JAERI 1310 o CO 111 Study on the Solid State Chemistry of Ternary Uranium Oxides March 1988 13 ffi % Fir Japan Atomic Energy Research Institute *«•: {• Him Wififli; * a *-fl '-f. I fit n Hi b<« )t;iii g$ii. .viil Illlii iiifi fliii He; r )j«,'i KII;! ii:* fik *ff *'i *• i' Art dCi i'-*1 i:-?Sli) H»t ji»v <n;! ft-tiM ••;•-» I * K;.i| ("'• i •' I- --7;>i;) •># PI' <i>i)ib'mft'VrttWX.:ftiV.%> J;i|>an Aluinu- KDITRJ1 Kcscnivh Inslitiili' Hoard (it I'xlilciis 'I'liyniii'ii l-'ukctii iChirl Kflitiiii Jun Ak;iisln ^ ukii) Khimmiii Taken Kmnm Ynshiaki Futiimura Hideo Kzurr Taiian Iwala Katsuichi Ikawn MivuKi HaRiwaia ^'.l^hilnlv.i Kancko Miroshi Kaw;inuir;i Yukici IshiKuni Ilirnshi Kudo Kcizcv Makuuchi Satoru Kawasaki Susumu Muraoka Naomoto Shikazono Yoshiu Muraci Shinzn Sailo Knzo Tachikawa Tatsuo Oku Yasun Suzuki Akira Yamamnto Tatsunki Takeda Kazuvuki Tamura JAKKI u .t,- h !i, T-fiiV-u J: JAERl reports are reviewed by the Board of Editors and issued irregularly. Inquiries about availability of the reports should be addressed to information Division Department of Technical Information, Japan Atomic Energy Research Institute, Tokaimura, Naka-gun, Ibaraki-ken 319-11, Japan. ©Japan Atomic Energy Kescarch Institute. 1988 Ifcili**})- H ¥ ISi i- il W % # PP m <• > '.£ !, $ r=i) m «* JAERI 1310 Study on the Solid State Chemistry of Ternary Uranium Oxides Toshiyuki Yamashita Department of Chemistry Tokai Research Establishment Japan Atomic Energy Research Institute Tokai-mura, Naka-gun, lharaki-ken Received September 9, 1987 Abstract With the increase of burnup of uranium oxide fuels, various kinds of fission products are formed, and the oxygen atoms combined with ihe consumed heavy atoms arc freed. The solid stale chemical and/or thermodynamic properties of these elements at high temperatures are complex, and have not been well clarified. In the present report, an approach was taken that the chemical interactions between UO2 and these fission products can be regarded as causing overlapped effects of composing ternary uranium oxides, and formation reactions and phase behavior were studied for several ternary uranium oxides with typical fission product elements such as alkaline earth metals and rare earth elements. Precise determination methods for the composition of ternary uranium oxides were developed. The estimated accuracies for x and y values in MyU^yOj-tx were ±0.006 and ±0.004, respectively. The thermodynamic properties and the lattice parameters of the phases in the Ca-U-O and Pr-U-O systems were discussed in relation to the composition determined by the methods. Crystal structure analyses of cadmium monouranates were made with X-ray diffraction method. Keyword: Ternary Uranium Oxides, Phase Behavior, Crystal Structure Analyses, Ca-U-O system, Pr-U-O system, Cadmium Monouranates, Thermodynamic Properties, Uranium Oxide fuels. Alkaline Earth Metals, Rare Earth Elements. JAERI1310 JAERI1310JAERI 1310 三元系ウラン酸化物の固体化学的研究 11 11 11 ~，:Ii;(*n; i (- r-1) W研究5 pJj' ，/.[似研究所化，，(・， 'ti; i1 ill1 ト手K fiIJ | 之J: 1987 1987 198 7 ft f| 9 JJ I) 9 11 ll-i企-J'I' 要旨 内町化物伊¥1' IUJ!I!l 川に(，，，い， t 州問 (1 にわ t.: る ~4 う r ~~ 'J.. IA.tM' )'t '1 すると 11.に， ，'， IL.{ ， UJdHl によりK: j l • :1- ~iU・か i位州 l する・ ':':ltM で小. これら Jしょの 1 ，'， 1 休 ft ・'j':/札止、および熱 Jrγ (f (J)ìt~~JIJIII"1 てあり. 充分前日)!さ れていIiい，4 re i >'.; i'. 4本、 d判刈 1世J; 山1ヘ' ζ[はl. U(υ} とこれ ら 4伐4 う汁r~烈1T刊'1村1I戊~J約物守切J と ω(化じじ，戸";"下j"戸':(的1ド内(HI州111川i， rt 川"リl1令~t .1札L ;i、4糸4 1111 ドτ寸! るγフtけ，- .，.~そ1む，と{り>， γ，ルレ力 IリI1 町t( t~金.~II.~川d や庁爪i 十.t町1 {(t自tl叫じ A本:1心i ど dω)f代~"dl(JI ，ト" '， r~N.I"" 物-!t: (，む :1 0，;.#，ウ 7' 〆限化物に'八、て，XWfL^lcn'T. '1 ' 1-.1&1:.(1むを，， -.ijliI<lo-^..l.y-^1M べ， , HI HI'fcWj&.-R*')/.:子制を:1<:め 1: ，. ~，Wlfi\;ici;i>TlIi" ・先においてはi ./}L~Lミウフン償化物 U) ホ1Ii1\i. viWMWifru)M';'もう HI 川、ィ、け f Mj';rc*>1'1、てあることからレ4 C i«>0. •Hiw.jWHiI ， lω ぷ料 htl<約 (*'j20mR20mg)> に~.JLて.熊本ic J.| L T. WS*Mh\ および念 IIIÍ 比の定 I.H，'， J!'[か.それそれ，Hi A'. ZU-cil. '0 • 0.00，006 6 とi 10 < ，0.00004 4てある制 •C<fc5tflli>K5>IJnJ.-£liHfcl成分析訟をlilJ it Ltこ.これをl A:. C^l-III^"1¥ 、て力ルンウムおよびT * 't •> ^ Afc J;y'7 7 うセ寸ンムを frι 、九 P じ .fl~ ウラ:/ l¥1.i化物の熱心 γ: 的刊'cfを， Hlil ¥i.と ωIlll i!1lにお L て品品Ltニ.また.こ れら 1，'小 'fif，j; ω陥{正数の m，，¥i. fli( l!'t を;どめた， x t~ 川 tlí iJ， 1 こより.力トミウムーウラン照時aω" ，liMrf高治 を解析 L tニ. r JAERI 1310 CONTENTS 1. Introduction I 1.1 Background and objectives of this study 1 1.2 Review on ternary uranium oxides wity alkaline earth metals 3 2. Study on analytical methods for the determination of the composition of ternary uranium oxides 12 2.1 Gravimetric method by addition of alkali or alkaline earth metal nitrates .... 12 2.1.1 Introduction 12 2.1.2 Principle of the method 13 2.1.3 Experimental 14 2.1.4 Results and discussion IS 2.2 Cerium(IV)-iron(II) back titration method 17 2.2.1 Introduction 17 2.2.2 Theory 18 2.2.3 Experimental 19 2.2.4 Results ami discussion 20 3. Formation and some chemical properties of alkaline earth metal monouranates 23 3.1 Introduction 23 3.2 lixperimental 23 3.3 Results and discussion 24 4. The crystal structures of CdUO4 34 4.1 Introduction 34 4.2 Experimental 34 4.3 Structure analysis 37 4.4 Discussion of structure 40 5. Study on the phase behavior of CayU|_yO2+, solid solution 43 5.1 Introduction 43 5.2 Experimental 43 5.3 Results and discussion 44 6. Phase relations and crystal chemistry in the ternary PrOls-UO2-O2 system 51 6.1 Introduction 51 6.2 Experimental 52 6.3 Results and discussion 53 7. Reaction of lithium and sodium nitrates and carbonates with uranium oxides .... 65 7.1 Introduction 65 7.2 Experimental 67 7.3 Results and discussion 67 8. Conclusions 76 Acknowledgements 80 References 81 JAERI 1310 § 1. If rim 1 1.1 flf'ftwfl-irtinn'j i 1.2 r/u^j II i-.si^W •> v > ;./i.ftfftftnncii!-!-t*Wi\:^tiS,;(i 3 2. ^u#:o v >N$(tft«*IHj!i»iiiibJ; 12 2.1 rtVliWii'Ua'l i-.Hfi^Wfl'ilBfifewS-'JUlci^lKft'PW/A 12 2.1.1 [11*61; 12 2.1.2 klj/l-onm 13 2.1.3 -li !£ M 2.1.4 UiTt%'% is 2.2 -t''J-v-'. .IV* tt'lli^SjiKiJ.- 17 2.2.1 :tLi')!C 17 2.2.2 I'l1 ,« IS 2.2.3 X V; 1H 2.2.4 M'lli ?i% 2ii 3. .. ;>/>r -i- /; n \M\fc\ti ••'; v >N«,W)'| ijtl<lL.4;J.y(t'?fl'jfl H 2H 3.1 ltlV)i; 23 3.2 X W 23 3.3 ?,', 'U i 11< 2.| 4. C.iL'O, ^iVnViMffl M 4.1 It L V)ic M 4.2 '/i M M 4.3 fftJ&WHf 37 4.4 NMlcra-t^ft 4(1 5. caa1, ,o,.Mtiiko)W>M)iizmtz>Br?i « 5.1 IILWIC -13 5.2 -ii K 43 5.3 *,V«i^« 44 : 6. l'rO,...-L'O.-O:l .n:i?;IZtJlt<>H\mi&£*,'i{i,',{l:?- 51 6.1 liLWC 51 6.2 -ii 14; 52 6.3 MlUi^ 53 7. ') +^A^J;y+ I- ') Vt.oMtfctlAtS.^lltl-iimiiitmiti ^ yicol^lt; 65 7.1 liLWIC 65 7.2 -li It 67 7.3 *,';«i>i« ; 67 8. 'iti ,,fii 76 M U 80 •%%m 81 JAERI 1,310 1. 1 ntroduction 1.1 Background anrt objectives of this study As nuclear fuels, pressed and sintered pellets of uranium dioxide. UO2, has widely been used in light water reactors such as pressurized and boiling water type reactors. Uranium dioxide crystallizes in cubic fluorite type structure, and it has several advantages when used as nuclear fuels. That is to say, UO2 has high chemical and thermodynamical stability and shows no phase transformation up to its melting point, and it can retain fission products in its crystal lattice to a large extent. Recently, the demand to use the nuclear fuels until such higher burnups as 40,000 45,000 MWd/t seems to become rather pressing from economical reason. However, the increase in burnup makes the following chemical phenomena prominent in the UO2 fuel: '1) accumulation of solid and/or gaseous fission products, (2) oxygen nonstoichiometry of (he uranium dioxide, (3) redistribution of fission products and actinides under high thermal gradients. Fission products react with the fuel matrix UO2 to form ternary or polynary uranium com- pounds or separate oxide phases. The chemical compounds formed are greatly dependent on the oxygen potential of the system which gradually increases with the increase of burnup accompanied by augmentation of O/U ratio of the UOj fuel due to fission. Besides that, if the fission products are transported to the outer surface of the fuel through the solid and/or gas phase, there is a possibility that they react with the cladding material, which may cause its failure. It has been reported that the oxygen potentia' also governs the chemical interaction between fission products and the cladding materials 111. The study of fission products' be- havior in relation to the oxygen potential is, therefore, of basic importance for the assessment of the irradiation behavior of nuclear fuels.