ML20040G405
| ML20040G405 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 01/27/1982 |
| From: | Dircks W NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | |
| References | |
| TASK-PII, TASK-SE SECY-82-035, SECY-82-35, NUDOCS 8202120276 | |
| Download: ML20040G405 (4) | |
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January 27, 1982 i
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POLICY ISSUE (Information) g@s O
FOR:
The Commission
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OEC M U-1 FROM:
William J. Dircks FEB 11982> y Executive Director for Operations nug g g y ~
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SUBJECT:
TMI-1 STEAM GENERATOR PROBLEM i
PURPOSE:
To provide the Commissioners with infonnation c the status of the tube leak problems on the TMI-1 steam generators.
DISCUSSION:
At the Commission briefing on TMI-l status held on December 21, 1981, the nature and extent of the leaking steam generator tubes at TMI-l was discussed. At that time, it was stated that at least two months were needed for the utility to identify the causes and correct the problem.
On January 25, 1982, at the staff's request, General Public Utilities (GPU) presented an update on this problem. The licensee has nearly completed eddy current testing (ECT) of all tubes in both steam generators. To date, approximately 2250 tubes have been identified to have defects. There are also indications on many other tubes, which will re. quire additional testing using a more sensitive probe to verify the presence of defects. At the present time, it is estimated that several thousand additional tubes may have defects needing repair.
The licensee has stated that virtually all defects are located in the upper tube sheet area of the tube.
Based on extensive metallography tests on two tubes, there is now evidence that the mechanism appears to be intergranular attack from the primary side, instead of the secondary side, resulting in the development of very tight circum-ferential cracks. There is evidence of sulphur and chlorine impurities in every defect *on the two removed tubes examined.
Contact:
R. Jacobs, DL/NRR 49-27471 8202120276 820127 PDR SECY 82-035 PDR
Tne Commission
' -DISCUSSION:
The licensee is conducting a broad based program in the (continued) areas of eddy current testing, tube failure analysis, accident analysis and tube repair techniques. The licensee presently estimates that it will take at least six months to resolve the problem.
The staff has some additional areas of concerns related to the steam generator degradation problem at TMI-1.
A corrosive agent may exist, or have existed, in
the reactor system at TMI-l which could have corroded other primary pressure boundary materials.
.- The plugging of large groups of tubes as an interim solution may not be a viable solution without signi-ficant derating to avoid the erosion-corrosion effects of_coisture droplets that can impinge on the superheated portion of the tubes. The licensee is having thermal hydraulic studies performed to evaluate this concern.
The staff and its consultants will independently review eddy current data, operational chemistry data, suscepti-bility of other primary system materials and results of thermal hydraulic analyses. Additionally, staff consultants will be visiting Battelle and B&W (labs used by GPU) to review methods and results of tube examinations.
A copy of a news release from GPU Nuclear Corporation dated January 25, 1982 regarding the TMI-l steam generator reports is enclosed for your information.
l
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2 William
. Dircks Executive Director for Operations
Enclosure:
As Stated DISTRIBUTION Commissioners Commission Staff Offices ACRS Secretariat
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Post Office Box 480 Middlettwn, PA 17057 717 948-8197 Public Information Services For Furt!1er Informatron
Contact:
John Fidler For Release:
Imediately Date:
January 25, 1982 R
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STEAM. GENERATOR REPAIRS FOR TMI; UNIT 1 y
c Middletown, PA - Officials of GPU Nuclear Corporation said today that repairs s.
'l to steam generator tubes at Three Mile Island Nuclear Station's Unit 13 eactor prob t
r ably will result in at least a six month delay in the readiness of the reactor for restart.
Recent testing of steam generator tubes indicates the repairs,will be sub-stantially more extensive than initially anticipated, Company officials explained.
The Company had expected the unit to be ready for restart by the end of February, subject to permission from the U.S. Nuclear Regulatory Comission.
Additional testing and evaluation will be required before the full extent of the steam generator problem is known.
Company officials met with members of the NRC staff today to brief them on the information developed to date.
Company officials said it was uncertain whether the timing for restart of Unit 1 would be controlled by the steam generator problem or by a recent order of the U.S. Court of Appeals, if allowed to stand.
The Court has directed the NRC to make an environmental assesscent of psychological stress that might result frca return of Unit 1 to operation.
l The Unit I reactor was shut down for refueling at the time of the March 28, l
1979 accident that damaged TMI Unit 2.
Till Unit i remained closed for modifications, l
and for restart hearings before the NRC's Atomic Safety Licensing Board.
l Inspections and tests during the 21-years after the accident did not reveal any abnormal conditions, Company officials said.
Indeed, the hot functional tests l
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2
.o January 25, 1982
- 6-82N conducted in late sumer.showed no evidence of the problem.
It was not until a repressurization of the system in November that small leaks were discovered in the tubes in both Unit 1 s' team generators.
'The tubes nonna11y carry hot, pressurized radioactive water from the reactor.
This water causes non-radioactive water outside the tubes to turn' to steam. This steam tums the turbine, which in turn spins the generator to make electricity.
~
The tube leaks have resulted in minor additions to the routine levels of 7
- radioactive releases from the plant. All releases have been well within federal
.env.ironmental technica1' specifications.
The~two steam generators are about 70 feet high, and each contains approxi-mately 15,500 tubes, which are 52 feet long and five-eights of an inch in diameter..
~
The tubes are made of.inconel, an alloy of iron, chromium and nickel. Their walls are-three hundredttis of an inch' thick.
'in a. pressurized water reactor, such as Unit 1, the steam generators are' ee.
.where the plant's radioactive " primary system" and its non-radioactive " secondary sy' stem" pass each other to exchange heat. The steam generators adjoin the reactor
- in the Unit 1 containment building.
Nonna11y, there is no radioactivity in the
" secondary system."
- - [,
,, The Atomic Safety and Licensing Board has concluded extensive hearings into the restart of TMI-1. and has advised the NRC that the management of GPU Nuclear.
.e Corporation, technical modifications to the plant, and plans for emergency preparad-ness are sufficient to assure that Unit 1 can be restarted without endangering' the
~
halth and safety of the public.
~
l A special inquiry into cheating on NRC operator examinations has also been concluded, and a final report from the special hearing master is expected shortly.
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