Contamination control at the exit from radiation controlled

Contamination control at the exit from radiation controlled area and NPP site at Bohunice NPP Svitek Jaroslav, Bohunice NPP, Slovak Republic

Introduction Bohunice NPP-list of reactor units Name V 1 V 2 Unit PWR, Unit 1, VVER-230 PWR, Unit 2, VVER-230 PWR, Unit 3, VVER-213 Operation 1978 1980 1984 PWR, Unit 4, VVER-213 1985

Contamination monitors at RCA boundary The first measuring point Ø Surface contamination of clothes Ø Old fashioned monitors RZB-04 -04, RUSSI-1 The second monitoring point Ø Perssonel – new monitors APM-3 A Ø Small obhjects – new monitors CPO Ø May 2001 – new monitors were put in operation

RUSSI-01, RZB-04 -04 monitors Ø Ø Ø Ø 15 pcs detectors Each detector contains 2 pcs GM tubes type SBT 10 1071 cm 2 total monitoring area Measuring time – 5 seconds Alarm level set – 3 Bq/ cm 2 Entry/exit barriers Calibration source - 90 Sr

APM-3 A monitor - 1 Ø Two steps monitor Ø Alpha, beta and gamma-ray sensitive Ø 20 pcs LFP-800 detectors for monitoring of hands, bodies and feet Ø 2 pcs LFP-330 detectors for monitoring of heads Ø 4 pcs LFP- 800 detectors for monitoring of small objects ( items monitor ) Ø Feet, hands and body photosenzors Ø Over 2 x 16000 cm 2 of active monitoring area for total coverage of the body Ø 3200 cm 2 of active monitoring area in items monitor

APM-3 A monitor - 2 Ø Entry/exit barriers Ø Low P-10 gas consumption Ø Reader for ID-cards Ø Alarm set point – 45 Bq/cm 2 Ø Calibration source - 137 Cs

CPO monitor Ø Two large area scintillation detectors (1225 cm 2 each) Ø Lead shielding (25 mm) Ø Entry/exit barriers Ø Audible warning. Ø Calibration source - 60 Co Ø Alarm level set 90 Bq

Activity monitor at NPP site - PM 7 monitor Ø Walk through mode Ø Lead shielding Ø RDA of PM 7 monitor - (9. 2 – 10. 4) k. Bq Ø 6 pcs plastic scintillation detectors Ø Calibration source - 137 Cs Ø In operation since January 1998

Experience with installation PM 7 ü Measuring algorithm of PM 7 had been accommodated APM-3 A ü Problems with the control of the P 10 gas flow ü Large number of shoe soles contamination Corrective actions ü More frequent washing of the hot change rooms ü Deco foils at the entrance to the hot change rooms

The number of contamination Year No of object contamin. Other Radio – therapy 1998 No of personnel contamin. 37 6 6 5 1999 19 10 5 3 2000 22 7 5 2 2001 5 7 4 2 2001 -2002 after the modern. 0 0 3 3

Analysis of the events revealed: ü More than 70% events of personnel contamination was caused by insufficient characteristics of old equipment RZB-04 -04 and RUSSI-1 at the exit from RCA ü Less than 30% of personnel contamination was caused by human error - by violation of RP rules at the exit from RCA ü Up to 60% of events was caused by the contractors workers ü Up to 80% of all events was found at JE V-1 which was caused by a large extend of reconstruction works during the reconstruction and the higher contamination of the primary circuit ü All contamination events represent only negligible risk on the human health

Conclusion ü The first event of contamination at the personal site gates was found after the installation of monitors PM 7 ü The main cause of the taking out of the contamination from the RCA was the insufficient monitoring equipment at the RCA boundary ü The problem was eliminated by replacing old monitors through new ones