Devitrification of borosilicate glass

高放废物(HLRW)的地质处置在世界范围内和日本都有讨论。由于放射性废物被放置在地下区域，因此对于地质剂量来说，固化是必要的。本研究的目的之一是从地质处置点的角度对废渣的固化玻璃进行评价。首先，分析了15种化学成分的硼硅酸盐玻璃。硼硅酸盐玻璃主要由SiO_2、Al_2O_3和Na_2O组成。变化范围为SiO_2=45-50，Al_2O_3=5-10，B_2O_3=15-17，Na_2O=10-11。某些硼硅酸盐玻璃除含有主量元素外，还含有CaO(5-10wt%)、SRO(7.5-15)和Cs2O(7.5-15)。玻璃的析晶取决于化学成分。然而，在水热条件下，所有玻璃都会改变为反玻璃化。…获得的矿物质种类目前的加热实验主要分为三类：(1)沸石相，(2)含硼矿物和(3)硅酸盐矿物。沸石类矿物以沸石族矿物为主。沸石相包括方沸石-波露石、丝光沸石-锶丝光沸石、方沸石-锶方沸石、胶石-锶胶石和方镁石-锶方沸石。结果表明，所有的沸石分子都能在Na或Ca与Sror Cs之间形成固溶体。将15种起始硼硅酸盐玻璃分为6种类型，即NSrCs、CNSrCs、CNSr、CNCS、NSR和NCS。N和C分别代表Na_2O和CaO。沸石矿物物种强烈地依赖于起始的硼硅酸盐玻璃的化学成分，这是相当公认的。在200ﾟC的加热温度下，NSrCs和NSR玻璃主要生成斜方闪锌矿-闪锌矿，而黄长石-锶黄长石则主要生成。CNSrCs、CNsr和CNCS玻璃晶化成方沸石-闪锌矿和丝光沸石-锶丝光沸石。NCS玻璃只产生方解石-波卢石。另一方面，在250ﾟC的升温实验中，CNSrCs玻璃产生了方解石-斜方铅矿和方铅矿-锶方铅矿。方解石-斜方铅矿系列矿物的化学组成与胡兰石-锶方铅矿共生关系如下。(1)方解石系列矿种中Cs含量随加热时间的增加而增加。(2)方解石系列矿物中Cs的含量随时间的增加而变化较大。(3)方解石系列矿种的Na/Cs原子比随加热时间变化在0.9~1.5之间。这是由于在较长的加热时间下，锶取代方沸石-斜方闪石矿物中的钠或铯的化学特性所致。与丝光沸石共生的方沸石系列矿物与Na、Cs含量呈较好的线性关系。认为锶偏向于结晶学意义上的丝光沸石系列矿物。较少

Geological disposal of high level radioactive wastes (HLRW) has been discussed in the world as well as in Japan. Solidification of radioactive wastes is necessarry for the geological dosposal because the wastes is put in the underground area. One of the purpose of present study is to evaluate the solidified glass of the wastes from the geological disposal poit of view. Firstly, borosilicate glass of 15 kinds of chemical composition. The borosilicate glasses are composed pribcipally of SiO_2, Al_2O_3 and Na_2O.The chemical compositions (wt %) of the major constituent elements of borosilicate glasses are as follows. The variation is that SiO_2=45-50, Al_2O_3=5-10, B_2O_3=15-17, and Na_2O=10-11. In addition to the principal elements, CaO (5-10wt%), SrO (7.5-15)and Cs2O (7.5-15) are included in some borosilicate glasses. Devitrification of the glasses depends on the chemical composition. However, all glasses are altered to devitrification in hydrothermal condition. Mineral species obtained … More in the present heating experiments are grouped in three categories that (1) zeolite phases, (2) B-bearing minerals and (3) silicate minerals. Zeolite group minerals are mostly predominant. Zeolite phases include analcite-pollucite, mordenite-Sr mordenite, heulandite-Sr heulandite, gumelinite-Sr gumelinite, and wairakite-Sr wairkite. It is characterized that all zeolite mmeral species establish solid solution between Na or Ca and Sror Cs. 15 kinds of starting borosilicate glasses are categorized into 6 types, that is, NSrCs, CNSrCs, CNSr, CNCs, NSr, and NCs. N and C indicats Na_2O and CaO,respectively. It is recognized considerably that zeolite mineral species dipends on strongly the chemical composition of starting borosilicate glasses. At the heating temperature of 200ﾟC,NSrCs and NSr glasses produced anaicite-pollucite predominantly, and heulandite-Sr heulandite. CNSrCs, CNSr and CNCs glasses are crystallized to analcite-pollucite, and mordenite-Sr mordenite. NCs glass produced only analcite-pollucite. On the other hand, in the heating experimet at 250ﾟC,CNSrCs glass produced analcite-pollucite, and wairakite-Sr wairakite.The chemical compositions of analcite-pollucite series mineral species in paragenetic relation with heulandite-Sr heulandite arecaracterized as follows. (1) Cs concentration in analcite series mineralspecies increases with the increace of heating time. (2) Cs contents in analcite series mineral species vary widely with the increace of he ating time. (3) The Na/Cs atomic ratios in analcite series mineralspecies vary from 0.9 to 1.5 with heating time. It results from the chemical caracteristics that Sr substitutes Na or Cs in analcite-pollucite mineral species at longer heating time. On the other hand, analcite series mineral species in coexistence with mordenite show relatively linear relationship between Na and Cs contents. It is considered that Sr prefers crystallographically mordenite series mineral species. Less