# Toward Defect Engineering Strategies to Optimize Energy and Electronic Materials
## 2 Advanced Materials for Nuclear Applications
### Radiation Tolerant Materials  
The safe storage of nuclear waste is considered as a prerequisite for public support. The construction of new reactors differs as compared to previous generations in that nuclear waste solutions including packaging materials and appropriate repositories must be thought of and identified as part of the initial design [16].  
Nuclear waste management is a very difficult task due to the radiotoxicity and long half-lives of actinides and fission products. A feasible solution is to move nuclear waste to relatively stable geological formations. These repositories will be reinforced by barriers, for example corrosion-resistant cladding and compacted clay [17; 18]. Identifying waste-packaging materials to host high-level waste (HLW) is difficult due to their decay production and the formation of point defects. In essence, these will eventually destabilize the host crystalline oxides resulting in their amorphization and cracking.  
Nuclear materials operate at extreme conditions. To host nuclear waste, numerous systems have been investigated using both experimental and computer simulation techniques [19]. The synergetic application of techniques leads to the more thorough fundamental understanding of the impact of radiation damage in materials and can lead to progress. An example is by [PERSON] et al. [19], which determined that radiation tolerance in pyrochlore oxides (A\({}_{2}\)B\({}_{2}\)O\({}_{7}\)) is related to the ease with which that disorder can be accommodated. Previous work determined that oxides were defects that can readily form and are more resistant to radiation-induced amorphization and are thus important for the accommodation of radioactive waste [19].  
Inspired by nanotechnology, there has been interest in annihilating defects and radiation damage through the use of nanocomposites. This is a new class of radiation tolerant materials with nanometres thick layers (i.e., maximization of interfaces) that can lead to very radiation resistant materials. An example is the studies of [PERSON] et al. [20] on the radiation damage resistance in Cu-Nb multilayer nanocomposites (Figure 1). In this system, it was predicted using atomistic simulation that the interfaces in the nanocomposite effectively act as sinks for radiation-induced defects. As a word of caution, however, the application of finer grain wasteform materials will be a challenge due to the increased surface/area per unit volume that is thermodynamically less stable. This can be potentially problematic at the extended repository timescales.  
In the recent work of [PERSON] et al. [21], atomistic simulation was used to show that grain boundaries are not only sinks for radiation induced defects but can also emit interstitial atoms which can recombine with vacancies. This is considered to be important as it leads to concepts where grain boundaries will heal radiation-induced damage [21]. This is a breakthrough as the design principles relied on materials that could resist radiation damage, tolerate damage, or undergo lattice recovery. This is a further example of how nanotechnology can be used to produce designed grain-boundaries or interfacial structures to create advanced radiation tolerant materials.