ML19221B094
| ML19221B094 | |
| Person / Time | |
|---|---|
| Issue date: | 11/24/1975 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| NUREG-75-087, NUREG-75-087-05.4.1., NUREG-75-87, NUREG-75-87-5.4.1., SRP-05.04.01.01, SRP-5.04.01.01, NUDOCS 7907120413 | |
| Download: ML19221B094 (6) | |
Text
N U R EG-75/087 pa prog f
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U.S. NUCLEAR REGULATORY COMMISSION h[3[/OFFICE OF NUCLEAR REACTOR
\\.V SECTION 5.4.1.1 PUMP FLYWHEEL INTEGRITY (PWR)
REVIEW RESPONSIBILITIES _
Primary - Materials Engineering Branch (MTEB)
Secondary - None 1.
AREAS OF FEVIEW General Design Criterion 4 requires that structures, systens, and conponents of nuclear power plants important to safety be protected against the effects of nissiles that might result from equipment failures. Because flp heels have large masses and rotate at speeds of 900 rpu or 1200 rpn during normal reactor operation, a loss of integrity could result in high energy missiles and excessive vibration of the reactor coclant pu'"p assembly. The safety consequences could be significant because of possible damage to the reactor coolant system, the containment, or the engineered safety features.
The following areas relating to reactor coolant pump flywheel integrity are reviewed:
1.
Materials Selection Reactor coolant pamp flywheels are of a simple geometric shape, and are made of ductile ma te ri al. Their quality can be closely controlled and their service conditions are not severe; therefore, the use of suitable material, coupled with adequate design and inservice inspection can provide a sufficiently small probability of a flywneel failure that the consequences sf failure need not be protected against.
Information in the applicant's safety analysis report (SAR) on materials selection and the procedJres used to minimize fiaos and improve necnanical properties is reviewed to establish that sufficient information is provided to permit an evaluation of the adequacy of the flywheel materials.
2.
Fracture Toughness The fracture toughness of the materials, including materials tests, correlation of Charpy specimens to fracture toughness parameters, or the alternate use of a nil-ductility transition reference temperature (RTNDT), are rMwed to esWish M W @ eel materials will exhibit adequate fracture toughness at nornal operating temperature.
USNRC STANDARD REVsEW PLAN
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3.
Preservice Inspection The descriptive information is reviewed to verify that the bore of the flywheel is cachined to final dimensions if it is flame cut, and that ultrasonic and surface inspections are performed on all finished machined surfaces.
4.
Flywheel Design The flywheel design information including allowabie stresses, cesign everspeed considerations, and shaf t and bearing design adequacy, is reviewed.
5.
Overspeed Test The applicant's overspeed test procedures are reviewed to estabiish their adequacy.
6.
Inservice Inspection A description of the preservice and postoperational phases of the inservice inspection program, including types of inspections, areas inspected, frequencies of inspection, and flaw acceptance criteria, is reviewed.
II. ACCEPTANCE CRITERIA The acceptance criteria for the areas of review described in Section I of this plan are provided in Regulatory Guide 1.14, " Reactor Coolant Pump Flywneel Integrity," and are as follows:
1.
tuterials Selection The applicant's selection of flywheel material is acceptable if it is in accoraance with the following criteria:
The flywheel material must be produc?d by a process (such as vacuum melting or degassing) that minimizes flaws in the raterial and improves its fracture toughness properties.
The material must be examined and tested to neet the following criteria:
a.
The nil-ductility transition (NDT) temperature of the flywheel r'aterial, as ebtained fron drop-weight tests (DWT) performed in accordance with the specifica-tion ASTM E-203 (Ref. 3), snould be no higher than 100F.
b.
The Charpy V-notch (C ) upper-shelf energy level in the Neak" direction (WR y
orientation in plates) cf tne flywheel material should be at least 50 f t-lbs.
A minimum of three C specimens should be tested from each plate or forging, in y
accordance with ASTM A-370 (Ref. 4).
2.
Fracture Toughness The following fracture toughness criteria are derived from Regulatory Guide 1.14, C.l.c, and the ASME Boiler and Pressure Vessel Code-(hereafter "the Code"),Section III, Appendix G.
The pump flywheel fracture toughness properties are acceptable if they are in compliance with the following criteria:
The minimun static fracture tcughness of the material at the normal operating tempera-ture of the flywheel should be equivalent to a critical stress intensity factor, KIc' of at least 150 ksi vE Cornliance can te demonstrated by either of the following:
}hh 5.4.1.1-2
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a.
Testing of the actual material to establish the K valu at the normal operating k
temperature, b.
Determining that the normal operating temperature is at least 100*F above the RTNDT' 3.
Preservice Inspection The following preservice inspection criteria are derived from Regulatory Guide 1.14, C.l.d, C.l.e. and C.l.f.
The applicant's preservice inspection program including finish machining and ultrasonic and surface inspections is acceptable if in compliance with the following criteria:
a.
Each finished flywheel should be subjected to a 1001 volumetric examination by ultrasonic methods using procedures and acceptance criteria specified in Code Section III, NB-2530 for plates, and NB-2540 for forgings.
b.
If the flywheel is flame cut from a plate or forging, at least 1/2 inch of uaterial should be lef t on the outer and bore radii for machining to final dimensions.
c.
Finish machined bores, keyways, splines, and drilled holes should be subjected to magnetic particle or liquid penetrant examination.
4.
Flywheel Design The following flywheel design criteria are derived from Regulatory Guide 1.14, C.2.
The applicant's flywheel design is acceptable if in compliance with the following criteria:
The flywheel should be designed to withstand normal conditions, anticipated tr;nsients, the design basis loss-of-coolant accident, and the safe shutdown earthquake without loss of structural integrity.
The design of the pump flywheel should meet the following criteria:
a.
The combined stresses at the normal operating speed, due to centrifugal forces and the interference fit of the wheel on the shaf t, should not exceed 1/3 of the ninimum specified yield strength or 1/3 of the measured yield strength in the weak direction of the material if appropriate tensile tests have been performed an the actual material of the flywheel, b.
The design overspeed of a flywhee should be at least 10; above the highest anticipated overspeed. The antic' pated overspeed should include consideration of the maximum rotational speed of t.1e flywheel if a break occurs in the reactor coolant piping in either the suction or discharge side of the pump. The basis fcr the assumed design overspeed should be submitted to the staff ~or review.
c.
The combined stresses at the design overspeed, due to centrifugol forces and the interference fit, snould nct exceed 2/3 of the minimum specifiec yield strength, or 2/3 of the measured yield strength in the weak direction if appropriate tensile tests have been performed on the actual material of the flywheel.
d.
The shaf t and the bearings supporting the flywhcal should be able to withstand any codination of loads from normal operation, anticipated transients, the design basis loss-of-coolant accident, and the safe shutdown earthquake.
147 04 5.4.1.1-3
d.
Overspeed Test The following overspeed test criterion is taken from Regulatory Guide 1.14, C.3.
The applicant's Comitment to perform an overspeed test is acceptable if each flywheel assembly is to be tested at the design overspeed of the flywheal.
6.
Inservice Inspection (ISI)
The following inservice ins ection program criteria are derived from Regulatory Guide 1.14, C.4.
The applicanc's ISI program is acceptable if in compliance with the following:
a.
A volumetric examination by ultrasonic methods of the areas of higher stress con-centration at the bore and keyway at approximately 3-1/3 year intervals, during the refueling cr maintenance shutdown coinciding with the inservice inspection schedule as required by the Code,Section XI.
Removal of the flywheel is not required.
b.
A surface examination by liquid penetrant or magnetic particle methods of all exposed surfaces, and look volumetric examination by ultrasonic methods at approxi-mately ten-year intervals, during the plant shutdown coinciding with the inservice inspection schedule as required by the Code,Section XI.
Removal of the flywheel is not required.
c.
A preservice baseline inspection incorporating all the procedures of a and b above, which should establish initial flpheel conditions, accessibility, and practicality of the program, d.
Examination procecures and acceptance criteria should be in conformance with the requirements specified in II.3.a.
III. REVIEW PROCEDURES The reviewer will select and emphasize material from the procedures described below, as may be appropriate for a particular case.
For each area of review, the following review procedure is followed:
1.
Materials Selection _
The materials selection, including the procedures to minimize flaws and improve nechanical properties described by the applicant, are reviewed and compared with the rec;uirenents of Section II.1 of this plan. If it is a new material not used in prior licensing cases, the materials selection is reviewed and evaluated to establish its acceptability. Based on past evaluations, the following materials are suitable for pump flywheels provided that the/ reet all the criteria listed in II. I and II. 2 of this plan: ASME SA-533-B Class 1, ASME SA-503 Class 2, and AS'iE SA-516 Grade 65 (Ref. 2).
2.
Fracture Toughness The fracture toughness properties of the flywheel materials, including test data where applicable, are reviewed and compared with tne requirements of Section 11.2 of this plan. Two alternative nethods for deriving the fractse toughness of the flywheel materials are acceptable. The value of the critical stress intensity factor is based on 5.4.1,1 4 f
y-I DD
fracture mechanics testing, while the use of the reference temperature approach is based on the stated normal operating temperature of the flywheel and the actual 8
reference nil-ductility transition temperature of the materials, if an operating license review, or as specified, if a construction permit review.
3.
Preservice Inspection The preservice inspection program. including finish machining, and ultrasonic and surface ins?ections described by the applicant is reviewed and compared with the requirements of Section 11.3 of this plan. The extent to which the ultrasonic inspections proposed and the acceptance criteria in the SAR agree with Code Section III, HB-2530 for plate materials or NB-2540 for forgings, are reviewed.
4.
Flywheel Design The design and stress analysis procedures used for the flywheel are reviewed, including the following areas:
a.
Load combinations at normal operating speed and allowable stresses.
b.
Design overspeed and basis for selection of design overspeed.
c.
Load combinations or design overspeed and allowable stresses.
d.
Shaft and bearing load combinations.
The information given in the SAR is compared and evaluated against Section 11.4 of this plan.
5.
Overspeed Test The arplicant should confirm that an oversked test will be run in compliance with Section II.5 of this plan.
6.
Inservice Inspection _
The inservice inspection program described by the applicant in the plant technical specifications, including areas to be inspected, metnods of inspection, frequency of inspection, and acceptance criteria, is reviewed and compared with the requirements of Section II.6 of this plan.
IV.
EVALUATION FINDINGS The reviewer verifies that sufficient information has been provided in accordance with the requirements of this review plan, and that his evaluation supports conclusions of the following type, to be included in the staff's safety evaluation report-
"The probability of a loss of pump flywheel integrity can be minimized by the use of suitable ruterial, adequate design, preservice spin testing, and inservice inspection.
"The aoplicant's selection of materials, fracture toughness tests, design procdures, preservice overspeed spin testing program, and inservice inspection program for reactor coolant pump flywheels have been reviewed and found acceptable on the basis of conformance with Regulatory Guide 1.14, " Reactor Coolant Pump Flywheel Integrity," and established industry codes and standards.
5,4.1.1-5
"The use of suitable materials with adequate fracture toughness, conservative design procedures, preservice testing, and inservice inspection for flywheels of reactor coolant pump motors p* ovide reasonable assurance of the structural integrity of the flywheels in the event of design overspeed transients or postulated accidents.
Conformance with the recommendations of Regulatory Guide 1.14 constitutes an acceptable basis for satisfying in part the requirements of General Design Criterion 4."
V.
REFERENCES 1.
10 CFR Part 50, Appendix A, General Design Criterion 4, "Envircnmental and Missile Design Bases."
2.
ASME Boiler and Pressure Vessel Code, Sections II, III, and XI, American Society of Mechanical Engineers.
3.
ASTM E-208-69, " Standard Method for Conducting Drop-Weight Test to Cetermine Nil-Ductility Transition Temperature of Ferritic Steels," Annual Book of ASTM Standards, Part 31, hnerican Society for Testing and Materials.
4.
ASTM A-370-72, " Methods and Definitiens for Mechanical Testing of Steel Products,"
Annual Book of ASTM Standards, Part 31, American Society for Testing and Materials.
5.
Regulatory Guide 1.14. " Rear. tor Coolant Pump Flywheel Integrity" (originally Safety Guide 14).
)kf })f 5.4.1.1-6