IAEA-TECDOC-844 Characteristics and use of urania-gadolinia fuels INTERNATIONAL ATOMIC ENERGY AGENCY The IAEA does not normally maintain stocks of reports in this series. However, microfiche copies of these reports can be obtained from INIS Clearinghouse International Atomic Energy Agency Wagramerstrasse 5 0 10 P.Ox Bo . A-1400 Vienna, Austria Orders should be accompanied by prepayment of Austrian Schillings 100, in the form of a cheque or in the form of IAEA microfiche service coupons which may be ordered separately from the INIS Clearinghouse. originatine Th g Sectio f thino s publicatio IAEe th An i was: Nuclear Material Fued san l Cycle Technology Section International Atomic Energy Agency Wagramerstrasse5 0 10 x P.OBo . A-1400 Vienna, Austria CHARACTERISTICS AND USE OF URANIA-GADOLINIA FUELS IAEA, VIENNA, 1995 IAEA-TECDOC-844 ISSN 1011-4289 © IAEA, 1995 Printe IAEe th AustriAn y i d b a November 1995 PLEASE BE AWARE THAT MISSINE TH AL F LO G PAGE THIN SI S DOCUMENT WERE ORIGINALLY BLANK FOREWORD In BWRs, the issue of power mismatch between fresh fuel assemblies and partially burned fuel assemblies causing the power in the former to be depressed was recognized at an early stage. Since the earlier absorbers used to address this issue presented inconveniences, the use of gadolinium in urania-gadolinia fuel became routine in all BWRs soon afte decisioe th r f Generano l Electri implemeno ct Dresden mid-1960se i t th i t n i n2 . fueR l vendorBW e th l sAl have since progressively adopte dtotae gadoliniath f f o l o t Ou . 420 reactors around the world with an installed capacity of 330 GW(e), approximately 90, wit installen ha d capacit GW(e)0 7 f BWRsyo e ar , . Experience with gadolinia ove pase rth t twenty years has become statistically significant, providing confidence in the concept. When advanced duty conditions (i.e. extended burnup, increased reactor cycle lengths and/or in-out core refuelling schemes) were considered and implemented in PWRs, f burnablo e us e th absorber r thasfo t reactor type also came into consideration. Theres i an obvious advantag t sacrificinno n ei fuee positiond gth ro l r burnablsfo e absorberso s , integral burnable absorbe attractivn a r fues wa l e choice gooe .Th d experience accumulated with gadolini face ath tfued thaan l t some fuel vendors were fabricatind an g R bothBW PWR fuel made gadolini prime ath e choic meeo et needse th t . recene Inth t past extendee ,th d dutie fuelR ,sPW considerer fo d an R d botBW r hfo an perceivee dth d advantage usinn si g burnable absorber WWERn s i same th r esfo reasons aPWRn i s s increase e prospectdth r gadolinisfo a utilizatio hastened nan e needth r dfo higher gadolinia contents. Against this background IAEe ,th A considere t dappropriati o et launch in 1990 a Co-ordinated Research Programme on Technology and Performance of Integrated Burnable Absorbers for Water Reactor Fuel (in short "BAF"). The aim was to issue a report summarizing the various aspects of burnable absorber utilization. The participation was on a voluntary basis. This report is the result of the inputs of the participant Co-ordinatee th o st d Research Programme. The IAEA would like to express its appreciation for the work performed by the participants and, in particular, to acknowledge the contributions of H. Bairiot (Belgium), D. Farrant (United Kingdom . OnufrieV d an ) v (Russian Federation e draftinth n d i ) gan review of this report. The scientific secretaries of the programme were successively P. Chantoin and G. Sukhanov of the IAEA, Division of Nuclear Fuel Cycle and Waste Management. EDITORIAL NOTE In preparing this publication for press, staff of the IAEA have made up the pages from the original manuscript (s). The views expressed do not necessarily reflect those of the governments of the nominating Member States or of the nominating organizations. Throughout the text names of Member States are retained as they were when the text was compiled. The use of particular designations of countries or territories does not imply any judgement by publisher,the legalthe IAEA, to status the as of such countries territories,or of their authoritiesand institutions delimitationthe of or theirof boundaries. The mention of names of specific companies or products (whether or not indicated as registered) does implyintentionnot any infringeto proprietary rights, should construednor be it an as endorsement or recommendation on the part of the IAEA. CONTENTS INTRODUCTION ...............................................7 . 1. STRATEGIC CONSIDERATIONS FOR THE USE OF BURNABLE ABSORBERS .... 9 1.1. Introduction ............................................. 9 1.2. Applications of burnable absorbers ............................. 9 1.3. Advantages and disadvantages of burnable absorber fuel ............. 10 1.4. Choice f integrateso d burnable absorbers .......................2 1 . UNIRRADIATE2 D GADOLINIA FUEL PROPERTIES ......................7 1 . 2.1. Structure and chemistry of the (U,Gd)O2 solid solutions .............. 17 2.2. Physical properties .......................................3 2 . 2.3. Mechanical properties .....................................0 4 . 2.4. Neutronic properties ....................................... 44 3. FUEL MANUFACTURING ......................................0 5 . 3.1. Fabrication processes ...................................... 50 3.2. Quality control ........................................... 53 4. DESIGN AND MODELLING CONSIDERATIONS ........................ 59 4.1. Principle f gadoliniso a fuel rod, assembl reactod yan r core design ......9 5 . 4.2. Modelling .............................................5 7 . EXPERIENC5 E WITH GADOLINIA FUEL .............................3 8 . 5.1. Utilizatio f gadolinino a fuel ................................3 8 . 5.2. Nuclear dat Neutronia— c measurements .......................0 9 . 5.3. Thermal-mechanical behaviour ..............................2 9 . 5.4. Behaviour under reactivity initiated accidents ..................... 99 . FUE6 L CYCLE BAC......................................D KEN 3 10 . 7. CONCLUSIONS ............................................. 105 APPENDI : XI GADOLINIU ERBIUD REVIEA MAN M- RESOURCE F WO S AND SUPPLY ...................................... 107 APPENDIX II: GADOLINA FUEL UTILIZATION IN FRANCE ................. 114 APPENDIX III: GADOLINIA FUEL UTILIZATION IN JAPAN ................. 121 APPENDI : GADOLINIXIV A FUEL UTILIZATIO REPUBLIE 1 TH NN 15 KOREI F CO . .. A APPENDI : XGADOLINIV A FUEL UTILIZATIO BELGIUNN I M ..............7 17 . ABBREVIATIONS .............................................5 18 . PARTICIPANTS IN THE CO-ORDINATED RESEARCH PROGRAMME ........... 191 INTRODUCTION Burnable absorber fuels (BAF utilizede beine ar ) ar r g,o considere r utilizationdfo n ,i l BWRsal mosn i , t PWR mord san e recentl WWERsn yi topie thereforTh s c.i e relevano t approximately 330 out of the 420 operating reactors in the world, representing 280 of the GW(e0 33 ) installed capacity worldwide lighe f th thi o t n sI . importance IAEe s th , Aha decide issudo t e this report providin overaln ga lvariou e vieth f wo s aspect f BAFso . With e exceptioth f Chapte no e whol th , e1 r repor devotes i t urania-gadolinio dt a fuel ("Gd fuel")1, the most commonly used BAF, and a comprehensive technical review of this topic provideds i , althoug repore hth t doe t includsno completea e surve l examplesal f yo d G f o utilization throughou industrye th t repore Th organize.s i t followine th dn i g way: Chapter 1. Strategic considerations: describes the reasons for application of BAFs, their advantage disadvantaged san varioue th d ssan absorbers being utilized. underlyine Th larga o t eg e extensucces fuedu d s G almoso i lt t f so 0 3 t years industrial utilizatio BWRsnn i applicatioe Th . PWRno t mors i e recent, as more challengin coresgR condition addition I PW . n i t no t me s e havb o et Gd fuel alternativo ,tw typeF eBA s have been develope utilizee ar d dn i dan commercial PWRs. They present advantages and disadvantages which are compare thin di s chapter. Chapter 2. Unirradiated gadolinia fuel properties: outlines the differences between Gd fuel propertie fueU d l propertiessan . homogeneousls i Eved G nf i y disperse uraniue th dn i m oxide matrix t woul,i d normally be expected to affect the properties of the fuel for three reasons. Firstly naturae th , l structur oxid d body-centerea G s ef i e o d cubic lattice, while U oxide is a face-centered cubic lattice. Secondly, Gd is a trivalent atom, unlik whic, eU tetravalenhs i nuclean i t r fuel. Thirdly absorptioe ,th n cross sections of the various Gd isotopes interfere with the resonances of the U isotopes. Both of the first two differences influence or are likely to influence the physical and mechanical properties of BAF in "as-fabricated" conditions. Moreover, the fabrication technique influences the dispersion of Gd within the fuel. Chapter 3. Fuel manufacturing: deals with the specific fabrication processes and quality control techniques for Gd fuel. Although fabrication techniques to produce perfectly homogenous Gd fuels have been developed l industriaal , l fabrication processe basee a sar n do mechanical blending of the two ingredients. Specific quality controls are implemented to verify the proper dispersion of Gd within the BAF fuel and specifiee th d fuepositioninF lfue e BA rod th e l n sth assemblyi f go . Chapte . 4 r Desig modellind nan g considerations: describe specifie th w csho properties of Gd fuel and the manufacturing constraints are taken into account for utilization of Gd in BWRs, PWRs and WWERs and how the modelling codes incorporate Gd fuel properties. 1 urania-gadolinia fuel is usually called "gadolinia fuel" within the nuclear industry. In this report, for convenience, the abbreviation "Gd fuel" is being used. Design flexibility is afforded by the use of Gd: the location of the Gd fuel rods within the fuel assembly and the axial shaping of the Gd along the Gd fue tunele rodsb varioun do t ,ca s design objectives (e.g. reduced fabrication cost, improved design margins, improved reactivity evolution and so on).