About the Nuclear Design and Risk Analysis Group

The Nuclear Design and Risk Analysis Group, D-5, is a multidisciplinary team of scientists and engineers. We provide modeling and analysis capabilities to design and evaluate the potential risks of complex systems, with a focus on nuclear systems. D-5 goes beyond just providing an answer: we provide an answer in context to the overall decision process. We ensure that decision makers have all available knowledge to make an informed regulatory, design, or risk decision.

D-5 is a recognized leader in the design of space nuclear power and propulsions systems. Other areas where D-5 provides national technical leadership include radiation transport code development (MCNPX) and applications, the modeling and assessment of international nuclear terrorism risks, and the risk analyses of nuclear facilities, nuclear reactors, and nuclear weapons.

D-5 uses a wide range of methods and tools to accomplish these nuclear systems analysis tasks, including core competencies in nuclear reactor design, thermal hydraulics, computational fluid mechanics, application of radiation transport codes (such as MCNPX), probabilistic risk and safety assessments, probabilistic system and vulnerability modeling, facility hazards and safety analysis, nuclear weapons and high-explosives safety analysis, risk-based decision support analysis, probabilistic structural capacity analysis, natural phenomenal risk analysis, and custom software and engineering tool development.

D-5 can provide answers to a broad range of questions involving nuclear systems analysis. The following are additional descriptions of D-5 focus areas, including discussions of recent accomplishments.

Nuclear Safety and Regulatory Analyses

D-5 supports several Nuclear Regulatory Commission (NRC)-directed research activities in the areas of safety performance and regulatory issues affecting the design and operation of nuclear power plants. Currently, D-5 is working in conjunction with the University of New Mexico on an experimental program to examine the long-term (30-day) chemical processes occurring in post-loss-of-coolant-accident containment environments in support of the NRC's effort to resolve a long-standing generic safety issue (GSI-191).

D-5 is also active in providing 10 CFR 830-based safety analysis for the Laboratory and other National-Nuclear-Security-Administration (NNSA)-regulated nuclear facilities. Facilities and projects that D-5 is active involved with include the

• TA-55 ventilation system safety basis analysis,
• new chemistry and metallurgy research (CMR) building design,
• TA-18 critical assemblies facility safety analysis,
• TA-18 early move of special nuclear material,
• radioactive liquid waste facility hazards analysis, and
• CMR building life extension justification assessment.

Among the new capabilities added in D-5 this year was the acquisition of a new probabilistic structural mechanics team by way of transfer from Engineering Division. Within the structural mechanics team's portfolio is the LANL Seismic Hazards Assessment Program. (Salmon insert)

Code Development

The MCNPX Monte Carlo radiation transport effort in D-5 made significant breakthroughs in 2005, both politically and technically.

The political breakthrough was the agreement with X Division for cooperation and ultimate unification of the MCNP and MCNPX code development efforts at LANL. D Division will continue to maintain and even expand its role. The basis for the cooperation/ unification is an agreement reached August 25, 2005, and forwarded to both the X and D Division leaders. Cooperative efforts are already underway. Until MCNPX and MCNP become a unified code, they will be released internationally as a single package. The first combined release occurred in January 2006. A coordination board and technical review committee have been established. Funding for unification has been secured from the Advanced Strategic Computing Initiative. Technical work toward unification is already underway.

The MCNPX technical breakthroughs have been spectacular. Particle tracks, fluxes, heating and other quantities can be displayed in real time superimposed over geometry plots--perhaps the most significant MCNP(X) graphics advance in many years. MCNPX can now do burnup/depletion—the first continuous-energy fully self-contained capability of its kind in any major Monte Carlo radiation transport code. In addition, problems that have stymied Monte Carlo developers for decades have now been solved for MCNPX. These problems include variance reduction with pulse height tallies and efficient eigenfunction convergence in nuclear criticality calculations.

D-5 developed and maintains the Transient Reactor Analysis Code (TRAC). This powerful system-level analytical tool has multiple applications to complex systems, including nuclear power plants, experimental facilities, and space reactors. In addition, TRAC is a best-estimate tool to predict complex system responses to off-normal events. D-5 is also assisting the NRC as it begins the licensing activities associated with new reactor designs and other advanced systems.

Risk-Based Decision Support

D-5's core capabilities include qualitative and quantitative economic analysis, risk analysis, and decision support for a wide cross section of Laboratory projects and programs. Recent and ongoing activities of this type include

• assessment of subcritical experiment program risks;
• planning and analysis support for the Laboratory's Enterprise business systems development project;
• Tri-Lab security technology initiative;
• down-select support for the Reliable Replacement Warhead (RRW);
• macroeconomic impacts of attacks on the financial sector;
• recent prioritizations include detonator technologies, security upgrades, and software systems;
• resource allocation analysis for emergency response teams;
• development and analysis of Laboratory childcare options;
• estimation of Laboratory restart costs; and
• analysis of Laboratory safety data.

Small Reactors

D-5 has a dedicated team of engineers focused on the development of space fission reactors. This team has developed several innovative reactor concepts, including a compact, robust, and highly safe reactor that is cooled by heat pipes. Several prototype units of the heat-pipe-cooled reactor have been built and tested successfully by D-5 and the National Aeronautics and Space Administration (NASA). NASA intends to use this reactor to enable ambitious, electrical power-rich exploration anywhere in our solar system.

Global Nuclear Risk Analysis Architecture

(Voss insert)

Weapons Safety

D-5's work in the area of stockpile stewardship supports the Laboratory's mission to reduce the danger of nuclear mishaps. Our expertise in this area is focused on designing safety into nuclear weapons production and maintenance processes, conducting nuclear explosive risk and damage assessments, and evaluating the safety of testing programs related to nuclear weapons. In addition, we have developed custom software to be used in these assessments.