#### Q1: In terms of these HALEU/HBU evaluation, what is the most important difference between PWRs and BWRs?
#### Q1: In terms of EE+HBU SCALE code assessments, what is left to be done for PWRs and BWRs?
A1: PWRs designs up to 8% enrichment are fairly straightforward whereas BWRs designs are more complex. The prototype BWR designs developed in this phase had a maximum of 10% enrichment. At high burnup, the difference between the 56-group and 252-group library is more pronounced for the BWR than it was for the PWR, reaching 300 pcm in some cases, which although still fairly low, does exceed the 200 pcm target for differences between libraries.
A1: This assessment focuses on lattice physics. PWRs designs up to 8% enrichment are fairly straightforward whereas BWRs designs are more complex. The prototype BWR designs developed in this phase had a maximum of 10% enrichment. At high burnup, the difference between the 56-group and 252-group library is more pronounced for the BWR than it was for the PWR, reaching 300 pcm in some cases, which although still fairly low, does exceed the 200 pcm target for differences between libraries. Due to lack of validation data for these conditions, we are left with this as the only recommendation for code improvement. Future assessments will look at core-level figures of merit versus the lattice level ones from these reports.
#### Q2: X?
#### Q2: What is the main difference between PWRs and BWrs lattices with EE+HBU and nominal enrichment and burnup, in terms of physics?
A2: Y.
A2: Increasing enrichment results in a slightly harder spectrum. Increasing enrichment from 5 to 8% also results in a lower flux magnitude (~15%), assuming plants operate at the same specific power. The majority of effects can be explained by these two changes. Taking into account that both discharge burnup and enrichment will increase together, changes at EOC (assuming longer cycles) and EOL are minimal.
> R. Cumberland, R. Sweet, U. Mertyurek, B. Hall, W. Wieselquist. "Isotopic and Fuel Lattice Parameter Trends in Extended Enrichment and Higher Burnup LWR Fuel Vol II: BWR Fuel". ORNL/TM-2020/1835 (2021).
For convenience, the conclusions from each report is included below.
* Files may be downloaded from the [releases page](https://code.ornl.gov/scale/analysis/haleu-hbu-latt-phys/-/releases).
* This repository also contains frequently asked questions about the report, with answers in the [FAQ](https://code.ornl.gov/scale/analysis/haleu-hbu-latt-phys/-/blob/master/FAQ.md).
For convenience, the conclusions from the report is included below.
