Design features of a prompt gamma neutron activation analysis system at HANARO

The design features are described of a prompt gamma neutron activation anal ysis system at HANARO, a 30 MW research reactor in the Korea Atomic Energy Research Institute. The beam consists of polychromatic thermal neutrons dif fracted by a set of pyrolytic graphite crystals at orders n in the range 1 less than or equal to n less than or equal to 6 at a Bragg angle of 45 degr ees on a horizontal beam line. A neutron flux of 1.0 10(8) n.cm(-2) S-1 is calculated at the sample position from the reflectivity of the crystal whic h has been confirmed in a measurement of a diffracted neutron spectrum usin g a time-of-flight spectrometer and gold-wire activation. The fast neutron and gamma backgrounds will be low due to the use of a diffracted beam and a tapered collimator. The detection system comprises a 30% n-type HPGe detec tor, signal electronics and a fast ADC. The first application of this syste m Mlill be the analysis of boron concentration in biological samples for ne utron capture therapy. Construction of the beam line and the arrangement of the detection system is proceeding.