a. One of the three following methods shall be used to evaluate the deposited dose:
¾ abstract simple shielding such as planar or spherical shell geometry, as specified in clause 6.2.2.1;
¾ 3-D sector shielding, as specified in clause 6.2.3;
¾ 3-D physics-based Monte-Carlo analysis, as specified in clause 6.2.4.
NOTE They are ordered in increasing accuracy and rigour.
b. In establishing the shielding contribution to a component’s RDM, and when the simulation models less than 70% of the equipment mass, then the model is conservative, and additional margin shall not be applied to doses computed in geometries with the 3-D sector shielding method specified in clause 6.2.3.
NOTE 1 This is true when approximate geometry models are used which are demonstrably conservative (e.g. lacking modelling of some units, harness, mass and fuel).
NOTE 2 3-D sector analysis methods (slant/solid or Norm/shell) for electron dose calculations are not always worst case. In one study a corrective factor of about 2 was needed for the Slant/Solid method and 3.4 for the Norm/Shell.
c. In establishing the shielding contribution to a component’s RDM, and when 3-D physics-based Monte-Carlo analysis specified in clause 6.2.4 is used for electron-bremsstrahlung dominated environments, it shall be demonstrated that the achieved RDM includes the uncertainties (including the level of conservatism in the shielding and the systematic and statistical errors in the calculation).
NOTE 1 Examples of electron-bremsstrahlung dominated environments are geostationary and MEO orbits.
NOTE 2 When 3-D Monte-Carlo analysis is used for ion-nucleon shielding in heavily shielded situations (e.g. ISS and other manned missions) greater margins are used.