Isolation of 14C species from spent ion exchange resins and their stabilisation

有机离子交换树脂用于民用核燃料循环的许多不同领域，从铀矿石浓缩和精炼以及轻水反应堆和乏燃料储存池中冷却剂水成分的化学控制，到燃料后处理和核退役操作产生的含放射性元素的流出物的去污。这些材料是广泛的放射性元素的有效“海绵”，因此它们被广泛使用。英国已经储存了大约600立方米的乏燃料（即，使用过的）离子交换树脂（SIERs），其需要处置，并且每年继续产生2.5至13 m3的SIERs的处置是有问题的;存在几个关键问题，其包括：材料的14 C库存。这种同位素的半衰期为5，730年，以14 CO 32-和H14 CO 3-的形式结合，如果允许进入环境，它们具有极强的移动的和生物学可利用性。14 C气体在处置环境中的释放提供了14 C向生物圈的快速迁移途径;2. SIERs在处置环境中通过放射性衰变过程的降解产生有机络合剂分子，这可能有助于放射性元素从SIERs快速运输到生物圈;3. SIERS在储存环境中的降解也可能产生化学有毒气体，如苯、苯酚和氨，这使得储存极为困难。这些问题需要对SIERS进行处理，以满足废物处置的验收标准。这通常是通过使用热或化学过程进行销毁来实现的。在这项提案中，我们的目标是开发一种有前途的化学处理途径，用于破坏SIERs，称为湿式氧化。湿氧化已在其他地方成功地试验用于销毁SIERs的非放射性替代物，然而，以前使用的特定方法不会产生副产品残留物，这些残留物可固定在适合在英国处置的材料中。我们提出了两种新的方法，湿氧化过程中，不仅会产生更适合于固定的副产品，但也有一个更大的破坏效率比以前的试验。此外，我们将开发和优化定制的水泥，陶瓷和玻璃废物形式，以固定SIER降解。我们将提供一个强大的科学基础的化学形态和局部分布的放射性核素在SIERs和我们开发的固定矩阵，并了解他们在处置环境中的行为，以支持安全和及时处置的SIER wastes.A显着的新奇性，这项研究是验证我们的新的处理和固定方法的SIERs使用真实的放射性材料。经过优化的过程中使用非活性SIERS上述，我们将把它们应用到真实的放射性SIER从英国退役计划。如果成功的话，这项工作将是朝着证明树脂的有效处理方案迈出的重要一步，允许早期现场终止重大危害。

Organic ion exchange resins are utilised in many different areas of the civil nuclear fuel cycle, from uranium ore concentration and refinement and chemical control of coolant water composition in light water reactors and spent fuel storage ponds, to decontamination of radioactive element-containing effluents arising from fuel reprocessing and nuclear decommissioning operations. These materials are effective "sponges" for a wide range of radioactive elements, hence their widespread use. The UK has stockpiled approximately 600 m3 of spent (i.e., used) ion exchange resins (SIERs), which require disposal, and continues to produce between 2.5 to 13 m3 per year.The disposal of SIERs is problematic; there are several key issues, which include:1. The 14C inventory of the materials. This isotope has a half life of 5,730 years and is incorporated as 14CO32- and H14CO3-, which, if allowed to enter the environment are extremely mobile and biologically available. Release of 14C gas in a disposal environment provides a rapid 14C migration pathway to the biosphere;2. The degradation of SIERs in a disposal environment through radioactive decay processes produces organic complexant molecules, which may facilitate rapid transport of radioactive elements from SIERs to the biosphere;3. The degradation of SIERs in a storage environment may also yield chemically toxic gases such as benzene, phenol and ammonia, which make storage extremely problematic.These issues require the SIERs to be treated so as to meet waste acceptance criteria for disposal. This is typically achieved by destruction using thermal or chemical processes. In this proposal, we aim to develop a promising chemical treatment route for the destruction of SIERs, known as wet oxidation. Wet oxidation has been successfully trialled elsewhere for the destruction of non-radioactive surrogates for SIERs, however, the specific methods previously utilised do not give rise to by-product residues that are amenable to immobilisation in a material suitable for disposal in the UK. We propose two novel approaches to wet oxidation processes that will not only generate by-products more suitable for immobilisation, but that also have a greater destruction efficiency than those previously trialled. Furthermore, we will develop and optimise tailored cement, ceramic and glass waste forms for the immobilisation of SIER degradation. We will provide a robust scientific underpinning of the chemical speciation and local distribution of radionuclides in SIERs and the immobilisation matrices we develop, and understand their behaviour in disposal environments, to support the safe and timely disposal of SIER wastes.A significant novelty of this research is the verification of our new treatment and immobilisation methods for SIERs using real radioactive materials. After optimisation of the processes described above using inactive SIERs, we will apply them to real radioactive SIER from the UK decommissioning programme. If successful, this work will be a significant step towards demonstrating an effective treatment option for the resin, allowing early site termination of a significant hazard.