The Facility for Rare Isotope Beams (FRIB) will produce unprecedented quantities of radioactive nuclei when it comes online in about 5 years. The objective of this study was to assess the feasibility of collecting radon and noble gas isotopes from the cooling water system of the beam dump. The production of hydrogen gas in the beam dump results in two-phase flow in the section of the cooling system from the beam dump, a spinning titanium drum, to a gas-liquid separator, the head space of which is flushed with nitrogen gas to reduce the hydrogen concentration below 2% in the gas phase. Partitioning of noble gases into the gas phases poses a challenge for harvesting radon and noble gas isotopes of interest. Membrane contactors will allow radionuclides to be harvested from the primary cooling flow during FRIB operation by implementation in a secondary bypass stream. Membrane contactors allow constant extraction of gases across a hollow fiber-supported membrane. Depending on the characteristics of the membrane, these devices can be made chemically specific: allowing fine-tuning of the extraction process. A promising new technology for purification of noble gases of interest is an adsorption-based process at room temperature using selective, solid-state adsorbents called a metal-organic-frameworks (MOF). An important advantage of MOFs is their chemical tunability; one MOFs can be synthesized to be optimally selective for Kr, Xe or Rn at room temperatures. MOFs have higher efficiency, selectivity, and capacity at room temperature over current xenon adsorbents like activated charcoal and Ag-loaded zeolites at cryogenic temperatures. In addition, MOFs require limited pre-treatment of the intake gases and no cryogenic operation. Based on the design specifications, it appears feasible to harvest selected radon isotopes (211Rn, 221Rn, 223Rn) from the FRIB beam dump cooling system. Harvesting useful quantities of 225Rn appears unrealistic due to its 5 minute half-life. Off-line harvesting from the gas loop is not recommended for shorter-lived radon isotopes (221Rn, 223Rn), due to the total volume of gas, lower radon concentration and time constraint posed on off-line harvesting by decay. Off-line harvesting of longer-lived noble gas isotopes (211Rn, 76Kr) from the gas loop is feasible and will yield useful quantities of these isotopes.

Feasibility of harvesting radon and noble gas isotopes from the FRIB Beam Dump

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.