Passive Diffusion Sampler

Passive diffusion samplers have now been in use in the UK for the measurement of tritium at environmental levels in the form of HTO and HTO + HT for more than ten years. Passive samplers offer an attractive alternative to conventional dynamic samplers as, once installed, run without operator intervention, require no power and, with no moving parts to wear out, are virtually maintenance free. RCD have developed a robust weather-proof unit which allows the determination of HTO in air at environmental levels over a period weeks to months. If desired RCD can also modify the samplers to allow the determination of the levels of atmospheric HTO+HT and also ¹⁴CO₂.

RCD can supply suitable samplers as part of a full analytical service with vacuum extraction and tritium measurements carried out at the low level laboratory at Lockinge. The only additional information that is required is the average relative humidity and temperature details for over the sampling period.

Dynamic HTO / HT Discriminating Dry Bed Absorber Sampler

The RCD HTO/HT discriminating dry bed sampler is designed for the collection of both water bound (HTO) and diatomic (HT) tritium from a gas stream. The sampler is a dynamic device which uses silica gel in three self-sealing removable cartridges to first extract moisture (HTO), after the catalytic conversion (room temperature) of HT to HTO, HT from the gas stream over an integrated time period. The absorbed water is then extracted from the silica gel cartridges and it's tritium content determined by liquid scintillation counting.

The sampler is manufactured to vacuum standards to run at slightly less than atmospheric pressure with the pump situated nearest the outlet port, drawing the sampled gas through the complete system. Air flow rate is indicated by a rotameter mounted on the front of the instrument. The flow rate is adjusted using a flow adjust valve, which varies the proportion of the incoming gas stream directed to the silica gel cartridges.

The sampler is supplied either with a dual pump system (main and back-up pumps) with an integrated pump failure alarm or a one pump system incorporating a pump failing early warning alarm. If the pump motor begins to fail a flashing LED indicates this has occurred and requires maintenance in the next few weeks. Should the motor fail before it is changed, voltage free contacts give a second alarm which can be routed to a remote alarm unit. In the case of a two motor system switch over, to the standby pump occurs automatically, but this is similarly indicated by the flashing LED.

The sampler operates using a 230v, 50Hz, single phase power supply (110v units can be supplied). It also contains a rechargeable internal back-up battery, and has the facility to be operated from an external 12v DC power supply.

Tritium HTO Bubbler Sampler

The RCD bubbler HTO is designed for the collection of water bound tritium (HTO) from a gas stream. The instrument is a development of the HTO/HT dry-bed absorber systems described above.

The sampler is a dynamic device which uses water in the two bubbler bottles to extract moisture from a gas stream over an integrated time period. At the end of the sampling period aliquots of the water are removed and their tritium content measured. The HTO concentration in the gas stream can then be derived.