Neutron-absorbing materials

For a source of fast neutrons, the neutron-absorbing materials within the shielding are arranged as follows:

• It is particularly recommended to use a retarder rich in hydrogen in the shield head, which quickly slows down these neutrons until they reach a thermal or epithermal state (via only a small number of collisions).
• In order to reduce the flux of thermalised neutrons, it is essential to use a material with a large effective cross-sectional area for thermalised neutron absorption, downstream of the retarder. Boron is an ideal material, and also has the advantage of emitting only low-energy capture gamma rays (0.5 MeV).

Neutron-absorbing materials reduce exposure to neutron radiation.

They are suitable for activities using neutron emitting sources: nuclear industry, cyclotron, medical accelerator, etc. The wide range of highly hydrogenated matrices (paraffin, polyethylene) loaded with boron or lithium and in brick, plate and cylindrical form can meet special needs in the design phase and during operation.

PARAFFIN

Paraffin brick
Dimensions (mm): 200 x 100 x 50
Weight: 0.9 kg

Paraffin
Atomic density of hydrogen/cm³	8,13 x 1022
Hydrogen mass %	14,96%
Natural distribution of hydrogen isotopes	99,98% 1H
Density (gr/cm³)	0,90
Gamma resistance	106Gy
Maximum recommended use temperature	40°C
Melting point	55°C
Colour	Translucent/ white
Odour	None
Mechanical properties	Mediocre
Water absorption	Negligible

PARABORE-25

Paraffin brick containing 25% boron
Dimensions (mm): 200 x 100 x 50
Weight: 1.26 kg

Parabore-25
Atomic density of hydrogen/cm³	6,79 x 1022
Hydrogen mass %	9,72%
Natural distribution of hydrogen isotopes	99,98% 1H
Atomic density of boron/cm³	1,6 x 1022
Natural distribution of boron isotopes	19,6% 10B 80,4% 11B
Boron mass %	≥ 25%
Density (gr/cm³)	1*
Gamma resistance	106Gy
Maximum recommended use temperature	40°C
Melting point	55°C
Colour	Dark grey / black
Odour	None
Mechanical properties	Mediocre
Water absorption	Negligible

POLYETHYLENE

Hydrogen-rich polyethylene in plate, brick, or cylindrical form

Polyethylene
Atomic density of hydrogen/cm³	7,90 x 1022
Hydrogen mass %	13,38%
Natural distribution of hydrogen isotopes	99,98% 1H
Density (gr/cm³)	0,93
Macroscopic crosssection of thermal neutrons	0,03 cm-1
Gamma resistance	5 x 106Gy
Neutron resistance	2,5×1017 n/cm²
Maximum recommended use temperature	80°C
Melting point	135°C
Colour	White
Odour	None
Mechanical properties	Excellent
Water absorption	Negligible

POLYBORE-5

Polyethylene containing 5% boron in plate, brick, or cylindrical form

Polybore-5
Atomic density of hydrogen/cm³	7,48 x 1022
Hydrogen mass %	11,7%
Natural distribution of hydrogen isotopes	99,98% 1H
Atomic density of boron/cm³	2,99 x 1021
Natural distribution of boron isotopes	19,6% 10B 80,4% 11B
Boron mass %	≥ 5%
Density (gr/cm³)	1,07
Macroscopic cross section of thermal neutrons	2,28 cm-1
Gamma resistance	5 x 106Gy
Neutron resistance	2,5×1017 n/cm²
Maximum recommended use temperature	80°C
Melting point	135°C
Colour	White
Odour	None
Mechanical properties	Excellent
Water absorption	Negligible

POLYBORE-25

Polyethylene containing 25% boron in plate, brick, or cylindrical form

Polybore-25
Atomic density of hydrogen/cm³	6,55 x 1022
Hydrogen mass %	9,3 %
Natural distribution of hydrogen isotopes	99,98% 1H
Atomic density of boron/cm³	1,6 x 1022
Natural distribution of boron isotopes	19,6% 10B 80,4% 11B
Boron mass %	≥ 25%
Density (gr/cm³)	1,17
Macroscopic cross section of thermal neutrons	15,5 cm-1
Gamma resistance	5 x 106Gy
Neutron resistance	2,5×1017 n/cm²
Maximum recommended use temperature	80°C
Melting point	135°C
Colour	Dark grey / black
Odour	None
Mechanical properties	Excellent
Water absorption	Negligible

POLYTHIUM-7

Polyethylene containing 7.5% lithium in plate, brick, or cylindrical form

Polythium-7
Atomic density of hydrogen/cm³	5,44 x 1022
Hydrogen mass %	8,59 %
Natural distribution of hydrogen isotopes	99,98% 1H
Atomic density of lithium/cm³	6,96 x 1021
Natural distribution of lithium isotopes	92,6% 7Li 7,4% 6Li
Lithium mass %	7,56 %
Density (gr/cm³)	1,06
Macroscopic cross section of thermal neutrons	0,51 cm-1
Gamma resistance	5 x 106Gy
Neutron resistance	2,5×1017 n/cm²
Maximum recommended use temperature	80°C
Melting point	135°C
Colour	White
Odour	None
Mechanical properties	Excellent
Water absorption	Negligible

SILIBORE-5

Flexible silicone sheet containing 5% boron

Silibore-5
Atomic density of hydrogen/cm³	6,62 x 1022
Hydrogen mass %	7,5 %
Natural distribution of hydrogen isotopes	99,98% 1H
Atomic density of boron/cm³	0,4 x 1022
Natural distribution of boron isotopes	19,6% 10B 80,4% 11B
Boron mass %	≥ 5%
Density (gr/cm³)	1,34
Macroscopic cross section of thermal neutrons	10,4 cm-1
Gamma resistance	5 x 106Gy
Neutron resistance	2,5×1017 n/cm²
Maximum recommended use temperature	200°C
Colour	Dark grey / black
Odour	None
Mechanical properties	Low
Water absorption	Negligible

SILITHIUM-25/79

Flexible silicone sheet containing 25% lithium 6

Silithium-25/79
Atomic density of hydrogen/cm³	5,44 x 1022
Hydrogen mass %	1,3 %
Natural distribution of hydrogen isotopes	99,98% 1H
Atomic density of lithium/cm³	6,96 x 1021
Natural distribution of lithium isotopes	21 % 7Li 79 % 6Li
Lithium mass %	25 %
Density (gr/cm³)	2,25*
Gamma resistance	5 x 106Gy
Neutron resistance	2,5×1017 n/cm²
Maximum recommended use temperature	200°C
Colour	White
Odour	None
Mechanical properties	Low
Water absorption	Negligible