Ambient air samples for tritium (as HTO) can be collected using the solid adsorbent silica gel. The purpose of this study was to determine the maximum practical sampling volume and overall collection efficiency for water vapor collected on silica gel columns and to demonstrate the use of an impinger-based system to load water vapor onto silica gel columns. Breakthrough volumes (Vb) were measured and chromatographic efficiencies (expressed as the number of theoretical plates, N) were calculated for a 20 degrees C to 50 degrees C temperature range, with the relative humidity at approximately 30%. The tests yielded relative breakthrough volumes (air volume/adsorbent depth, m3 cm(-1)) of 0.36 for 20 degrees C, 0.20 for 30 degrees C, 0.15 for 40 degrees C, and 0.077 for 50 degrees C. For 18-cm columns, the average tritium tracer recoveries at 20 degrees C were 71% with no observed breakthrough for air volumes up to 5 m3, while at 40 degrees C mean tritium tracer recoveries dropped from 75% for volumes < or = 3.0 m3, to 0% for a volume of 5.0 m3. Frontal chromatographic profiles were measured for water vapor migrating through silica gel columns that were divided into 5 segments. The chromatographic efficiency of the silica gel columns was determined by graphical evaluation of the chromatography profiles. At a sampling rate of 0.25 L min(-1) and 30% relative humidity, the number of theoretical plates per adsorbent depth were 0.55 N cm(-1) at 20 degrees C, 0.68 N cm(-1) at 30 degrees C, 0.51 N cm(-1) at 40 degrees C, and 0.30 N cm(-1) at 50 degrees C. Chromatographic theory was used to estimate the overall collection efficiency of the silica gel columns as a function of the ratio of the sampling volume to breakthrough volume and the chromatographic efficiency. For a 9.5 m3 sample volume, 30% relative humidity, 0.25 L min(-1) sampling rate, and a 54-cm column, the overall collection efficiency was above 99.9% at 20 degrees C, above 95% at 30 degrees C, just below 80% at 40 degrees C, and <<80% at 50 degrees C.

SummaryAmbient air samples for tritium analysis (as the tritiated water vapor [HTO] content of atmospheric moisture) are collected for the Hanford Site Surface Environmental Surveillance Project (SESP) using the solid adsorbent silica gel. The silica gel has a moisture sensitive indicator which allows for visual observation of moisture movement through a column. Despite using an established method, some silica gel columns showed a complete change in the color indicator for summertime samples suggesting that breakthrough had occurred; thus a series of tests was conducted on the sampling system in an environmental chamber.The purpose of this study was to determine the maximum practical sampling volume and overall collection efficiency for water vapor collected on silica gel columns. Another purpose was to demonstrate the use of an impinger-based system to load water vapor onto silica gel columns to provide realistic analytical spikes and blanks for the Hanford Site SESP. Breakthrough volumes (VJ were measured and the chromatographic efficiency (expressed as the number of theoretical plates N) was calculated for a range of environmental conditions. Tests involved visual observations of the change in the silica gel's color indicator as a moist air stream was drawn through the column, measurement of the amount of a tritium tracer retained and then recovered from the silica gel, and gravimetric analysis for silica gel columns exposed in the environmental chamber.For all tests, flows were 1 to 1.5 L/min with the relative humidity at approximately 30 % . Visual observations and gravimetric tests were conducted from 20°C to 50°C. Tracer tritium recovery tests were conducted at 20°C and 40°C. The basic test apparatus was an air pump connected to a primary silica gel column (18-cm x 5.9-cm diameter) with flow rates measured and controlled with a rotameter. For the tracer tritium tests, an impinger was installed upstream of the primary column and a backup silica gel column was added to prevent loss of tritium to the test chamber environment. Samples were prepared for analysis by vacuumdistillation and counted by liquid scintillation. The visual observations yielded relative breakthrough volumes (air volume/adsorbent depth [m3/cm]) of 0.36 for 20°C 0.20 for 30"C, 0.15 for 40°C and 0.077 for 50°C. Average tritium tracer recoverieS at 20°C were 71 % with no observed breakthrough. Mean tritium tracer recoveries at 40°C dropped from 75% for volumes S3.0 m3, to 0% for a volume of 5.0 m3.Moisture loading and frontal chromatographic profiles were measured for water vapor migrating through the silica gel columns. Moisture indicating silica gel was packed into a 5-segment column, using metal screens to divide the segments. Moist air was drawn through the column until the third segment showed a partial color change of the indicator. The mlumns were disassembled and each segment was weighed and the moisture content was calculated. Moisture loadings (g H,O/g silica gel)ranged from 0.063 to 0.16 for the first and second segments, 0.027 ...

There is an urgent need to standardise the numbering configuration of radiation portal monitor sensing panels. Currently, manufacturers use conflicting numbering schemes that may confuse operators of these varied systems. There is a similar problem encountered with the varied choices of coloured indicator lights and coloured print lines designated for gamma and neutron alarms. In addition, second-party software that changes the alarm colour scheme may also have been installed. Furthermore, no provision exists for the colour blind or to provide work stations with only black ink on alarm printouts. These inconsistencies and confusing set-ups could inadvertently cause a misinterpretation of the alarm, resulting in the potential release of a radiological hazard into a sovereign country. These issues are discussed, and a proposed solution is offered.