 The NBR technique (Natural Background
Rejection) allows the detection of even the smallest contributions of
artificial gamma radiation in presence of any natural radiation background. This
technique, developed by Thermo Eberline ESM, continuously monitors the average energy and
the distribution of the gamma radiation. Irregularities are detected in fractions of a
second. This results in high statistical certainty and - even in the case of well shielded
sources - extremely short measuring times.
The graph at the right side clearly demonstrates this function. The red curve represents
the natural background radiation which may change within an area rapidly due to geological
structure or building materials. The blue line shows the derived NBR signal with a peak
where artificial radiation has been detected. Comparison of the 'peak to noise ratio'
clearly shows that even very small contributions of artificial radioactivity can be
detected within a varying natural radiation background.
Features
- Compensation of natural gamma radiation fluctuations
- Compensation of self shielding effects (e.g. by the passing vehicle). Even sources that
are very well shielded can be detected.
- Distinguishes between natural effects (e.g. fertiliser, bricks,...) and artificial
radiation from e.g. hidden sources.
Typical applications:
- Large scale radioactivity monitors for trucks and trains FHT 1388
in the steel and recycling industry
border control (illicit trafficking of nuclear material)
gate monitors for nuclear research centers and power plants
- Medium sized monitors for pedestrians and conveyors FHT 1372
- Crane mounted systems for the steel and recycling industry FHT 1374
- GPS supported radiation detection and mapping system FHT 1376
- Hand held radioactivity detectors for detail investigations FHT 672 with survey meter FH 40 G
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