ML20197E512
| ML20197E512 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 05/13/1986 |
| From: | Standerfer F GENERAL PUBLIC UTILITIES CORP. |
| To: | Travers W Office of Nuclear Reactor Regulation |
| References | |
| 0427A, 427A, 4410-86-L-0077, 4410-86-L-77, NUDOCS 8605150273 | |
| Download: ML20197E512 (2) | |
Text
GPU Nuclear Corporation Nuclear
- mrs r8o a
Middletown, Pennsylvania 17057-0191 717 944 7621 TELEX 84-2386 Writer's Direct Dial Number:
(717) 948-8461 4410-86-L-0077 Document ID 0427A May 13,1986 TMI-2 Cleanup Project Directorate Attn: Dr. W. D. Travers Director US Nuclear Regulatory Commission c/o Three Mile Island Nuclear Station Middletown, PA 17057
Dear Dr. Travers:
Three Mile Island Nuclear Station, Unit 2 (TMI-2)
Operating License No. OPR-73
~
Docket.No. 50-320 Safety Evaluation Report for Core Stratification Sample Acquisition, Revision 3 Attached are responses' to your coments on the Safety Evaluation Report (SER) for Core Stratification Sample Acquisition, Revision 3, as transmitted by NRC/TMI-86-038, dated. April 23, 1986 Note that changing conditions in the Reactor Vessel require a modification to the GPU Nuclear plan for controlling drill string lengths in containment, as presented in GPU Nuclear letter 4410-85-L-0248, dated December 31, 1985. A di,scussion of the revised plan is included in the response to Comment 1.
Sincerely,
. Standerfer Vice President / Director, TMI-2 FRS/RBS/eml Attachment k
k GPU llucleaf Corporation is a oubsidiary of the General Public Utilities Corporation Doof
'It
CO M 1:
Describe your program to measure and control the length and reference position of the drill string, such that adequate clearance to the reactor vessel wall is maintained.
GPU NUCLEAR RESPONSE:
The use of drill rod (pipe) is controlled by an operating procedure approved pursuant to Technical Specification 6.8.2.
The procedure limits the amount and type of drill pipe available on the defueling work platform (DWP) at any time; thus, only authorized drill string configurations are possible. The procedure also rerpires each pipe handling step in a hole drilling evolution to be verified by the defueling SRO.
Each piece of drill rod and casing is inspected and will have its length verified by QC to a tolerance of +/- 1/2 inch. Each piece of drill rod and casing will have its length etched on the upper end so that the equipment operators can clearly identify the length of the piece being handled. The drill rod and casing necessary for each individual sample (i.e., including extra " set-up" pieces) will be staged into the containment building via a Unit Work Instruction (UWI). This UWI requires QC verification of the length of each piece of drill rod and casing being staged into containment and stored on elevation 347'.
This UWI will allow additional " set-up" pieces of pipe, required to adjust for unevenness in the core debris bed, to be staged onto the DWP. These pieces will be removed from the DWP and will be staged on elevation 347' prior to taking the core sample unless retention of these pieces is necessary to reach the target depth.
In summary, the UWI and core bore procedures administratively limit the amount of drill string and casing available on the DWP to a length which precludes contacting the reactor vessel lower head.
COMNENT 2i Describe how you will insure full thread engagement of the drill string.
GPU NUCLEAR RESPONSE:
Drill string pipe joints are made manually at the top of the drilling machine where the pipe joint is visible. The operating procedure requires visual verification that no more than one thread (i.e.,
approximately 1/4 inch) is exposed at each joint. Manual joining of the pipe also allows operators.to feel the engagement of the thread; thus, proper thread engagement is assured visually and manually. Operators will have undergone training and will be qualified on the pipe assembly and disassembly operations.
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