The ELTRA ONH-2000 oxygen/nitrogen/hydrogen analyzer is used to measure oxygen, nitrogen, and hydrogen content of various samples from radioactive or nonradioactive sources. It is located in the carbon, nitrogen, oxygen, and hydrogen (CNOH) glovebox. Sample size is typically >1 gram solid sample analysis. Sample preparation associated with performance of this procedure is covered under separate work control.
The ELTRA ONH-2000 oxygen/nitrogen/hydrogen analyzer's remote electrode furnace is enclosed in the CNOH glovebox, and the analyzer cabinet, electrode-cooling system, and associated controls are located outside the glovebox. A single analysis will simultaneously measure oxygen/nitrogen in a helium carrier gas or oxygen/hydrogen in a nitrogen carrier-gas stream. The oxygen is measured in the form of CO2 by an infrared (IR) detector, and hydrogen or nitrogen is measured by a thermal conductivity (TC) detector. The solid sample (~0.5 g) is weighed and placed inside a sample loading mechanism, on top of the electrode furnace. A graphite crucible is loaded into the electrode furnace, where it is heated to high temperature (~3,000°C) by a low voltage (~6 VDC) and high current (~1,200 A) passing through the crucible in an inert atmosphere. This high temperature results in the outgasing of entrapped gases from the graphite crucible. The sample is placed in the hot crucible, where it melts and releases oxygen in the form of CO, by reaction with the graphite. Any hydrogen and nitrogen are released as diatomic gases from the sample. The furnace exhaust is filtered by a glass wool filter inside the glovebox to remove any dust or large particulates. The gas stream exits the glovebox through a high-efficiency particulate air (HEPA) filter to remove any radioactive particulates, before entering the analyzer cabinet. The gas stream enters a hot copper-oxide furnace (350°C) or Schultz reagent (ambient temperature) to oxidize all CO into CO2. The oxygen content is then measured by high- and low-range infrared (IR) cells to determine oxygen content of the sample by CO2 IR absorption. The gas stream then passes through sodium hydroxide and magnesium perchlorate (anhydrone) reagents to remove all CO2 and water. The gas stream then passes through a TC cell to measure nitrogen or hydrogen by thermal-conductivity detection. The gas stream is then returned to the suspect exhaust ventilation. Additionally, the helium or nitrogen carrier gas is purified in the analyzer cabinet by solid sorbent traps containing sodium hydroxide to remove CO2 and anhydrone, and to remove water, in order to provide a lower background for IR absorption measurements. Total combustion analysis time is less than 1 minute for obtaining O/N or O/H measurements.
The ONH-2000 is capable of simultaneous determination of oxygen/nitrogen or oxygen/hydrogen. Determination of all three elements requires two samples. Temperature of up to 3,000⁰C are used to convert oxygen to CO(g), nitrogen to N2(g), and hydrogen to H2(g). The CO(g) is then further oxidized to CO2(g) using a copper oxide catalyst and measured in two IR cells of varying path lengths. Hydrogen and nitrogen are measured in shared thermal conductivity cells.
Sample sizes range from 100 to1,000 mg depending on the material. Detectable oxygen and nitrogen ranges from 1 to 20,000 ppm. Hydrogen is may be measured in the range of 0.01 to 1,000 ppm. Sample measurement time takes less than 100 seconds depending on the analysis and concentration of the analyte.
Sample size is typically > 1 g.