ML19221A845
| ML19221A845 | |
| Person / Time | |
|---|---|
| Issue date: | 08/31/1975 |
| From: | NRC OFFICE OF STANDARDS DEVELOPMENT |
| To: | |
| References | |
| REGGD-01.014, REGGD-1.014, NUDOCS 7907100083 | |
| Download: ML19221A845 (4) | |
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Havision 1 U.S. NUCLEAR REGULATORY COMMISSION August 1975 REGLA ORYGUDDE OFFICE OF STANDARDS DEVELOPMENT REGULATORY GUIDE 1.14 REACTOR COOLANT PUMP FLYWHEEL INTEGRITY A. INTRODUCTION conditions that would cause such overspeed. Methods ef limitmg potential pamp overspeed are also under investi-General Design Cntenon 4. " Environmental and ga tion.
Missile Design Bases," of Appendix A, " General Design Critena for Nuclear Power Plants," to 10 CFR Part 50, if the Oywheel of the reactor coolant pump is
" Licensing of Production and Utdization Fa cih tie s,'
corsenatisely designed and made from suitable mate-requires that nuclear power plant structures, sptems, nals with closely controlled quahty,if adequate design and components important to safety oe pretected resiew of new configurations is provided, and if ade-against the effects of missiles that might result from quate msenice inspection is provided, the probabdity of equipment failures. This guide dessnbes a method a flywheel failure is suf0ciently small that the conse-accet table to the NRC staf f of implementmg this quences of failure need not be piokctedagamst.
requirement with regard to minimizmg the potential for failures of the flywheels of reactor coolant pump motors Mater-Is for rump Alywhcc s should be manufac-5 in hght-water-cooled power reactors.
tured by processes the misunsae Raws and result in adequate fracture targhncss tn both the transserse and B. DISCUSSION longitudmal rolling ducetions. Matenajs produced by vacuum meltingand deg. sag or the electroslag remelt.
The 0) wheels on reactor coola,t pump motors mg process arelmwn to have improved cleanhness and provide inertia to ensure a slew decrease in coolant now toughne s. Mate anatenal should be cross rolled to a raua m order to present fuel damage as a result of a loss of of at least 1 to 3, sufficient to actueve acceptable power to the pump motors Dunng operat:en at normal isotropy. Fracture toughness is achined more readdy in speed, a Hywheel has su fficien t kinetic energy to thitis.er plates, and fabncation of lammated Oywheels by p.aduce high-energy missiles and excessne vibration of awabhw them from seseral plates is acceptabb the reactor coola nt pump assembly if the Gywhc.cl should fail. Overspeed of the pump rotor anemMy As en example, past esaluations h.ne shown that dunng a transient increases both the potential for failure ASMI: SA 533a Class I and SA-508 Classes 2 and 3 and the kinetic energy of the flywheel The safety matenals generally have suitable tougimess for typical consequences could be sigmficant because of posst$'e flywheel apphcations provided stress concentrations are damage to the reactor coolant systeri, the containment, kept withm reasonable limits and the reference tempera-or other equipment or systems impor: ant to safety, tuie RTN97, determined in accordance with Article NR2331(a) of Section 111 of the ASME Code ' is at Methods of predictma the loss-of-coolant accident least 50 C (90 F) below the lowest temperature at (LOCA) oserspeed conditions ue under continumg which operating speed is achiesed For other matenals investigation. The hmit ou pradicted pump overspeed in that may be considered for 0 wheels, the strength and 3
the event of a !.DCA should be less than the calculated toughness properties should be evaluated and justified entical speed for faihur of the Oywheel. The conserva.
for this appbcation.
tism inheteilt la the latter calculation, coupled with a realiMig pred4c!%QIt g maximum rotationa] speed, is Copes may be obtamed from the Amencan Societs of corisidered to provide adequate margin because of the Mechanical i npneen, Uruled I nrjneenng Center, 34 5 1 ast low probabibty of occurrence of the specific LOCA 47th Street, New York, New York 10017.
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7907100053
The non ductile fracture analysis called for in The desired results of the analy ses desenbed in regulatery posnion C.2 d should be based on apprepnate 12 tory positions C.2.c. d, and e are quantitative conse rs atn e assumptions for stress !esel, Oaw size,
_ mates of the marpns agamst fracture or excessive temperature, and fracture roughness at the location of dcformation dunng overspeed because such estimates, in t e re st. The non-d uc tile fracture cntenon used to coupled wrth adequate proustons against oserspeed, predxt the entical fracture speed should be based on provide the best basis for assurance that the piobability iruttal mstabihty of the flaw as defined m ASTM E 399.
of failure under normal and transient conditions is
'Ihe justi0 cation for the stress analysis method used m sufficiently small that the con,equences of failure need the fra:ture analyus should desenbe the treatment of not be protected agamst.
stresses ansmg frem mterference fits and thermal stresses when they are supenmposed on th? stresses caused by C. REGULATORY POslTION rotational forces. Justification for the Gaw stie estimate should consider it to be the maumum expected size of 1.
Material and Fabrication flaw that could conceivably escape detection, and should conuder matenal thickness. method and 3equency of a.
The flywheel matenal should be of closely nondestructive inspection, and anclysis cf Oaw grow th m controlled quality. Plates should conform to ASTM A20 faugue tf that is sigmficant. The effect cf cracks and should be produced by the vacuum-ruitmg and emanatmg from such structural disontmui% as key-degassing process or the ele.:troshg remdting process.
ways ar.d bolt holes should be esaluated. Ju3 3f cation Piate material should be cross-rolled to a ratio of at least i
for the fracture toughness assumed for the : taterial I to 3.
should desenbe the properties to be metsured t.ansverse to the rolling direction in the tests of each plate of b.
Fracture toughness and tensile properties of matenal. The range of fracture toughness test tempera-each plate of Oywheel material should be checked by tures should includt the lowest grvice temperature at tests that yield results suitable to confirm the applica-2 which overspeed could occur. If not, the basis used for bility to that flywheel of the properties used in the any extrapolation should be justified.
fracture analyses called for in regulatory positions C.2.c, d, and e.
In doing the fracture analysis desenbed in regulatory All Game-cut surfaces should be removed by position C.2.d, engmeering judgment should be used to c.
select for analysis only those locations t}at appear to machining to a depth at least 12 mm (1/2 inch) below have the most severe sets of conditions. Seventy is a the flame-cut surface.
function of stress level, flaw size, and fraeture toughness at the location of interest. Companson of perhaps three d.
We'dm g, includmg tack welding and repair or four cases in terms of Kj/Kje, the ratm of the welding should not be permitted m the finished flywheel imposed stress intensity factor at some nonunal speed to unless the welds are inspectable and considered as the material toughness, should locate to most severe sets potential sources of flaws in the fracture analysis.
of condiuons. Evaluation of the critical speed for fracture, which may require techniques that go beyond 2.
Design hnear elasuc fracture mechanics, may then focus on one The flywheel assembly, including any speed-entical location.
a.
limiung and antirotation devices, the shaft, and the Excessive deformation dunng overspeed of the bearings, should be designed to withstand normal condi-flywheel is of concern because damage could be caused tions, anticipated transients, the design basis loss-of-by separation of the Gywheel from the shatt.1 or the coolant accident, and the Safe Shutdown Earthquake purpose of this guide, excessive deformation means any loads without loss of structuralintegrity.
deformation such as an enlargement of the bore that cou!d cause such separation directly or could cause an b.
Design speed should be at least 125'T of normal unbalance of the Dywheel leading to structural fat!ure or speed but not less than the speed that could be attained separadon of the Oywheel from the shaft. The calcula-dunng a turbine overspeed transient. Normal speed is tion of detonnation should employ elastic. plastic meth-defined as the synchronous speed of the a.c. dnve motor ods unless it can be shown that stresses remain withm at 60 hertz.
the elastic range.
An analysis should be conducted to predict the c.
The geometry of the 0 wheel and pump motor cntical speed for ductile fracture of the flywheel. The 3
design should facilitate preservice and mservice inspec-methods and limits of parapaph F-1323.l(b)in Section non of all high-stress regions (bore, keyway, and bolt 111 of the ASME Code are acceptable. If another method hole regions) without the need for removal of the flywheel from its shaft and preferably without the need for removmg the rotor from the motor assembly.
new results should be induded a' rar: of the TSAR.
2 125 050 1.14-2
is used, justi0catmn should be provided. The analysis b.
Inservice mspection should be performed for shou?d be submitted to the NRC staff for evaluation) each Cywheel as follows-d.
An analy sis should be conducted to predict the entical speed fer nonduettle fracture of the Gywheel.
(1) An in-place ultrasonic volumetnc examina-tion of the areas of higher stress concentradon er the Justification should be gnen for the stress analysis bore and keyway at approximately 3-year intervals, method, the estimate of Raw size and location, which should take into account imtial size and Gaw growth in dunng the refuelmg or maintenance shutdown coin-senice, and the vajues cf fracture toughness assumed for ciding with the inservice inspection schedule as required the matenal. The analysis should be submitted to the by Section XI of the ASME Code.
NRC ataff for eva'uatien.'
(2) A surface examination of t.'s exped sur-e.
An analysis should be conducted to predict the cr tical speed for excessive
- deformation of the fly.
faces and complete u!trasonic volumetnc examination at mel. The analysis should be submitted to the NRC approximately 10 year mtervals, dunng the plant shut-st. ff fer evajuation.2 down comcidmg with the inservice insection schedule as required by Secuon XI of the ASME Code.
f.
The normal speed should be less than one-half of the lowest of the entical speeds calculated in regulatory positions C 2.c, d, and e above.
(3) Examination procedures should be in accordance with the requirements of Subarticle IWA 2200 of Section XI of the ASME Code, g.
The predicted LOCA overspeed should be less than the lowest of the entical speeds calculated in (4) Acceptance entena should conform to the regulatory pos4twns C.2 c., d, and e.
recommendations of regulatory position C.2.f.
3.
Testing (5) If the examination and evaluation indicate n increase in flaw size or growth rate greater than tach fivwheel assembly should be spin tested at the design spee5 of the fh whee).
predicted for the serv ce hfe of the dywheel, the results of the examination and evaluation should be submitted 4.
to the staff for evaluation.
Inspection D. IMPLEMENTATION Following the spin test desciibed m regulatory a.
posidon C.3, each finished flywheel should receise a check of cntical dimensions and a nondestructne exam.
The purpose of this section is to provide informa-ination as follows:
tion to applicants and licensees regardmg the staff's plans for utihzing this regulatory guide.
(!) Areas of higher stress concentrations, e g.
bares, keyways, splines, and dnlled holes, and surfaces Except in those cases in w hich the apphcant adjacent to these areas on the Gnished flywheel should proposes an acceptable alternative method for com-be exammed for surface defects in accordance with plymg with speciGed portions of the Cornmiss. ion's paragraph Nik2545 or NB-2546 of Section ill of the regulations, the positions of this guide will be used by the NRC staff as follows.
ASME Code usmg the procedures of paragraph NB 2540.
No hnear indications more than 1.6 mm (1/16 inch) 1.
The recommenda: ions of regulatory positions long, othe than lammations, should be permitted.
C.1, C.2, C.3, and C.4.a w,Il be used in evaluating (2) Each finshed flywheel should be subjected submittals for construction permit apphcations docketed to a 10if J mlumetne examinatica by ultrasonic meth.
on or after January 1,1976. If an applicant wishes to use the recommendations of regulatory positions C.I.
ods usmg procedures and acceptance entena specified in C.2, C.3, and C.4.a of this regulatory guide in developing paragraph NB-2530 (for plates) or paragraph NB 2540 submittals for an appbcation docketed before hnuary 1, (for forgmes) of Section ill of the ASME Code.
1976, the pertinent portions of the appbcation will be evaluated on the basis of this guide.
'The analy ses outhried in regulatory povtmns C.2.c. d, and e 2.
The recommendations of regulatory position should preferably be submitted in topical reports rather than on a case +y-caw basis far thow fly w heel designs that will haw C.4.b will be used Hi evaluating procedures used in mulhrle arrik atons.
inservice inspections conducted on all plants after January 1,
1976. If a hcensee washes to use the S'
recommendations of regulatory position C.4
' As aenned in the thuumn 125 OS 1.14-3
regulatory guide in performing the inspection before quently become effective per paragraph G ) of @ 50 552 January 1,1976, the pertinent portions of the inspec-for any portion of the inspection.the pertinent portions tion procedures will be evaluated on the basis of this of the inspection procedures will be evaluated on the basis of those editions and addenda.
guide. Where requirements of Section XI are recom.
mended, examinations conducted during c:ch 40-monti inspection pened should mcet the code edition and ali 3.
The recommendations of this guide will be used sddenJJ that were in effect per paragraph (b) of 10 CFR s 50.55a 6 months prior to the mspectio.1 period. If 2 in evaluating all topical reports on flywheel integrity bcensee wishes to use editions and addenda that subse.
after January 1,1976.
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