Nuclear Criticality

ANSWERS supplies a range of Criticality Software, including:

MONK® - A Monte Carlo program for nuclear criticality safety and reactor physics analyses.

Its advanced geometry modelling capability and detailed continuous energy collision modelling treatments provide realistic 3D models for an accurate simulation of neutronic behaviour to provide the best estimate of neutron multiplication factor, k-effective.

WIMS - A general purpose reactor physics program for core physics calculations.

Its range of templates cover a wide range of standard configurations ensuring quick and accurate solutions. The user of WIMS can benefit from being able to rapidly survey a criticality safety problem and identify key limiting parameters for further analysis.


We have a wide experience of modern criticality assessment over the entire range of Pu, U235 (high and low enrichment) and U233 systems, throughout the nuclear fuel cycle. From fuel manufacture to storage and waste operations, we are specialists in criticality assessment of the unusual as well as of the routine.

ANSWERS' Criticality Services Team provides a comprehensive and integrated source of criticality expertise which is ready to assist you to meet your project requirements.

Our capabilities include:

  • Criticality safety analysis/assessment
  • Production of independent peer reviews
  • Detailed knowledge of regulatory requirements
  • Broad design and operational support experience
  • Skilled usage of calculation tools from the ANSWERS Software Service (MONK,WIMS) as well as other international criticality codes (KENO, MCNP)
  • Supplementary skills in calculation methods and limitations, nuclear data and experimental activities
  • Training

Your plant is safe from accidental criticality, certainly. But could it be safer - and more economic to run? Are the right criticality constraints being applied in the right places? Are your workers struggling to meet obsolescent clearance conditions written for operations which have since changed?

Our team has wide experience of modern criticality assessment over the entire range of fissile systems encountered throughout the nuclear fuel cycle. From fuel manufacture to storage and waste operations, we are specialists in criticality assessment of the unusual as well as of the routine.

We have experience in the following:

Criticality Assessment

  • Dry and wet fuel stores
  • Shipping Casks
  • Spent fuel repackaging
  • Waste storage

Regulatory Support

  • Fuel transport
  • Waste repository
  • IAEA Guidelines
  • Peer review

Operations Support

  • Reprocessing operations
  • Utility operations
  • Decommissioning
  • Research reactors

Design Support

  • Shipping Casks
  • Fuel stores
  • Decommissioning planning

Methods Development

  • Burnup credit
  • Software development
  • Nuclear data validation

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