Belgian technical experience regarding shielded cells Topics of the - PowerPoint PPT Presentation

Geert CORTENBOSCH, Bel V Belgian technical experience regarding shielded cells

Topics of the presentation  Situation in Belgium  Type of events – Radioactive gas releases – Underpressure loss – Fire – Handling – Contamination  Points of attention

Situation in Belgium (1/3) Bel V = Subsidiary of the FANC (Federal Agency for Nuclear Control) Bel V + FANC = regulatory body in Belgium, Bel V = TSO Bel V: to carry out the surveillance of the Belgian nuclear installations within the frame of the Belgian laws and regulations FANC Bel V AVN Controlatom Techni-Test

Situation in Belgium (2/3)  7 NPP’s (Doel & Tihange)  Research Centre at Mol (SCK•CEN)  Waste (Belgoprocess)  MOX fuel (Belgonucléaire)  Isotope production (IRE)  Research reactor Thetis (UG)  Universities  Hospitals

Situation in Belgium (3/3)  Bel V = Technical Support of the Federal Agency for Nuclear Control – Nuclear Safety Assessments : Safety Evaluation Reports – Conformity checks of new plants/installations or modifications : issuance of licenses – Inspections : written reports

Radioactive gas release  Unplanned release of I-131 due to unexpected chemical reactions (oxydo-redox reaction) in a tank collecting liquid wastes of shielded cells – Weak dilution – Simultaneous transfer – Waste had short decay time – Slow decomposition rate of H2O2 – Transfer under vacuum

Radioactive gas release – lessons learned  Filtration – Chemical form – Efficiency  Chemical fluxes management – Separation – Avoid involuntary tranfers – Traceability – Use of minimal quantities  Air monitoring – Available at any time – Diversity and redundancy – Discrimination

Loss of underpressure in hotcell  Unexpected opening of a door by actuation on a non- protected touch-sensitive screen – Resulted in the loss of underpressure in a cell during 48 hours (cell contained 800 Ci – 29,6 TBq (I-131 in a basic form)

Loss of underpressure – lessons learned  There was no sound alarm and no alert message on screen  Touch-sensitive screen not protected towards untimely actions and absence of software protection  No traceability of underpressures  No procedures regarding emptying of lines

Fire  Fire in oil remnants (sparks during cutting out phase of a glove box) – Fire-resistant blanket, did not work – Extinction system did not work (fold in the hose) – Housekeeping  Fire in rubber band of a wheel  Fire in the rubber part of a remote handling system in contact with a heater

Fire – lessons learned  Appropriate fire detection and extinction available at any time (verification through regular testing)  Prior to every manipulation, handling task should be analyzed  Line clearance after any operation  Training of operators

Handling of radioactive products  Bringing out of a supplementary tube containing Cs isotopes (doserate 2.9 Sv/h) via a La Calhène port during a distallation phase – Dose of 124 µSv for the operator  Fall of a La Calhène jar between air lock door and a transport container

Handling of radioactive products – lessons learned  Set-up of a procedure regarding measurement and bringing out of the cell  Input in an ALARA database  Training of the personnel  Work preparation

Contamination  Work on damaged irradiated products lead to contamination of shielded cells, workplace and operators – Irradiated products presented a burnt aspect (production of dust, material could easily be broken) – 2000 Bq max internal contamination

Contamination – lessons learned  Lack of interrogative attitude  Appropriate monitoring and interlock system  Adequate protection means (gloves, respiratory protection, contamination check)  Transfer valves actuated pneumatically  Training of operators (procedures)

Points of attention  Ventilation  Product fluxes  Monitoring  Process  Filtration  Failsafe components  Training  Alarms  Fire protection  Leaktightness  Interlocks  Transfers between airlocks

Thanks for your attention Any questions ?