Software for control and operation of CIEMAT’s on-line airborne monitoring system

T3.2-P04: A system for the simultaneous and continuous measurement ofAirborne gamma emitters with Ge and scintillation detectors

N. Navarro Ortega1, L. Yagüe Rodríguez1, J.L. Márquez Fernández1, G. Benito Díaz1, C. Pérez Jiménez2, J.C. Sáez Vergara1 (jc.saez@ciemat.es)

1CIEMAT, Avenida Complutense 40, 28040 Madrid, Spain (www.ciemat.es)2TECNASA, Primera 27, 28016 Madrid, Spain (www.tecnasa.es)

ESMERALDA REFERENCE STATION FOR RADIOLOGICAL ENVIRONMENTAL MONITORING

INTRODUCTION

The environmental station ESMERALDA was established at CIEMAT-Madrid premises in 1996 as a reference site for thestudy of the radiation instruments aimed to perform continuous or long-time investigations of the environmental radiationand airborne radioactivity. In the frame of the CSN-CIEMAT co-operation in the Quality Assurance of the radiologicalnetworks, a REA station was installed in ESMERALDA in 1997 and a prototype station for continuous airborne gammaspectrometry based on High Purity Germanium detector (HP-Ge) was mounted in 2003.

In 1992, the Consejo de Seguridad Nuclear, CSN, (Nuclear Safety Council) implemented the Spanish National EnvironmentalSurveillance Radiological Automatic Network, REA, that continuously monitors radiation levels in order to give early warningof incidents having potential transboundary implications. The network includes 25 automatic radiological and meteorologicalstations distributed nation-wide. Each ERA station provides dose rate measurements and also monitors airborneradionuclide concentrations (Alpha, Beta, Rn and radioiodine) and meteorological parameters every 10 min to the CSNEmergency Room, SALEM.

Parameter Quantity, Units REA detector CIEMAT detector

Gamma dose rate H*(10), µSv/h Proportional Counter+ Geiger-Müller

High PressureIon Chamber

Alpha man-madeairborne

ActivityConcentration,

Bq/m3

ZnS/Plasticscintillator

ProportionalCounter(passive)

Beta man-madeairborne

ActivityConcentration,

Bq/m3

ZnS/Plasticscintillator

ProportionalCounter(passive)

Rn gas in air

ActivityConcentration,

Bq/m3

Not available Ion chamber

Rn progenyin air

EquivalentEquilibrium

Concentration,Bq/m3

ZnS/Plasticscintillator

(Pseudocoincidences)

Si surfacebarrier

Iodine in air Concentration,Bq/m3

7.6x7.6 cm NaI:Tl(single windowspectrometry)

HP Ge spectrometry

(passive)

Meteorological parameters: Air temperature (°C), Atmospheric pressure(hPa), Solar irradiation (kJ/m2), Wind speed (m/s), Wind direction (°), Humidity(%) and Rainfall (l/m2).

AIR SAMPLING COLLECTION SOFTWARE

SIDE CHANNEL VACUUM PUMP

• Becker VariAir Speed Flow pump model VASF 1.120/2.

• Maximum air suction rate: 65 m3/h.

• Working air suction rate: 30-35 m3/h.

• Computer control and continuous flow rate monitoring.

GAMMA SPECTROMETRY DETECTORS

• HP-Ge Detector 35% Efficiency with electricallyrefrigerated cryostat.

• Several scintillation detector types in combination withUniversal Digital Multichannel Analyser: NaI:Tl 5x5 cm, LaBr3:Ce 2.5x2.5 cm and CeBr3 2.5x2.5 cm.

• Computer control of the moving paper filter mechanism.

• Lead shield around the measuring chamber.

• Two detectors can be arranged for simultaneous airbornemeasurements.

• Control of pump, moving filter and detectors.

• Two modes of operation for data collection: routine (60 min) and warning (10 min).

• Remote access for approved users.

PARTICIPATION OF CIEMAT IN THE METROERM PROJECT

The EURAMET Joint Research Project ‘Metrology for radiological early warning networks inEurope’ (MetroERM), co-ordinated by the Physikalisch-Technische Bundesanstalt(Germany), was signed by 13 Metrological European organizations on Jan 1st 2014 and willlast for three years. In the Work Package 2 ‘Airborne radioactivity monitoring networks’, ledby the National Physical Laboratory (United Kingdom), CIEMAT is responsible for somedeliverables in the task ‘Development of novel and improved instrumentation for airborneradioactivity for field-station use’.

Detector efficiency calibration using spiked filters reproducing the geometry and measurement conditions

Certified home-made spiked filterRealistic

measurement HP-Ge Gamma Spectrum Efficiency Calibration

Influence of particulate deposits located in the vicinity of the detector’s field of view evaluated

Standard position (0°) 90° position 180° position Out of lead shielding

CONCLUSIONS

• Full control of pump, moving filter and gamma spectrometers.

• Continuous comparison of gamma spectra from HP-Ge and a scintillator.

• Two modes of operation for data collection: routine (60 min) and warning (10 min).

• Automatic safe record keeping in local and network databases of the data from alldetectors at ESMERALDA (ambient dose equivalent, Rn and Airborne gammaspectrometry.

• Remote access for authorised users.

• A system for the simultaneous and continuous gamma spectrometry measurement of particulate airborne radioactivity inthe ESMERALDA reference site at CIEMAT that combines a HP-Ge detector with scintillation detectors is presented.

• Performance of this system is being evaluated in the Project ‘Metrology for radiological early warning networks inEurope’ (MetroERM) in the framework of the European Metrology Research Progamme.

ACKNOWLEDGMENT

The MetroERM project is jointly funded by the EMRP participating countries within

EURAMET and the European Union.