Deuterium Removal Unit (DRU)
The isotopic purity of the hydrogen obtained using Deuterium Removal Unit (DRU) is the world record! Deuterium concentration is less than 6 ppb (6·10-9)! Combining with chemical purity provided by continuous cleaning with CHUPS system (Oxygen, Nitrogen, Water content at the level of some ppb), this is the purest gas in the world.
DRU was designed and manufactured in PNPI during the fall and winter of 2005-2006. The final installation, tests and protium manufacturing were carried out in spring, 2006 in PSI. The separation characteristics of the column were studied in details. Due to the absence of direct prompt method of deuterium measurements, the indirect method of chromatographic analysis for ortho- and para- isomers of hydrogen was used to estimate the column’s separation efficiency. The DRU parameters are controlled and measured with the slow control system based on DAQ32 and AICS modules.
The height equivalent to a theoretical plate (HETP) for the column is 2.2 cm. It is one of the best ever obtained results for columns of low and medium cryogenic power. For the present column, HETP value is almost constant in a wide range of vapour flow rate.
The column has the separation power in excess for the goal to be sought. Output deuterium concentration lower than 0.1 ppm almost does not depend on the initial concentration (natural hydrogen can be used!).
The pure orthohydrogen useful for some experimental physics applications can be produced by the setup as well as protium.
After the selection of column’s operating parameters and the development of its operating algorithm the protium production run was performed. Several modes of isotope purification were used. As a result about 1.3 m3 of deuterium depleted hydrogen was obtained. CHUPS system was put into the mode of continuous hydrogen circulation through the column to remove deuterium.
The productivity of the system in the “feed through” mode is 500 L/day. In the mode of circulation through CHUPS system it comes to 150 L/day. The mode of Rayleigh depletion is considered to be inefficient because of small initial amount of hydrogen in the column.
The method of measurement of low deuterium content in hydrogen (1 ppm and less) is suggested. It is based on deuterium enrichment by a factor of 40 (and even more) in the reboiler.
This work is also of great importance for Detritiation Plant of PIK reactor as in accordance with a new developing design of the plant the cryogenic column with close parameters is needed. A good packing was developed and tested, successful experience was gained.
Hydrogen produced by cryogenic distillation was measured to have the concentration of the deuterium less than 6 ppb (6·10-9). The hydrogen analysis was carried out on large tandem accelerator at Institute of Particle Physics, ETH-Zurich, Switzerland . For the present time it is the most precise and sensitive method of hydrogen isotopic analysis and it confirmed the producing of most isotopically pure hydrogen in the world.
The best isotopic pure hydrogen available commercially in form of light or heavy water has impurity level of some ppms (10-6). Therefore the hydrogen obtained with DRU has the best isotopic purity allover the world.