# Presentation: 356172

## Fuel Material Development Challenges for Extended Nuclear Power Performance for Advanced Actinide Fuels

**James S. Tulenko**
**Professor, University of Florida**
**Director, Laboratory for Development of **
**Advanced Fuels and Materials**
**Workshop on Basic Energy Needs for Advanced Energy Systems**
**Panel on Advanced Actinide Fuels, including Matrix Fuels**

## Fuels Material Development

**Research in nuclear actinide fuels must seek to find materials and processes that improve and extend performance and reduce costs.  The added objective to incorporate and destroy waste actinides complicates an already challenging task.**
**To do so we must understand all the basic phenomena that occur in the fuel and the fuel’s response both in processing and operation.**
**We must consider how the fuel materials are affected by fabrication, operation and the back end stages of storage, reprocessing, re-fabrication and disposal. **

## Fuels Material Development (Con’t)

**Fuel is the consumable part of the reactor, therefore it is important to modify response to fuel consumption, allowing the fuel to remain longer in the reactor.  The addition of actinides, to be consumed, greatly effects the material and nuclear behavior under irradiation. We must study the materials making up the fuel assembly.  Understanding how they perform under irradiation, along with their resistance to temperature, pressure, radiation, stress, fretting, neutron flux, hydriding, and corrosion and how they are affected by manufacturing processing. **

## Fuels Material Development (Con’t)

**We must remember:**
**Incorporation of actinides in the fuel increases the cost of fuel, requiring higher burnups for the fuel to be economic.**
**Fuel forms must be compatible with coolant and cladding material. **
**Fuel itself should be first line of defense retaining fission products, with clad the second and ultimate line of defense**
**Transients and burnup extension present the greatest challenges to material performance.**

## Fuels Material Development (Con’t)

**Basic science of thermal conductivity of materials must be understood.**
**Improving thermal conductivity of the fuel form will reduce melting concerns, fuel swelling, fission gas release, columnar grain growth, can eliminate pellet cracking, and potentially eliminate LOCA concerns and mitigate other accident conditions.**

## Fuels Material Development (Con’t)

**Improved Fuel Lifetime involves obtaining better fuel characteristics (address rim effect, lower fuel swelling, lower fuel restructuring, increased resistance to radiation effects and lower release of fission gases), better burnable poison materials, better cladding, and a better fuel assembly structure performance under irradiation.**

## Fuels Material Development (Con’t)

**The fuel assembly structure is subject to stress, radiation growth, coolant lift, coolant or mechanical vibration, erosion and corrosion.  The control structures are subject to a compressive stress induced by the force of the hold down springs of the top assembly nozzle. As the assembly undergoes radiation growth, this force increases, unless there is relaxation in the spring.  These forces can cause bowing and twist which can seriously interfere with control insertion and fuel handling and cause fuel assembly interference.**

## Need Modeling and Simulation of Nuclear Fuel Processing and Performance

**There is a great need for development of both a first principles fuel processing and a fuel performance code.  I know of no currently available fuel processing codes.  All current fuel performance codes are empirical, based on irradiation measurements and are limited to the range and materials tested.  Development of codes ****with detailed materials input from databases of nuclear materials behavior determined from thermodynamic, atomic-level and electronic-level calculations and simulations ****would allow material performance to be assessed quickly and with minimum expense, with only selected materials requiring expensive and time consuming irradiation confirmatory tests.  **

## Need Nuclear Testing and Processing Facilities

**Finally, there is a strong need for new nuclear fuel characterization, testing and nuclear fuel processing facilities.  The shutdown of testing facilities around the world has greatly reduced the ability and increased the cost to test fuel.  Similarly we need improved processing facilities to handle the actinides that are to be reinserted in the fuel in order to be destroyed. Finally, we need fuel characterization facilities that can handle actinide laden fuel.**

##   Nuclear Fuel Performance Measures 

**Fabricability**
**Irradiation performance**
- Fuel Failure
- Fuel Burnup Capability
- Materials Redistribution
- Material Compatibilities
- Fission Gas Retention
- Fission Product and Alpha Radiation Effects
- Thermal Analysis
- Fuel-Coolant Heat Transfer
- Fuel Centerline Temperature
- Fuel Thermal Conductivity
- Fuel and Clad Melting Point
- Recyclability

-   Nuclear Fuel Performance Measures

## Determination of Nuclear Properties

- We must not forget Nuclear properties of materials.
- Neutronic Analysis of Material
- keff versus EFPD
- Doppler feedback
- Temperature/Pressure Coefficients
- Control Worth
- Void Coefficient
- Kinetics-transient behavior

## What Research Should BES Fund

**Fundamentals of sintering, **
**Modeling and simulation of fuel processing (fuel processing is currently an art and not a science,**
**Modeling and simulation of fuel in-reactor performance, including fundamentals of irradiation and fission product effects in fuels,**
**Verification or generation of actinide material properties in material databases,**
**5.   Fundamental understanding of thermal conductivity in fuel type materials,**

## What Research Should BES Fund (Con’t)

**6. New or improved testing facilities including advanced analytical instruments in which we can use transuranic isotopes to develop the needed property measurements ,**
**7. Development of new material compositions with improved properties (nano-technology).**
**8.  Understanding of the basic structure and phase diagrams of spent fuel and advanced fuel materials (Pu, Zr, Am, Np, Cm oxide or metal composition phase diagram(s)).**

## Summary

**We need to develop an economic, zero defect actinide bearing fuel which meets the requisite temperature, irradiation and burnup performance requirements of the Global Nuclear Energy Program.  We need the basic understanding of these material properties under irradiation and nuclear facilities and computer codes to enable this development on a timely and economic basis.  This is our challenge**