The Neutron Transport Equation Of ¦Á Eigenvalues ​​calculated

Alpha eigenvalue is an characteristic parameter in neutron chain reaction physics. It describes the variational velocity of neutron flux along with time. It has important significance in critical and subcritical experiment research. On the one hand, it can make theoretical estimate for experiment assembly in advance. On the other hand, it can compare with experimental value and check up the theoretical computation method and nuclear data. But the theoretical computation of a eigenvalue has some special difficulty. The iteration procedure is likely to diverge in deep subcritical system and lead to calculation failure. As a elementary explore, three SN programs are written in this paper to compute a eigenvalue in deep subcritical system using different methods.The k indirect method is a common method to compute a and it has the advantageof high precision. But when computing deep subcritical system, it has some difficulty inevitably. The reason is studied from both ration calculation and qualitative analysis. Theconclusion is that when , the energy group g will be supercritical, so theiteration will not converge and the computation will fail. It's not appropriate to set - to theleft side of neutron transport equation when computing α in deep subcritical system.The r indirect method deals with α/v according to actual situation. When a new αgetting from interpolation is positive, set - to the left side of neutron transport equation asusual. When a<0, move α/v to the right side and look upon it as source term. Thecalculation result shows that the r indirect method can compute α deeper than k indirect method in subcritical system. But the y indirect method has no inner iteration, itcan't ensure the convergence of neutron flux and it will also fail in deep subcritical.Some improvement are made on the ground of direct method, such as adding the outer iteration and adopting dynamic convergent criterion to accelerate it, introducing the iteration step factor, adding the flux criterion to main iteration, etc. Compared with the other twocomputation methods, the modified direct method has the advantage of wide calculational range and high precision. It is an effective method to solve the difficulty of alpha eigenvalue computation in deep subcritical system.A kind of terse technique is put forward to compute α in the system with cavity. It makes use of the mirror reflection boundary condition. The calculation result shows that the terse technique can save much calculation tune (more than 30%). In fact, its result is more accurate, because it doesn't take any approximation in the cavity region. The terse technique can also popularize to the system with pure absorption medium.