Cell Retrofit Program


Background 

The recommended working life of the radioactive sources in the detection cells has expired after     10 years of use.

Use beyond working life limit may cause a radiation hazard to operating personnel.

Sources can be replaced by new ones with reduced radioactivity and extended working life of 20 years.

The cell retrofit programme has already been executed by three European Armed Forces operating more than 4,000 M43A1 detectors.

Source Ageing Process

The original M43A1 radioactive sources have a   high doping density: 250 Ci (9.25 MBq) per          2 cm (16 mm diameter).

Due to the concentration gradient, Americium diffuses from the doped matrix into the covering layer. 

After approximately 10 years from production, contamination of more than 20 Bq may occur on  the source surface.

As the M43A1 has an open air flow system (no membrane inlet), radioactive contamination may escape from the detector and generate a radiation hazard to the environment.

Countermeasures

Radioactive sources have to replaced in order to continue safe operation of the equipment.

New sources have lower radioactivity (25 Ci = 925 kBq), increasing the operational life of the detector to 20 years.

Loss in sensitivity (factor of 3) can be either compensated by a resistor change on the cell electronics board or tolerated to improve interference rejection.

Cell blocks are replaced as entire units to facilitate handling and to refurbish cells.

Detector is furnished with outlet particle filter to monitor the output and to eliminate any future risk.

 

Replacement Procedure

  • Cell modules are disassembled.

  • Cell blocks are removed and disposed off.

  • Cell electronics and mechanics are retained.

  • Cell electronics is modified.

  • New cell blocks are mounted into modules.

  • Modules are calibrated in reference detectors.

  • Modules are fitted to detectors.

  • Outlet filters are mounted.

 

Detection Cell

The detection cell is contained in the cell module which is shielded by a zinc cast metal housing.

The module comprises the housing, the cell block, and the cell electronics.

The cell block is a tefzel body which incorporates the radioactive source, the manifold, electronics, baffles, and spacers.

The radioactive source is mounted on a gold-coated screen. 

 

 

Radioactive Source   

The radioactive source is a 16mm diameter disk punched out of a foil.

The foil has a multilayer structure and is manufactured by cold-rolling of a sandwich block   of metal plates.

The substrate is a 0.2mm silver plate covered by    a 1m gold interface layer. 

The active matrix is a 1m gold layer doped with radioactive Americium-241 oxide. 

The active layer is covered by a 2m gold/palladium alloy protection layer.  

 

 

Statement of Work                                              

         Replacement of M43A1 Detection Cells

 

The replacement may be combined with an overhaul of the detector units. In this case the complete detectors and not only the cell modules will be shipped to the repair facility. The retrofit programme is carried out at the premises of our partner company Bruker Saxonia Analytik GmbH at Leipzig, Germany.

 

1. Removal of cell modules

The cell modules are removed from the detectors and stored in containers.  

2. Transportation to our repair facility

The containers are transported to the repair facility by   a forwarding company authorised for transportation of radioactive material. 

3. Disassembling of cell modules  

The cell modules are opened and the detection cell and the exhaust hose are separated from the mechanical parts and electronic boards, which are maintained for re-use.

4. Removal and disposal of detection cells  

The detection cells and exhaust hoses are removed and disposed off in compliance with all applying legal regulations.

5. Installation of new detection cells with reduced radioactivity   

The modules are fitted with new detection cells containing radioactive sources with a reduced radioactivity of 925 kBq and a working life of 20 years. 

6. Modification of cell electronics  

The cell electronics are modified by change of two resistors to restore the original sensitivity.

7. Assembling of modules 

The modules are assembled using the original mechanical and electronic parts.

 

8. Calibration and test in reference detector units 

The modules are installed in reference detector units, tested and calibrated using the simulant DPM.

9.Quality inspection 

Calibration and test protocols are provided.

10. Packaging and shipping of cell modules 

The cell modules are packed in the original containers and shipped back.