The PTB Thermal Neutron Calibration Facility

The PTB Thermal Neutron Calibration Facility consists of sixteen 241Am-Be neutron sources
mounted in a high-purity graphite block with dimensions of 150 cm x 150 cm x 180 cm at
depths of between 115 cm and 135 cm from the front surface. The reference position for
calibrations is 30 cm from the front surface of the graphite moderator device and 75 cm above
the floor. Fluence values and dose equivalent quantities were determined by means of
measurements and calculations for neutrons and (in some cases) for photons as well. The field
is highly thermalized: 98.4 % in terms of fluence, and 86 % in terms of dose equivalent rate.
The thermal neutron fluence rate at the reference position is (68.3 ± 1.9) cm-2s-1. The reference
field is well-suited for the calibration of radiation protection devices.
Zusammenfassung