docket No. 50-206
^.
Response to Request for Additional Information Concerning IE Bulletin 85-03 San Onofre Nuclear Generating Station u>
Unit 1
References:
- 1) IE Bulletin 85-03, "Motor-Operated Valve Common Mode Faflures During Plant Transients Due to Improper Switch Settings,"
dated November 15, 1985
- 2) May 19, 1986 letter from 3. L. Rainsberry (SCE) to
- 3. B. Martin (NRC - Region V),
Subject:
Docket Nos. 50-206, 50-361 and 50-362, San Onofre Nuclear Generating Station, Units 1, 2 and 3
- 3) September 22, 1987 letter from R. P. Zimmerman (NRC Region V) to Kenneth P. Baskin (SCE)
Reference 1 requested Southern California Edison (SCE) to develop and implement a program to ensure that switch settings on certain safety-related motor operated valves are selected, set and maintained correctly to accommodate the maximum differential pressures expected on these valves during both normal and abnormal events within the design basis. By Reference 2, SCE provided a description of the program requested by Reference 1 for San Onofre Units 1, 2 and 3.
By Reference 3 the NRC requested specific additional information needed to assure valve operability before the San Onofre Unit 1 program (Reference 2) can be approved. Accordingly, SCE hereby provides the responses to the 87lO290131~ 671023 PDR ADOCK 0)5000206 PDR I
Document Control Desk October 23, 1987 Reference 3 requests for additional information (Enclosure 1) which assure valve operability. Based on the enclosed information, no revision to the San Onofre program (Reference 2) has been made.
If you would like additional information concerning this matter, please let me know.
Subscribed on this otdday of 6 02e00A,, 1987.
Respectfully submitted, SOUTHERN CALIFORNIA EDISON COMPANY By:
P?__________
M. 0. Medford Manager of Nuclear Engineering and Licensing Subscri bed and sworn to b fore me this day of.
/1__
___7_
OFFICIAL SEAL C. SALLY SEBO Notary Public-California
}.
LOS ANGELES COUNTY Notary Public i and for the County of My Comm. Exp. Apr. 20, 1990 Los Angeles, State of California My Commission Expires: q
-t.-0
/9 Enclosure cc: D. F. Kirsch, Director, Division of Reactor Safety and Projects, Region V
- 3. 0. Bradfute, NRR Project Manager, San Onofre Unit 1
- 3. B. Martin, Regional Administrator, NRC Region V F. R. Huey, NRC Senior Resident Inspector, San Onofre Units 1, 2 and 3 RAI for San Onofre Unit 1 SCE RESPONSE TO NRC QUESTIONS CONCERNING IE BULLETIN 85-03, ACTION ITEM "e", RESPONSE
- 1. "Has water hammer due to valve closure been considered in the determination of pressure differentials? If not, please explain."
Response
Water hammer was not considered in the determination of pressure differentials. Water hammer is not considered a design criterion by the ASME code, nor (due to its transient nature) could it result in a sustained differential pressure (d/p) which would affect motor-operated valve response time. The design characteristics of the valves tested (size, rating, stroke time) remain the same as the original design. If a pressure differential due to water hammer were to occur during a valve open signal, full thrust would be applied until the valve is off its seat, at which time no d/p would exist. Accordingly, it would not be appropriate to consider water hammer in MOV testing.
- 2. "On Page 3 of Attachment 1 of the response of 05-19-86, MOVs 18 and 19 are identified as part of the AFW system. In Zone B-3 of drawing 5178110-1,.these valves are shown on the discharge side of the HPSI system. Please resolve this apparent discrepancy."
Response
MOVs 18 and 19 are on the discharge side of the charging pumps and are actually classified as part of the Reactor Coolant Pump system. They provide a flowpath bypassing the reactor coolant pump seal injection filters that allows for cold leg injection to the reactor coolant system. These valves are controlled by hand switch in the Control Room.
There are no automatic functions associated with the valves. After safety injection has occurred, these valves are opened as a part of the sequence to align cold-leg injection to the RCS. Although not part of the requested HPSI system, SCE included these valves since they could see a d/p during a safety injection operation and thus meet the intent of the selection criteria for IE Bulletin 85-03. They were added.to the Auxiliary Feed Water system page as a matter of convenience due to space. The "Valve Function" description listed in the table for these valves is correct.
-2
- 3. "On Drawing 5178115-6, zones G-5, G-7, C-4 and C-6, valves 853A, 853B, 851A and 8518 of the HPSI system are shown as P/H valves. On Figure 4.1 (revised per Appendix C) they are shown as MOVs. Please resolve this apparent discrepancy. If they are MOVs, revise Attachment 1 of the response of 05-19-86 to include these valves."
Response
The valves HV-851A, HV-851B, HV-853A, HV-853B are shown on drawing 5178115-6 correctly. They are pneumatic/hydraulic valves and do not meet the selection criteria for IE Bulletin 85-03. Figure 4.1 of the Final Safety Analysis is not current. SCE is currently updating the FSA per 10 CFR 50.72(e)(3)(ii).
The updated FSA will reflect the current configuration.
- 4. "Please expand the proposed program for action items b, c, and d of the bulletin to include the following details as a minimum: (a) commitment to a training program for setting switches, maintaining valve operators, using signature testing equipment and interpreting signatures, and (b) description of a method possibly needed to extrapolate valve stem thrust measured at less than maximum differential pressure."
Response (a):
SCE has established a formal training program, accredited by INPO, for maintenance personnel who perform work on Limitorque motor operated valves. This includes setting of switches and maintaining valve operators. SCE also has designated personnel who use valve signature testing equipment and interpret these signatures. At least one person of any crew performing maintenance on MOVs must have completed this training program. These individuals have participated in a SCE formal training program, also accredited by INPO. However, SCE reserves the ability to use Vendors of the equipment in use to perform these functions in lieu of a SCE formal training program.
Response (b):
As specified in Action Item "b" of the bulletin response, the valve stem thrust was calculated for the tabulated design basis differential pressure. These calculations were performed separately for gate, globe, and butterfly valves. For all valves the calculations included stem blowout force and packing drag (based on design pressure or maximum differential pressure, whichever was greater).
For gate valves, gate drag was included using maximum differential pressure. Double drag calculations were performed for all gate valves since a pressure differential can exist between the body and both the upstream and downstream piping. For globe valves, a plug force was also included.
These forces established a minimum required thrust to open and close the valve and a maximum required running thrust. The motor stall thrust values were then used to assure the maximum stem stress intensity will not be exceeded.
-3 As established by the plan for Action Item "c", the valves are tested against full d/p and then correct switch settings are established. The minimum thrust provided to open the valve is a value at least two and a half times the running thrust based on the d/p test MOVATS data. If the thrust at torque switch trip is less than the unseating thrust, then the torque switch bypass setpoint is set out further in time than the point of transition to running thrust. The minimum closing thrust setpoint is the opening thrust if the value is based on the design basis test, otherwise the stem blowout force is added. The bypass (protection) margin limit switch is based on the above setpoint determination and the valve stroke time. This setpoint is at 25+/- 5% for gate valves and 20+/- 5% for globe valves.
For tests that cannot be performed at full d/p, linear extrapolation from the actual test pressure to the design basis pressure is performed to obtain the maximum thrust. This method is verified as sufficient by ensuring the torque bypass limit switch is set beyond in time the peak thrust values as shown on the MOVATS valve signature and by utilizing a minimum open thrust value of 2 1/2 times the running thrust.
This has been demonstrated satisfactory on valves tested with full d/p.
As stated in the response to Action Item "d", the values for minimum required thrust and maximum allowable thrust are approved and added (see attached) through the engineering design change process to the valve electrical elementary diagrams.
GEH:8976F
Attachment to RAI for San Onofre 1 THRUST SETPOINT DETERMINATION SHEET VALVE NUMBER VALVE TYPE ACTUAL TEST PRESSURE ____ PSI DESIGN BASIS PRESSURE _____ PSI AS LEFT DATA OPEN LB CLOSE _____ LB PRESSURE TEST DATA OPEN _____ LB CLOSE LB (unseating thrust)
(total thrust)
CALCULATION DATA FOR OPEN LB CLOSE _____ LB MINIMUM REQUIRED THRUST RUNNING THRUST OPEN LB CLOSE _____ LB TIME AT TRANSITION VALVE STROKE TO RUNNING THRUST SECONDS TIME SECONDS TIME AT WHICH TORQUE SWITCH BYPASS LIMIT SWITCH DROPS OUT OF CIRCUIT SECONDS MINIMUM REQUIRED THRUST OPEN LB CLOSE LB PULLOUT THRUST AT 100%
VOLTAGE LB STALL THRUST AT 75%
VOLTAGE LB STALL THRUST AT 100%
VOLTAGE LB MAXIMUM ALLOWABLE THRUST OPEN LB CLOSE LB CORRESPONDING MAXIMUM STEM STRESS INTENSITY MAXIMUM ALLOWABLE STEM STRESS INTENSITY TORQUE SWITCH BYPASS SETPOINT TO BE SET AT _____
+
PERCENT OPEN ON THE OPEN CYCLE. SET AT 99 + 1% ON THE CLOSE CYCLE.
COMMENTS: