Svitek Jaroslav, Bohunice NPP, Slovak Republic 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 Unit Operation V1 PWR, Unit1, VVER-230 1978 PWR, Unit2, VVER-230 1980 V2 PWR, Unit3, VVER-213 1984 PWR, Unit4, VVER-213 1985

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

RUSSI-01, RZB-04-04 monitors 15 pcs detectors    Each detector contains 2pcs GM tubes type SBT 10    1071 cm2 total monitoring area    Measuring time – 5 seconds    Alarm level set – 3 Bq/ cm2    Entry/exit barriers    Calibration source - 90Sr

APM-3A monitor - 1 Two steps monitor    Alpha, beta and gamma-ray sensitive    20 pcs LFP-800 detectors for monitoring of hands, bodies and feet    2 pcs LFP-330 detectors for monitoring of heads    4 pcs LFP- 800 detectors for monitoring of small objects ( items monitor )    Feet, hands and body photosenzors    Over 2x16000 cm2 of active monitoring area for total coverage of the body    3200 cm2 of active monitoring area in items monitor

APM-3A monitor - 2 Entry/exit barriers Low P-10 gas consumption Reader for ID-cards Alarm set point – 45Bq/cm2 Calibration source - 137Cs

CPO monitor Two large area scintillation detectors (1225 cm2 each) Lead shielding (25 mm) Entry/exit barriers Audible warning. Calibration source - 60Co Alarm level set 90 Bq

Activity monitor at NPP site - PM7 monitor Walk through mode  Lead shielding RDA of PM7 monitor - (9.2 – 10.4) kBq 6 pcs plastic scintillation detectors Calibration source - 137Cs In operation since January 1998

Experience with installation   PM 7 Measuring algorithm of PM7 had been accommodated APM-3A Problems with the control of the P10 gas flow Large number of shoe soles contamination Corrective actions More frequent washing of the hot change rooms Deco foils at the entrance to the hot change rooms

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

Analysis of the events revealed:   Analysis of the events revealed:  More than 70% events of personnel contamination was caused by insufficient characteristics of old equipment RZB-04-04 and RUSSI-1at the exit from RCA  Less than 30% of personnel contamination was caused by human error - by violation of RP rules at the exit from RCA  Up to 60% of events was caused by the contractors workers  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  All contamination events represent only negligible risk on the human health

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