【作者】 吴明慧；

【导师】 欧阳世翕； 李强；

【作者基本信息】 中国建筑材料科学研究总院 ， 材料学， 2011， 博士

【摘要】 随着核能的发展，资源利用与环境安全的矛盾逐渐尖锐。通过材料学研究解决核电站运行中带来的放射性废物问题，缓解其对环境造成的压力，是一条非常有效的途径。中低放射性废物的水泥固化技术一直是放射性废物安全处置研究的热点，本文在总结前人研究成果的基础上，系统地讨论了模拟中低放射性废物对固化体性能的影响。基于模拟放射性废物，针对模拟中放固体废物（即模拟放射性废离子交换树脂）与模拟低放液体废物（即模拟放射性废液）进行了水泥固化技术的研究。采用新的实验设计方法，在满足国家标准GB14569.1-93要求的前提下，设计出具有“双效”作用的固化胶凝材料配合比及具体应用配方，并制定了较为完善的工艺流程，为优化中低放废物的水泥固化技术提供了理论与实际指导。依据基于伪蒙特卡洛理论的统计学实验设计方法—均匀设计法，开展了7因素28水平的实验设计研究。该设计以硅酸盐水泥为基础，配以促凝剂，双掺无机添加剂沸石和硅灰，通过优化工艺流程对模拟含硼放射性废树脂进行固化，最终获得了废树脂体积包容量不低于50%且符合国家标准GB14569.1-93参数要求的配方：三种配方中的模拟含硼废树脂体积包容量分别55%（S₁）、60%（S₂）和52%（S₃），其固化体28d抗压强度分别为7.04MPa，7.62MPa和9.65MPa，并表现出良好的抗冲击、抗冻融与抗浸泡性能。S₁与S₃固化体标准试样中S_r2+的42天浸出率分别为8.89×10^-4cm/d和9.92×10-5cm/d，S₂在21天时浸出的S_r2+已经检测不到。S₁、S₂与S₃试样Cs2+的42天浸出率分别为3.81×10^-4cm/d、4.95×10^-4cm/d和1.33×10^-4cm/d。综合比较分析，推荐S₂作为含硼放射性废树脂水泥固化的优选配方。同时，采用相同的固化胶凝材料配合比，在水灰比0.6的情况下，实现了对模拟含硼废液的有效固化，获得了L₂与L₃配方：其中，L₂和L₃模拟含硼废液水泥固化体28天抗压强度分别为16.53MPa和19.13MPa，凝结性能、抗冲击、抗水、抗冻融与耐辐照性能均符合国家标准GB14569.1-93的要求。L₂和L₃试样中Cs²⁺的42天浸出率分别为5.18×10^-4cm/d和7.75×10^-4cm/d，Sr²⁺的42天浸出率分别为7.39×10-6cm/d和5.28×10-6cm/d。经过综合比较，推荐L₂为含硼放射性废液优先选择的水泥固化配方。以废液水泥固化浆体的流动性能，凝结性能，强度性能为基础，系统地研究了体系中原材料对模拟废液浆体性能的影响。采用XRD，SEM/EDS，IR等检测技术，探讨了原料对固化体微观结构与宏观性能的影响，分析了水泥的水化过程与水化产物，并解释了水化机理。通过对硼元素存在状态与形式的进一步研究发现，在固化过程中，废树脂上所吸附的硼元素，会大量带入水泥浆体中，与水泥的一次水化产物反应生成CaO·B₂O₃·6H₂O和B-AFt，并延缓水泥颗粒的水化过程，硼元素以最终三配位的BO₃3-和四配位的BO45-两种状态存在。随着含硼浓度的增高，缓凝的作用会逐渐加强；随着水灰比的增大，也呈现相似规律。在0.3-0.5水灰比的范围内，当硼酸溶液浓度大于3%时，水泥硬化浆体中主要是未水化的水泥与大量CaO·B₂O₃·6H₂O。由于骨架产物CSH与AFt急剧减少，以及生成的硼酸钙片状形态不利于强度的发展，造成了水泥凝结硬化的延迟和抗压强度的下降。研究结果表明：当模拟树脂的体积含量超过65%时，浸泡过程中将会引起固化体开裂。沸石与硅灰能够改善固化体的孔结构，有助于提高硬化浆体的致密性。配方中的促凝剂对水泥的促凝效果在一定程度上抵消了硼元素对水泥造成的缓凝作用，加速了水化的进程，提高了固化体的强度。更多还原

【Abstract】 With the increasing development of nuclear energy all over the world, thecontradiction between resource utilization and environmental security becomes moreand more serious. It has been proved that material solidification technique will be aneffective approach to deal with the radioactive waste of nuclear industry. For low andintermediate level radioactive waste, cement solidification is a hot researchpiont. Thiswork focus on cement solidification technology based on simulations of low andintermediate level radioactive waste including solid waste （radioactive ion exchangeresins） and liquid waste （radioactive steam residue）. These researches will help us todevelop a new way to design binding material with double efficacy and the cementsolidification formula to meet the requirements of state standard GB14569.1-93, andto improve the process of cement solidification.The experiments with7factors and28levels were performed using uniformdesign method derived from pseudo-Monte Carlo theory. By using Portland cement,the nuclear waste resin, containing boron, was solidified with accelerator anddual-doped inorganic additives such as zeolite and silica fume. The optimizedformulas have been developed, by which the waste resin volume is greater than50%in capacity and meet the requirements of state standard GB14569.1-93. In the three compositions, the volume capacities of formulas are55%（S₁）,60%（S₂） and52%（S₃）, and the compressive strength at28d are7.04MPa,7.62MPaand9.65MPa, respectively. The solidification product shows good impulse strength,freezing thawing resistance and anti-penetration property. The leaching rates of Sr2+at42d, for standard formula samples of S₁and S₃, are8.89×10^-4cm/d and9.92×10^-5cm/d, but rarely be detected for S₃at21d. The leaching rates of Cr2+at42dfor all standard formula samples are3.81×10^-4cm/d,4.95×10^-4cm/d and1.33×10^-4cm/d, respectively. According to the comparison and analysis, S₂isrecommended as the optimized formula of boron containing waster resin cementsolidification. Meantime, using the same component design, it solidifies the simulated boron containing liquid waste successfully, with a w/c value of0.6. The formulas of L2and L3are listed as below:The compressive strength of the solidification products for L2and L3at28d was measured to be16.53MPa and19.13MPa, respectively. It meets the requirements of state standard GB14569.1-93for condensation performance, impulse strength, freezing-thawing resistance and radiation. The leaching rates of Sr2+at42d for standard formula samples of L2and L3are5.18×10-4cm/d and7.75×10-4cm/d. The leaching rate of Cr2+at42d for all standard formula samples are7.39x10-6cm/d and5.28x10-6cm/d respectively. Thus L2is strongly suggested as the optimized formula for boron containing radioactive waste solution cement solidification.The relationships between the microstructure and macroscopic performances of solidification form for each formula have been investigated by means of XRD, SEM/EDS, IR and other advanced techniques. The hydration process, products of cement and hydration mechanism has been also discussed.Boron ion adsorbed on the surface of waste resin, which forms CaO·B2O3·6H2O and B-AFt by reacting with cement hydration products, infiltrates the cement paste deep during solidification. It also slows down the hydration process of cement particle. The resultant structure of boron is3-fold BO33-and4-fold BO45-. With the increase of boric acid concentration, the degree of inhibition increases gradually. With W/C ratio increases, it performs in a similar way.When boric acid concentration exceeds3%and the W/C ratio is between0.3-0.5, the main phase in cement harden paste is determined to be un-hydrated cement particles and large number of CaO·B2O3·6H2O. Due to dramatically decrease of CSH and AFt and the existence of the framework structure and plate shape calcium borate appear in the solidification products, the compressive strength and harder process are strongly influenced.The results indicate that, when the resin volume capacity exceeds65%, cracks are easily formed in the cement solidification form during soaking in water. Zeolite and silica fume doped are valid to improve the pore structure and the density of hardened paste. Accelerator eliminates retarding cement setting effect by boron ion, and it accelerates the hydration process and improves the strength of the cementsolidification form.更多还原