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

Geert CORTENBOSCH, Bel V

Belgian technical experience regarding shielded cells

 Situation in Belgium  Type of events

– Radioactive gas releases – Underpressure loss – Fire – Handling – Contamination

 Points of attention

Topics of the presentation

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 Controlatom AVN Bel V 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

• ut of the cell

 Input in an ALARA database  Training of the personnel  Work preparation

Contamination

 Work on damaged irradiated products lead to contamination

• f 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  Monitoring  Filtration  Training  Fire protection  Interlocks  Product fluxes  Process  Failsafe components  Alarms  Leaktightness  Transfers between airlocks

Thanks for your attention

Any questions ?