1.1 This specification defines criteria for boron-based neutron absorbing material systems used in racks in a pool environment for storage of nuclear light water reactor (LWR) spent-fuel assemblies or disassembled components to maintain sub-criticality This specification defines essential criteria for all material combinations in boron-based neutron-absorbing material systems used for nuclear spent fuel storage racks in nuclear light water reactors, spent-fuel assemblies, or disassembled components.