The Development Of The Green’s Function Nodal Method Procedure And Pin Power Reconstruction

With the increasing of reactor core construction’s complexity, there is moreheterogeneous in the reactor core, so the reactor core diffusion calculation suffers large errorswith the application of the homogeneous cross sections generated by the conventionalhomogenization methods, which can’t further meet the needs of engineering design, and theapplication of discontinuity factor in the advanced homogenization methods can significantlyreduce this deviation. The traditional Green’s function nodal method procedure (NGFM) isestablished for the partial neutron current space coupled equations, in which it is inconvenientfor the application of the discontinuity factor. The main goal of this paper is to develop it andestablish the second boundary condition Green’s function nodal method procedure (NNGFM)based on the Neumann boundary condition, it is convenient to make use of discontinuityfactor because of the net neutron current, so the calculating accuracy of NNGFM is largelyenhanced. Meanwhile, in order to obtain the nodal’s pin power distribution, we couple theNNGFM and pin power reconstruction procedure PINPOW, and the new coupled procedureprocesses disconctinuity factor and pin power reconstruction traits.First this paper introduces the basic theory of discontinuity factor, and the steady-stateand transient equation of NNGFM with discontinuity factor, and then the basic theory ofPINPOW and heterogeneous pin power reconstruction are also described. And in order tohave a clearer understanding to the procedure’s construction we also provided the calculationflow map of every procedure in this paper. Finally, in order to ensure the credibility of thecalculating results, both benchmark examples and Qinshan Phase II reactor core are applied toverify the NNGFM and its coupling procedure, and simulate3as the reference procedure inthe Qinshan Phase II reactor core calculation.There are the following conclusions by two types of numerical verification: because ofthe application of discontinuity factor in the development Green’s function nodal method, asopposed to the traditional Green’s function, which can significantly reduce the deviation ofradial power distribution in the strong heterogeneous core (such as boiling water reactor, thereactor with water reflector, etc.) calculation, and also improve the accuracy of eigenvalue,NNGFM can meet the needs of engineering design. For the coupling procedure, as NNGFM’shigh accuracy with discontinuity factor, PINPOW which utilize NNGFM calculating result information can well restitute the neutron flux distribution in the nodal, and in the QinshanPhase II reactor core numerical calculation, there is very small deviation comparing tosimualte3’s calculating result, so the coupling procedure can be applied in the engineeringproject’s pin power reconstruction calculation.