ML20155F571
| ML20155F571 | |
| Person / Time | |
|---|---|
| Issue date: | 05/31/1988 |
| From: | Zech L NRC COMMISSION (OCM) |
| To: | John Miller OFFICE OF MANAGEMENT & BUDGET |
| Shared Package | |
| ML20154Q748 | List: |
| References | |
| NUDOCS 8806160431 | |
| Download: ML20155F571 (4) | |
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,# jog UNITED STATES y'[patec- y g NUCLEAR REGULATORY COMMISSION t y a WASHINGTON, D. C. 20555
% . . . . . $ May 31, 1988 CHA IR M AN The Honorable James C. Miller III, Director Office of Management and Budget Washington, D.C. 20503
Dear Mr. Miller:
In accordance with the statutory obligation to respond to recommendations made by the General Accounting Office (GAO) within 60 days of their publication, we hereby submit our responses to the GA0 recommendations in its report entitled "Action Needed To Ensure That Utilities Monitor and Repair Pipe Damage."
The GA0 it.itiated its survey following the pipe rupture event at Surry Unit 2 in December 1986. As indicated in the report, the U.S. Nuclear Regulatory Commission (NRC) responded rapidly to the Surry event and implemented a plan of action to address this issue industrywide. Licensee inspections for erosion / corrosion in ;
single phase pipe systems are either completed or are scheduled for the next refueling outage at all plants. This program was developed by industry and approved by the NRC. A similar approach 1 that will provide uniform results f rom existing utility two-phase piping inspection programs has been initiated. The NRC staff will j inspect selected plants by October 1988 to determine the adequacy I of individual plant programs. If industry programs are not adequate, the NRC will implement additional regulatory requirements.
Specific responses to the GA0 recommendations are enclosed.
1 Sincerely, l b.
Lando W. Z ,
Enclosure:
Responses to GAO Recommendations
RE_SPONSE TO GA0 REPORT (GA0/RCED-88-73) RECOMMENDATIONS Recomendation No.1 (Chapter 4 of Report)
The GA0 report stated that erosion / corrosion in single-phase pipe systems is an emerging issue that was not anticipated by either NRC or the nuclear utility industry. Before the accident at Surry, neither NRC nor the industry believed nuclear plants were susceptible to deterioration caused by this condition.
However, the accident at Surry showed that utilities should monitor for erosion / corrosion damage in single-phase pipe systems.
The GA0 report recommended that "the Chainnan, NRC, require utilities to inspect all nuclear plants to develop data regarding the extent that erosion / corrosion exists in pipe systems, including straight section of pipe."
NRC Response:
As the GAO report stated, erosion / corrosion in single-phase pipe systems was not anticipated. Before the accident at Surry, neither the NRC nor Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code required utilities to monitor erosion / corrosion in balance-of-plant (80P) piping systems. Eight days after the accident at Surry, the NRC issued a notice to all licensees providing details about the Surry pipe failure and additional information to permit licensees to determine if the circumstances of the Surry pipe failure were applicable to their plants.
During the following six months, two supplemental notices were issued to provide updated infonnation about erosion / corrosion to the utilities.
Additionally, the NRC issued Bulletin 87-01 requesting licensees to submit informai. ion on their programs for monitoring the thickness of pipe walls in high-energy single-phase and two-phase carbon steel piping systems. On August 4,1987, the NRC issued a notice to alert all licensees to the significant unexpected pipe wall thinning of the safety-related portion of the feeowater lines at Trojan. In addition, at the request of the NRC, the ASME Section XI Comittee formed a special working group on wall thinning to develop requirements and standards for erosion / corrosion monitoring of safety-related Class 2 piping systems.
Many nuclear utilities initiated inspection programs on their own initiative shortly af ter the Surry accident. In addition, many utilities already had in place inspection programs that addressed two-phase pipe systems. However, the extent of the inspection programs varied. During the second calendar quarter of 1987, the Nuclear Utilities Management and Resource Council (NUMARC) and the Electric Power Research Institute (EPRI) developed unifonn guidelines for the inspection, repair, and replacement of single-phase pipe systems susceptible to ervsion/ corrosion. These guidelines address both curved and straight sections of pipe. By letter dated June 12, 1987, the NRC infonned NUMARC that the industry program for single-phase pipe systems was acceptable, subject only to minor coments. The industry is also developing a similar inspection program to provide a unifonn approach to two-phase pipe system programs.
Recent reports to NUMARC indicate that all plants have comitted to conduct inspections for erosion / corrosion. As of June 1, 1988, 81 of 113 plants will
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have completed inspections. An additional 17 plants will complete inspections by October 1988. The remaining 15 plants are pre-comercial, in extended outages, or have an older sister plant that will conduct inspections by October 1988. These remaining 15 plants will complete inspections before start-up following their next refueling outage or prior to initial plant operations, as applicable.
The NRC is continuing its review of pipe wall thinning and is inspecting selected plants to review their inspection results and to assess the effectiveness of the erosion / corrosion menitoring programs. NUMARC has obtained full participation and implementation of its programs to address the pipe wall thinning issue. ASME Section XI Comittee is developing a new requirement for pipe wall thinning inspection. These initiatives will be the basis for any additional NRC requirements, if they are necessary, to address the pipe wall thinning issue. The NRC intends to close out this issue by the end of December 1988.
The NRC's objective is to assure that proper action is taken to correct problems. In the meantime, the objective of having plants establish programs to detect and correct pipe wall thinning has been achieved by the industry efforts described above. Thus, it was not necessary for the NRC to issue further specific requirements. The industry program results will be closely menitored by NRC. If not effective, the NRC will promptly issue requirements covering needed industry actions.
Recomendation No. 2 (Chapter 4 of Report)
The GAO report stated that NUMARC has recomended a three-tier approach for utilities to identify and correct erosion / corrosion damage, but the industry has not adopted these recomendations. Therefore, no industry wide comitment exists to ensure that all utilities take actions to ensure the integrity of pipe systems, and short of an NRC requirement, no guarantee exists that utilities will do so.
The GA0 report recomended that "the Chairinan, NRC, require utilities to replace pipe that does not meet the industry's minimum allowable thickness s ta nda rds . "
l NRC Response.
Since the Surry 2 event in December 1986, the NRC has conducted several surveys a on pipe wall thinning caused by erosion / corrosion. The latest, conducted in July 1987, requested all licensees to provide information on the following l items: (1) the code or standard to which the high-energy, carbon-steel piping I was designed and fabricated; (2) the scope, extent, and sampling criteria of ,
inspection programs to monitor pipe wall thinning of safety-related and non- l safety-related high-energy carbon-steel piping systems; (3) the results of '
all inspections that have been performed to identify pipe wall thinning; and l (4) plans for revising existing pipe monitoring procedures or for developing l I
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3 new or additional inspection programs. All licensees responded to the request, and the results provide an initial database on the extent to which erosion / corrosion exists in operating plants. All plants that identified significant erosion / corrosion in the survey indicated that they had replaced the affected piping.
As stated in NRC Bulletin 87-01, all licensees have either explicitly or implicitly comitted to maintain the functional capability of high-energy piping systems. An important part of this comitment is that piping will be maintained within allowable thickness values. Thus, there is no need for the Comission to issue requirements since the commitments satisfy our safety Co'1Ce rns . ;
Recommendation No. 3 (Chapter 4 of Report) 1 l
Since neither NRC regulations nor industry standards require monitoring for erosion / corrosion in single-phase pipe systems, GA0 be:ieves that NRC needs a mechanism to ensure that utilities periodically assess the integrity of pipe i systems in their plants. '
The GA0 report recommended that "the Chairman, NRC, require utilities to 1 periodically monitor pipe systems and use the data developed during these l inspections to monitor the spread of erosion / corrosion in the plants." '
NRC Response:
As stated in response to recortmendations 1 and 2, all operating plants have completed, or are scheduled to complete, an initial erosion / corrosion inspection of single-phase pipe systems and any needed repair or replacement of I piping. The industry (NUMARC/EPRI) guidelines state that future inspection ,
frequencies will be based on individual plant results from the first l inspection. In addition, a similar inspection program is being developed by 1 the industry for two-phase pipe systems. The Institute for Nuclear Power Operations (INPO) issued a significant operating event report on erosion /
corrosion and is inspecting all plants to assess licensees' implementation of short- and long-term programs. Additionally, the ASME Boiler and Pressure Vessel Code Section XI Comittee is developing requirements and standards that l j
require utilities to monitor erosion / corrosion in safety-related secondary piping systems. The NRC is monitoring industry efforts in regard to inspection and repair of areas affected by erosion / corrosion and will inspect 4 approximately 10 plants by October 1988 to review the results of the initial I inspections and to determine the long-term adequacy of individual plant programs. If industry programs are not adequate, the NRC will implement additional regulatory requirements by the end of calendar year 1988.
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