Model TASC-HT-HTO-C14

Features:

  • Ultra-reliable tritium (HT and HTO) and C-14 (CO and CO2) air sampler
  • Includes mass flow air control for consistent, precise sampling
  • Collects both HT and HTO with cascaded triple vials to ensure virtually 100% collection efficiency
  • Thermal oxidizer with temperature indicator to convert HT to HTO and CO to CO2, regulated range 455 – 475 °C
  • Sensitivity for 3H: 10-9 µCi/ml (10-9 Ci/m3) for 7-day period at 100 ml/min
  • Sensitivity for 14C: 10-10 µCi/ml (10-10 Ci/m3) for 7-day period at 100 ml/min

Description:

The Model TASC-HT-HTO-C14 is a high-quality and reliable tritium and carbon-14 in air sampler.  It is the same as our Model TASC-HT-HTO but includes C-14 (CO and CO2) collection by using a solid sodium hydroxide collection medium called Ascarite.  Airborne tritium in the sample stream is continuously collected in vials filled with a liquid collection medium (water or glyocol).  The amount trapped increases linearly with elapsed time.  At regular intervals, the sampling is stopped, the contents removed and assayed using liquid scintillation counting to determine the amount of radioactivity collected.  Knowing the collection flow rate and the results of the scintillation assay, the average sample activity can be calculated for the period of time over which the sample was collected.   Passive samplers, although they do not provide real-time data, provide a low-cost and highly effective method of measuring to extremely low levels, thereby ensuring compliance with local regulations.

The TASC-HT-HTO-C14 is carefully designed and engineered so that it is easy to use, reliable, and consistent.  It has been in service for over 23 years, and many of the original units are still working to this day which is a testament to its reliability.  The sample holder tubing is made of 304/316 stainless steel which is cut, bent into shape, and brazed directly into sample holder caps which hold the sample collection bottles.  The whole assembly is leak tested, sandblasted for a uniform finish free of burs and oxidation, and finally electroplated for a bright nickel finish.

The TASC-HT-HTO-C14 collects both elemental tritium (HT) and tritium oxide (HTO).  First, the sample air is filtered by a high efficiency HEPA filter (99.99% at 0.1 microns) to remove dust and other particulates.  Next, HTO is directly trapped in the first set of vials, while the HT fraction of airborne tritium is trapped in the second set of vials by converting HT into HTO by means of a tube furnace.  Cascaded sets of vials are used to ensure virtually 100% sample collection.

A separate panel is included for C-14 collection (CO and CO2) and includes up to 4 drying columns containing indicating Drierite™, a polycarbonate tube containing Ascarite C-14 sample collection medium (solid NaOH, granular form, 20-30 mesh), and associated hose connections.  Analysis of the C-14 concentration is obtained by acidification of the Ascarite media in a closed distillation system, which releases the CO2 to be captured downstream in a liquid scintillation cocktail in countable form.  Testing has shown the distillation yield to be 95±5%.  Dividing the counting efficiency by the elapsed flow rate will yield the C-14 concentration.

A highly reliable mass flow meter precisely controls the flow rate through the sampler at a consistent value.  The mass flow rate is adjusted at the factory to 100±3 scc/min, and is set by a potentiometer on the flow controller circuit board.

The front panel of the instrument has digital displays for flow rate, elapsed time, tube furnace temperature, as well as a visual indicator for low sample flow.

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