RNAA

RNAA – Reactor-Neutron Activation Analysis

Instrument responsible: Ibolya Sziklai-László, Dénes Párkányi

Neutron activation analysis (NAA) is a method for quantitative composition analysis of chemical elements based on the conversion of stable nuclei in the sample to radioactive nuclei by nuclear reactions, followed by the quantitation of the reaction products via their gamma radiations. The k0-standardized neutron activation analysis (k0-NAA), combined with high-resolution and high-throughput gamma-ray spectrometry, offers mostly non-destructive, multi-elemental analysis for many branches of science and technology. NAA has inherently favorable characteristics, negligible matrix effect, excellent selectivity and high sensitivity. Even small amount (few tens of milligrams) of samples (mostly solid) can be measured, in which about 35-75 elements in less than 0.01 μg quantities can be determined.

Samples for NAA are irradiated with neutrons in the core of the reactor. Short and long time irradiations are also possible in two designated vertical channels of the reactor. Short irradiations are done by means of a pneumatic rabbit system, whereas samples for long irradiations are loaded into the rotating channel.

The gamma-rays emitted from the sample are counted in low-level gamma-spectroscopic counting chamber to reduce the external background. In our NAA laboratory there are three low-level gamma-spectroscopic chambers, which are built from pre-World War II steel (free of any man-made radioactivity), have 10 cm thick wall covered with 2 mm thick Cu-layer inside to attenuate the X-rays. There are three different high-purity Ge detectors and two digital gamma spectrometers to detect the gamma-rays and collect the gamma spectra.

rnaa

Table 1. Technical details of the irradiation and counting

There are three different high-purity Ge detectors and two digital gamma spectrometer to detect the gamma-rays and collect the gamma spectra. See details of the detectors and spectrometers (2014) in Table 2 and 3.

Detectors

Efficiency

Resolution @

59.5 keV

Resolution @ 1332.5 keV

Dewar

ORTEC PopTop 55195-P "D5"

55%

0.95 keV

1.75 keV

30 l

Canberra GC3618 "D4"

36%

0.80 keV

1.80 keV

30 l

Canberra GC1318 "D3"

13%

0.95 keV

1.80 keV

30 l

 

Digital Spectrometers

Software (energy range)

Info

ORTEC DSpecPlus

MAESTRO (30-2500 keV)

DSP-based, Zero-Deadtime Mode

ORTEC DSpec502

MAESTRO (30-3300 keV)

DSP-based, Two channel, Zero-Deadtime Mode

Table 2&3. Main specifications of the high-purity Ge detectors and digital spectrometers

The spectra are evaluated with the gamma spectroscopy package Hyperlab 2013.1. This includes automatic peak search, energy calibration the nonlinearity option, and net peak area computation, efficiency correction. For quantitative evaluation, the KayZero for Windows 3 program is used, based on the k0 standardization.

       

Figure. 1. The “D5” gamma spectrometer of the NAA laboratory

Reference:

László Szentmiklósi, Dénes Párkányi, Ibolya Sziklai-László, Upgrade of the Budapest neutron activation analysis laboratory, J. Radioanal. Nucl. Chem. (2016) online first, DOI 10.1007/s10967-016-4776-7