Description of absorbent materials used

Neutron absorbing materials for the control of reactors

Figure 1 - Macroscopic neutron absorption cross sections for the most common materials (natural isotopic content for B4C)

Figure 2 - Self-screening effect

Figure 3 - PWR fuel assembly with control cluster

Figure 5 - Simplified AIC transmutation chain

Figure 6 - Microstructure of irradiated AIC (4 REP cycles): the dark areas correspond to the tin-rich hexagonal phase, with a higher proportion at the periphery of the rod, according to

Figure 7 - Microscopic cross sections of neutron absorption reactions by 10B (n, α) and (n, 2α) as a function of neutron kinetic energy.

Figure 8 - Structural elements of the boron carbide crystal lattice B4C

Figure 10 - Simplified dysprosium transmutation chain

Figure 11 - Phase diagram of the Dy2O3-TiO2 system, from

Figure 12 - Comparative efficiency of natural B4C, AIC, Hf and Dy2TiO5 absorbers in PWR neutron spectrum (7 mm diameter pellets or rods) as a function of irradiation time.

Figure 13 - Simplified Hf transmutation chain

Figure 14 - Evolution of 181Ta, 183W and 184W concentrations in a hafnium absorber element irradiated in VVER, according to.

Figure 16 - Microscopic neutron absorption cross-section of rare earths usable as poisons (the cross-sections of the various absorbing isotopes are considered for natural relative concentrations).

Figure 17 - Simplified gadolinium transmutation chain

Figure 19 - Simplified samarium transmutation chain

Figure 20 - Simplified europium transmutation chain

Figure 21 - Legend for figures showing reaction and decay chains. Data mainly from AlEA  (cross sections) and BNL  (decay periods).