D2O isotope effects on hydrolysis and ionization equilibria in high-temperature water

CANDU反应堆是加拿大独特的蒸汽发生技术，其设计基于在闭环中使用重水将热量从反应堆堆芯传递到蒸汽发生器。 这个“一次冷却剂系统”中重水的pH值受到严格控制，以尽量减少腐蚀和放射性迁移的影响。 优化一回路冷却剂化学特性需要使用轻水系统中确定的数据，建立温度高达300°C时金属氧化物、溶解气体和pH控制添加剂化学行为的详细模型。 现在用来校正这些模型的方法，在轻水和重水系统的化学平衡常数之间的差异是基于室温下的研究。本提案旨在进行一项确定性的实验室研究，为核反应堆中遇到的极端温度和压力（250至300°C和10 MPa）下简单酸和碱的H2O和D2O之间的平衡常数差异提供基本数据和理解。 将在相同条件下，使用最先进的仪器，在H2O和D2O中进行化学平衡常数的高精度测量，这些仪器由惰性材料制成，可以承受高温水中存在的腐蚀性条件。 全世界只有少数这样的文书。结果将被用来开发一个改进的实用模型，用于估计D2O同位素对金属水解和金属氧化物溶解度的影响程度，在CANDU运行条件下。该项目将通过提供优化一回路pH值以减少进料管变薄的标准，为旨在延长现有反应堆寿命的研究做出贡献。 它将通过提供对极端温度和压力条件下D2O同位素对化学平衡的影响的基本了解，为加拿大在重水技术方面的领导作用作出长期贡献。

CANDU reactors are a uniquely Canadian steam-generation technology in that their design is based on the use of heavy water in a closed loop to transfer heat from the reactor core to the steam generator.   The pH of the heavy water in this "primary coolant system" is tightly controlled to minimize the effects of corrosion and radioactive transport.  Optimizing primary coolant chemistry requires detailled models for the chemical behaviour of metal oxides, dissolved gases and pH-control additives at temperatures as high as 300°C, using data determined in light water systems.  The methods now used to correct these models for the differences between chemical equilibrium constants in light-water and heavy-water systems are based only on room temperature studies. This proposal is for a definitive laboratory study to provide fundamental data and understanding for the difference in equilibrium constants between H2O and D2O, for simple acids and bases at the extreme temperatures and pressures encountered in nuclear reactors (250 to 300°C and 10 MPa).  High precision measurements of chemical equilibrium constants will be made in H2O and D2O under identical conditions, using state-of-the-art instruments, constructed of inert materials to withstand the corrosive conditions that exist in high temperature water.  Only  a few such instruments exist worldwide. The results will be used to develop an improved practical model for estimating the magnitude of D2O isotope effects on metal hydrolysis and metal oxide solubility, under CANDU operating conditions. The project will contribute to research aimed at extending the lifetime of existing reactors  by providing criteria for optimizing primary circuit pH to reduce feeder tube thinning.  It will make a long term contribution to Canada's leadership role in heavy water technology by providing a fundamental understanding of D2Oisotope effects on chemical equilibria under extreme conditions of temperature and pressure.