ML20238B263
| ML20238B263 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 08/24/1987 |
| From: | Wilson R GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| 5000-87-1351, 5211-87-2158, NUDOCS 8709010141 | |
| Download: ML20238B263 (4) | |
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GPU Nuclear Corporation GPU Nuclear
- e r s r 8o o
a Middletown, Pennsylvania 17057-0191 717 944 7621 TELEX 84 2386 Writer's Direct Dial Nurnber:
August 24, 1987 5211-87-2158 5000-87-1351 U.S. Nuclear Regulatory Commission Attn: Document Control Desk
' Washington, DC 20555 Gentlemen:
Three Mile Island Nuclear Station, Unit 1 (TMI-1)
Operating License No. DPR-50 Docket No. 50-289 Long Term Corrosion Test Program for Three Mile Island Unit 1 In Reference 1, GPUN provided the final report of the Long Term Corrosion Test Program.
In the review of the final report (Reference 2) HRC concludes that the Long Term Corrosion Tests " partially achieve the desired results that will i
demonstrate the cessation of primary side intergranular attack (IGA) and/or stress corrosion cracking," and that "The eddy current examinations of the tubes were not sufficiently accurate to enable the staff to determine whether or not cracks grew during the test." GPUN believes that clarification is necessary, as provided below.
The primary method for demonstrating the cessation of primary side intergranular attack (IGA) or intergranular stress assisted cracking (IGSAC) has been the inservice inspection program, which consists of inspection of a random sample of tubes in both steam generators, and inspection of all tubes with degradation penetrating greater than or equal to twenty percent of throughwall, in accordance with Technical Specification 4.19.
Inservice inspection was performed during Outage 5M and again during Outage 6R. These inspections were performed using a.540" standard differential probe, with any indications confirmed by use of an 8 x 1 absolute probe.
This inspection technique, unique to TMI-1, was developed to support the TMI-1 OTSG return to service. The inspection technique employed as part of the Long Term Corrosion Test Program was not the same as the technique employed for TMI-l inservice inspection.
8709010141 870824 DR ADOCK 05000289 PDR O
GPU Nuclear Corporation is a subsidiary of the General Public Utllities Corporation
v 5211-87-2158 In the Atomic Safety and Licensing Board Initial Decision on Steam Generator Repair (October 31, 1984), the Board ruled that "The purpose of the long term corrosion test program, the operations phase of which has now been completed, is to verify that sulfur-induced stress-assisted cracking (IGSAC) will not reinitiate or propagate in the TMI-l steam generators under actual operating conditions. The tests were designed to confirm that metallurgical, environmental, geometric and surface conditions which exist after the repair of the tubes are not detrimental to tube integrity.
From the test program, it will be possible to conclude whether the proposed chemistry limits are acceptable, whether the peroxide cleaning was beneficial or damaging, and whether the changes in electrochemical potential during operations will cause reinitiation of cracking."By letter dated July 6,1984 (Reference 3), GPUN provided a quarterly update on the Long Term Corrosion Test Program.
In response, the NRC staff concluded (Reference 4) that the GPUN reported results
"... indicate that tests which simulate actual plant conditions with water chemistry maintained at maximum anticipated impurity concentrations continued to show no evidence of crack propagation or initiation." The NRC staff also concluded that "These test results verify the applicability of the long term corrosion test program by demonstrating that corrosion continues to propagate in water chemistry conditions where it would be predicted to propagate."
In January 1985, GPUN submitted TDR 638 (Reference 5) which further discussed the results of the Long Term Corrosion Test Program; and concluded that j
results of the metallographic examination of the Long Term Corrosion Test i
umples confirmed that in the absence of intentionally added aggressive sulfur
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species, normal operations would not cause corrosion of TMI-l 0TSG tubing.
In ALAB-807 (May 8,1985), the Atomic Safety and Licensing Appeal Board ruled that "Long term corrosion tests of actual TMI-l steam generator tubes l
conducted by the applicant indicated that, under normal reactor coolant conditions, corrosion would not reoccur... The long term corrosion tests performed by the applicant provide additional evidence that the IGA damage has not resulted in any immediate reduction in the ability of the tubes to maintain their integrity during plant operation.
In subjecting actual TMI-l i
tube specimens to six heatup/cooldown cycles, these corrosion tests closely simulated the typical cperating environment of the steam generator tubes during steady stata and transient conditions.
The tests showed that, in the normal reactor coolant environment, corrosion would not recur in the steam generator tubes." GPUN has eliminated the use of sodium thiosulfate and has changed procedures and procurement specifications to assure that introduction of sulfur to the RCS is minimal and is monitored.
Water chemistry is rquiarly checked to assure conditions are controlled within specification.
Based on this, no additional damage of the type experienced in November 1981 is anticipated.
p W
5211-87-2158 No information is prov. ded in the Long Term Corrosion Test Program final i
report which compromises earlier conclusions by GPUN, the NRC Staff, the Atomic Safety and Licensing Board, or the Atomic' Safety and Licensing Appeal Board. Thus, we believe that-the results of the Long Term Corrosion Test Program satisfied the intended puroose.
No NRC response to this letter is required.
l Sjnce ely,
.Lu 1
R. F. W 1 son i
Vice President and Director
]
Technical Functions RFW/SMK:jh/0962A cc:
J. Stolz, NRC 1
G. Edison, NRC R. Conte, NRC
References:
1.
GPUN letter 5211-85-2106 dated July 29, 1985, H. D. Hukill to J.. F. Stolz, " Final Report on the Long Term Corrosion Test Program."
2.
NRC letter dated May 11, 1987, Gordon Edison to Henry D. Hukill, "Long Term Corrosion Test Program for Three Mile Island Unit 1 (TAC #59435)"
t 3.
GPUN letter 5211-84-2172 dated July 6,1984, i
R. F. Wilson to J. F. Stolz, "Long Term Corrosion Test Program."
]
4.
NRC letter dated July 13, 1984, John F. Stolz j
to Henry D. Hukill, " Staff Review of TMI-1 Steam Generator Leakage and Long-Term Corrosion Tests."
j 5.
GPUN letter 5211-85-2010 dated January 14, 1985, R. F. Wilson to John F. Stolz, " Steam Generator Eddy Current Test Result Evaluation."
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