Preliminary Selection of Device Materials to Locally Transform Thermal into SFR Neutron Spectrum

Table 1

Elements with the highest absorption capability classified with descending thermal microscopic absorption cross sections ().

Element	Symbol	Atomic number	(barns)	Reasons to reject
Gadolinium	Gd	64	49000	-
Samarium	Sm	62	5922	-
Fermium	Fm	100	5800	Large Z
Europium	Eu	63	4600	-
Californium	Cf	98	2900	Large Z
Cadmium	Cd	48	2450	-
Plutonium	Pu	94	1017.3	Large Z
Dysprosium	Dy	66	920	-
Boron	B	5	767	-
Berkelium	Bk	97	710	Large Z
Actinium	Ac	89	515	Large Z
Iridium	Ir	77	425	-
Mercury	Hg	80	374	Problematic properties^1
Protactinium	Pa	91	200.6	Large Z
Neptunium	Np	93	180	Large Z
Promethium	Pm	61	168.4	Rare
Einsteinium	Es	99	160	Large Z
Erbium	Er	68	160	-
Rhodium	Rh	45	144.8	Rare
Hafnium	Hf	72	104	-

High toxicity, high vapor pressure even at room temperature, low boiling point, producing noxious fumes when heated, and relatively low thermal conductivity.