Development work currently being carried out on the finite-element diffusion code FENDER

The computer code FENDER has been developed at AEE Winfrith to solve the multigroup diffusion equation using the finite-element method. The code in its current form is suitable for the solution of practical problems in radiation shielding. Used with specially adjusted diffusion constants it may be applied to cases involving deep penetration of bulk shields to give economical estimates of neutron and gamma flux distributions. One of its principal applications is the provision of importance functions for Monte Carlo acceleration when an adjoint solution of the diffusion equation, even if approximate, can lead to significant savings in computer time. The second main function of FENDER is to form a sound base from which to explore developments of the finite-element method, which is relatively new in the field of radiation shielding. This paper is mainly devoted to a description of the work currently undertaken at AEEW to extend the capabilities of the code. Details of the code are summarized