diff --git a/300s School/NUCE 2100 - Fundamentals of Nuclear Engineering/2024-09-17 Module 5 Nuclear Fission Basics.md b/300s School/NUCE 2100 - Fundamentals of Nuclear Engineering/2024-09-17 Module 5 Nuclear Fission Basics.md
index f63eea2f..26939384 100644
--- a/300s School/NUCE 2100 - Fundamentals of Nuclear Engineering/2024-09-17 Module 5 Nuclear Fission Basics.md	
+++ b/300s School/NUCE 2100 - Fundamentals of Nuclear Engineering/2024-09-17 Module 5 Nuclear Fission Basics.md	
@@ -40,4 +40,7 @@ There are more formulas in the slides. K can be based on material properties
 Fission is most efficiently caused by thermal neutrons (energy < 1eV), but neutrons from fission are born at something like \>2MeV. 7 orders of magnitude reduction -- usually kinetic losses by neutrons colliding with things.
 
 Different neutron moderators require a different number of collisions to bring the energy down to thermal. The closer the mass is to that of a neutron, the better. Hydrogen is best, then deuterium, then beryllium, then carbon (graphite).
-
+# Module 5.3 - PWR and BWR Reactors
+Fuel pellots. Small boys. Stacked into fuel elements 12 feet high. about 300 per rod
+14x14 lattice or 17x17. That is one fuel assembly.
+Zirconium is used as the cladding. Low neutron absorbtion cross section.