ML20105A828
| ML20105A828 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 01/31/1985 |
| From: | Wilson R GENERAL PUBLIC UTILITIES CORP. |
| To: | Stolz J Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20105A831 | List: |
| References | |
| 5211-85-2023, RFW-0397, RFW-397, NUDOCS 8502040539 | |
| Download: ML20105A828 (2) | |
Text
D 3
GPU Nuclear Corporation UDM7 100 Interpace Parkway Parsippany, New Jersey 07054-1149 (201)263 6500 TELEX 136-482 Writer's Direct Dial Number:
January 31, 1985 5211-85-2023 RFW-0397 Office of Nuclear Reactor Regulation Attn:
J. F. Stolz, Chief Operating Reactor Branch No. 4 Division of Licensing U.S. Nuclear Regulatory Commission Washington, DC 20555
Dear Mr. Stolz:
Three Mile Island Nuclear Station Unit 1 (TMI-1)
Operating License No. DPR-50 Docket No. 50-289 Steam Generator Repair Limits In various conversations with your staff.we informed you that we intend to plug TMI-l steam generator tubes with indications in the free span which exceed the repair limit. Technical Specification 4.19.4.a.6 defines the repair limit as:
"...the imperfection depth at or beyond which the tube shall be repaired or removed from service because it may become unserviceable prior to the next inspection. This limit is equal to 40% of the nominal tube wall thickness, unless higher limits are shown to be acceptable by analysis and approved by the NRC." (Emphasis added)
We have in the past repaired tubes based on the general 40%
through-wall repair limit. Detailed analyses have shown other, more specific limits to be acceptable to prevent a tube from becoming unserviceable prior to the next inspection. Therefore, in accordance with the provisions of Technical Specifications 4.19.4.a.6, GPU Nuclear requests staff approval of revised repair limit criteria which more accurately reflect the capability of the steam generator tubes, the capabilities of eddy current testing at TMI-1, and the nature of the eddy current indications. The prcposed criteria and their bases are set forth in the j
attached TDR-645, " Basis for Plugging and Stabilizing Criteria for OTSG 1
Tubes," January 1985.
The current repair limit defines as acceptable a tube with a defect extending up to 40% of the tube wall thickness. The defect may be up to 360* circumferential extent. This however is based on the state-of-the-art 8502040539 850131 PDR ADOCK 05000289 np p
PM V
wu Nuclear Corporation is a subsidiary of General Pubhc Utihties Corporation l
i
~ ~
.A
.2-current. examination techniques andfanalyses typical of the mid 1970's. With
.rtoday's eddy current technology, tube defects can be better characterized in Lterms of circumferential extent'and volume,.as well as through wall extent.
Recent analyses demonstrate the acceptability of tubes-based on the extent
~ f.both depth and. length of theidefect. These analyses show that many tubes o
'with defects exceeding 40% through wall;are acceptable because they would i ot be a size or configuration at-the time of ECT detection nor would they n
be during the interval between inspections to adversely affect the required
' degree of. tube' integrity. Hence,.the' proposed criteria are based-on the total. cross 1section of unimpaired tube wall remaining, rather than a
~
consideration of through wall extent alone.
The analytical bases for.the proposed criteria have been previously 1 recognized and approved. These analyses have been documented in GPU Nuclear's' TR-008, the safety. evaluation for the kinetic expansion repair process, and'in NRC's NUREG-1019. Both documents recognize that some tubes (with greater than 40% through. wall defects need not be repaired because the defect size would not significantly affect tube integrity.
While staff approval is required by Technical Specification
~
14.19.4.a.6, the proposed criteria for which we seek NRC approval are not
~. subject:to the requirements _of 10 CFR 50.59. Their use constitutes neither
~ a_ change in facility or the__ procedures as described-in-the safety analyses
< report for-TMI-1. We have, nevertheless,. evaluated the criteria in accordance with the provisions _of section 50.59.
_Use of the proposed criteria-does not require a change in.the technical specifications, and does not involve ^an unreviewed safety question as defined in section 50.59. Use of-the criteria does not involve the
. possibility of an accident or_ malfunction.not previously evaluated or an-increase in the consequences of an accident., As shown in the attached JTDR-645 the margin _of safety, for the proposed criteria is no less than the licensing basis for the current repair limit and hence the probability of occurrence of an accident or malfunction has not been increased.
The proposed repair limit'is an. application of a previously reviewed andLapproved' technical approach.. It reflects current detection capabilities
- and-a more appropriate measure'of.-tube. integrity which does not' reduce safety margins. We are now in the process of. plugging'and: stabilizing those tubes which must be removed _from service based on this proposed criteria, and therefore request that you give'our request prompt consideration.
cere
(~ '.
Y.
n
. F.
ils n
~o Director, echnical Functions
' dis:0991f
' Attachment p
scc: - R. Conte-
-H. Silver Dr.<T." Murley
<C. McCracken-m