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Safe Design of Shipping Packages Against Brittle Fracture

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Safe Design of Shipping Packages Against Brittle Fracture IAEA-TECDOC-717 Guidelines lor safe design of shipping packages against brittle fracture August 1993 FOREWORD ininte n th 1992h . meetin e Standinth f go g Advisory e GrouSafth en pTransporo f o t Radioactive Materials recommende publicatioe dth f thino s TECDO efforn a Cn promoto i t t e the widest debat criterie brittle th th r n eeo a fo fracture safe desig f transporno t packagese Th . published I AHA advice on the influence of brittle fracture on material integrity is contained in Appendix IX of the Advisory Material for the IAEA Regulations for the Safe Transport of Radioactive Material (1985 Edition, as amended 1990). Safety Series No. 37. This guidance is limited in scope, dealing only with ferritic steels in general terms. It is becoming more common for designers to specify materials other than austenitic stainless steel for packaging components date ferritin Th ao . c steels canno assumee b t applo dt otheo yt r metals, hence the need for further guidance on the development of relationships describing material properties at low temperatures. methode Th s describe thin di s TECDOC wil consideree b l Revisioe th y db n Paner fo l inclusio e 1996th n ni Editio IAEe th f Ano Regulation Safe th er Transporsfo f Radioactivo t e Materiasupportine th d an l g documents f accepteI .Revisioe th y db n Panel, this advice will candidata e b upgradinr efo Safeta o gt y Practice interie th n I m. period, this TECDOC offers provisional advice on brittle fracture evaluation. It is acknowledged that, at this stage, the views expressed do not necessarily reflect those of the governments of Member States or organizations under whose auspices this manuscrip s producedwa t . CONTENTS CHAPTE . R! INTRODUCTIO N ..........................................7 . CHAPTER 2. DRAFT APPENDIX IX OF SAFETY SERIES No. 37: "GUIDELINES FOR SAFE DESIGN OF SHIPPING PACKAGES AGAINST BRITTLE FRACTURE" ..............................9 . CHAPTE . R3 JUSTIFICATIO CRACE TH F KNO INITIATIO N METHODOLOGY .....7 1 . CHAPTE . R4 JUSTIFICATIO SAFETF NO Y FACTORS .......................3 2 . CHAPTER 5. JUSTIFICATION OF REFERENCE FLAW SIZE .................... 29 CHAPTER 6. JUSTIFICATION OF MATERIAL FRACTURE TOUGHNESS .......... 33 CHAPTER 7. JUSTIFICATION OF STRESS CONSIDERATIONS .................. 39 LIS ABBREVIATIONF TO S ............................................9 4 . CONTRIBUTORS TO DRAFTING AND REVIEW .............................. 51 Chapter 1 INTRODUCTION l"\\o paragraph 198e th 5 f so Editio f IAEno A Safet Regulatione yth . Serie6 . sNo r sfo the Sale Transpor f Radioactivo t e Materia amendes (a l d 1990), infe neee r acceptablth r dfo e material properties at low temperatures, specifically at -40°C. These are para. 528 — a l\pe A requirement which also has to be met by Type B designs — and para. 556 — a requiremenB e >p l t apphing onl Typo yt packageseB associatee Th . d guidance information e 198ith n 5 Editio f IAEo n A Safet , yAdvisor 37 Serie . No s y Materiae IAEth r Afo l Regulations for the Safe Transport of Radioactive Material (as amended 1990), is essentially containe Appendin di , InfluencxIX f Brittlo e e Fractur Materian eo l Integrity. AppendiX xI is ho\\e\er limite than di t deali t s only with ferritic steel thed san n onl generan yi l termst I . relies heavily on the extensive database of these materials" low temperature properties which have been compiled since World War II, beginning with the 'Liberty Ship' problems. It is becoming more common for designers to specify materials other than austenitic stainless steel for nuciear packaging components. Such materials include ductile iron, alloy steel, titanium, depleted uranium, aluminum and borated stainless steel. All of these metals can exhibit non-ductile failur t sufficientlea temperaturw lo y t stressea d ean s belo yiele wth d strength of the material, and specifically when flaws are present. The data on ferritic steels associated \\ith low temperature properties cannot be assumed to apply to other metals and therefor necessare th e y relationships will developede havs realizeb wa o et t i dthio d T sen . that further guidance to applicants/designers would be required and that revision of Appendi f Safet o s thereforX xI wa y 7 Serie3 . e necessarysNo . Method describee ar s thin di s TECDOC usee b whicapplicants/designery dy b hma s demonstrato t competeno et t authorities thamateriale th t s chosen will maintai e packagnth e integrity at lo\\ temperatures with respect to shielding, containment, and subcriticality requirements. More precisely, it details methods that can be used to technically justify the design depending upo amoune nth f materialo t s data available specified an , s varying degrees of conservatism to be applied to these data to give assurance that failure will be prevented. The effort to revise IAEA Safety Series No. 37 began with a US Department of Transportation (DOT) proposal to the IAEA Continuous Review Committee, in June 1989, to incorporate criteria in Safety Series No. 37 to evaluate brittle fracture of nuclear material tiansportation packages. The Continuous Review Committee accepted the US proposal. At meetinthh e8t f SAGSTRAMgo Decemben i , r 1990 Science th , Technologd ean y Agencf yo Japan further propose conveno dt no-cosea t Consultants Services Meeting orden (CSMi o )rt writ e brittlth e e fracture evaluation criteria. SAGSTRAM provide e IAEdth A with five specific objectives for the CSM to address: ( 1) Revie papee wth Sorensony rb t al. e ,Proposa A :" Internationan a r fo l l Brittle Fracture Acceptance Criterio r Nucleanfo r Material Transport Cask Applications". (2) Conside l packaginal r g materials with brittle fracture characteristics. (3) Address issues of "catastrophic flaw, failure prediction, and NDE methods for significant flaws". (4) Prepare proposed advisory material for inclusion in Safety Series No. 37. (5) Submit a Consultants Report to the IAEA. conveneM TheCS n 9-1do 1 October 199 wrotd 1an edrafa t revisio Appendio nt x I f SafetXdrafe o Th ty . AppendiSerie37 . s, No Influenc xIX f Brittleo e Fractur Materian eo l Integrity, was given to CSM delegates to distribute among their own experts for a ninety day review. Comments from this review were then collate d evaluatean d a secon t a d d CSM, convene 3 Apri1- n l do 1992 . Durin e ninet th gy commen da y t period memberM CS , s were also given writing assignments that for basie m th thif so s TECDOC assignmente Th . s were collate Februarn di y 1992 and reviewed as a whole by the CSM members prior to the second meeting. secone focuseTh M d CS agreemen n do finae th lf o tversio drafe th f t no Appendi X xI to Safet improvementd an y 7 Serie3 . sNo thio st s TECDOC drafe Th t. Appendix, renamed "Guidelines for Safe Design of Shipping Packages against Brittle Fracture", will be considered by the Revision Panel for inclusion in the 1996 revision of the Regulations and supporting documents e TECDOCTh . , whic s agreewa h d upon durin e thirgth d CSM, convenen o d 21-22 October 1992, offers provisional guidance to applicants/designers on brittle fracture evaluatio e interith n ni m periode drafth f t I Appendi. s acceptexi Revisioe th y db n Panel, consideration mus givee b t upgradino nt g this TECDO Safeta Co t y Practice interime th n I . , Chapte f thio s2 r TECDOC contain e drafsth t Appendi s Safeto t it n X i xI y 7 Serie3 . sNo entirety numberine Th . g system chose Chapten ni appropriats i 2 r drafo et t Appendif o X xI Safety Series No. 37. Chapters 3 to 7 provide technical justification for elements of the provisional guidance detailed in Chapter 2. Chapte2 r DRAFT APPENDI SAFETF O X XI Y SERIE: 37 . SNo "GUIDELINES FOR SAFE DESIGN OF SHIPPING PACKAGES AGAINST BRITTLE FRACTURE" This appendix provides guidanc r evaluatiofo e f brittlo n e fractur f structurao e l component radioactivn i s e materials (RAM) transport packages o basiTw c. methode ar s discussed: (i) I-Aaluatio f ferritio n c steels using Charp r nil-ductilito y y transition temperature measurements correlated to fracture resistance; and (ii) Assessmen f fracturo t e resistance base linear-elastia n do c fracture mechanics design evaluation. The first metho addresses di provido dt e consistency with generally accepted practice for e\ aluating ferritic steels. The second method, which accounts for the majority of guidance in this appendix, provides a methodology for evaluating brittle fracture that is suitable to a \\ide range of structural materials. This guidance does not preclude alternative methods that proper!e ar } justifie package th y b d e designe accepted competene an r th y db t authority. Many materials are known to be less ductile at low temperatures and high loading rates tha t moderata n e temperature d statian s c loading conditions r exampleFo . e abilitth , f o y ferritic steel absoro t s b energy increases markedly ove a narror w temperature rangee Th . highest temperature at which complete brittle fracture occurs for ferritic steels is defined as the nil-ductility transition temperature (NDTT). Similar behaviour is exhibited by other materials, suc ductils ha e iron (DI), some aluminium alloys mand an , y plastic elastomersd san . Loadin f theso g e materials under low-ductility condition n lea o ca unstablt sd e crack propagation \\ ith subsequent brittle fracture, even when the nominal stresses are less than the material yield strength. Small crack-like defect materiae sufficiene th b n y i s ma linitiato t t e this unstable growth.
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