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Enviromental Radiation Monitoring

Why Environmental Radiation Monitoring ?

Environmental Radiation Monitoring (ERM) networks have been established in Europe and world-wide for the protection of people and the environment from ionizing radiation. The Purpose of radiation monitoring, actuated through networks, is to:

  •  detect radioactive contamination of the environment
  •  assess resulting dose to man
  •  provide fast and reliable information to decision makers about:
    •  areas affected,
    •  strength of the contamination,
    •  relevant radio nuclides,
    •  actual and future exposure of men in the affected areas

Which are the challenges of Environmental Radiation Monitoring?

Today, one of the major challenges for the future improvement of ERM networks is to obtain fast and reliable spectrometric information to characterize the radiological situation based on radio nuclides in air and deposited to the ground. This requires the development of large volume room-temperature semiconductor detectors to replace legacy Geiger-Müller and proportional counters which are typically used since about 50 years.

Which are the detectors requirements?

A detector suited to best fulfill the mission of future ERM should allow the deconvolution of complex Chernobyl-like spectra and have a minimal crystal size of ~6 cm2 to assure the detection of a homogeneous surface contamination of Cs137 with an activity concentration of 300 Bq/m2 within 30 min, corresponding to an increase in dose rate of ~ 1 nSv/h. The detector covering the low dose rate range will be complemented using PIN diodes to extend the dose rate range up to approximately 1 Sv/h. As well, good performance of future detectors in the low energy region requires the ratio of the full-energy peak to the Compton continuum (Peak-to-Compton (P/C) ratio) of 50:1 @ 1.33MeV of Co60. To monitor radioactivity in the environment, spectrometric gamma dose rate detectors are operated as stationary and mobile systems exposed to considerable variety of harsh situations and climate conditions. Hence the detectors should be designed shock-resistant and the stability should be guarantee for a large range of temperatures and humidity.

The following list of requirements is considered as relevant for the specification of a detector to best fulfill the mission of future ERM detectors:

Sensitivity:  1 nSv/h
Energy resolution:  less than 0.5 % @ Cs-137
Dose rate range: 1 nSv/h to 100 µSv/h
Peak to Compton ratio: 50:1 @ 1.33MeV of Co-60
Temperature range:    from -30 to +50   
Humidity:    up to 95%
Power consumption below 100 mW  

Today only 1-2cm3 (Cd,Zn)Te detectors are available. Hence a considerable technical and scientific effort will be required to develop large size detectors fulfilling the above mentioned requirements.