ML20004D395
| ML20004D395 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 06/05/1981 |
| From: | Colbert W DETROIT EDISON CO. |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0313, RTR-NUREG-313 EF2-53472, GL-81-03, GL-81-3, NUDOCS 8106090345 | |
| Download: ML20004D395 (5) | |
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June 5, 1981 8
EF2 - 53472 ro U. S. Nuclear Regulatory Cossaission Office of Nuclear Reactor Regulation Washington, D. C.
20555 Attention:
Mr. Darrell G. Eisenhut, Director Division of Licensing Gentlemen:
Reference:
Enrico Fermi Atomic Power Plant, Unit 2 NRC Docket No. 50-341
Subject:
Implementat!on of NUREC-0313, Revision 1 Letter from D. G. Eisenhut to Holders of Construction Permits and Applicants for Operating Licenses (BWRs),
February 26, 1981 (Generic Letter 81-03)
Fermi 2 has incorporated many changes to minimize stress corrosion cracking to improve overall plant reliability. Descriptions of these changes are in Sections 5.2.3.2.1.1, 2, and 3 of the FSAR; a copy of these sections is attached.
In response to the February 26, 1981 request from Division of Licensing, Darrell Eisenhut, a review has been made on the Fermi 2 plant for pressure boundary piping, safe ends, and fitting material for nonconformance to matarial requirements of NUREG-0313, Revision 1.
The following deviations were found:
Pipe and Fittings:
Recirculation System 28-inch suction and discharge lines 20-inch and 24-inch tees to RHR System 4-inch tees to RWCU 22-inch manifold I
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June 5,1981 Page 2 Safe Ends:
Recirculation suction (two 28-inch)
Recirculation discharge (ten 12-inch)
Jet pump instrumentation (two 4-inch)
Core differential pressure (one 2-inch)
The safe ends are solution annealed. They were welded to the vessel nozzles after the vessel was heat treated to prevent sensitization.
Fermi 2 was issued its CP in September 1972. Vessel and recirculation system pipe were manufactured very early in the plant construction cycle. The systema are now in place nearly ready for the ASME Section III Hydrotest. To change out these items would 5s an extreme hardship..
By definitions in NUREG-0313, Revision 1,Section IV, all components listed above are classified as NOT SERVICE SENSITIVE. Fermi 2 agrees to implement the augmented inservice inspection and leak detection alternatives described in Section IV.B.1. of that report.
In regards to the suggested changes to our Technical Specifications, j
we agree to incorporate 3.4.3.2, Part e and ACTION d.
We also agree to incorporate 4.0.6, providing " conform to the guidelines stated in NUREG-0313, Revision 1..." includes and accepts the adoption of augmented inspection programs detailed in that document for non-conforming lines.
Very truly yours, t
Y William F Colbert Technical Director Enrico Fermi 2 MLB Attachment i
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June 5, 1981 Page 3 bec:
L. W. Schuerman F. E. Gregor E. Lusis A. E. Wegele R. M. Berg Document Control GED/16/2.0-2.2
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5.2.3.2.1.1 Piping Modifications Operating experience has shown that the line most susceptible to IGSCC is the recirculation pump discharge valve bypass line.
General Electric has developed operating procedures which do not require the use of this line, thereby enabling the line to be removed from the system.
The 4-inch sweepolets in the 28-inch recirculation pipe are closed with caps clad with Type 308L stain-less steel.
The design and installation of the caps includes in-corporation of geometries necessary for inservice UT examinations.
12 The other line cusceptible to IGSCC cracking is the reactor core spray line.
The initial design of this line for Fermi 2 specified carbon steel with a short stainless steel transition piece con-nected to the RPV stainless steel safe-end.
This transition piece has been changed to carbon steel; the safe-end has been changed to Inconel with a carbon steel extension piece.
Much of IGSCC work done by General Electric concerned the recir-culation system.
This system is exposed to reactor coolant and is fabricated of Type 304 stainless steel.
Most of this system is 28-inch and 22-inch pipe.
General Electric studies show 're-sidual stress levels in welds in this pipe are below the thres-hold to develop IGSCC.
To further reduce residual stress levels at field welds, special welding procedures were adopted which reduced the weld heat input to 50,000 joules per inch and which prohibited weld bead straightening.
In addition, special restric-tions were placed on internal grinding.
To minimize susceptibil-ity of the weld natal to IGSCC the weld metal should be 81 ferrite.
The General Electric studies show welds in 12-inch pipe in the recirculation system risers to be much closer to the IGSCC thres-hold.
To minimize IGSCC susceptibility of these pieces, they were peturned to the shop fr solution annealing and for application of a nonsusceptible inlay to the ends.
The inlay extends beyond the heat-affected zone from field welds.
Thus, no sensitized 12-inch pipe is exposed to reactor coolant.
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l 5.2-18b Amendment 12 - June 1978 l
v ru i 5.2.3.2.1.2 CRD Systcm Modificationa Some BWR plants have experienced IGSCC in the collect retainer tube in their control rod drives.
Heretofore, the water to the drives came from the condensate storage tank.
This water is not charac-teristically low in dissolved oxygen.
General Electric recommended the normal source of water for the CRD system be changed to the outlet of the condensate trestment system (which is very low in dissolved oxygen) with the condensate storage tank as the~ alternate.
Fermi 2 has incorporated this change.
(See Torus Water Management System *, Subsection 9.2.8.)
5.2.3.2.1.3 Inservice Ir.90ectj er. Leak Detection 1
NUREG-0313, July 1977, presents requirements for inservice inspec-tion and leak detection for lines which conform to methods to min-1mize crack susceptibility, for lines which do not conform, and for lines which are and which are not service sensitive.
The modifications discussed in the previous Subsections signifi-cantly reduce susceptibility to IGSCC and effectively bring all Fermi 2 lines in conformance with NUREG-0313.
Since the recircula-tion system lines (except for the bypass line) have not experienced cracking in service they are categorized as nonservice sensitive.
Therefore, no augmen,ted inspection is required for these lines.
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