ML20054L048
| ML20054L048 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 06/30/1982 |
| From: | Garrity J Maine Yankee |
| To: | Clark R Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.D.1, TASK-TM GL-81-36, JHG-82-120, MN-82-124, NUDOCS 8207070110 | |
| Download: ML20054L048 (6) | |
Text
.
1
- 'i ' HAllHEE Arom/CP0l1/ERCOMPARH e aucugr,j,in"gQ's lilAlllE }b' (207) 623-3521 O
June 30, 1982 MN-82-124 JHG-82-120 United States Nuclear Regulatory Commission Washington, D. C. 20555 Attention:
Mr. Robert A. Clark, Chief Office of Nuclear Reactor Regulation Operating Reactor Branch #3 Division of Licensing
References:
(a) License No. DPR-36 (Docket No. 50-309)
(b) USNRC Letter, dated September 29, 1981 (c) MYAPCo Letter to USNRC dated March 30, 1982,,MN-82-65
Subject:
Evaluation of Safety and Relief Valve Operation
Dear Sir:
The purpose of this letter is to provide the Maine Yankee Atomic Power Company response to the WC request for a July 1,1982 submittal that addresses the functionability of the pressurizer safety valves and power-operated relief valves (FORV's) that are installed in the Maine Yankee sy stem.
Item II.D.l. A of NUREG-0737 required that utilities operating and/or constructing Pressurized Water Reactor (PWR) power plants provide evidence, l
si.pported by test, of safety and relief valve functionability.
l In response to these requirements, the Electric Power Research Institute (EPRI) implemented a generic test program on behalf of the PWR utilities.
Maine Yankee has been a participant in the EPRI Program.
The NRC Generic Letter 81-36, dated September 19, 1981, contains a schedule for the submittal of test results and the submittal of plaht-specific reports.
In accordance with this schedule, Iesults of the EPRI program summarized in various EPRI reports, were forwarded to the m.: on April 1, 1982, in parallel with distribution to the participating utilities.
l l
l B207070110 B20630 PDR ADDCK 05000309 e
eor p
l M AINE Y ANKEE ATOMIC POWER COMPANY United States Nuclear Regulatory Commission June 30, 1982 Attention: Mr. Robert A. Clark Page 2 The utilities operating and constructing Combustion Engineering (C-E) designed plants have, through the C-E Owners Group, requested that C-E implement a program to evaluate and apply the EPRI test results. To facilitate an expeditious evaluation of the test data, the C-E Owners Group program was initiated in April,1982, and is currently in progress. Maine Yankee is a participant in this program.
The approach taken by the C-E Owners Group is to show that particular EPRI tests were directly representative of plant-specific safety and relief valve models and valve installations, and that acceptable valve operation was demonstrated. The portion of the program related to PORV's has already been completed.
Accordingly, C-E Report CEN-213, entitled " Summary Report on the Operability of Power Operated Relief Valves in C-E Designed Plants," is being forwarded separately to the NRC by the C-E Owners Group. Maine Yankee considers Report CEN-213 to provide the required information on PORV operability for Maine Yankee.
A review of the EPRI tests has determined that the safety valves used at Maine Yankee were represented in the EPRI Program and the test conditions enveloped the range of fluid conditions recommended by NUREG-0737. Safety valve discharge for Maine Yankee is limited to steam conditions.
Currently detailed plant specific evaluation and application of the EPRI data is being performed as part of the Owners Group Program.
In addition, iq3ut from the valve manufacturers is being requested.
That information is expected to be received during the third quarter of 1982, and will then be incorporated into the C-E evaluation.
If valve adjustments are necessary, they will be identified in the C-E evaluation based on performarce demonstrated by the EPRI Tests. The results will be presented in a C-E Owners Group Report that is scheduled for completion in December,1982. Since Maine Yankee is a participant in the program, the operability of safety valves in the Maine Yankee System (s) will be addressed by this report.
Our intent is to provide you with a final report, which will serve as our final submittal, by December 31, 1982.
Plant specific information is attached in Appendix A as follows:
1.
Description of overpressure protection system 2.
Test condition justification 3.
PORV operability 4.
Safety valve operability 5.
Block valve operability 6.
Plant s3ecific piping analysis
MQlNE YANKEE ATOMIC POWER COMPANY United States Nuclear Regulatory Commission June 30, 1982 Attention: Mr. Robert A. Clark Page 3 Maine Yankee will submit further information in accordance with the following schedule.
1.
Additional plant specific test condition justification 8/1/82 2.
Final safety valve operability justification with CE Owners Group 1/1/82 3.
Final plant specific piping evaluation 1/1/83 Very truly yours, MAINE YANKEE ATOMIC POWER COMPANY J. H. Garrity, Senior Director Nuclear Engineering & Licensing JHG:pjp Attachment - Appendix A (3 pages)
MAINE YANKEE ATOMIC POWER COMPANY APPENDIX A 1.
Description of Over-Pressure Protection System The OPPS at Maine Yankee is comprised of the following Components:
Three Code Safety valves Model Number 31709KA manufactured tyf Dresser Industries with set points of 2485, 2510, and 2535 psig, respectively.
Two-Power Operated Electromatic Relief Valves Model Number 31533VX manufactured by Dresser Industries with a set point of 2400 psig.
Two PORV Block Valves which are 2-1/2" solid wedge gate valves manufactured by Anchor Darling and equipped with Limitorque SMB-00-10 motor operators.
Each safety valve has its own 3" inlet pipe without a loop seal that discharges into individual 6" discharge lines which are combined downstream into a 10" line to a quench tank located at the bottom of the containment.
The PORV's are tee'd from a common pressurizer nozzle with 3" lines to the 2-1/2" block valves and via 2-1/2" lines to the PORV's.
The PORV's discharge into 4" lines which are cotpled via a 6" header to the same tank as the safety valves.
2.
Test Condition Justification A report prepared by Combustion Engineering as part of the EPRI Test Program was submitted by David Hoffman from Consumers Power Company.
That submittal was referenced by Maine Yankee in our submittal on March 30,1982 (Reference c).
As a result of that report, additional work was performed by Maine Yankee to analyze the case of an extended HPSI event.
Maine Yankee is unique to other C-E designed plants in that the HPSI pumps are capable of lifting the PORV's.
Based on conservative application of HPSI pump head / flow performance and set point tolerances, the two HPSI pumps are also marginally capable of lifting the safety valves.
The flow for the extended HPSI condition is less than 200 gpm per pump at the PORV set point and less than 100 gpm per pump at the safety valve set point A plant specific analysis of the extended event has been performed by Maine Yankee utilizing a Retran model.
The results of that analysis shows the PORV openirg on steam.
Transition to water will not occur since it is assumed that operator action will be taken within 20 minutes. A worst case conservatively analyzed event disregarding the PORV's would result in a transition to liquid discharge out through the safety valves after a period of 27 minutes.
This is more than ample time for the operator to take action to trip the HPSI pump, and normalize pressurizer conditions.
' 06-30-82 m
o MAINE VANKEE ATOMIC POWER COMPANV Additionally, even without operator action the PORV's would successfully pass the water which falls within the as-tested condition in the EPRI Test Program. One PORV is more than sufficient to avoid a challenge to the safety valves on any extended HPSI Event.
3.
NRV Operability As reported in the cover letter, the PORV operability for Maine Yankee is evaluated in C-E Report CEN-213 entitled, " Summary Report on the Operability of Power-Operated Relief Valves in C-E Designed Plants."
4.
Safety Valve Operability Maine Yankee's safety valves are located on longer inlet lines than most other C-E designed plants.
The inlet line lengths run from 12 to 14 feet for the three safety valves. Maine Yankee has initiated an engineering analysis of the inlet piping with the plans to shorten the inlet piping since the results of the EPRI Test Program indicated that stable valve operation can best be assured with short inlet lines.
Although Maine Yankee has inlet line lengths more typical of plants with loop seals, the piping is arranged to insure that steam only is contained in the inlet piping.
Maine Yankee did perform in-site tests on the safety valves during the Hot Functional Test Program in 1972. At that time, each valve was blown as orginally installed. A total of 8 tests were successfully run with some setpoint adjustments made during the tests.
The inlet / discharge piping and quench tank arrangement is the same today as during those tests.
The test was run by raising the pressurizer pressure by a combination of pressurizer heaters and charging pumps.
In l
all cases, stable blowdown was witnessed by experienced personnel in-side the containment.
After the tests were completed, safety valve maintenance required only minor seat relapping. There was no damage to the valves or indication that other than stable smooth blowdown had occurred.
In spite of these successful in-site tests, as previously discussed, Maine Yankee is proceeding with a redesign of the safety valve inlet piping to shorten the existing piping.
The results of that effort in combination with detailed evaluation and application of the EPRI Data which is being performed as a part of the Owners Grote will be submitted to the USMC by 1/1/83.
5.
Block Valve Operability The block valves at Maine Yankee are Anchor Darling 21/2" wedge gates equipped with SMB-00-10 operators.
The design of these valves is very similar to the Velan 3" gate valves successfully tested in the EPRI Test Program at the Marshall Steam Station.
l 06-30-82
MAINE YANKEE ATOMIC POWER COMPANY Followirg these successful tests, Maine Yankee, upon consulation with the valve manufacturer, modified the Limitorque Operaters to increase the maximum closirg torques delivered by the motor operators. After that modification and prior to start-up following the last refueling on July 9,1981, an in-site test of the block valve closure with full flow was performed. The test was run by opening the block valve with the PORV open. Once full flow was verified, the block valve was closed.
The valve stroked opened and closed as designed. Closure time was less than 14 seconds.
The valve closed leak tight as verified by subsequent measurements.
The successful results of both the EPRI tests on similar valves and the successful in-site tests at Maine Yankee clearly demonstrate the operability of the PORV block valves as installed at Maine Yankee.
6.
Plant Specific Piping Analysis The safety and relief valve piping at Maine Yankee is arranged such that water cannot collect in either the inlet or discharge lines.
Piping loads are restricted to steam loads and the lower water loads which could occur as a result of an extended HPSI Event.
Additionally, the Low Temperature Over Pressure Protection System can impose low pressure water loads on the discharge piping for the PORV's.
Re-analysis work has started for the discharge piping. This analysis is coupled with changes in the inlet piping configuration to shorten the safety valve inlet lines as discussed in Section 4 of this appendix.
Preliminary evaluation by the contractor performing the pipirg analysis indicates that past piping analysis was sufficiently censervative such that the pipirg loads predicted for Maine Yankee based on results from the EPRI Test Program will be bounded by past piping analysis.
Maine Yankee will submit the results of the plant specific piping re-analysis which will be benched marked by the contractor to the EPRI Test Program results before 1/1/83.
I 3-06-30-82 G