An infinite slab of moderator of thickness 2a contains at its center a thin sheet of 235 u of thickness t. derive the one-group criticality condition, using d and t to represent the diffusion parameters of the moderator σaf and to represent the macroscopic cross section of the ^235 u. plot the thickness t as a function of σaf using the criticality condition. explain the relationship between t and σaf in combinations that lead to a critical system. use eta = 1.80, d = 1.0 cm,| l = 56 cm, and a = 15 cm.

After an atomic bomb has been dropped, the damage continues to get worse. why is this?

Aproton is projected toward a fixed nucleus of charge +ze with velocity vo. initially the two particles are very far apart. when the proton is a distance r from the nucleus its velocity has decreased to 1/2vo. how far from the nucleus will the proton be when its velocity has dropped to 1/4vo?

Two horizontal plates with infinite length and width are separated by a distance h in the z direction. the bottom plate is moving at a velocity u. the incompressible fluid trapped between the plates is moving in the positive x-direction with the bottom plate. align gravity with positive z. assume that the flow is fully-developed and laminar. if the systems operates at steady state and the pressure gradient in x-direction can be ignored, do the following: 1. sketch your system 2. identify the coordinate system to be used. 3. show your coordinates and origin point on the sketch. list all your assumptions. 5. apply the continuity equation to your system. nts of navier stokes equations of choice to your system 7. solve the resulting differential equation to obtain the velocity profile within the system make sure to list your boundary conditions. check units of velocity 8. describe the velocity profile you obtain using engineering terminology. sketch that on the same sketch you provided in (1). 9. obtain the equation that describes the volumetric flow rate in the system. check the units.