ML18064A754
| ML18064A754 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 05/04/1995 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18064A753 | List: |
| References | |
| NUDOCS 9505110202 | |
| Download: ML18064A754 (3) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST TO ADOPT CODE CASE N-474-2 TO USE ALLOY 690 CSB-564) FORGING MATERIAL FOR
1.0 INTRODUCTION
CONSUMERS POWER COMPANY PALISADES PLANT DOCKET NO. 50-255 The staff has reviewed and evaluated the licensee's request and supporting information to adopt this code case addition to the code requirements for the Palisades Nuclear Plant.
10 CFR 50.55a(a)(3}, states that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if (i) the proposed alternatives would provide an acceptable level of quality and safety.
The licensee has requested approval to adopt American Society of Mechanical Engineers (ASME) Code Case N-474-2 for Class 1 components within the Palisades primary coolant system.
This code case has been adopted by the ASME but has not yet been endorsed by the NRC under Regulatory Guide 1.85, "Materials Code Case Acceptability ASME,Section III Division 1."
2.0 EVALUATION
REQUEST TO ADOPT CODE CASE N-474-2 TO USE ALLOY 690 (SB-564)
FORGING MATERIAL Component Identification ASME Class 1 Components ASME Code Case N-474-1 Requirements ASME Code Case N-474-1, "Design Stre~s Intensities and Yield Strength Values for Alloy 690 With a Minimum Specified Yield Strength of 35 ksi, Class 1, Components Sect ion II I, Division l," was approved by ASME on March 5, 1990, and was endorsed for use by the NRC under Regulatory Guide 1.85. This code case allows the use of N06690 material, certified to ASME SB-163, "Specification for Seamless Nickel and Nickel Alloy Condenser and Heat Exchanger Tubes"; ASME SB-166, "Specification for Nickel-Chromium-Iron Alloy (UNS N06600 and N06690) Rod, Bar, and Wire"; ASME SB-167, "Specification for Nickel-Chromium-Iron Alloy (UNS N06600 and N06690) Seamless Pipe and Tube";
and ASME SB-168, "Speci.fication for Nickel-Chromium-Iron Alloys (UNS N06600 and N06690) Plate, Sheet, and Strip."
9505110202 950504 PDR ADOCK 05000255 P
PDR ASME Code Case N-474-2 Reguirements ASME Code Case N-474-2, "Design Stress Intensities and Yield Strength Values for Alloy 690 With a Minimum Specified Yield Strength of 35 ksi, Class 1 Components, Section Ill, Division l", was approved by the ASME on December 9, 1993. This revision of the code case included the use of forged N06690 material certified to SB-564, " Specification For Nickel Alloy Forging," for use in Class 1,Section III construction.
Licensee's Basis for Reguest Inspections at Palisades have determined that Primary Water Stress Corrosion Cracking {PWSCC), which is a potential failure mechanism of N06600 components, has degraded one power operated relief valve safe end and two pressurizer temperature element nozzles made of N06600 material. Consumers Power Company {CPCo) is currently developing contingency plans in the event that PWSCC cracking is detected in other N06600 nozzles or safe ends during future inspections. These contingency plans include the procurement of N06690 material for posstble use in repair or replacement of N06600 items.
N06690 is known for its excellent corrosion resistance in various environments, including typical PWR [pressurized-water reactor] environments.
It has been shown to be less susceptible to PWSCC than N06600.
Consumers Power Company is in the process of purchasing N06690 forgings so that potential critical path time during the inspection outage can be minimized in the event that repair or replacements of large nozzles or safe ends are necessary.
N06690, a nickel-chromium-iron alloy, has already been accepted by the U.S. NRC per Code Case N-474-1 for use in Class 1 construction.
Code case N-474-1 approved the use of the N06690 material for condenser and heat exchanger tubing; rod, bar, wire, plate, sheet or strip; and as seamless pipe and tube.
However, N06690 produced as a forging {SB-564) was not addressed by Code Case N-474-1.
Code Case N-474-2 has since been issued and includes N06690 material produced as a forging to SB-564. Since forged N06690 material retains essentially the same corrosion resistance and mechanical properties as N06690 produced in other shapes under Code Case N-474-1, it should be equally acceptable for use in a primary coolant system environment.
Pursuant to 10 CFR 50.55a{a)(3), it is requested that Code Case N-474-2 be endorsed for use at Palisades on the basis that forged N06690 material (SB-564) meeting the requirements of the Code Case is an acceptable material to be used in construction of Class 1 components conforming to the requirements of Section Ill, Division 1.
Revision 2 of the Code Case requires that the material produced as a forging meet the same requirements as N06690 material produced as
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}........ tube, rod, bar, wire, seamless pipe, plate, sheet and strip, such that the material as a forging will be acceptable for Class 1 construction.
3.0 EVALUATION/CONCLUSIONS The staff has reviewed the licensee's request for approval to use an alternative pursuant to 10 CFR 50.55a(a)(3)(i).
Input from the licensee has stated that the use of Alloy 690 (SB-564 forgings) is only a contingency option, which the utility acknowledges may or may not be implemented.
The staff agrees with the licensee that the use of the provisions of ASME Code Case N-474-2, allowing the use of forged (SB-564) Alloy 690 material, constitutes a reasonable, safe alternative to the existing requirements contained in Regulatory Guide 1.85 in that it has adequate corrosion resistance and mechanical properties for the uses desired. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), use of the licensee's proposed alternative for adoption of Code Case N-474-2 for Class 1 component at the Palisades Nuclear Plant is authorized as requested as it provides an acceptable level of quality and safety.
Principal Contributor:
C. Czajkowski Date:
May 4, 1995