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1.         NAME AND TITLE

RPS-DET 2.0: The Radioisotope Power System Dose Estimation Tool Version 2.0



SCALE 6.2.3 (6.2.3 versions tested to-date)


Matlab Runtime (2018b versions tested to-date)



No auxiliary libraries required.



Contains all standard cross section and data libraries included with distributions of SCALE 6.2.3.


This project was funded by The National Aeronautics and Space Administration’s (NASA) Radioisotope Power System Program Office, Cleveland, OH, USA

Software development was provided by staff from the Oak Ridge National Laboratory (ORNL) Reactor and Nuclear Systems Division (RNSD), Oak Ridge, TN, USA


            Matlab, Java, Windows 7 and 10


RPS-DET is a Matlab-developed, library-based, graphical user interface (GUI) simulation tool that allows users to easily generate, simulate, and analyze particle transport calculations for radioisotope power systems (RPSs) using the SCALE software suite. RPS-DET has current, historic, and potential-future geometries of RPSs used in NASA’s RPS program for powering deep-space and planetary missions. These RPSs contain plutonium oxide (PuO2) as a fuel source and portions of the emitted neutron and gamma spectra from this fuel escape to interact with the surroundings. Estimating the biological, instrumental, and/or material concerns induced by this radiation for a given mission/scenario requires simulation or experimental data. RPS-DET provides analysts with a simulation tool to simplify the start-to-finish analysis of radiation studies of various RPSs in deep space, on planetary surfaces, and in occupational Earth-based scenarios.


RPS-DET includes libraries of representative pre-built geometries that can be selected by a user from convenient GUIs. These geometries are divided into two general categories: RPSs and environments. For example, a user can choose a single RPS to simulate from ~10s of different RPS designs in the library, all with different fuel configurations, materials, and sizes. The selected RPS can then be placed into any number of pre-built environments, ranging from terrestrial settings (concrete rooms, shipping casks, etc.), to transit spacecraft (deep space probes, satellite orbiters, entry descent landing capsules, etc.), to planetary surface settings (Mars, Titan, Europa, Enceladus, etc.). Certain geometries allow the user to rotate an RPS in the given environment to simulate crane operations, rover placement, storage, and other off-axis scenarios. Once the simulation geometry is selected, the user may specify fuel characteristics such as plutonium assay, impurity content, and age. All of these factors affect the gamma and neutron emission behavior of the fuel, and the user can tailor the fuel or can simply choose a default fuel, and then the age can be selected accordingly. Once the geometries and fuel characteristics are chosen, the user can use RPS-DET to write, execute, and post-process particle transport simulations using SCALE’s sequences of ORIGEN and MAVRIC.


The outputs of RPS-DET are particle and dose tallies, which are represented in the form of Cartesian mesh tallies. A mesh tally is a three-dimensional geometry subdivided into multiple smaller volumetric pixels, or voxels, that serve as units that count or tally the energy-dependent particle flux. The user can interact directly with these mesh tally values, or they can be used with flux-to-dose conversion coefficients to determine dose estimates of various materials not present in the geometry. The user can interact with either visual or tabulated tally data through RPS-DET, or second-party applications available in the SCALE software distribution can be used specifically for viewing mesh tallies, geometries, and particle spectra.


RPS-DET serves as an interface between the user and the SCALE software suite for the purposes of simplifying particle transport problems related to RPS radiation. While a user not skilled in the art of particle transport may rely exclusively on RPS-DET to manage simulations, a more experienced user will have the ability to change the SCALE input files generated by RPS-DET by editing, omitting, or adding features specific to their interests that RPS-DET may not include. Furthermore, while RPS-DET will have active software support, maintenance, and user feedback, all users of RPS-DET will automatically be SCALE users, which allows them to benefit from the extensive user support base of the SCALE development program as well.


Detailed descriptions of RPS-DET’s functionality can be found in the RPS-DET User Manual (available through RSICC.). Brief descriptions of the main GUI and the SCALE software that it controls are presented here. Detailed information regarding SCALE can be found in the SCALE User Manual.

RPS-DET is a Matlab-developed GUI that prepares and formats text files (ASCII) for SCALE and post-processes SCALE output files. While RPS-DET does not handle physics calculations, it does provide a simple interface for preparing, simulating, and analyzing SCALE simulations.

SCALE is a software suite comprising several nuclear-related software solutions or sequences ranging from reactor physics, isotope decay, and particle transport. The inputs generated by RPS-DET use two of SCALE’s sequences:

1. ORIGEN: Oak Ridge Isotope Generation code, used by RPS-DET for source-term development and isotpic decay calculations

2. MAVRIC: Monaco with Automated Variance Reduction using Importance Calculations, used by RPS-DET for particle transport calculations

Brief excerpts from the SCALE User Manual are included below to describe the methods of solution used and leveraged by RPS-DET.


ORIGEN (Oak Ridge Isotope Generation code) calculates time-dependent concentrations, activities, and radiation source terms for a large number of isotopes simultaneously generated or depleted by neutron transmutation, fission, and radioactive decay… As a stand-alone SCALE module, ORIGEN provides additional unique capabilities to (1) simulate continuous nuclide feed and chemical removal, which can be used to model reprocessing or liquid fuel systems, and (2) generate alpha, beta, neutron and gamma decay emission spectra.


The MAVRIC sequence (Monaco with Automated Variance Reduction using Importance Calculations) will perform radiation transport on problems that are too challenging for standard, unbiased Monte Carlo methods. The intention of the sequence is to calculate fluxes and dose rates with low uncertainties in reasonable times even for deep penetration problems. . . . In addition to materials input, the user will also supply the geometry description using the SCALE General Geometry Package; source description as a function of position, energy, and direction; tally descriptions (fluxes in which regions, at what point detectors, or over what mesh grids); response functions (function of energy); planes for the mesh used by Denovo; and which tally or tallies to use as the Denovo adjoint source. Output consists of tables detailing the region and point detector fluxes (and their responses), as well as files for mesh tallies.


While RPS-DET is distributed through RSICC, NASA is the software sponsor and reserves the right to pre-approve, allow, or deny access to users at any time for any reason. RPS-DET is considered Export Controlled under EAR 99 and therefore shall not be available to or distributed to non-US nationals. RPS-DET has been determined not to fall under International Traffic in Arms Regulations (ITAR) requirements.



While runtimes from RPS-DET–generated SCALE files will largely depend on the computational power of the user’s computer, the largest spatial problems available in the libraries producing reasonable statistical uncertainties in mesh tallies at far reaches of the geometry can be obtained on a modern desktop computer in just a few hours. Users can set the maximum runtime based on the problem’s requirements for statistical uncertainty in the region of interest and the available computational time/power.


This version of RPS-DET does not employ parallel processing, so most modern desktop computers can adequately process RPS-DET–generated input files with SCALE. RPS-DET–generated input files can also be processed on a desktop computer and then independently run on a separate remote cluster, or a more powerful desktop computer with SCALE installed can be used if computational power limitations become evident.


Currently, RPS-DET is tested and operational only on Windows machines; it has been tested on Windows 7 and 10.

10.       REFERENCES

B. Rearden and M. Jessee, “SCALE Code System,” Oak Ridge National Laboratory (ORNL), Technical Report ORNL/TM-2005/39, Aug. 2016.


The package can be transmitted on a DVD, which includes zipped tar files with executables, sample inputs, test problems, documentation and reference material; alternately, a digital version distributed via a download link can be provided.


October 2019