ML20149L661
| ML20149L661 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 02/16/1988 |
| From: | Wilson R GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| 5000-88-1480, TAC-63044, TAC-63045, NUDOCS 8802240353 | |
| Download: ML20149L661 (4) | |
Text
i GPU Nuclear Corporation U Nuclear c ; ;::; " : : :,oros, 2o1-316-7o00 TELEX 136-482 Writer's Direct Dial Number:
Po 88E480 1
U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C.
20555 Gentlemen:
Subject:
Oyster Creek Nuclear r nerating Station e
Plan for Detecting / Mitigating Intergranular Stress Corrosion Cracking (IGSCC) in Reactor Coolant System Piping License No. DPR-16 Docket No. 50-219
Reference:
Letter from USNRC "Inspection of Recirculation and Isolation Condenser Piping in Cycle llR Outage" (TAC 63044 and 63045) dated 14 Nov 86.
In regard to the IGSCC program for Oyster Creek, GPU Nuclear wishes to inform NRR of our planned 12R outage workscopo including IGSCC and stress mitigation plans.
This is in response to your request to submit our program at least three months prior to the beginning of the 12R outage (see reference), bpects of this program were previously discussed with a Region 1 representative during a site inspection the week of November 2, 1987.
Inspections Oyster Creek systems susceptible to IGSCC include Recirculation, Cleanup, Isolation Condenser, Core Spray, and Shutdown Cooling.
Those portions of the above systems to be monitored for IGSCC are (see !!ote 1):
o Recirculation; entire system o Core Spray; portions of system subjected to temperatures greater than 200*F.
(see Note 2) g2240353080216 p
ADOCK 05000219 (Dk PDR 5841 f GPU Nuclear Corporaton is a subs d ary of General Pubhc Ut.1t es Corporat on 1
o Shutdown Cooling; all stainless steel welds o Isolation Condenser; entire system (see Note 3) o Cleanup; from the Recirculation System out to the second Reactor Coolant boundary isolation valve NOTE 1 - In all systems, welds to be considered are those four inches and greater in' diameter.
NOTE 2 - Portions of Core Spray may be susceptible to IGSCC because of proximity to the Reactor Vessel and free communication of lines with Reactor Coolant at rated temperature.
Inspections and stress mitigations will be performed on those sections of the system subjected to 200*F or greater.
NOTE 3 - Because of IGSCC experience within the Isolation Condenser System beyond the second boundary isolation valve, the entire system is considered for development of the inspection sample.
Twenty percent of all welds within the defined program scope boundaries (except in the cases of Recirculation and Isolation Condenser welds outside the second boundary isolation valve) will be inspected.
A sumary of the weld inspections planned for 12R and the inspections completed during the previous two outages is as follows:
SYSTEM OUTAGE 10R llR 12R RECIRCULATION 31 67 13 CORE SPRAY 3
16 9
CLEANUP 8
10 10 SHUTDOWN COOLING 2
6 3
ISOLATION CONDENSER INSIDE DRYWELL 19 12 14 0UTSIDE DRYWELL 115 58*
19 TOTAL 178 169*
68+
- Included 1810R weld overlays
+ Includes the 3,11R weld overlays (2 Recirc,1 Isolation Condenser) 5841 f i
In selecting inspection samples, emphasis has been placed on joints containing geometric reflectors and those being difficult to diagnose during the 11R inspections.
In addition, selection criteria has included those elements related to greater IGSCC susceptibility.
In the event that IGSCC is detected within the initial sample during the inspections, the sample shall be expanded in accordance with ASME Section XI. "; second sample shall be approximately equal in size to the initial one.
Thesa additional selections will remain within the system determined to contain new defects.
Expanded sample welds shall also be within the "IGSCC-Concern" boundaries of the systems that have already been established.
If any cracks are found in the second sample set, all of the accessible /inspectable welds in the system will be examined.
To the extent that one or more weldments are considered more susceptible than others, they will be considered in the initial sample.
However, most j
welds in this category were examined with EPRI-qualified techniques during the last (11R) refueling outage. Joints to be stress improved will be subject to the same inspection frequency as those not stress improved.
In addition to welds selected for inspection under the 20 percent criteria, one stress improved weld with an unrepaired flaw (crack detected during 11R) will be inspected.
The three welds repaired in 11R will be examined in 12R.
Logic for IGSCC Mitigation Acceptable mitigation methods for IGSCC include Hydrogen Water Chemistry (HWC), Induction Heating and Mechanical Stress Improvements (IHSI and MSIP), and the use of Non-IGSCC susceptible materials in system construction.
HWC was successfully tested at Oyster Creek during January,1986.
Full-scale implementation of this crack mitigating technique is planned for operating cycle 12 under the provisions of a 10CFR50.59 review.
Stress improvement (IHSI) was applied to sixty-two (62) Recirculation System welds during the 11R outage.
Stress Improvement Planned stress improvement workscope for the 12R outage is as follows:
1 1
l 5841 f
o 2 Recirculation system safe-ends (4 welds) o 2 Core Spray safe-ends (4 welds) o 2 Isolation Condenser safe-ends (4 welds) o Both Core Spray Loops (portions greater than 200*)
(N 22 welds) o 10 Isolation Condenser welds nes" safe-ends NOTE: The order and degree of implementation of IHSI or MSIP for the 12R outage is subject to change based on concurrent outage work, plant conditions, etc.
In the event that any coments or questions arise, please contact Mr. M. W.
Laggart at (201) 316-7968.
Very truly yours,
- b. &*m fu R. F. Wilson Vice President Technical Functions RFW/DJ/pa cc: Mr. William T. Russell, Administrator Region I U.S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA. 19406 NRC Resident Inspector Oyster Creek Nuclear Generating Station Forked River, N.J.
08731 Mr. Alex Dromerick, Jr.
U.S. Nuclear Regulatory Comission 7920 Norfolk Avenue Phillips Building, Mail Stop 316 Bethesda, Maryland 20014 5841f