ML20107K937
| ML20107K937 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 04/23/1996 |
| From: | Lesniak M COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9604290090 | |
| Download: ML20107K937 (4) | |
Text
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Commonweahh litison Company 14oo opus Place j
Downers Grove, IL G)515-5701 April 23,1996 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555
Subject:
Response to Request for Additional Information Regarding Relief from Insenice Inspection Program Requirements for Pressurizer Surge Nozzle-to-Vessel Weld and Pressurizer Surge Nozzle Inner Radius Section Byron Nuclear Power Station, Units 1 and 2 Facility Operating Licenses NPF-37 and NPF-66 NRC Docket Nos. 50-454 and 455 Braidwood Nuclear Power Plants, Units 1 and 2 Facility Operating Licenses NPF-72 and NPF-77 NRC Docket Nos. 50-456 and 457 Reference 1:
M. Lesniak (Comed) letter to the USNRC Document Control Desk transmitting Relief from Insenice Inspection Program Requirements for Pressurizer Surge Nozzle-t&Vecsel Weld and Pressurizer Surge Nozzle Inner Radius Section dated March 23,1996.
Reference 2:
G.F. Dick, Jr. (NRC) to D. Farrar (Comed) Request for Additional Information regarding the Pressurizer Weld Request dated April 17,1996.
In a March 28,1996, letter to the Nuclear Regulatory Commission (NRC) Commonwealth Edison Company (Comed) requested approval of a relief request for examination of the pressurizer surge nozzle to vessel weld and the pressurizer surge nozzle inner radius section (Reference 1). la the NRC letter of April 17,1996 (Reference 2), a request for additional information (RAI) was transmitted to Comed regarding the pressurizer weld relief request. Attached is Comed's response to those questions.
If you have any questions concerning this correspondence, please contact this office.
Sincerely, N
SM Marcia T. Lesniak Nuclear Licensing Administrator 42{ggg y@
4 Attachment
/
cc:
H.J. Miller, Regional Administrator - R11I Ok t G.F. Dick, Byron Project Manager - NRR
'90003 11 Peterson, Senior Resident Inspector - Byron
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C.J. Phillips, Senior Resident Inspector - Braidwood kmla.byrbwd:isi:presurai. doc:1 A Unicom Company
i ATTACHMENT Response to RAI concerning Byron /Braidwood Relief Requests NR-19 and NR-24 1.
Ouestion Compared to other similar plants, the Byron /Braidwood estimates for erecting scaffolding, disconnecting and replacing heater cables and removing and replacing insulation appear high. Are these estimates and the associated dose estimate of 154 man-rem for all four units? Please explain what is involved with disconnecting the heater cable.
Response
The 154 person-Rem dose estimate to perform the pressurizer surge nozzle UT inspections is for a single unit. The estimate is based on actual dose rate data recorded at Braidwood Unit 2 on 3/16/96. The total time estimates used to achieve the overall dose estimates were assembled at Byron Station by the on-site mechanical cortractor engineers.
To supplement the dose estimates, dose rates were recently recorded at the Byron Station Unit I during the present refuel outage. The dose rates were slightly less than those recorded at Braidwood. Based on the differences, the Byron Unit I dose estimate is more closely estimated at 124 person-Rem.
The total time estimates include time for disconnection /reconnection of the heater cables. 412 hours0.00477 days <br />0.114 hours <br />6.812169e-4 weeks <br />1.56766e-4 months <br /> (approximately 60% of the total hours for cable activities) are applicable in the radiation area at the pressurizer. There are 78 heaters in the pressurizer, each with a cable that is supported by "Kellum" grip hangers from an auxiliary steel structure below the pressurizer.
Each heater has a cable with two conductors. To disconnect each heater cable, a rubber boot seal must be removed and the conductors must be determinated at bolted lug terminations. Once determinated, the cable must be temporarily supported at another location. The process is reversed for reconnection.
The heater assembly is very susceptible to damage at the termination point. The lugs from the cable wires are bolted to lugs which, at the other end, are soldered to pins encased in ceramic insulators. These insulators are very fragile and highly susceptible to breakage. Should an insulator be inadvertently damaged, total heater replacement is n: quired.
2.
Question Can complete volumetric examination of the adjacent nozzle safe-end weld be performed?
Can complete volumetric examination of the other pressurizer noules he performed? Will the remaining Class 1 nozzle-to-vessel welds and inside radius (IR) sections receive complete volumetric examinations?
Response
A " complete" exam is considered to be an exam that meets the ASME Section XI requirements.
Complete volumetric examination can be performed on the nozzle-to-safe end weld of the pressurizer surge nozzle. This inspection would be performed only from the safe end side of the weld. Limitations posed by the geometry of the nozzle preclude data acquisition from the nozzle side of the weld. This weld is scheduled for examination on all four units as shown below.
Byron Unit 1 BIR07 Present Outage Byron Unit 2 B2R07 3/98 Outage Start Braidwood Unit i AIR 06 3/97 Outage Start Braidwood Unit 2 A2R06 9/97 Outage Start k:nla:byrbwd;isi:presurai. doc:2 I
Complete volumetric examination of pressurizer nozzles other than the surge nozzle can be
. performed. These examinations include inner radius UT, nozzle-to-vessel weld UT, and nozzle-to-safe end weld UT. The required volumetric examinations have been completed at both Braidwood units and at Byron Unit 2. At Byron Unit 1, a portion of the exams are completed and the remaining exams are scheduled in the present refuel outage, BIR07.
Regarding other Class 1 vessel nozzles. complete volumetric examination can be completed on the reactor vessel nozzles and steam generator primary system nozzles. The applicable reactor vessel nozzle exams, for all 8 nozzles, are the inner radius UT, nozzle-to-vessel weld UT and nozzle-to-safe end weld UT. The reactor vessel nozzles will be inspected by UT methods from the inside of the nozzle during the 10 year reactor vessel examinations. The schedule is as follows.
Byron Unit 1 BIR07 Present Outage Byron Unit 2 B2R07 3/98 Outage Start Braidwood Unit 1 AlR06 3/97 Outage Start g
i Braidwood Unit 2 A2R06 9/97 Outage Start The applicable steam generator exams, for all nozzles, are the inner radius UT and the nozzle-to-elbow UT. These welds have inspection schedules as follows.
Inner Radius Byron Unit 1 BIR07 Present Outage Byron Unit 2 Complete Braidwood Unit 1 ReliefGranted Braidwood Unit 2 A2R05 Present Outage Nozzle-to-Elbow Byron Unit i BIR07 Present Outage Byron Unit 2 Complete Braidwood Unit 1 Complete Braidwood Unit 2 A2R05 Present Outage 3.
Question It is important to understand the potential benefit of removing the insulation (e.g., the percentage of the examinations that could be completed). Therefore, clarification regarding potential coverage with the insulation removed is needed.
a.
In the " Basis for Relief"it is stated that scanning from the nozzle side is not possible and scanning from the shcIl side is limited by the heater penetrations and that coverage is limited to 60% Does this estimate include coverage for all four directions?
Response
Yes, the estimate of examination coverage represents the average of scans in all four directions using standard 45 degree and 60 degree angles. The axial scan (for circumferential reflectors) from the nozzle side is the most limited due to nozzle geometry. The axial scan from the shell side is limited by geometry and also by interference with the heater penetrations. Scanning circumferentially (for axial reflectors) is rartially limited in both directions by geometry, k:nla:byrbwd isi:presurai. doc:3
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3b Frr the IR section, it is strt:d thit the geometry is Eot conducive t3 typicil ultrasonic techniques. It is understood that conventional techniques will not be
)
effective for examining most IR sections and that special techniques employing -
compound angles must be used to intermgate this agion. has the use of compound angles been considend? What pementage of the Code-required volume can be examined if the insulation wen removed?
Response
3b Yes, the use of compound angles for the inner radius section examination has been considered. It is estimated that 100% of the Code-required inner radius examination volume can be covered with a manual examination technique utilizing six separate compound angles. However, performing the examination with compound angles will require a significant amount of time in a high dose field. Additionally, the developtrent or sizing techniques which can account for the inherent geometric and access limitations will be n: quired. Equipment procurement to support sizing will also be necessary.
4.
Question The regulations [10 CFR 50.55a(g)(3)(i)] mquire that for facilities with construction permits issued on or afterJuly 1,1974, access to enable the performance o lasersice examinations r
be pro 5ided for Class 1 components. It appears that this requirement is not met for the pmssurizer surge nozzle. Please explain. What would be required to modify or replace the insulation so that access for examination would be provided?
Response
Byron and Braidwood stations are in compliance with the regulations [10 CFR 50.55a(g)(3)(i)]
on the basis that all of the nozzles on the pressurizer are accessible for inservice inspection if the insulation and heater cables are removed.
With insulation and heater cables removed, volumetric examination coverage for the nozzle-to-vessel weld of the pressurizer surge nozzle could be performed with approximately 60%
coverage. The geometry of the vessel nozzle and adjacent heater penetrations dictates the level of volumetric examination that can be achieved on the nozzle-to-vessel weld. Complete volumetric examination could be completed for the pressurizer surge nozzle inner radius, nozzle-to-safe end weld and safe end-to-pipe weld.
Modification of the insulation details to improve accessibility to the nozzle would require the following activities as a minimum:
New insulation designs which are safe, constructable, and economically feasible, Review and/or performance of seismic analyses to account for differences and consequences, Acquisition of acceptable insulating materials, and Budgeting of funds for design and installation of the new insulation.
With regards to replacement of the insulation, the original designer / supplier of the pressurizer insulation is the Diamond Power Corporation. Ownership of this company has since been transferred to others. Replacement of the insulation would require the acquisition oflike-for-like insulation materials, fabrication to the same design specifications by the original supplier (or alternate supplier), disconnection /reconnection of the heater caldes and the removal / installation ofinsulation materials under the same radiation conditions discussed in the original relief request.
It should be noted that modification or replacement of the insulation, the geometry of the pressurizer is unchanged and the coverage of the nozzle-to-vessel weld via UT examination remains unchanged.
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