ML20236D911

Safety Evaluation Re Reactor Coolant Pump Flywheel Integrity.Matl,Fabrication,Design & Insp Aspects of Flywheels Acceptable

ML20236D911
Person / Time
Site:	05000601
Issue date:	10/26/1987
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20236D909	List: ML20236D905 ML20236D911
References
NUDOCS 8710280408
Download: ML20236D911 (3)

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m~ _f[E 9.' i ENCLOSURE:1' -

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M RIOc UNITED STATES - j

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NUCLEAR REGULATORY COMMISSION  !

~ WASHINGTON, D, C. 20555

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...... j SAFETY EVALVATION BY THE OFFICE OF NUCLEAR REGULATION CONCERNING REACTOR COOLANT PUMPS (FLYWHEEL INTEGRITY) .i FOR.

. WESTINGHOUSTTESAR SP/90 DOCKET NO. 50-601 l 5.4'1.5

. . PUMP FLYWHEEL INTEGRITY.

The. safety objective of this review is to assure that the integrity of the primary reactor coolant' pump flywheel is maintained to prevent

,, failure at normal operation speeds and speeds that might be reached under accident conditions and thus preclude the' generation of missiles.  ;

The basis for review is ' outlined in St'andard Review Plan (SRP), Section  !

5.4.1.1 and the Regulatory Guide 1.14. which describes and recommends a method acceptable to the NRC staff in implementing General Design Criterion 4, " Environmental and'Hissile Design Bases" of Appendix A of L10 CFR Part 50 with regard to minimizing the. potential for failure of flywheels of the reactor coolant pump.

. EVALUATION-  !

(a) Materials and Fabrication The flywheel consists of two . thick plates bolted together. Each plate is fabricated from SA-533, Grade B, Class '. .; teel. The flywheel material is produced by a process that minimizes flaws in  ;

the material and-improves its fracture toughness properties. -The materials as well as-finished flywheels are subjected to 100 percent ~

volumetric ultrasonic inspection using procedures and acceptance standardsspecified'ipijectionIIIoftheASMECode.

The nil-ductility transition temperature (NDTT) of the flywheel material is no higher than 10 F. The Charpy V-notch energy level is at least 50 foot-pound with a 35-mil lateral expansion at 70'F in both the parallel and normal orientation with respect to the rolling .

direction of the flywheel material. Hence, the reference j temperature RTNDT. of the 10 F can be assumed.  ;

j (b) Design Basis i

The calculated stresses at the operation speed, due to centrifugal l forces and the interference fit on the shaft are within the j Regulatory Guide 1.14 limit. The pump runs at about 1190 rpm and j

E may operate briefly at overspeed up to 110 percent during the loss l of outside power. The design speed is 125 percent of the operating j speed; hence, the flywheels are also tested at 125 percent of the  !

maximum synchronous speed of the motor. The combined stresses at the design overspeed, due to interference fit and centrifugal forces i are within the Regulatory Guide 1.14 limit. l I

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The flywheels can be inspected by reiaoving the cover; hence, any:

crack.that developed can be noticed. - The inservice inspection program, a 100% volumetric ultrasonic inspection,'follows requirements of Section XI of the ASME Code and the recommendations of Regulatory Guide'1.14.

(c) Conclusion-l ,

We have' reviewed:the material, fabrication, design and inspection aspects of the pump flywheels for conpliance with Regulatory Guide-1.14. We have concluded that the structural integrity of the flywheels is'. adequate to withstand the forces imposed.by overspeed transients without the loss of function, and the flywheel will be inspected periodically to assure that the integrity is maintained.

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ENCLOSURE.2-y REQUEST FOR ADDITIONAL INFORMATION RELATEC:TO WESTINGH0VSE RESAR SP/90 DESIGN  !

-MATERIALS ENGINEERING ASPECTS .,

DOCKET NO.- 50-601 .

1. -SRP Section 6.2.7, Fracture Prevention of Containment Pressure

. Boundary. is addressed in Module 1. Section 6.5.4. The response to .

-the: requirements of the fracture.' toughness criteria for Class 2 l ferritic materials used for all containment; pressure boundary' ,

1 components be determined by the Sunmer 1977 Addenda of Section III.

of the ASME Code is.too general. We cannot determine the l acceptability of the materials within the context of General Design-Criterion 51. The materials fracture toughness must meet the requirements of Class 2 Components of the Summer 1977 Addenda of-Section III or.their equivalent.

252.1 Verify that the aging and tempering temperatures of heat treatable. i materials used in the control rod drive mechanisms are specified to eliminate coolant (4.5.1,susceptibility)to Module 5 stress corrosion cracking in reactor 252.2 What materials, cther than austeniti: stainless steels of limited coldwork-(maximum yield strength of 30 ksi) are used for reactor internals? (4.5.2, Module 5) 252.10 What is the basis (date, experiments, experience, etc.) for the use of Incoloy 800 as tube support plate material? (5.4.2.1, Module 4) 252.11 What steps have been taken to avoid corrosion / erosion of J tubes attached to the feedwater ring? (5.4.2.1, Module 4) 252.12 What are the fracture toughness requirements .for ferritic steel .,

pressure boundary components in ESF systems? (6.1.1, Module 1,10) 252.13 What are.the fracture toughness requirements for ferritic steel l pressure boundary components in main steam and feedwater gj; components?(10.3.6, Modules 6&8)

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