Nuclear Energy Advanced Modeling and Simulation (NEAMS) Challenges and Challenge Problems

Building the modeling and simulation capabilities needed to support an expanding nuclear energy infrastructure will require overcoming a wide range of challenges inherent to the technology as well as challenges to a particular code.

To be successful, NEAMS must support the full range of nuclear technologies supported by the Office of Nuclear Energy’s (NE) Research and Development (R&D) Roadmap.  NEAMS must develop models that effectively simulate the complex physics and chemistry of a given process, and must do so with geometry and time scales that produce high-fidelity results appropriate to the problem.

One way of demonstrating the ability to address these challenges is to establish one or more “challenge problems.” These challenge problems will become the first critical test of NEAMS codes and methods.

Nuclear Technology Challenges

To achieve its vision, NEAMS will have to create simulation capabilities for a number of different technologies, components and facilities that will comprise future nuclear energy systems.  These technologies include advanced fuels that will be used in future reactors, new reactor configurations and materials, alternative cooling and heat transport systems, and advanced control, safety and containment systems.  To support the design and operation of separations and fuel fabrication facilities, NEAMS will be required to create plant simulation tools similar to those used by modern petrochemical plants, yet accommodating features that are unique to nuclear energy applications.  NEAMS will also have to create simulation capabilities that will span the technologies and systems required for safeguards and waste management.

Physics Challenges

Physics challenges involve understanding and modeling the transport of radiation and its effects on materials, the transfer of heat and mass, the chemical reactions of various materials, and many other phenomena and processes. Currently there are many simulation capabilities that model a single physical effect and sometimes they are loosely coupled with one another. For NEAMS to be successful, this coupling must be done tightly when needed and with the correct dimensionality to produce simulation results that are comparable to actual physical tests and thus reliably predictive. Other large modeling and simulation programs have successfully confronted these challenges, and NEAMS will utilize the approaches developed by them to deal with this difficult issue.

Length and Time Scale Challenges

Nuclear Energy Multi-scale Challenge

The length scales involved with doing this are quite significant (about 15 orders of magnitude). At one end, NEAMS will be created and used to simulate interactions at the atomic scale to understand how materials will perform in advanced reactors. On a much different scale, NEAMS will have to create simulations of how the earth propagates shock waves from a seismic event and understand how safety systems will respond. Fortunately for NEAMS, techniques for spanning a wide range of length scales have been developed by scientists and engineers in the weapons complex and their approaches can be adapted for nuclear energy applications.

NEAMS will also have to create capabilities that span large ranges of time scales. This includes physical interactions that take place very quickly (microseconds) like those that can occur in a reactor during reactivity insertion accident conditions to those that span over thousands of years like material degradation in a geologic repository or disposal environment. Slow processes that culminate in a very fast or sudden reaction will be particularly challenging.

Challenge Problem

A significant program management tool that will inform R&D activities is the concept of “challenge problems.” Challenge problems provide a focus for development of methods and tools and will establish relevancy to the targeted nuclear energy advances. Each Integrated Performance and Safety Code (IPSC) is working to define and solve a unique challenge problem. These problems will have several attributes such as: (1) they will support the NE R&D Objectives, (2) they will address the real needs of stakeholders, (3) they will break new technical ground, (4) they will be computationally demanding and scientifically complex, (5) they will be predictive, and (6) they will represent physical phenomena and enable the validity of the predictions to be demonstrated. The challenge problems will allow NEAMS management to guide development activities, foster and organize collaborations, and obtain “buy-in” from the NEAMS customers by demonstrating that the program is working on issues relevant to the nuclear community.