ML023020498
| ML023020498 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 10/29/2002 |
| From: | Olshan L NRC/NRR/DLPM/LPD2 |
| To: | Mccollum W Duke Energy Corp |
| References | |
| TAC MB4458 | |
| Download: ML023020498 (4) | |
Text
Leonard Olshan - ONS 1EOC-20 Inspection Scope-NRC-3-14-02.doc Page 1 3/14/02 ONS 1EOC-20 Steam Generator Inspection Plans ECr Inspection Scope Bobbin Coil (0.510 dia. MF) 100% A-OTSG 100% B-OTSG Lane and Wedge MRPC (0.460 dia. Plus Point)
Two Rows Around Sleeved Tubes MRPC Upper Tubesheet Roll 100% A-OTSG (0.460 dia. Plus Point) 100% B-OTSG MRPC Re-rolls Upper Tubesheet (0.460 dia. Plus Point)
MRPC 1-600 Plugs 100 100 Bobbin Sleeve Exam 100 (0.410 dia.)
100 Sleeve Upper and Lower Rolls (0.400 dia Plus Point) 100% A-OTSG 100% B-OTSG
% A-OTSG
"% B-OTSG
"% Sleeves A-OTSG
"% Sleeves B-OTSG 100% Sleeve Rolls A-OTSG 100% Sleeve Rolls B-OTSG Kidney Region (Sludge Pile) 100% A-OTSG (0.460 dia. Plus Point) 100% B-OTSG RPC Special Interest (0.460 dia. Plus Point)
- 1) 2)
100% Bobbin indications regardless of location 100% of all dents regardless of size or location SLeonard Olshan - ONS 1 EOC-20 Inspection Scope-NRC-3-14-02.doc Page 1
Leonard Qshian - ONS 1EOC-20 Inspection Scope-N RC-3-14-02.doc Page 2 3/14/02 Plugged Tube Inspection Scope The proposed industry action plan lists the following recommendations for OTSG plants per BWOG Letter to NEI:
"During the next scheduled outage for each OTSG plant, all plugs susceptible to over-pressurization defined by BWOG Letter to NEI (OG-01-1814) will be removed, so that the tube can be inspected for signs of swelling. Alternatively, UT methods may be used to determine if water is present in the tube. If water is not present, the tube cannot over-pressurize and therefore no action is required for that outage."
The B&WOG letter to NEI (OG-01-1814) defines locations susceptible to SEVER as a result of over pressurization as follows:
- 1. The tube has a plug that has been repaired in such a way that the joint integrity has been improved without removing existing water from the tube, AND
- 2. The tube passes through a drilled hole in the uppermost tube support plate. Note:
This is based on a FIV analysis and is currently being questioned by the NRC.
Populations susceptible to OVERPRESSURIZATION include the following categories:
- 1. All locations where an Alloy 600 rolled plug was removed from the UTS and replaced without dewatering.
- 2. All locations where an existing rolled plug was re-rolled under NCRs issued as a result of loose rolled plugs being discovered at Oconee-3 in 1994.
Plugs Requiring Inspection/Repair A. Tubes that require the upper plug to be removed
- a. Tubes with a ribbed plug in the outlet and a ribbed plug replaced with a rolled plug in the inlet for the drilled tube hole locations.
- b. Tubes with a repair weld in the lower and 1600 tipper.
B. Tubes that require UT.
- a. Tubes with a repair weld in the upper and a lower 1600.
- b. Tubes with rerolled plugs C. Tubes that require explosive plug inspection
- a. Tubes with repair upper weld and a lower explosive.
Leonard Qishan - ONS 1EOC-20 Inspection Scope-NRC-3-14-02.doc Page 3 3/14/02 D. Tubes that require adjacent tubes be stabilized
- a. Tubes with unique plug combinations where removal or UT is not possible.
Plug Populations on Unit I Plug Category SIG ]A SIG 1B A-Remove Upper Plug 1
16 B-UT Inspection for water 31 119 C-Eddy Current Plugs 19 177 D-Adjacent tubes stabilized 0
3 I
I UT Inspection Process A process for inspection the tubes to verify if water is present has been qualified for application if the lower plug is either a flat bottom plug or one with a threaded connection at the end of the plug. This process can measure the water level to 235".
Therefore the acceptance criteria for acceptable water level will be 180" or approx. 27%
full. Tubes with less than this amount of water will be acceptable for continued operation for one more cycle prior to SIG replacement. If water level exceeds this amount, the tube will be dewatered or plugged around since we can not verify the actual water level. Tubes that have verified through wall defects will not require repair since tube swelling is not possible if a leak path exists.
Davis-Besse Welded Tube Issue Recent inspection of welded plugs by Davis Besse indicated that two welded plugs previously installed may have developed cracking in the weld areas Also, a recent reanalysis offatigue cycles for welded plugs by FANP indicates that the allowed heatup and cooldown cycles for welded plugs will be lower than previously calculated.
However, the review of this data indicates that no welded plugs installed at ONS-1 have exceeded the new allowed fatigue cycles. Therefore, during the ONS-1 outage we will visually inspect all welded plugs to verify absence of leakage and overall condition of plug. We have performed this inspection in previous outages with no indications of degradation of welded plugs.
Leonard Olshan - ONS 1 EOC-20 Inspection Scope-N RC-3-14-02. doc Page 3
Leonard Olshan - SFXDB4.pdf Page 1 ONS-1B TUBE SEVER OF TUBE 78-124 78-124 Severed Tube LTS EXP PLUG 1971 LTS EXP PLUG Defect this outage, identified for capture UTS Not Plugged until 1974 with EXPLOS UTS RWP in 1993 77-123: Plugged in 1991 for 38% ODI @14S+0.68 77-124: Plugged in 1993 for 74% ODI @ 13S + 0.62 78-123: Plugged in 1999 for VOLs above LTS (See Note Above) 78-124: Possible Sever (See Note Above) 78-125: Plugged in 1979 for 55% ODI @ 12S 79-127: Currently In-Service 79-128: Plugged in 1995 for ODI @ 12S + 1.44 12:22 PM 04/17/02 Leonar~d Olshan - SFXDB4.pdf Page1