1. A Sensor Based On Plastic Scintillator for Alpha, Beta and Gamma Monitoring in Liquid Effluents A.Tarancón 1, J.F.García 2 and G. Rauret 1 1 Departament de Química Analítica, Facultat de Química. Universitat de Barcelona. Av/ Diagonal 647, 08028 Barcelona 2 Departament de Pintura, Facultat de Belles Arts. Universitat de Barcelona. C/ Pau Gargallo 4, 08028 Barcelona (Spain) E-mail: jfgarcia@apolo.qui.ub.es, alex.tarancon@ub.edu Channels SENSOR SIGNAL CARACTERIZATION (B-A) Parameter is obtained by applying the second derivate to the signal profile: δ 2 Bq/δV 2 =0 SIGNAL PROFILE (0.2, 1, 4, 10, 14 and 20ml) SPECTRA Different pulse volumes (P.V.) (0.2ml to 60ml) of 90 Sr90Y, 134 Cs and 240 Pu were loaded into the sensor (flow = 0.5ml/min) QUALITY PARAMETERS Time (s) Eff(%) or Counts(Bq) LIMIT OF DETECTION (L.O.D) WILL IMPROVE DRASTICALLY IF ALPHA-BETA DETECTOR AND GAMMA DETECTOR ARE MEASURED IN COINCIDENCE ACKNOWLEDGEMENTS: The authors thanks the CICYT for Financial support: PPQ2002-00264 BIBLIOGRAPHY - Patent Applications nº P200500480: Sensor Radioquímico para fluidos. A. Tarancón, J.F. García y G. Rauret - Development of a radiochemical sensor for liquid effluents. Part I. A. Tarancón, J.F. García y G. Rauret. Analytica Chimica Acta 538 (2005) 233-239 - Development of a radiochemical sensor for liquid effluents. Part II. A. Tarancón, A. Padró, J.F. García y G.Rauret. Analytica Chimica Acta 538 (2005) 241-249 CONCLUSIONS The radiochemical sensor can be applied to the DETERMINATION ON- LINE, REMOTELY, AND CONTINUOUSLY OF ALPHA, BETA, AND BETA-GAMMA RADIONUCLIDES included in liquid effluents. Relative errors for 90 Sr/ 90 Y and 134 Cs in the alpha-beta receptor are lower than 10% for contamination volumes higher than 5 ml. For 240 Pu relative errors are less than 15%. For 134 Cs in the gamma receptor similar values were obtained. RESULTS WILL IMPROVE WITH NEW DESIGNS ADAPTED TO SPECIFIC PROBLEMS. 0 50100150200250300350 0 20 40 60 80 100 120 140 Counts(Bq) ACTIVITY QUANTIFICATION 0 5 10 Activity 25 Bq/ml Activity 141 Bq/ml Activity 338 Bq/ml Relative Error (%) 7 ml 12 ml 7 ml ACTIVITY QUANTIFICATION 0 5 10 15 20 25 30 35 Activity 97 Bq/ml Activity 262 Bq/ml Activity 282 Bq/ml Relative Error (%) 12 ml ACTIVITY QUANTIFICATION 0 5 10 Activity 12 Bq/ml Activity 21 Bq/ml Relative Error (%) 8 ml 14 ml 3 Bq/ml 90 Sr 90 Y in the ALPHA-BETA DETECTOR 134 Cs in the GAMMA DETECTOR 134 Cs in the ALPHA-BETA DETECTOR 240 Pu in the ALPHA-BETA DETECTOR ACTIVITY QUANTIFICATION 0 5 10 15 20 Activity 94 Bq/ml Activity 383 Bq/ml Activity 542 Bq/ml Relative Error (%) 7 ml 12 ml The Sensor was calibrated to modelize the relationship between detection efficiency and the volume loaded (P.V.) versus de (B-A) parameter. Then it was applied to quantify the activity an the volume of a serie of unknown contamination pulses of different volume and activity ACTIVITY DETERMINATION OF UNKNOWN SAMPLES Relative errors increase when pulses lower than 5ml are quantified. VOLUME QUANTIFICATION 0 5 10 15 20 25 Activity 97 Bq/ml Activity 262 Bq/ml Activity 282 Bq/ml Relative Error (%) 7 ml 12 ml VOLUME QUANTIFICATION 0 5 10 Activity 95 Bq/ml Activity 383 Bq/ml Activity 542 Bq/ml Relative Error (%) 7 ml 12 ml VOLUME QUANTIFICATION 0 5 10 15 Activity 141 Bq/ml Activity 338 Bq/ml Relative Error (%) 7 ml 12 ml 25 Bq/ml VOLUME QUANTIFICATION 0 5 10 Activity 3 Bq/ml Activity 12 Bq/ml Activity 21 Bq/ml Relative Error (%) 8 ml 14 ml P.V. (ml) Time (s) Efficiency (%) Background (Bq) L.O.D. (Bq/ml) 90 SR 90 Y in ALPHA- BETA DETECTOR 0.2105.50.613.0 6012001170.809.1·10 -2 240 Pu in ALPHA- BETA DETECTOR 0.2100.130.499.4 6012002.80.561.6 134 Cs in GAMMA DETECTOR 0.2100.0340.1775.9 6012001.20.130.77 INTRODUCTION On-line radioactivity monitoring in liquid effluents is an increasing need according to the present international regulations. Classical activity determination procedures include the sequence of sampling, chemical treatment, measurement and data treatment. These steps are man-power consuming, generate a great amount of waste and introduce an important delay between the potential pollution event and its detection and quantification. To overcome these limitations, we have developed a RADIOCHEMICAL SENSOR (PATENT PENDING Nº:P200500480) for liquid effluents capable to send information about the specific activity and volume of a contamination episode to a remote position, on line and continuously. The sensor developed is capable to detect and quantify the contamination pulses of alpha, beta and gamma emitters of different volumes and activity levels included in a continuous stream. SENSOR DESCRIPTION AND OPERATION The sensor patented is composed of two parts: Receptor and Transductor. Receptor is made of plastic scintillator. It is divided in two concentric cylinders: the internal ALFA-BETA DETECTOR and the external GAMMA DETECTOR. A modified 1414 Liquid Scintillation detector was used as transducer. A peristaltic pump introduce the effluent into the sensor. Two bundles of optical fibers connect each part of the sensor with the transducer. Both detector were not measured simultaneously. SIGNAL DETECTED IN THE ALFA- BETA DETECTOR: BKG+ γ +β + α SIGNAL DETECTED IN THE GAMMA DETECTOR: BKG+ γ