ML17286B234
| ML17286B234 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 12/30/1991 |
| From: | Eng P Office of Nuclear Reactor Regulation |
| To: | Sorensen G WASHINGTON PUBLIC POWER SUPPLY SYSTEM |
| References | |
| IEB-88-008, IEB-88-8, TAC-M69707, NUDOCS 9201090243 | |
| Download: ML17286B234 (9) | |
Text
Docket No. 50-397 December 30, 1991 Mr. G.
C. Sorensen, Manager Regulatory Programs Washington Public Power Supply System 3000 George Washington Way P.O.Box 968
- Richland, Washington 99352
Dear Mr. Sorensen:
DISTRIBUTION NRC 5 Local PDRs BBoger NVirgilio TQuay PEng OGC BMozafari 14/H/25 RZimmerman, RV PD-V r/+
Plant File DFoster
SUBJECT:
REVISED RECOMMENDATIONS FOR NRC BULIETIN 88-08)
ACTION 3 AND SUPPLEMENT 3
By letter dated December 18, 1991, the NRC informed you of the NRC staff's determination that the WNP-2 response to NRC Bulletin 88-08 was consistent with the modification or monitoring alternatives stated in the Bulletin.
Our letter included an enclosure entitled, "Evaluation Criteria for Responses to NRC Bulletin 88-08, Action 3 and Supplement 3."
Although the enclosure is technically correct, further reviews have resulted in a number of editorial changes to the text.
Enclosed is the revised evaluation for your information.
No response is required.
We apologize for any inconvenience this may cause you.
Should you have any questions, please contact me.
Enclosure:
As stated cc w/enclosure:
See next page Sincerely, Original Signed By:
Patricia L. Eng, Project Manager Project Directorate V
Division of Reactor Projects III/IV/V Office of Nuclear Reactor Regulation
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Enclosure EVALUATION CRITERIA FOR RESPONSE TO NRC BULLETIN 88-08 ACTION 3 AND SUPPLEMENT 3
1.0 OBJECTIVE To provide continuing assurance for the life of the plant that unisolable sections of piping connected to the reactor coolant system (RCS) will not be subjected to thermal stratification and thermal cycling that could cause fatigue failure of the piping.
2.0 PURPOSE To provide guidelines for evaluation of licensee responses, including acceptable procedures and criteria to prevent crack initiation in susceptible unisolable piping.
3.0 IDENTIFICATION OF POTENTIALLY SUSCEPTIBLE PIPING (1)
Sections of injection piping systems, regardless of pipe size, which are normally stagnant and have the following characteristics:
A.
The pressure is higher than the RCS pressure during reactor power operation.
B.
The piping sections contain long horizontal runs.
C.
The piping systems are isolated by one or more check valves and a closed isolation valve in series.
D.
For sections connected to the RCS:
a.
Water injection is top or side entry.
b.
The first upstream check valve is located less than 25 pipe diameters from the RCS nozzle.
Examples of such sections in PWRs are the safety injection lines and charging lines between the reactor coolant loop and the first upstream check valve, and the auxiliary pressurizer spray line between the charging line and the main pressurizer spray line.
(2)
Sections of other piping systems connected to the RCS, regardless of pipe size, which are normally stagnant and have the following characteristics:
A.
The downstream pressure is lower than RCS pressure during reactor power operation.
B.
The piping systems are isolated by a closed isolation valve, or a check valve in series with a closed isolation valve.
C.
There is a potential for external leakage from the isolation valve.
Examples of piping containing such unisolable sections in PWRs are the residual heat removal (RHR) lines.
Examples of such piping for BWRs are the RHR lines and the core spray injection lines.
4.0 ACCEPTABLE ACTIONS The following actions are considered as acceptable responses to Bulletin 88-08, Action 3 and Supplement 3,
as applicable, provided that the requirements of Bulletin 88-08, Action 2 have been satisfied.
(1)
Revision of system operating conditions to reduce the pressure of the water upstream of the isolation valve below the RCS pressure during power operation.
(2)
Relocation of the check valves closest to the RCS to be at a dist-ance greater than 25 pipe diameters from the nozzle.
(3)
Installation of temperature monitoring instrumentation for detec-tion of piping thermal cycling due to valve leakage.
A.
Type and location of sensors.
a.
Temperature sensors should preferably be resistance temperature detectors (RTDs).
b.
RTDs should be located between the first elbow (elbow closest to the RCS),
and the first check valve (check valve closest to the RCS).
co For the auxiliary pressurizer spray line, RTDs should be installed near the "tee" connection to the main pressurizer spray line or on the cold portion (ambient temperature) of the line.
d.
RTDs should be located within six inches of the welds.
e.
At each pipe cross section, one RTD should be posi-tioned on the top of the pipe and another RTD on the bottom of the pipe.
B.
Determination of baseline temperature histories.
After RTD installation, temperature should be recorded during normal plant operation at every location over a period of 24
hours.
The resulting temperature versus time records represent the baseline temperature histories at these locations.
Baseline temperature histories should meet the following criteria:
a.
The maximum top-to-bottom temperature difference should not exceed 50'F.
b.
Top and bottom temperature time histories should be in-phase.
co Peak-to-peak temperature fluctuations should not exceed 60'F.
C.
Monitoring time intervals.
a.
Monitoring should be performed at the following times:
l.
At the beginning of power operation, after startup from a refueling shutdown 2.
At least at six-month intervals thereafter, between refueling outages b.
During each monitoring period, temperature readings should be recorded continuously for a 24-hour period.
D.
Exceedance Criteria.
Actions should be taken to modify piping sections or to correct valve leakage if the following conditions occur:
a.
The maximum temperature difference between the top and the bottom of the pipe exceeds 50'F.
b.
Top and bottom temperature histories are in-phase but the peak-to-peak fluctuations of the top or bottom temperatures exceed 60'F.
co Top and bottom temperature histories are out-of-phase and the bottom peak-to-peak temperature fluctuations exceed 50'F.
dt Temperature histories do not correspond to the initially recorded baseline histories.
(4)
Installation of pressure monitoring instrumentation for leakage detection in injection lines.
(Pressure monitoring is not the preferred method since pressure measurements cannot provide a measurement of thermal cycling in the unisolable pipe sections.)
f
A.
Type and location of sensors.
aa Pressure sensors should preferably be pressure transducers.
b.
Pressure transducers should be installed upstream and downstream of the first check valve.
c ~
For systems having a pressure higher than the RCS
- pressure, pressure transducers may be installed upstream and downstream of the first closed isolation valve.
(The downstream section is the pipe segment between the isolation valve and the check valve.)
Monitoring time intervals.
a.
Monitoring should be performed at the following times:
l.
At the beginning of power operation, after startup from a refueling shutdown 2.
At least at six-month intervals thereafter, between refueling outages b.
Pressure readings should be recorded continuously for a 24-hour period.
Exceedance criteria.
Actions should be taken to modify piping sections or to correct valve leakage if the following conditions occur:
a.
For pressure measurements across a check valve, the downstream pressure (RCS pressure) is equal to or less than the upstream pressure at any time during power operation.
b.
For pressure measurements across a closed isolation valve, the doi-.tream pressure is equal to or greater than the upstream pressure at any time during power operation.
Mr.
G.
C, Sorensen Washington Public Power Supply System WPPSS Nuclear Project No.
2 (WNP-2) ceo Mr. J.
W. Baker WNP-2 Plant Manager Washington Public Power Supply System P.O.
Box 968, MD 927M
- Richland, Washington 99352 Regional Administrator, Region V
U.S. Nuclear Regulatory Commission 1450 Maria Lane, Suite 210 Walnut Creek, California 94596 G. E.
C. Doupe, Esq.
Washington Public Power Supply System 3000 George Washington Way P. 0.
Box 968, MD 396
- Richland, Washington 99532 Mr.'R.
G. Waldo, Chairman Energy Facility Site Evaluation Council Mail Stop PY-ll Olympia, Washington 98504 Mr. Alan G. Hosier, Licensing Manager Washington Public Power Supply System P. 0.
Box 968, MD 956B
- Richland, Washington 99352 Mr. A. Lee Oxsen, Assistant Managing Director for Operations Washington Public Power Supply System P. 0.
Box 968, MD 1023
- Richland, Washington 99352 Mr. Gary D. Bouchey, Director Licensing and Assurance Washington Public Power Supplv System P. 0.
Box 968, MD 280 Richland>
Washington 99352 Chairman Benton County Board of Commissioners P.
O.
Box 190
- Prosser, Washington 99350-0190 Mr. R.
C. Sorensen U.
S. Nuclear Regulatory Commission P. 0.
Box 69
- Richland, Washington 99352 Nicholas S. Reynolds, Esq.
Winston E; Strawn 1400 L Street, N.W.
Washington, D.C.
20005-3502
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