Abstract

Savannah River Tritium Enterprise has used LaNi_4.25Al_0.75 (LANA75) hydride beds to store hydrogen isotopes for over two decades. A benefit of using LANA75 is that the ³He generated from tritium decay is retained in the hydride material, allowing the hydride beds to deliver high-purity product gas. A disadvantage is that the ³He accumulates in the LANA75 material over time, which forms a heel that cannot be removed under normal operating conditions. The heel traps hydrogen in the bed, slowly reducing the operational capacity of the bed as the heel grows. Eventually, the ³He begins to release from the material, preventing the delivery of high-purity product. The hydride beds are replaced when (1) operational capacity is reduced such that it is impactive to routine operations, and/or (2) product purity is not maintained due to ³He release.

Several beds were operated beyond their design life. One of these beds was selected to undergo heating beyond its normal operating temperature to evaluate the possibility of removing a portion of the hydrogen and helium heel to improve bed function until a replacement could take place. This bake-out removed a portion of the hydrogen and helium heel, and preliminary data indicate that bake-outs may partially regenerate the beds. The bed’s performance will continue to be monitored, and additional bake-outs will likely be performed. Performing bake-outs results in increasing the recovery of ³He, more efficient end-of-life activities (such as isotopic exchange), and extension of the useful service life of the bed.

摘要

萨凡纳河Tri企业使用LaNi _4.25 Al _0.75（LANA75）氢化物床存储氢同位素已有二十多年了。使用LANA75的一个好处是，由decay衰变产生的³ He被保留在氢化物材料中，从而使氢化物床可以输送高纯度的产品气。缺点是³ He随着时间的推移会积聚在LANA75材料中，这会形成脚跟，在正常操作条件下无法将其移除。脚后跟将氢捕获在床中，随着脚后跟的增长，床的工作能力会逐渐降低。最终，³他开始从物料中释放出来，阻止了高纯度产品的交付。当（1）操作能力降低，从而影响常规操作，和/或（2）由于³ He释放而不能保持产品纯度时，更换氢化物床。

几张床超出了设计寿命。选择这些床中的一个床进行加热，使其温度超过其正常工作温度，以评估去除一部分氢气和氦气尾气以改善床功能直到发生更换的可能性。这种烘烤去除了一部分氢气和氦气残留物，初步数据表明，烘烤可能会部分再生床层。床的性能将继续受到监控，并且可能会进行其他烘烤。进行烘烤可提高³ He的回收率，更有效的报废活动（例如同位素交换）并延长床的使用寿命。