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The PBMR has inherently safe characteristics as a result of the
  • Design
  • Materials used
  • Fuel and
  • Physics involved
This is why, should a worst-case scenario occur, no human intervention is required in the short or medium term.
In all existing power reactors, safety objectives are achieved by means of custom-engineered, active safety systems.
Why do PBMRs behave differently from other nuclear reactors in crises?
Nuclear accidents are principally driven by too much heat. This surplus or residual heat is called decay heat and is caused by radioactive decay of fission products. Put simply, if you do not cool the reactor sufficiently, the heat will cause the nuclear fuel to release radioactivity that cannot be contained.
In "conventional" reactors, heat is removed by active cooling systems (such as pumps), which rely on the presence of coolant such as water. Any such system may fail and therefore they are duplicated in conventional reactors to make sure that there will be support, should the first line of defence fail. Secondly, so-called containment buildings are constructed which is nothing less than strongly armoured containers to create a barrier to the release of radioactivity.
With the PBMR, this basic danger of overheating is independent of the state of the reactor coolant. PBMR combines very low power density of the core (1/30th of the power density of a Pressurised Water Reactor), and the resistance to high temperature of fuel in billions of independent particles which creates an inherent ceiling to temperature control.
The helium, which is used to transfer heat from the core to the power-generating gas turbines, is chemically inert. It cannot combine with other chemicals and is non-combustible. Since air cannot enter the primary circuit, oxygen cannot get into the high temperature core to corrode the graphite used in the reactor. Thus chemical reactions and oxidation, two of the great dangers in conventional reactors are sidelined by the construction of the PBMR.
Eskom, Pebble Bed Modular Reactor (SOC) and the National Nuclear Regulator of South Africa agreed on a staged licensing process. The stages are:
  1. Construction and installation
  2. Fuel to site/fuel load/initial criticality and power ascension
  3. Operation
  4. Decommissioning
At each licensing stage, a full safety case demonstrating compliance with regulatory requirements must be submitted to the Nuclear Regulator. All the elements for licensing of stage one were concluded on.
Why won't the PBMR ever cause a second Chernobyl?
  Safety is the backbone of the global nuclear sector and is enshrined on all actions of each and every member of the nuclear environment.  
  The safety culture assessment review team concluded that the safety at PBMR is generally strong.  Throughout the organisation, the overwhelming majority of employees are committed to safety in design.  
Last Updated: 6 February 2017
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