ML20153H030
| ML20153H030 | |
| Person / Time | |
|---|---|
| Issue date: | 02/22/1988 |
| From: | Stello V NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | |
| Shared Package | |
| ML20153H026 | List: |
| References | |
| FOIA-88-318, TASK-PII, TASK-SE IEB-87-001, IEB-87-1, SECY-88-050, SECY-88-50, NUDOCS 8809090066 | |
| Download: ML20153H030 (6) | |
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1 SECY-88-50 February 22, 1988
%gy gg (Information) t For:
The Comissioners From:
Victor Stello, Jr.
Executive Director for Operations STATUS REPORT ON PIPE WALL THINNING (RESPONSES TO
Subject:
NRC BULLETIN 87-01 ON PIPE WALL THINNING IN NUCLEAR POWERPLANTS)
To supplenent SECY 87-90A with the results of the survey on pipe
Purpose:
wall thinning in operating plants and the industry practice for monitoring erosion / corrosion.
SECY 87-90A was issued to infonn the Comission of the results
Background:
of staff review of the Nuclear Utility P.anagement and Resources Comittee (NUPARC) program on pipe wall thinning in high-energy, single-phase carbon steel piping systems. Although the program was generally acceptable, the staff expressed concerns that not all utilities had comitted to the program and that NUPARC had no specific plans to implement its programs at all plants.
In addition, the staff requested that NUMARC expand its program to include high-energy, two-phase piping in its current program and low-energy piping systems in its long-range program.
Because of the imediate concern about high-energy, carbon steel systens, NRC Bulletin 87 01, "Pipe Wall Thinning in Nuclear Power Plants, was issued on July 9,1987. The staff requested all licensees to provide the following information within 60 l
days of receiving the bulletin:
the code or standard to which the high-energy, carbon steel piping was designed and fabricated the scope, extent, and sampling criteria of inspection progrars to monitor pipe wall thinning of safety-related and non-safety-related high-energy carbon steel piping systems the results of all inspections that have been performd to identify pipe wall thinning plans for revising existing pipe monitoring procedures or developing new or additional inspection programs Q f 0 g 6 08001e j
NELSON 80-310 PDR t
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Contact:
P. Wu, NRR 49-20826 v
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. The Comissioners The staff review of licensee responses to the bulletin showed Discussion:
ofMechanicalEngineers(ASME) that, before the American Society (BPVC) Section 111 rules for Boiler and Pressure Vessel Code piping pumps and valves were revised in 1971, the secondary coolant systems in nuclear power plants were designed and fabricated in accordance with the American National Standards Institute (ANSI) requirements of ANSI B31.1. Fifty-seven percent of the licensed units belong to this category. After 1971, safety-related portions of the secondary coolant systems were designed and fabricated in accordance with ASME BPVC Section !!! rules, while non-safety-related portions of the secondary coolant systems continued to be designed and f abricated in accordance with ANSI B31.1 requirements. Forty-three percent of the licensed units belong to this category.
Por two-phase, high-energy, carbon steel piping systems, the responses to the bulletin indicated that programs exist at all inspection locations plants for inspecting pipe wall thinning, are generally established in accordance with the 1985 guidelines described in Electric Power Research Institute (EPRI) document NP-3944, "Erosion / Corrosion in Nuclear Plant Steam Pising:
Causes and Inspection Program Guidelines." However, secause these guidelines are not required to be implemented, the scope and the extent of the program varies significantly from plant to plant.
Responses to the bulletin indicated that limited inspections of the single-phase feedwater condensate systems were conducted in the majority of plants after the Surry Unit 2 incident. Most plants developed their single-phase pipe wall thinning monitoring programs because of the events at Surry Unit 2 and at the Trojan plant. Some plants apparently developed programs after NRC Bulletin 87-01 was issued. Based on the responses to NRC Bulletin units out of a total of 110 still have not established 87-01, 23 an inspection program for monitoring wall thinning in single-phase lines. Of these units,17 are operating and 6 are under construction.
In early June 1987, NUMARC, in conjunction with EPRI, developed guidelines for inspection and repair of sinsile-phase piping.
These guidelines utilize a computer code w;.'ch identifies and i
prioritizes inspection locations based on plant-specific factors, i
such as fluid velocity, piping geometry, system temperature, and i
water chemistry. Areas that are subjected to flow disturbances, such as elbows, branch connections, piping, and fittings down.
stream of control valves or flow orifices, are preferentially selected locations for inspection. By letter dated June 12, i
1987, the NRC staff infortned NUMARC that, with minor coments, these guidelines were found acceptable. About 60 percent of the j
responses indicated that the licensees intend to adopt the NUMARC guidelines and the EPRI computer code to select inspection points i
and initiate repairs, if necessary. As discussed later, the
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. The Comissioners staff has been verbally informed that, as of December 1987, 90 percent of the utilities intend to adopt the guidelines.
The inspection frequency for pipe wall thickness measurements and replacement / repair decisions is based on a cos61 nation of In general, the predicted and measured r.rosion/ corrosion rates.
pipe wall thickness acceptance criteria use measured well thick-nesses and an erosion / corrosion damage rate to predict when the pipe wall thickness will approach its code allowable minimum The acceptance criteria provide guidance for wall thickness.
determining if a piping component needs to be replaced or repaired ice.ediately or for projecting when a piping component should be replaced at some future time.
The primary method of inspection reported was ultrasonic testing (UT), sup>1emented by visual examination and, in a few cases, by radiograpiy. Pipe wall thickness measurements were either made The by or verified by certified level 2 or level 3 inspectors.
NRC staff considers this to be an adequate inspection technique.
The systems and components reported as experiencing pipe wall thinning in the responses to the Bulletin 87-01 are itsted in.
Wall thinning problems in single-phase pipino occurred primarily in the feedwater-condensate system, whi!e the problems in two-phase piping, although varied in extent, have been reported in virtually all operating plants in a variety of Plants that were reported to have pise wall thinning systems.
in feedwater-condensate systems are listed in Enclosure 2.
Although inspection of single-phase lines is not scheduled until the next refueling outage for a nuster of plants, the-l available results from plants already inspected indicate a wide-spread problem.
f The staff's review also showed that wall thinning in feedwater-condensate systems is more prevalent among pressurized water reactors (PWRs) than boiling-water reactors (BWRs). At the present time, licensees of 27 PWRs and 6 BWRs have identified various degrees of wall thinning in feedwater piping and fittings.
During a meeting with the NUMARC Working Group on Piping Erosion /
Corrosion held on December 10, 1987, the staff was told that 90 percent of the utilities have connitted to the NUMARC guidolines and the EPRI computer code.
However, this information was obtained af ter receipt of HRC Bulletin 87-01 responses and is, therefore, not reflected in the bulletin responses. The staff was also informed that EPRI has begun work on a new computer code and The staff expressed concern at program for two-phase pioing.
the meeting that HUMARC 1as not taken steps to ensure that all plants implement consistent guidelines for both single-phase and two-phase systems. This concern was expressed in a letter to NUMARC on June 12, 1987 and repeated in 4 December 15, 1987 letter.
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. The Comissioners The staff review indicates that the pipe wall thinning problem is widespread for single-phase, and two-phase, high-energy carbon Sumary:
Monitoring programs exist for two-phase systems steel systems.
However, the scope and extent of the at virtually all plants.
programs vary from plant to plant, and failures continue to occur.
Industry guidance has been developed for single-phase piping and the majority of plants are comitted to use the guidelines.
Industry has not acted to ensure implementation at all plants.
The staff is satisfied with EPRI's progress in developing a computer code to aid in the inspection of single-phase piping.
We believe that NUMARC should improve efforts to implement the single-phase program at all plants and implement a program to We are address the issue of two phase pipe wall thinning.
working with NUMARC to resolve this matter.
The staff also is continuing its review of pipe wall thinning and will assess the results obtained from inspections to be performed This assessment will be during the spring refueling outages.
accomplished by visiting up to ten plants to review their inspection results and requesting the results from additional inspections via a generic letter. These results, combined with NUMARC's position regarding participation and implementation of its programs to address the pipe wall thinning issue, will be the basis for any staff recommendation on additional regulatory The staff anticipates actions to address the wall thinning issue.
that its review will be completed by December 1988, and will provide the basis for new requirements in single-phase and two-The staff is prepa. ring an Information Notice phase systems.
to licensees to transmit the results of its review of responses to Bulletin 87-01. The staff will continue to keep the Comission informed of its efforts in this area.
~c V tor Stello, Jr. /
i Executive Director for Operations
Enclosures:
1.
Systems / Components Experiencing Pipe Wall Thinning 2.
Plants Experiencing Pipe Wall Thinning in Feedwater-Condensate Systems 1
ENCLOSURE 1 SYSTEMS / COMPONENTS EXPERIENCING PIPE WALL THINNING Two-Phase Line Single-Phase Line main steam line main feedwater lines.
straight runs, fittings turbine cross-over piping main feedwater recirculation to turbine cross-under piping condenser, straight runs, fittings extraction steam lines feedwater pump suction line, straight runs, fittings moisture separator reheater feedwater pump discharge line, fee / water heater drain straight runs, fittings i
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condensate booster pump recirculation line fittings stear generator letdown lines, straight runs, fittings 1
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ENCLOSURE 2 PLANTS EXPERIEM0!NG P1PE WALL THINNING IN FEEDWATE Type of Comercial Degraded C aponent Plant Unit Reactor Operation Fittings or Straight Runs _
Dresden 2
BWR January 1970 elbows Duane Arnold BWR March 1974 elbows, reducers, straight runs Pilgrim 1
BWR June 1972 elbows BWR May 1969 elbows River Bend i
BWR Octeber 1985 recirculation line Oyster Creek BWR June 1986 straight runs Arkansas 1
PWR August 1974 elbows, drain pump discharge Perry piping Arkansas 2
PMR December 1978 undefined Calvert Cliffs 1 PWR October 1974 elbows, reducers, straight runs Calvert Cliffs ?
PWR Nov mber 1976 elbows, reducers, straight runs PWR October 1984 recirculation line elbows Diablo Canyon 1 PWR April 1984 elbows, straight runs Callaway Diablo Canyon 2 PWR August 1985 elbows, and Y Donald Cook 2
PWR March 1978 elbows PWR August 1973 elbows, straight run Haddam Neck PWR July 1967 recirculation line Ft. Calhoun Millstone 2
PWR October 1975 elbows, heater vent pipiny North Anna 1
PWR April 1978 elbows, straight runs North Anna 2
PWR June 1980 elbows, straight runs H. B. Robinson 2 PWR September 1970 recirculation lines San Onofre 1
PWR June 1967 reducers, heater drair niping San Onofre 2
PWR July 1982 heater drain piping San Onofre 3
PWR August 1983 heater drain piping f
Salem 1
PWR December 1976 recirculation line Salem 2
PWR August 1980 recirculation line Shearon Harris PWR October 1986 recirculation line Surry 1
PWR July 1972 fittings j
i Surry 2
PWR March 1973 fittings Sequoyah 1
PWR July 1980 elbows, straigby. run Sequoyah 2
PWR November 1981 elbows PWR December 1975 elbows, reducers, straight runs Turkey Point 3
PWR October 1972 feedwater pump suction line Trojan fittings 1ry 1974 straight run in emergency Fort St. Vrain HTGR*
feedvater line Rancho Seco PWR W. ember 1974 straight runs downstream of MFW loop isolation valve or MFPs miniflow valves High Temperature Gas Reactor
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