ML20154P208
| ML20154P208 | |
| Person / Time | |
|---|---|
| Site: | Millstone, Haddam Neck, 05000000 |
| Issue date: | 09/20/1988 |
| From: | Mroczka E NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| A07335, A7335, IEB-88-008, IEB-88-8, IEIN-88-001, IEIN-88-1, NUDOCS 8809300154 | |
| Download: ML20154P208 (8) | |
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EEEE General Offices
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(203) 665 5000 September 20, 1988 Docket Nos. 50-213 50-245 5M 5U U3 AU7113 Re NRC Bulletin No. 88-08 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Vashington, DC 20555
References:
(1)
C.
E.
Rossi letter to all licensees, "NRC Bulletin No. 88-08: Thermal Stresses in Piping Connected to Reactor Coolant Systems", dated June 22, 1988.
(2)
C.
E. Rorsi letter to all licensees, "NRC Bulletin No. 88-.08, Supplement 1: Thermal Stresses in Piping Connected to Reactor Coolant Systems", dated June 24, 1988.
(3)
C.
E. Rossi letter to all licensees, "NRC Bulletin No. 88-08, Supplement 2: Thermal Stresses in Piping Connected to Reactor Coolant Systems", dated August 4, 1988.
(4)
C.
E.
Lossi letter to all licenseer, "NRC Infor-mation Notice No.
88-01:
Safety Injection Performance", dated Januacy 27, 1988.
Gentlemen:
Haddam Neck Plant Hillstone Nuclear Pover Station, Unit Nos. 1, 2, and 3 Response to NRC Bulletin No. 88-08 Thermal Stresses in Piping Connected to Reactor Coolant Systems 1
Reference (1), with supporting information in References (2) and (3),
requested licensees to investigate their plants to determine if conditions which caused cracked piping at several units could exist elsewhere.
This issue vas originally raised by Reference (4).
In response to Reference (1), Connecticut Yankee Atomic Power Company (CYAPCO) and Northeast Nuclear Energy Company (NNECO) revisited 1
actions taken in response to Reference (4).
Reference (1) requests that licensees:
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U. S. Nuclcer R:gulatory Commissicn
. A07335/ Peg 2 2 September 20, 1988 i
1.
Reviev systems connected to the RCS to determine whether unisolable sections of piping connected to the RCS can be.sub-jected to stresses from temperature stratification or temperature oscillations that could be induced by leaking valves and that were not evaluated in the design analysis of the piping.
For those addressees who determine that there are no unisolable sections of piping that can be subjected to Juch stresses, no additional actions are requested except for the report required below.
I This reviev vas conducted at all four units.
At Millstone Unit Nos. 1 and 2, no such piping sections were discovered.
Therefore, for these units, no further action is required.
At Haddam Neck and Hillstone Unit No. 3, the potential for this problem does exist.
Attachments 1 and 2 describe the situations and respond to the rest of the Reference (1) action items.
Please contact us if you have any questions.
1 Very truly yours, CONNECTICUT YANKEE ATOMIC POWER COMPANY NORTHEAST NUCLEAR ENERGY COMPANY W
M/
- i E. J. fr6ckka
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Senior Vice President l
STATE OF CONNECTICUT )
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) ss. Berlin i
COUNTY OF HARTFORD
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Then personally appeared before me, E. J. Mroczka, who being duly svorn, did state that he is Senior Vice President of Connecticut Yankee Atomic Power Company and Northeast Nuclear Energy Company, Licensees herein, that he is J
authorized to execute and file the foregoing information in the name und on i
behalf of the Licensees herein, and that the statements contained in said information are true and correct to the best of his know dge and belief.
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- ..es I.htch 31.1833 V. T. Russell, Region I Admin'istrator cca l
A. B. Vang, NRC Project Manager, Haddam Neck Plant M. L. Boyle, NRC Project Manager, Millstone Unit No.1 D. H. Jaffe, NRC Project Manager, Millstone Unit Nos. 2, and 3 i
J. T. Shedlosky, Senior Resident Inspector, Haddam Neck Plant V. J. Rays.ond, Senior Resident Inspector, Millstone Unit Nos. 1, 2 and 3 1
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Docket Nos. 50-213 50-245 50-336 50-423 107335 Attachsent,1 Response to NRC Bulletin No. 88-08 Haddam Neck Plant Thermal Stresses in Piping Connected to Reactor Coolant Systems o
September 1988
Haddam Neck Plant Description of Problem:
The charging system fill header has high pressure, (2550 psig) lov temperature (115'F) vater from the charging pump discharge on one side of each of four normally shut motor operated isolation valves (one per loop).
The reactor coolant system, on the other side of the valves, is at 2000 psig and 537'F. These 1 1/2 inch isolation valves are not routinely leak checked.
If they were to leak, the potential for thermal stresses in the unisolable portion of piping downstream does exist.
Requested Action:
2.
For any unisolable sections of piping connected to the RCS that may have been subjected to excessive thermal stresses, examine nondestructively the velds, heat-af fected zones and high stress locations, including geometric discontinuities, in that piping to provide assurance that there are no existing flavs.
Response
During the next refueling outage, (currently scheduled to begin in September 1989) CYAPC0 vill perform nondestructive examination of selected velds, heat-affected zones, and elbows dovnstream of the fill header isolation valves.
Since this is potentially a high radiation exposure task, analysis vill first be performed to attempt to determine the areas most susceptible to thermal stress cracking.
These creas vill be examined first.
If problems are noted, examinations vill be extended to other areas in that line.
The concerns of Reference (3) vill be addressed in these examinations.
Requested Action:
3.
Plan and implement a program to provide continuing assurance that unisolable sections of all piping connected to the RCS vill not be subjected to combined cyclic and static thermal and other stresses that could cause fatigue failure during the remaining life of the unit. This assurance may be provided by (1) redesigning and modifying these sections of piping to vithstand combined stresses caused by various loads including i
temporal and spatial distributions of temperature resulting from leakage across valve seats, (2) instrumenting this piping r
to detect adverse temperature distributions and establishing appropriate limits on temperature distributions, or (3) providing means for ensuring that pressure upstream from block valves which might leak is monitored and does not exceed RCS pressure.
J
. Response:
During the next refueling outage (currently scheduled to begin in September 1989), the following actions vill commence:
Install instrumentation downstream of each fill header isolation valve to determine if adserse temperature' distributions exist.
The information obtained during the subsequent operating cycle vill help determine if unacceptable thermal stresses exist.
Perform stress analysis with the temperature data obtained.
l This vill determine if the piping is being subj ected to excessive thermal stresses.
Depending on the results of the above, an Integrated Safety Assessment Program (ISAP) evaluation vill be conducted to determine the need and schedule for any necessary work to eliminate valve leakage, modify the piping to withstand thermal stresses, or prevent the upstream piping from exceeding RCS pressure.
4.
P Jt Docket Nos. 50-213 50-245 M
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Response to NRC Bulletin No. 88-08 i
j Millstone Nuclear Power Station, Unit No. 3 i
i Thermal Stresses in Piping Connected to Reactor Coolant Systems j
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Hillstone Nuclear Pover Station, Unit No. 3 Description of Probleat There are two potential problem areas at this unit. The first concerns the charging pump to safety injection interface.
High pressure (2550 psig), lov temperature (ll5'F) vater from the charging pump discharge is on one side of each of two parallel normally shut motor operated safety injection valves.
These valves supply a common header which is equipped with a check valve. This header then splits into fur lines (one for each loop), each with a check valve, which then discharges to the RCS cold legs (2300 psig, 557'F).
These safety injection valves are also contsinment isolation valves and are therefore l
leak tested each refueling outage.
However, if one or both vere to leak, the potential for thermal stresses in the unisolable portion of piping downstream does exist.
The second potential problem area is the pressurizer surge line. This problem is of a different nature than the first and arises due to relatively lov flows in a large pipe. This may cause thermal stratification.
Requested Action:
2.
For any unisolable sections of piping connected to the RCS that may have been subjected to excessive thermal.
stresser, examine nondestructively the velds, heat-affected zones and high stress locations. including geometric discontinuities, in that piping to provide assurance that there are no existing flavs.
Response
During the next refueling outage (currently scheduled to begin in May 1989), NNECO vill perform nondestructive examinations of the velds and heat-affected zones downstream of the indi-vidual loop check valves. The concerns of Reference (3) vill be addresed in these examinations.
Analysis to determine the potential for a problem with the surge line vill be performed.
If the results of the analysis indicate that excessive thermal stresses exist, appropriate portions of the surge line vill be examined during the next l
refueling outage.
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= e Requested Action 3.
Plan and implement a program to provide continuing assurance that unisolable sections of all piping connected to the RCS vill not be subjected to combined cyclic and static thermal and other stresses that could cause fatigue failure during the remaining life of the unit. This assurance may be provided by (1) redesigning and modifying these sections of piping to withstand combined stresses caused by various. loads including temporal and spatial distributions of temperature resulting from leakage across valve seats (2) instru-menting this piping to detect adverse temperature distributions and establishing appropriate limits on temperature distributions, or (3) providing means for ensuring that pressure upstream from block valves which might leak is monitored and does not exceed RCS pressure.
Response
Further analysis vill be undertaken to determine allovable t;wcmal stresses and the valve leakage required to induce l
those stresses. The safety injection line velds vill be l
inspected whenever leak testing of the isolation valves indicates that thermal stresses could be occurring.
Further analysis of the pressurizer surge.line is also ongoing.
Based on the results of those actions, further actions as called for in Item 3 vill be undertaken as necessary.
Depending on the results of the analysis, instrumentation may be required to further ascertain the problem.
If so, this vill be installed during the May 1989 l
outage. Evaluation of data vil occur during the following operating cycle.
Modifications, if required, vill be installed during thi following outage.
All actions are expected to be completed by the end of the November 1990 refueling outage.
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