ML19221B171
| ML19221B171 | |
| Person / Time | |
|---|---|
| Issue date: | 05/31/1975 |
| From: | NRC OFFICE OF STANDARDS DEVELOPMENT |
| To: | |
| References | |
| REGGD-03.029, REGGD-3.029, NUDOCS 7907200003 | |
| Download: ML19221B171 (3) | |
Text
U.S. NUCLEAR REGULATORY COMMISSION May 1975 1
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OFFICE OF STANDARDS DEVELOPMENT REGULATORY GU!DE 3.29 PREHEAT AND INTERPASS TEMPERATURE CONTROL FOR THE WELDING OF LOW-ALLOY STEEL FOR USE IN FUEL REPROCESSING PLANTS AND IN PLUTONIUM PROCESSING AND FUEL FABRICATION PLANTS A. INTRODUCTION llus guide dessnbes a method acceptable to the NRC staf f for meetmg these requnements with regard to the Section 50.M. " Contents of Applications; Tcchnical control of welding of low. alloy steel components for Infermationi of 10 CFR Part 50. " Licensing of Produe-fuel reprocessing plants and for plutenium processing tion and Utih/ation FacilitiesJ requires, among other and fuel fabrication plants tlungs, that each appheation for a construction permit or operatmg hcense for a fuel reprocessing plant include a B. DISCUSSION discussion of how the appbcable requirements of Appen-dix B "Quahty Assurance Criteria for Nuclear Power Plant 3 and Fuel Reprocessing Plantsf' to 10 Cl R Part 50 The American Society of Mechanical i ngineers Boiler will be satistied. As used in Appendix B. " quality and Pressure Vessel Code * ( ASME Cede), Section Ill, assurance-compraes all those planned and systematic
" Nuclear Power Plant Componentsf and Section Vill, actions necessary to proude adequate contidence that
" Pressure Vessels, specify requirements for fabricating safety-related structures, sy stenn, and components will components as indicated in the section titles. Many of perf onn satisfactorily in service. Appendix B requires,in the requnements of this Code can also be applied to part, that measures be established to ensure that special safety-related structures, sy stems, and components of processes, including weldmg are controlled and accomp-fuel reprocessing plants and plutonium processing and fuel fabncation plants. Specilie pottions of the ASME
- 9. hshed by quahtied personnel using quahtied procedures.
and that proper process monitoring be performed. Para-Code and of other applicable codes and standards have graph 70.D 0 of 10 CFR Part 70. "Special Nuclear ocen used for fabricating components for such plants.
Matenal," requires that each application fer alicense to Acceptable practices can ddfer significantly because possess and use special nuclear matenal in a plutonium there has not been sufficient guidance toward standard-processing and fuel fabncation plant contain a des-i/ation. In the mterest of standardi/ation, this guide
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cnption of the quality assurance program to be applied specifies procedures acceptabic to the NRC staf f for the to the design, tabncation, construction, testing. and control of preheat and in terpass temperat ures for operation of the structures, systems, and components of welding oflow alloy steels for use in the plans discussed the plant and that the description include a discussion of above. These procedures, which draw on those used for how the enteria of Appendix B to Part 50 u111 be met.
nuclear power plants, will provide a unifonn quality i
l Paragraph 704b) of 10 CFR Part 70 prosides that the level consistent with the function of safety-related Commission will approve construction of a plutonium structures, sy stems, and components of fuel reprocessing processmg and fuel f abrication plant when it has deter-plants and of plutomum processing and fuel labrication nuned that the design bases and the quahty assurance plants.
p agram preside reasonable assurance of protection j
agamst natural phenomena and the consequences af American Sodety of MeJu{o} kmc{rs} b Aer and
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potential accidents, noting that the enteria in Appendix P *
""'I C"de,19741 duion All references to the ASML j
B to 10 CFR Part 50 will be used by the Commission in
(!'de are to the 1974 edition. < opes may be obtained from the u
determining the adequacy of the quahty assuunce pro-Amencan smiety of Methamcal I nonem. Unned I nonecrmg gram.
Center,345 I ast 47th Street, New YmL N Y 10017 USNnC REGUL ATORY GUIDES Cum ments shouid he sent to the s.< rete, of two commiss.un u s Nut iea<
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Procedure Qualification in addition to the nnnimum preheat temperature, a nuumum interpass temirrature should be specified. If Sectun 111 and S'
.on Vill require adherence to the weld metal should tiansform at too high a tempera-Section IX, " Welding and Brazing QualificationC of the tuie, the required mechanical properties for the metal ASME Code, meludmg the reqnnements gosermng pro-nuy not be met. lhe maximum interpass temperature cedure quahtications for w elds Reuew of the r^ quire-varies for different steels, as does the minimum preheat ments of Section IX for prosedure qualiticatmns and the temperature, and should be selected on the basis of such tabncation requirements of Sections 111 and Vill influenemp factors as the chemical compositmn of the indicates the desirabihty of supplementary reqmrements steel.
to ensure adequate control of weldmg sanables in the production welding of low-alloy steels.
Production Welds The assurance of satisfactory welds in low-alloy steels can be increa3ed sigmticantly and. in particular, the pro-The procedure quahtication by itself does not ensure pensity for cracks (coid eracks) or reheat eracks forming that the production welds will be made within the in underbead areas and heat-affected zones (llAZ) can specified preheat temperature range. To ensure that the be nununized by maintaining proper preheat tempera-welds will be acceptable, the metal temperature should tures on the base metah concurrent with controls on be monitored dunng the weldmg process and through other weldmg variables.
postweld heat treatment.
Cold cracking can occur when the steel is hardened, ie, unJergaes a phase transformation to martensite in C. REGULATORY POSITION the llAZ and/or weld rnetal. The martensite exhibits bnttle tracture tendencies, and it may not be able to Weld f abrication* for low-alloy steel components withstand rapid cochng and the volume change associ-important to safety should comply with acceptable fab-ated with the phase transformation without the occur-rication requirements and should be performed by quah-rense of local cracking. This susecptibility to eracking fied welders and weldmg procedures in accordance with increases with higher stresses, such as those experienced the requirements of Section IX of the ASME Code with increased thickness or welding under constraint of supplemented by the following:
the parts bemg welJed, and aho increases with a de-crease in weldmg energy input. In order to avoid or min?
- 1. The procedure qui tication should require that:
mi/c the effects of hardenmg associated with phase transformation, a longer coohng time is needed for the
- a. A minimum pret eat and a maximum inte pass weld, m other words, the preheat temperature should he temperature be specified.
mamtained high enough to achiese an acceptable con.
dition of the phase transformation.
- b. The weldmg proceduce be quahtied at the minimum preheat temperature.
It is penerally recopii/ed that atomic hy drogen absorption and diffusion into and through the region
- 2. For production welds, the preheat tem perat u re being welded have an important in fluence on the should be maintained until a postweld heat treatment tendc7cy to form cracks. %)ule the lesel of hydrogen in has been performed weld tiller metal is low enough to preclude adserse ef fects in the welds, greater quantities of hydiogen can
- 3. Production weldmg should be monitored to verify be presert in the weld regwn from the dissociation of that the limits on preheat and interpass temperatures are moisture in hygroscopic welding fluxes or adsorbed on maintained.
metal surfaces if the weldmg fluxes and surfaces base not been properly dned before weld deposition. Em.
- 4. In the event that regulatory positions C.1, C.2, brittlement of metalin the weld area due to the presence and C.3 above are not met, toe weld is subject to of hydrogen generally occurs at lower temperatures and repetion. Ilowever, the soundness "f the weld may be nuy be prevented by prolonging the time the weldment veniled by an acceptable examination procedu r e.
is maintained at preheating tengrature or by per-forming a po<tweld heat tre_tuent. Prolonged time at D. !MPLEMENTATION preheating san prevent or interrupt hical hardening and assist in reduemp adverse effects of a potential hydrogen gradie n t. Tlus gradient would disappear by means of The purpose of this section is to provide information diff usion of the hy drogen be fore the weldmen t is to appheants and licensees regardmg the NRC staff's returned to room temperature. Therefore, the minimum plans for utilizing tlus regulatory guide.
preheat temperature should be established to ensure a desirable cooling rate for the weld,and this temperature should be maintained until a postweld heat treatment upphes also to v.cumg ana cu rerms af ter initial fabrica-has been achieved, th n w hen a postw cid stress-rehemg heat treatment is uwd
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Except in those cases in which the applicant proposes For those applications docketed on or before Novem-an acceptable alternative method for complying with her 3,1975, the NRC staff nuy reevaluate the appli-specified portions of the Commission's regulations, the cation on a case by-case basis to ensure that acceptable method described herein will be used in the evaluation weld quahfication and production.velding procedures of submittals in connection with applications for permits are being used, and licenses docketed after Nosember 3,1975.
e 156 116 3.29 3
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NUCLEAR REGULATORY COMMISSION W ASHINGTON. D. C.
20555 k7-p OFFICI AL B USIP4ESS MMML nec vony cou 5
PENALTY FOR PRIV ATE USE, $300 k
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