Flushing the radon away
21st October 2025
At a glance
> With many labs measuring ultra-low levels of radiation at basement level or underground to shield against cosmic radiation, radon presents a new source of background noise.
> The Hidex ULLA ultra-low level analyzer allows high-purity nitrogen gas (N2) to be flushed through its sample chamber, reducing radon levels to ALARA.
> This purges the ULLA's counting chamber, preventing radon's decay products from depositing on internal surfaces.
How the Hidex ULLA can detect ultra-low levels of radionuclides
The Hidex ULLA is the most sensitive liquid scintillation counter available since the discontinuation of the 1220 QUANTULUS. With a typical background below 1 CPM in the 25% tritium window, its ultra-low level counting enables environmental monitoring of 3H in and around nuclear facilities and measuring trace activity in sources of drinking water and food chains.
Mitigating the effects of cosmic radiation
For ultra-low level environmental monitoring, cosmic radiation can cause an undesirable increase in the background level. Typically, this would be insignificant for most types of radiation work, but for highly sensitive applications, even a single stray event per hour can cause issues. Many labs performing such sensitive work will be housed at basement level or underground, providing a natural shield and allowing researchers to improve the signal-to-noise ratio for rare events.
An increased risk of radon
However, this increases the risk of radon, which can be found in increased concentrations at basement level or underground. Radon and its radioactive progeny can act as another source of background. Its decay chain emits alphas, betas, and gammas, and this radon “plate out” can contaminate the laboratory environment. Even a single radon nucleus can produce several charged alpha and beta particles on its path towards stability.
So how does the ULLA deal with radon?
The Hidex ULLA has gas inlets that allows high-purity nitrogen gas (N2) to be flushed through the sample chamber, reducing background levels to ALARA; as low as reasonably achievable. This process purges radon from the counting chamber, preventing its decay products from depositing on internal surfaces. By removing radon “plate out”, the system minimizes false counts and allows for robust measurement of the lowest energy beta emissions. Without nitrogen flushing, even a perfectly shielded system would gradually accumulate radon decay products, and the background would climb over time.
Find out more
You can find out more about the Hidex ULLA and its ultra-low level counting by clicking the button below to speak to a product specialist directly.