乏燃料后處理中放射性核素的陶瓷固化體的結(jié)構(gòu)與化學穩(wěn)定性研究
發(fā)布時間：2018-08-16 15:59
【摘要】：軍用核退役設施以及核電事業(yè)的發(fā)展產(chǎn)生了大量的錒系核素,如Pu、U、Am、Cm和Np。這些錒系核素具有半衰期長以及毒性大的特點,必須將其固化于穩(wěn)固的基材中。由于陶瓷固化錒系核素時,核素可以作為組元與固化基材中的元素成鍵,所形成的固化體具有高包容性、高致密、核素浸出率低、抗輻照穩(wěn)定性和熱穩(wěn)定性好等優(yōu)點。因此,本文制備了三種新型陶瓷固化體(鈣鈦鋯石-燒綠石人造巖固化體、獨居石-磷釔礦固化體和鉬鎢鈣礦固化體),其中鈣鈦鋯石-燒綠石人造巖和獨居石-磷釔礦固化體研究用于UOX型乏燃料后處理產(chǎn)生的錒系核素固化以及軍用核設施退役產(chǎn)生的U和Pu元素固化,而鉬鎢鈣礦研究用于UMo型乏燃料中錒系核素和99Mo元素的固化。根據(jù)類質(zhì)同象原理,Ce3+和Gd3+離子用于模擬固化體中的+3價錒系核素(Pu3+, Cm3+, Am3+和Np3+),而Ce4+離子用于模擬+4價的錒系核素(Pu4+, Np4+,和U4+)(1)對于鈣鈦鋯石-燒綠石人造巖固化體Ca1-xZr1-xCe2xTi2O7+δ (0≤ x≤ 0.4),在制備過程中,部分Ce4+離子被還原為Ce3+離子。固化體中存在三種晶型,即單斜鈣鈦鋯石,四方鈣鈦礦以及立方燒綠石。隨著Ce3+和Ce4+離子含量的增加,固化體中的相結(jié)構(gòu)發(fā)生2M型鈣鈦鋯石→4M型鈣鈦鋯石→立方燒綠石的轉(zhuǎn)變。當Ce3+和Ce4+離子含量相對較高時,固化體中易形成4M型鈣鈦鋯石相。當Ce3+和Ce4+離子含量再次增加時,4M型鈣鈦鋯石結(jié)構(gòu)中的陽離子發(fā)生重排且陰離子發(fā)生相應的位移,致使其結(jié)構(gòu)轉(zhuǎn)變?yōu)榱⒎綗G石。固化體中模擬核素Ce的7天標準浸出量的數(shù)量級維持在10-6～10-7 g·m-2之間。(2)對于鈣鈦鋯石-燒綠石人造巖固化體Ca1-xCexZrTi2-xAlxO7 (0.2≤ x≤0.8),固化體中存在三種相結(jié)構(gòu),分別為2M型鈣鈦鋯石,立方燒綠石以及3T型鈣鈦鋯石。隨著Ce3+離子含量的增加,固化體中的相結(jié)構(gòu)發(fā)生2M型鈣鈦鋯石→立方燒綠石/3T型鈣鈦鋯石的轉(zhuǎn)變。固化體中模擬核素Ce的7天標準浸出量的數(shù)量級維持在10-5～10-6 g·m-2之間。(3)對于獨居石-磷釔礦固化體Gd1-xYbxPO4 (0≤ x≤ 1),固化體中相界與燒結(jié)溫度和模擬核素Gd含量有關(guān)。當燒結(jié)溫度為1600℃時,陶瓷Gd0.9Yb0.1PO4的相結(jié)構(gòu)由單相磷釔礦組成。獨居石→磷釔礦相變的晶面極易可能發(fā)生在沿[020]軸方向的(200)晶面。固化體中模擬核素Gd和Yb元素的浸出機理屬于溶解-沉淀型,且其標準浸出量在持續(xù)浸出7天后達到穩(wěn)態(tài)。Gd和Yb的7天標準浸出量數(shù)量級維持在10-5～10-6 g·m-2之間,且浸出量隨著固化體結(jié)構(gòu)中P04四面體的畸變程度的增加而逐漸增加。(4)對于固化體Gd1-xCexPO4 (0 x 1),固化體的最佳合成溫度應高于1300℃。當燒結(jié)溫度為1400℃時,固化體GdPO4的相結(jié)構(gòu)由獨居石和亞穩(wěn)相磷釔礦組成。隨著Ce3+含量的增加,固化體中結(jié)構(gòu)發(fā)生磷釔礦→獨居石的轉(zhuǎn)變,而固化體中獨居石的微觀形貌未發(fā)生顯著的變化。固化體中模擬核素Gd和Ce的浸出機理屬于溶解沉淀型,其浸出量在持續(xù)浸出7天后達到穩(wěn)態(tài),且與結(jié)構(gòu)中的P04四面體的畸變程度有關(guān)(畸變程度越高,浸出量越大)。Gd和Ce的7天標準浸出量的維持在10-4～10-5g·m-2之間。(5)對于鉬鎢鈣礦固化體Ca(1-x)(LiCe)x/2MoO4 (0≤ x≤ 1),隨著Ce3+和Li+離子含量的增加,固化體的晶胞參數(shù)呈現(xiàn)反向增大的變化趨勢,而平均晶粒尺寸呈現(xiàn)先增加后減小的變化趨勢。對于鉬鎢鈣礦固化體Ca(1-x)(LiGd)x/2MoO4 (0≤ x ≤ 1),結(jié)構(gòu)精修得到的固化體組成與名義組成基本一致。固化體的晶胞參數(shù)隨著隨著Gd3+和Li+離子含量的增加而逐漸減小。對于所有鉬鎢鈣礦固化體,其模擬核素(Ce和Gd)和Mo元素的浸出機理均屬于溶解-沉淀型,標準浸出量均在持續(xù)浸出7天后達到穩(wěn)態(tài),且模擬核素(Ce和Gd)和Mo元素的7天標準浸出量的大小均與其結(jié)構(gòu)中Mo4四面體的畸變程度有關(guān),畸變程度越高,7天標準浸出量越大。
[Abstract]:Military decommissioning facilities and the development of nuclear power industry have produced a large number of actinides, such as Pu, U, Am, cm and Np. These actinides have long half-life and high toxicity, which must be solidified in a stable substrate. Therefore, three new ceramic solidifiers (zircon-pyrochlore, monazite-yttrium phosphate and molybdenum-tungsten-calcium carbide) were prepared in this paper. Jushi-yttrium phosphate rock solidified body is used for the solidification of actinides produced by the reprocessing of UOX spent fuel and U and Pu produced by the decommissioning of military nuclear facilities. Molybdenum tungsten calcium ore is used for the solidification of actinides and 99Mo elements in UMo spent fuel. According to the principle of isomorphism, Ce3+ and Gd3+ ions are used to simulate the + 3 valence in solidified body. Actinides (Pu3 +, Cm3 +, Am3 + and Np3 +), and Ce4 + ions (Pu4 +, Np4 +, and U4 +) (1) for perovskite-pyrochlore artificial rock solidified body Ca1-xZr1-xCe2xTi2O7 + delta (0 < x < 0.4), some Ce4 + ions are reduced to Ce3 + ions during the preparation process. There are three crystal forms in the solidified body, namely monoclinic perovskite zirconium. With the increase of Ce 3+ and Ce 4+ ions content, the phase structure of the solidified body changes from 2M-type perovskite to 4M-type perovskite to cubic pyrochlore. When the content of Ce 3+ and Ce 4+ ions is relatively high, 4M-type perovskite-zircon phase is easily formed in the solidified body. When 4M-type perovskite-pyrochlore is formed, the cations rearranged and the anions shifted accordingly, resulting in the transformation of its structure into cubic pyrochlore. The 7-day standard leaching amount of simulated nuclide Ce in the solidified body is maintained between 10-6 and 10-7 g.m-2. (2) For the solidified body of perovskite-pyrochlore artificial rock, Ca1-xZrTi2-xAlxO7 (0.2 < 0.2 < 0.2 < 0.2). X < 0.8), there are three phase structures in the solidified body, namely, 2M-type perovskite, cubic pyrochlore and 3T-type perovskite. With the increase of Ce3+ content, the phase structure of the solidified body changes from 2M-type perovskite to cubic pyrochlore/3T-type perovskite. The order of magnitude dimension of the 7-day standard leaching amount of the simulated nuclide Ce in the solidified body takes place. (3) For monazite-yttrium phosphate rock solidified Gd1-xYbxPO4 (0 < x < 1), the phase boundary in solidified Gd1-xYbxPO4 is related to sintering temperature and simulated nuclide Gd content. (200) planes along the [020] axis. The leaching mechanism of simulated nuclides Gd and Yb in solidified solids belongs to the dissolution-precipitation type, and their standard leaching amounts reach a steady state after 7 days of continuous leaching. The 7-day standard leaching orders of magnitude of Gd and Yb are maintained between 10-5 and 10-6 g.m-2, and the leaching amount varies with the distortion degree of P04 tetrahedron in solidified solids. (4) For the solidified Gd1-xCexPO4 (0 x 1), the optimum synthesis temperature of the solidified GdPO 4 should be higher than 1300 C. When the sintering temperature is 1400 C, the phase structure of the solidified GdPO 4 is composed of monazite and metastable phase yttrium phosphate rock. The leaching mechanism of simulated nuclides Gd and Ce in solidified solids belongs to dissolution-precipitation type. The leaching amount of simulated nuclides Gd and Ce in solidified solids reaches steady state after 7 days of continuous leaching and is related to the distortion degree of P04 tetrahedron in the structure (the higher the distortion degree, the larger the leaching amount). The standard leaching amount of Gd and Ce in 7 days is maintained at 10-10. (5) For Ca (1-x) (LiCe) x/2MoO 4 (0 < x < 1) solidified body of molybdenum-tungsten-calcium ore, the cell parameters of solidified body increase inversely with the increase of Ce 3+ and Li + ions content, while the average grain size increases first and then decreases. For Ca (1-x) (LiGd) x/2MoO 4 (0 < x) solidified body of molybdenum-tungsten-calcium ore The lattice parameters of the solidified body decrease gradually with the increase of Gd3+ and Li+ ions. For all the solidified bodies, the leaching mechanism of simulated nuclides (Ce and Gd) and Mo elements belongs to dissolution-precipitation type, and the standard leaching amount is continuous leaching 7. The 7-day standard leaching amount of simulated nuclides (Ce and Gd) and Mo is related to the distortion degree of Mo4 tetrahedron in the structure. The higher the distortion degree is, the larger the 7-day standard leaching amount is.
【學位授予單位】：浙江大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TL24;TQ174.1
，
本文編號：2186465
[Abstract]:Military decommissioning facilities and the development of nuclear power industry have produced a large number of actinides, such as Pu, U, Am, cm and Np. These actinides have long half-life and high toxicity, which must be solidified in a stable substrate. Therefore, three new ceramic solidifiers (zircon-pyrochlore, monazite-yttrium phosphate and molybdenum-tungsten-calcium carbide) were prepared in this paper. Jushi-yttrium phosphate rock solidified body is used for the solidification of actinides produced by the reprocessing of UOX spent fuel and U and Pu produced by the decommissioning of military nuclear facilities. Molybdenum tungsten calcium ore is used for the solidification of actinides and 99Mo elements in UMo spent fuel. According to the principle of isomorphism, Ce3+ and Gd3+ ions are used to simulate the + 3 valence in solidified body. Actinides (Pu3 +, Cm3 +, Am3 + and Np3 +), and Ce4 + ions (Pu4 +, Np4 +, and U4 +) (1) for perovskite-pyrochlore artificial rock solidified body Ca1-xZr1-xCe2xTi2O7 + delta (0 < x < 0.4), some Ce4 + ions are reduced to Ce3 + ions during the preparation process. There are three crystal forms in the solidified body, namely monoclinic perovskite zirconium. With the increase of Ce 3+ and Ce 4+ ions content, the phase structure of the solidified body changes from 2M-type perovskite to 4M-type perovskite to cubic pyrochlore. When the content of Ce 3+ and Ce 4+ ions is relatively high, 4M-type perovskite-zircon phase is easily formed in the solidified body. When 4M-type perovskite-pyrochlore is formed, the cations rearranged and the anions shifted accordingly, resulting in the transformation of its structure into cubic pyrochlore. The 7-day standard leaching amount of simulated nuclide Ce in the solidified body is maintained between 10-6 and 10-7 g.m-2. (2) For the solidified body of perovskite-pyrochlore artificial rock, Ca1-xZrTi2-xAlxO7 (0.2 < 0.2 < 0.2 < 0.2). X < 0.8), there are three phase structures in the solidified body, namely, 2M-type perovskite, cubic pyrochlore and 3T-type perovskite. With the increase of Ce3+ content, the phase structure of the solidified body changes from 2M-type perovskite to cubic pyrochlore/3T-type perovskite. The order of magnitude dimension of the 7-day standard leaching amount of the simulated nuclide Ce in the solidified body takes place. (3) For monazite-yttrium phosphate rock solidified Gd1-xYbxPO4 (0 < x < 1), the phase boundary in solidified Gd1-xYbxPO4 is related to sintering temperature and simulated nuclide Gd content. (200) planes along the [020] axis. The leaching mechanism of simulated nuclides Gd and Yb in solidified solids belongs to the dissolution-precipitation type, and their standard leaching amounts reach a steady state after 7 days of continuous leaching. The 7-day standard leaching orders of magnitude of Gd and Yb are maintained between 10-5 and 10-6 g.m-2, and the leaching amount varies with the distortion degree of P04 tetrahedron in solidified solids. (4) For the solidified Gd1-xCexPO4 (0 x 1), the optimum synthesis temperature of the solidified GdPO 4 should be higher than 1300 C. When the sintering temperature is 1400 C, the phase structure of the solidified GdPO 4 is composed of monazite and metastable phase yttrium phosphate rock. The leaching mechanism of simulated nuclides Gd and Ce in solidified solids belongs to dissolution-precipitation type. The leaching amount of simulated nuclides Gd and Ce in solidified solids reaches steady state after 7 days of continuous leaching and is related to the distortion degree of P04 tetrahedron in the structure (the higher the distortion degree, the larger the leaching amount). The standard leaching amount of Gd and Ce in 7 days is maintained at 10-10. (5) For Ca (1-x) (LiCe) x/2MoO 4 (0 < x < 1) solidified body of molybdenum-tungsten-calcium ore, the cell parameters of solidified body increase inversely with the increase of Ce 3+ and Li + ions content, while the average grain size increases first and then decreases. For Ca (1-x) (LiGd) x/2MoO 4 (0 < x) solidified body of molybdenum-tungsten-calcium ore The lattice parameters of the solidified body decrease gradually with the increase of Gd3+ and Li+ ions. For all the solidified bodies, the leaching mechanism of simulated nuclides (Ce and Gd) and Mo elements belongs to dissolution-precipitation type, and the standard leaching amount is continuous leaching 7. The 7-day standard leaching amount of simulated nuclides (Ce and Gd) and Mo is related to the distortion degree of Mo4 tetrahedron in the structure. The higher the distortion degree is, the larger the 7-day standard leaching amount is.
【學位授予單位】：浙江大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TL24;TQ174.1
，
本文編號：2186465
本文鏈接：http://sikaile.net/kejilunwen/huaxuehuagong/2186465.html
最近更新
教材專著
