[ RadSafe ] NPL builds long range alpha detector

[ROY HERREN]

Public release date: 1-Nov-2010
 
Contact: David Lewis
david at proofcommunication.com
084-568-01865
National Physical Laboratory 

NPL builds long range alpha detector
The UK's National Physical Laboratory (NPL) has developed a new portable 
radiation detector that can assess the safety of potentially contaminated areas 
far quicker than current methods. The prototype was inspired by the aftermath of 
the murder of Alexander Litvinenko in London 2006. 

Litvinenko's death was due to radiation poisoning from polonium-210. It prompted 
wide-scale work to assess radiation levels at almost 50 premises in London that 
he had been prior to his death before opening them up again to the public, 
costing the Health Protection Agency £2 million. 

The clean up process took an extended period of time as scintillation counters 
were used to detect alpha particles and therefore measure the radiation levels. 
Alpha particles only have a range of about 2 cm and can be suppressed by surface 
moisture and roughness. Geiger counters also require a skilled operator to work, 
making it a painstaking and laborious process to scan wide areas very close to 
the surface. 

NPL has developed a prototype device which can detect the optical photons 
generated by alpha particles in air, thus having a far greater range.
Alpha particles can cause ionization of nitrogen in air, which in turn produces 
fluorescence photons that show up as discrete spectral lines in the UV band of 
the electromagnetic spectrum. These photons can travel much further than alpha 
particles and are not hindered by surface particles or roughness and can be 
transmitted through any UV transparent material such as plastic or glass. This 
means an area could be made safe before a contamination assessment is carried 
out.
NPL has developed a portable device for low-level monitoring in normal lighting 
conditions. Laboratory tests have shown that the prototype is capable of 
detecting alpha induced nitrogen fluorescence at distances greater than the 
range of alpha particles (2 cm). The prototype has demonstrated detection up to 
20 cm, limited currently by the optics on the device. However, the principle is 
completely scaleable with small devices having a range of cms and non-portable 
devices reaching kms.
Ray Chegwin, Business Development Manager at NPL, said: "NPL has a strong 
heritage of using world class measurement science to benefit society and 
industry in the UK and beyond. By producing a prototype that can measure 
radiation up to ten times further away than current methods we can greatly 
improve the time it takes to safely assess any suspected radioactive areas. Our 
prototype could have saved the time it took to monitor the areas relevant to the 
Litvinenko case, and cut the costs of such an essential operation. Of course, 
the detector could be used to support radiation safety and decommissioning 
operations in the nuclear industry, amongst others, and we're currently 
investigating these."
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Notes to editors
About the NPL Alpha Detector: 
The spectral range of the fluorescence photons emitted due to alpha ionisation 
of nitrogen are located in the predominantly UV range (300 – 490 nm) of the 
optical spectrum. Tests have been carried out to eliminate any possibility of 
the detected signal coming from beta or gamma radiation.
The device can operate in a sodium lamp room. In this environment, the light 
levels are similar to normal room light levels (lights on). The filtered 
detector is entirely blind to the wavelength of light emitted by sodium lights. 
The detector is also capable of detecting the fluorescence signal through any UV 
transparent material.
The optical housing has been designed so that any 1-inch optics can be inserted 
to select particular wavelengths. The device is modular; adapters could be made 
for larger optics, larger area detectors can also be used. Custom electronics 
have been designed and implemented to make the device portable. A lithium ion 
battery provides up to 8 hours of usage in field-based applications.
The National Physical Laboratory 
The National Physical Laboratory (NPL) in Teddington is one of the UK's leading 
science facilities and research centres. It is a world-leading centre of 
excellence in developing and applying the most accurate standards, science and 
technology available. NPL occupies a unique position as the UK's National 
Measurement Institute and sits at the intersection between scientific discovery 
and real world application. Its expertise and original research have underpinned 
quality of life, innovation and competitiveness for UK citizens and business for 
more than a century: 

	* NPL provides companies with access to world leading support and technical 
expertise, inspiring the absolute confidence required to realise competitive 
advantage from new materials, techniques and technologies 

	* NPL expertise and services are crucial in a wide range of social applications 
- helping to save lives, protect the environment and enable citizens to feel 
safe and secure. Support in areas such as the development of advanced medical 
treatments and environmental monitoring helps secure a better quality of life 
for all 

	* NPL develops and maintains the nation's primary measurement standards, 
supporting an infrastructure of traceable measurement throughout the UK and the 
world, to ensure accuracy and consistency. 

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