Primary Radiation Damage Cross Sections

Coordinated Research Project (CRP) approved on 13 Dec 2012, CRP Code F44003
duration 4 years, from Nov 2013 (1st RCM) - June 2015 (2nd RCM) - October 2017 (3rd RCM)
(initiated according the recommendations of Technical Meeting 1-4 Oct 2012)

supplemental Technical Meeting 13-16 June 2016

Scientific Background

   The displacement cross section is a reference measure used to characterize and compare the radiation damage induced by neutrons and charged particles in crystalline materials. To evaluate the number of displaced atoms Norgett, Torrens and Robinson proposed in 1975 a standard (the so-called NRT-dpa), which has been widely used from that time.
   Nowadays this formulation is recognized as suffering from some limitations: it is not applicable for compound materials, does not account for the recombination of atoms during the cascade evolution, cannot be directly validated and has no uncertainties/covariancies as evaluated cross sections usually have now.
   Upgrading of the dpa-standard means the inclusion of the results of the Molecular Dynamics (MD), Binary Collision Approximation (BCA) or other simulations for primary radiation defects (PRD), i.e. Frankel pairs (FP) and Interstitial Clusters, which survive after relaxation of the Primary Knockout Atoms (PKA) cascade. It is also called "athermal recombination-corrected dpa = arc-dpa".
   The essential advantages of the upgraded dpa-standard will be:
- non-dependence on the energy distribution of incident neutrons - this means more correct inter-comparison of radiation damage in the different facilities on the basis of the accumulated dpa-fluence
- it also becomes more feasible for comparison of neutron and charged particles or ion induced damage
- empirical validation against frozen defects at cryogenic temperature (NRT-dpa can never be observed)
- prediction of damage in polyatomic materials and alloys (NRT treats dpa in compounds by mathematical weighting of separated elements)
    However "We emphasize that the arc-dpa- and rpa-equations are not intended to replace the NRT-dpa, which is still valid as a convenient energy deposition unit and is useful for applications such as comparing different kinds of irradiations. Rather, they are an alternative if one wishes to have a somewhat more accurate estimate of the actual damage production or number of replaced (mixed) atoms." (see RCM-2 Report INDC(NDS)-0691).

Research Objectives

   To find ways overcome the drawbacks of the NRT standard employing the recent developments in primary radiation damage simulations. For this, engage in this project experts from the nuclear data and material research to perform:

Expected CRP Outputs

Specific issues to be addressed

   MD, BCA and other simulations of survived primary point defects in mono- and poly-atomic materials and thermal-spike-enhanced recombination

   Implementation of MD or BCA results in Nuclear Data and Codes

   Data Testing, Applications ...

Selection of Materials

   Mono elemental structural materials:

   Most practically important polyatomic (binary) materials: see collection of Efficiencies

Databases available (created/collected during CRP)

   NRT- and arc-dpa displacement and gas production cross sections
   arc-displacement cross sections for ceramics
   NRT-Damage Energy for Si and isotopes

Pictures illustrating sequence of phenomena to be studied for Iron (also a part of CIELO project) as the most practically important and starting element

Pictures illustrating sequence of phenomena to be studied for other Materials (C, Al, Si, Cr, Cu, W ...)

Web page content by S.Simakov
Web page design by V.Zerkin