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Radiation & Reactor Theory

Radiation & Reactor Theory

The Radiation and Reactor Theory (RRT) Group falls within the Research and Development Division of Necsa. The main focus of RRT is to research, develop and apply advanced calculation methods in the fields of radiation transport and nuclear reactor physics.

RRT has been involved in many theoretical reactor physics analyses the past twenty five years. These analyses cover different types of calculations, namely neutron reactor core calculations, criticality analyses as well as source term and radiation shielding calculations. An important aspect of the groups' activities is the research, development and use of the locally developed reactor core analysis system OSCAR-4. Since 1995 OSCAR-4 has been used extensively for reload and utilisation support calculations for the SAFARI-1 reactor (MTR). Other research reactor operators and research groups also use the code internationally.

Research & development

  • Maintain and expand a reactor physics competence in South Africa.
  • This competence is evidenced in the locally developed OSCAR-4 calculation system (applicable to MTRs and PWRs) and international publications.
  • The OSCAR-4 code system together with other internationally recognised code systems (SCALE, MCNP etc) is used in support of the local nuclear industry.
  • Participation in international research projects is also conducted continuously.


OSCAR-4 is an advanced neutron code system developed and maintained by the RRT group.

  • Methods research and development
  • Code and module development
  • Core analysis, reload and safety calculations
  • Users:
    o    SAFARI-1 at Necsa in South Africa
    o    HFR at Petten in Netherlads
    o    HOR at TU Delft in Netherlands
  • Customised for research reactors but also used for PWR reload analysis

SAFARI-1 support

"SAFARI-1 is one of the few research reactors that has a dedicated team of reactor physicists who develop their own customised reactor physics tools in support of the reactor utilisation."

This support enables SAFARI-1 to operate more economically and enhances the commercial exploitation of the irradiation facilities.

The calculation support provided by the RRT team forms a vital part of the safe, reliable and economical operation of SAFARI-1.  It includes

  • Safety analysis
  • Fuel reload optimisation and reload design
  • Irradiation rig design ensuring optimum neutron flux and neutron energy spectrum
  • Optimisation and maximisation of current and new isotope production
  • Low Enriched Fuel (LEU) studies and participation in the international RERTR (Reduced Enrichment for Research and Test Reactors) program
  • Examples:
    - The rig design for the Mo-99 target plates Mo-99 generators used for Medical applications
    - Design of rig for NTD silicon used in computers
    - Re-licensing of SAFARI and the redefinition of operating margins.
    - Beam characterisation and calculation support.

To supply this support the OSCAR-4 system plays a vital role. MCNP models are also employed for specific problems when required