SUMMARYThe goal of SHARP is to develop a suite of modern simulation tools for use on all reactor types of interest. Part of that desire is to build a heterogeneous neutron transport capability which gives accurate, detailed power distributions throughout the entire reactor core, of which we have focused our efforts on deterministic methodologies. The existing SHARP neutronics tool has demonstrated good accuracy when using conventional homogeneous modeling, but when applied on fully heterogeneous problems such as the Advanced Test Reactor (ATR) and Zero Power Reactors (ZPR), the results were not acceptable. These errors are primary attributable to the use of a three step cross section generation procedure (unit cell, lattice, and whole core). Given the success of the DeCART tool on thermal spectrum systems such as PWR, BWR, and VHTR, the subgroup methodology was identified as a potential means by which to resolve the cross section related problems in the NEAMS tools. The subgroup project in NEAMS is thus focused on creating a general purpose cross section methodology that is usable on both thermal and fast spectrum systems.The subgroup methodology is a well studied scheme appearing very early in the nuclear engineering literature. We investigated using the subgroup methodology as a potential means to handle fast reactor problems. A considerable amount of work was performed on the subgroup library software for NEAMS where several subgroup formulations were investigated. Further, while the subgroup method has been demonstrated to be accurate enough on several problems via our own experiences with DeCART, it is not clear what its accuracy will be on more complicated problems such as the ATR.In any case, one must have a capability to generate a library in which subgroup parameters can cover neutron spectrum characteristics of the reactor of interest. For better accuracy, we propose to use MCNP as an alternative pin-cell calculation means of generating the subgroup data and have developed a prototype code package to demonstrate the capability.With regard to fast spectrum systems, there are numerous concerns with the subgroup methodology in which the conventional Bondarenko iteration approach often used would not accurately handle the resonance interference effect that becomes more complex and important in a fast reactor. An alternative methodology involving the local escape cross section looks promising, but substantial research needs to be completed and a basic algorithm tested before success can be confirmed.Overall, the creation of a subgroup library application was not finished, primarily due to the fact that a bulk of the funding was moved into the next fiscal year. A better understanding of the underlying methodology was gained and a means by which to generate subgroup data was created. The work on the subgroup method for an Application Program Interface (API) is thus not complete and can be expected to continue into the next year.

SUMMARYAs part of the NEAMS activity in DOE, a fast reactor simulation program was launched in April 2007, termed SHARP. The initial goal of SHARP was to develop a suite of modern simulation tools specifically for the analysis and design of sodium cooled fast reactors, and this goal has since been extended to consider all reactor types of interest. As part of that work, a high-fidelity deterministic neutron transport code named UNIC was started, providing a common framework for fast reactor neutronics tools.Focusing on UNIC, spatial de-homogenization increased the typical neutronics problem with a few hundred million degrees of freedom (DOF) into ones with hundreds of trillions of DOF. Such problems are beyond the capabilities of existing supercomputers. With the advent of future computer hardware, these high-fidelity problems can be solved but only after a multiyear development program to adapt codes such as UNIC to that technology. UNIC can presently be used on smaller problems (single assembly, multiple assemblies) with today's hardware, but it is also necessary to provide tools to solve the larger problems of interest, albeit without the aforementioned level of spatial de-homogenization.To address the desire to demonstrate the coupling capability of NEAMS, part of the FY12 funding was focused on preparing the legacy codes, termed PROTEUS-Fast, which are fully capable of solving full-scale fast reactor problems. A bulk of the work this year was focused on preparing and distributing the PROTEUS-Fast codes for use by all NEAMS users.The demonstration of a full coupling capability will require more follow on work, but significant progress was made this year preparing the interface coupling routines and preparing PROTEUS-Fast for use. The primary targets of interest in PROTEUS-Fast are DIF3D, DIF3D-K (kinetics), and VARI3D (reactivity coefficients), with REBUS (fuel cycle) being an auxiliary component updated for convenience. All codes in PROTEUS-Fast were verified and added to the BuildBot regression test. Unfortunately, all of the older codes suffered significant problems from the deprecated coding practices used within them and resulting conflicts with modern compilers. After some work, all of these issues were resolved and we feel confident in releasing them for use by others NEAMS members.With regard to specific upgrades, DIF3D-VARIANT was upgraded with a few months of effort to allow the large scale problems of interest to be executed. After significant study, we choose not to modify VARI3D to include a transport option, but to develop a new code, PERSENT (partially funded by an external project) which uses the DIF3D-VARIANT transport solution option. The outstanding features missing from MC 2 -3 were added, and MC 2 -3 has been released to RSICC. All of the remaining PROTEUS-Fast codes are either finished with the copyright and licensing procedure or are actively going through it. While that process will delay the targeted August 2012 release to RSICC for a few more months, the codes are ready for immediat...