ML20215B431
| ML20215B431 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 06/10/1987 |
| From: | Heider L YANKEE ATOMIC ELECTRIC CO. |
| To: | Murley T NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM), Office of Nuclear Reactor Regulation |
| References | |
| FYR-87-63, GL-87-06, GL-87-6, NUDOCS 8706170326 | |
| Download: ML20215B431 (7) | |
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Telephone (617j 872-8100
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TWX 710-380-7619
^ YANKEEATOMIC ELECTRIC COMPANY
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1671 Worcester Road, Framongham, Massachusetts 01701' w.
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i June 10, 1987 l
FYR 87-63 United States Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 Attention:
Office of Nuclear Reactor Regulation j
Dr. T. R. Murley, Director
References:
(a) -License No. DPR-3 (Docket No. 50-29)
(b) USNRC Generic Letter 87-06 Subj ect:
Primary Coolant System Pressure Isolation Valves (GL 87-06)
Dear Sir:
The USNRC in Reference (b) requested information concerning the leak tight integrity of the reactor coolant pressure boundary at Yankee Nuclear-Power Station (YNPS).
Included in Reference (b) was a definition of Pressure Isolation Vs.lves (PIVs) to be used in this study.
Yankee has performed the requested study, and the results, including identification of all PIVs and a description of the measures performed to ensure the integrity of those valves is attached.
Yan~kee utilizes continuous monitoring techniques and periodic surveillance to ensure that valve leakage is detected in the early-stages and the appropriate actions taken to preclude-gross leakage caused by valve-failure. These measures provide a high level of-assurance that the leak tight integrity of the PIVs, as independent barriers against abnormal leakage, rapidly propagating failure, and gross failure of the reactor coolant pressure boundary, is being maintained.
8706170326 B70610 PDR ADOCK 05000029 Ap p
PDR p
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i United States Nuclear Regulatory Commission FYR 87-63 Attention:
Dr. T. E. Murley, Director June 10, 1987 We trust that this information is acceptable to you; however, should you have any questions please contact us.
Very truly yours, YANKEE ATOMIC ELECTRIC COMPANY L. H. Helder Vice President and Manager of Operations LHH/dlb Enclosure cc: USNRC Region i USNRC Resident Inspector, YNPS COMMONWEALTH OF MASSACHUSETTS)
)ss MIDDLESEX COUNTY
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Then personally appeared before me, L. H. Heider, who, being duly sworn, did state that he is Vice President and Manager of Operations, that he is duly authorized to execute and file the foregoing document in the name and on the j
behalf of Yankee Atomic Electric Company and that the statements therein are true to the best of his knowledge and belief.
b s'
Robert H. Groco Notary Public My Commission Expires August 29, 1991 J
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l ATTACHMFUT 1 i
Response to CL 87-06
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Pressure Isolation Valves I.
SUUTDOWN COOLING SYSTEM Pressure Isolation Valves i
MCS Suction Piping SC-MOV-551 and 553 1
MCS Discharge Piping SC-MOV-552 and 554 Provisions to Ensure RCPB Integrity J
These valves are categorized as ASME XI, Type A, and containment isolation valves. They are, however, exempted from 10CFR50, Appendix J, Type C, leak rate testing and are not leak tested by the IST Program at Yankee.
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Description The Shutdown Cooling System is utilized to remove decay heat when the Reactor Coolant System temperature and pressure is below 3300F and 300 psig.
I A flow diagram of the Shutdown Cooling System is presentd in FSAR l
Section 206.
The system takes suction from the hot leg of Main Coolant
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Loop No.
4, transfers the heat to the component cooling water through the d
shutdown cooler and injects the coolant back to Main Coolant Loop No. A cold leg.
A redundant loop parallel to this loop is also provided by the low pressure surge tank pump and. heat exchanger. The maximum design j
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pressure and temperature of this system are 425 psig and 330 F, respectively. The inlet and outlet pipe segments and the four MOVs which are located insido the vapor container are designed to operate at the 0
operating coolant pressure and temperature, 2500 psig and 650 F.
The rest of the piping and components outside the vapor container are designed for the low pressure and temperature mentioned above.
I The Shutdown Cooling System is not used during normal plant operation and the four MOVs are key locked closed with electrical power removed from the operator.
In addition, when power is restored to the operators, electrical interlocks are provided to prevent opening-one valve in each header when MCS pressure is above the design pressure of the low pressure portion of I
the Shutdown Cooling System. These measures provide adequate protection against rapid.y propagating failure and gross leakage caused by inadvertent valve actuation.
l Any minor PIV leakage occurring during normal plant operation, when the SCS is isolated, will cause the system pressure to increase to the set pressure of the SCS relief valves. These valves have sufficient capacity l
to accommodate full charging pump flow.
Relief valve discharge is normally directed to the low pressure surge tank.
Therefore, PIV leakage will not result in loss of total inventory.
Shutdown cooling PIV leakage would be reflected in an increased charging pump flow rate, which will
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automatically increase to maintain pressurizer level without a J
corresponding increase in bleed flow.
In addition to the steps taken in the SCS start-up procedure, other precautions are taken during power operation. On a monthly basis, the
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valvo control switches are verified locked closed with the keys removed, the power leads to the motor starters are verified to be removed, and the SCS safety valves are verified to be lined up.
Periodic inspections in the vapor container require that the piping between redundant isolation valves be checked for evidence of leakage resulting in warmer than expected downstream piping.
Although diagnostic procedures must be employed to isolate the source of leakage into the low pressure surge tank, adequate.information is available to detect PIV leakage and take the required action to protect-the low pressure SCS piping and ensure the integrity of the reactor coolant pressure boundary.
II.
SAFETY INJECTION SYSTEM Pressure Isolation Valves Loop 1 SI-V-18, 665, and 669 (Check Valves)
Loop _2 SI-V-20, 664, and 668 (Check Valves)
Loop 3 SI-V-21, 663, and 667 (Check Valves)
Loop 4 SI-V-19, 666, and 670 (Check Valves)
Description i
A flow diagram of the Safety Injection System is presented in FSAR I
Section 212.
The system is aligned during normal plant operation for the injection mode with all line valves open.
The PIVs (check valves) are categorized as ASME XI, Type A; however, they J.
are not subject to leakage testing by the IST Program at Yankee.
h Instead, PIV leakage detection is provided by a pressure switch located j
it the common low pressure piping of both the high and low pressure g
injection headers. The pressure switches alarm in the Control Room.
a Although not classified as a PIV, a third high pressare check valve, located within the RCPB in series with the valves listed above, provides added protection against overpressurization of connected low pressure piping due to PIV leakage.
Each header is provided with a relief valvo of sufficient capacity to protect the low pressure piping from overpressure caused by check valve back leakage. The relief valve discharge is directed to the vapor container via a tupture disc set at 240 psig.
Any fluid discharged will be detected by the installed leakage detection systems.
The RCPB leakage deteltion systemt at Yankee were the subject of extensive review dur'ing the Integrated Plant Safety Assessment Systematic Evaluation Program (dEP) (NUREG-0825).
The acceptability of these systems in meeting the leakage detection requirements of Standard Review Plan 5.2.5, Reactor Coolant Pressure Boundary Leakage Detection, is documented in the staff's SEP Final Report, NUREG-0825, dated June 1983.
Periodic inspections require that the piping between redundant isolation valves be checked for evidence of leakage resulting in warmer than expected piping.
Although valve seat leakage testing is act performed on these valves, sufficient measures are in place to control and monitor PIV leakage and take the required actions to protect the low pressure safety injection piping and ensure the integrity of the reactor coolant pressure boundary. ]
III. MAIN COOLANT DRAIN AND SAMPLE SYSTEM Pressure Isolation Valves Common Line Isolation Valvect Loop 1 Loop 2 Loop 3 VD-MOV-510 VD-V-719 VD-V-733 VD-V-734 SA-MOV-511 VD-MOV-505 VD-MOV-506 VD-h0V-507 i
High Pressure Loop 4 Pressurizer Bleed Sample VD-V-735 VD-MOV-509 SA-V-513*
VD-JOV-508 Description A flow diagram of the main coolant drain and sample piping is presented 1
in FSAR Section 201.
This system is not utilized during normal plant operation. The sample system outside containment is designed for full main coolant pressure.
Connection to lower pressure systems outside tho vapor container is made through normally closed isolation valves located outside the Reactor Coolant Pressure Boundary (RCPB). As defined in 10CFR50.2, the RCPB extends to the outboard containment isolation valves I
for systems which penetrate containment.
Thus,'VD-TV-202 and SA-TV-206 form the interface boundary. These valves are classified as ASME XI, j
Type A, and are subject to seat leakage testing in accordance with 10CFR50, Appendix J, as containment isolation valves. However, since these valves are normally open, the RCPB pressure isolation function is performed by the normally closed valves identified above.
As discussed above, this piping is isolated from low pressure systems outside the RCPB during normal operation, and the interfacing sample system piping is designed for full primary pressure.
Any leakage past any of the PIVs identified above will be detected by the primary system water balance performed once every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, which is capable of detecting leaks less than 1 gpm.
Diagncstic procedures will be required to isolate the source of leakage, however, the plant will be shut down if RCPB leakage exceeds Technical Specification limits.
- Valves VD-MOV-510 and SA-MOV-511 do not provide series isolation for SA-V-513. - -
a IV.
MAIN COOLANT VENT SYSTEM Pressure Isolation Valves Reactor Vessel Head Vent / Pressurizer Vent o
PR-MOV-558, 559,_560, and 561 Description A flow diagram of the Main Coolant Vent System is presented in FSAR Section 201.
The system discharges to containment via a rupture disc. set at 240 psig.
Gross leakago will be detected by the installed Main Coolant Leakage Detection Systems. Total maximum leakage is limited to a value less than the normal primary make-up capacity by an installed restriction orifice.
l Minor leakage will be directed to the low pressure surge tank and will not result in a loss of total primary inventory.
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Diagnostic procedures will be required to locate and isolate the source of RCPB leakage. However, overpressurization of connected piping is not possible since the drain path is lined up to the low pressure surge tank, the maximum flow rate is limited, and the piping is protected with a rupture disc.
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l Although valve seat leakage testing is not performed on these valves, sufficient controls and procedures are in place to monitor and control PIV leakage to protect the low pressure piping and ensure the integrity of the RCPB.
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