**3. Sample preparation/irradiation**

The Colombian Geological Survey serves the country by providing reliable scientific data through research into basic and applied subsoil geo-sciences; evaluating and monitoring threats of geological origin; exploring and monitoring petroleum resources, minerals and groundwater; the ability to study the elemental composition of samples such as rocks, soils, sediments, minerals, water and gases is a major asset. Collected samples are often taken to different laboratories for a variety of analyses if required by the research being conducted. Several analytical techniques ranging from Gravimetric Analysis and Atomic Absorption Spectrometry, to X-ray Fluorescence, Inductively Coupled Plasma Mass Spectrometry (ICP-MS), and Neutron Activation Analysis among others are available at the Colombian Geological Survey.

Geological materials analyzed by NAA need to be previously dried at room temperature, crushed, pulverized and sieved to a particle size of 150 μm (100 mesh, **Figure 16**). Once the sample is received (~ 50 g), moisture content needs to be determined in order to make future corrections referencing the dried sample. Samples are homogenized, weighed (0.250 ± 0.001 g), pressed and encapsulated in plastic hermetically sealed polyethylene vials.

**Figure 16.** Sample preparation process: (a) drying (b) grinding and (c) screening.

Samples for long-lived element activation (days to years) are placed at the periphery of the core and vials with samples are arranged in racks as shown in the following diagram (**Figure 17**). These racks are placed in vacuum-sealed Ziploc bags before irradiation in the G3-G4 positions (**Figure 18**).

The following elements can be determined after a 4-h irradiation operating at 30 kW: Sm, Lu, U, La, Nd, Eu, Hf, Ce, Yb, As, Sb, Ba, Br, Cd, Gd, Ga, Ho, Mo, W, Th, Cr, Cs, Sc, Ir, Ni, Se, Ag, Ta, Tb, Tm, Rb, Fe, Co, Zn, Zr. The neutron flux is measured by 5 mg Al + 0.1% Au rectangular foils as previously shown in **Figure 17**. Measurement required to obtain the correction factor fφ. Samples for short-lived element activation (seconds to a few hours) are irradiated inside the core at positions D3 or C4 (**Figure 18**). These samples are encapsulated in cylindrical pressure-sealed polyethylene containers, packed in pairs into rabbits (polyethylene vials) and transferred into the core by the pneumatic transfer system.

**Figure 17.** Rack sample configuration (left) neutron flux monitors attached to vials (right).

**Figure 18.** Reactor core schematic (IAN-R1).

**Figure 16.** Sample preparation process: (a) drying (b) grinding and (c) screening.

among others are available at the Colombian Geological Survey.

pressed and encapsulated in plastic hermetically sealed polyethylene vials.

**3. Sample preparation/irradiation**

40 Advanced Technologies and Applications of Neutron Activation Analysis

**Figure 15.** Pneumatic transfer system controls.

The Colombian Geological Survey serves the country by providing reliable scientific data through research into basic and applied subsoil geo-sciences; evaluating and monitoring threats of geological origin; exploring and monitoring petroleum resources, minerals and groundwater; the ability to study the elemental composition of samples such as rocks, soils, sediments, minerals, water and gases is a major asset. Collected samples are often taken to different laboratories for a variety of analyses if required by the research being conducted. Several analytical techniques ranging from Gravimetric Analysis and Atomic Absorption Spectrometry, to X-ray Fluorescence, Inductively Coupled Plasma Mass Spectrometry (ICP-MS), and Neutron Activation Analysis

Geological materials analyzed by NAA need to be previously dried at room temperature, crushed, pulverized and sieved to a particle size of 150 μm (100 mesh, **Figure 16**). Once the sample is received (~ 50 g), moisture content needs to be determined in order to make future corrections referencing the dried sample. Samples are homogenized, weighed (0.250 ± 0.001 g), Sample irradiation in these rabbits ranges from 40 s at 5 kW for the analysis of uranium and thorium using delayed neutron counting techniques and up to 5 min at 30 kW for the analysis of short-lived elements (Al, Ca, Mg, Ti, V, Dy, Mn, K and Na).

controlled from ports 1 and 2 located in the neutron activation and delayed neutron counting

Colombian Neutron Activation Analysis Laboratory (CNAAL): Applications and Development…

http://dx.doi.org/10.5772/intechopen.74395

43

Additionally, there is a peripheral pneumatic transfer system that was part of the original design (1965) and is used to irradiate samples in a position adjacent to the core (Position A6). This old system was used from 1968 to 1992 for radioisotope production (24Na, <sup>32</sup>P, <sup>82</sup>Br, <sup>198</sup>Au

The rack containing the flux monitors and samples is positioned in the middle of the frontal face of the core, irradiated during 4 h at 30 kW (**Figure 20**) and subjected to a thermal neutron

**Table 1** presents a summary of the experimental conditions used for the analysis of short-,

Method Direct comparator Direct comparator

Flux monitor Al + 0.1% Au 0.5 mg Al + 0.1% Au 0.5 mg

Measurand Mass fraction Mass fraction Sample/comparator (mass) 0.250 ± 0.001 g 0.200 ± 0.001 g

Reactor power 20–30 kW 30 kW Irradiation position D3 or C4 G3-G4 Irradiation time 1–5 min 4 h

Decay time 1 5 min 3–7 days

Reading time 1 5 min 3 h Reading 1 geometry 50 mm 30 mm Decay time 2 60 min 21–28 days

Reading time 2 10 min 4 h Reading 2 geometry 10 mm 15 mm

**Pneumatic transfer system Rack system**

**4. Automated sample positioning system for gamma spectrometry**

Photon energy (keV) Nuclide dependent Nuclide dependent

and decreased doses received by the staff [18].

**Table 1.** Experimental irradiation conditions.

Automation allows greater control of counting geometries, less error in positioning, increased productivity in the analyses, increased control and quality assurance of the analytical data

rooms, respectively.

and 99Mo) [17].

flux of around 2.3 × 1011 neutrons cm−2 s−1.

**Characteristic Value/description**

medium- and long-lived elements.

The IAN-R1 nuclear reactor was built by the Lockheed Western Export Company and was commissioned in 1965 as a graphite-reflected pool-type research reactor, cooled by natural convection with light water. The current core consists of 50 fuel elements made of U-ZrH1.6 enriched up to 19.75%. The reactor is licensed by the Ministry of Mines and Energy (Nuclear Regulatory Body) to operate at the maximum steady-state power of 30 kW, and it is located inside a cylindrical tank made of carbon steel 6 × 10−3 m thick, 5.25 m tall and 2 m in diameter with capacity to store up to 16 m3 of water.

The nuclear reactor's instrumentation and control systems were fully upgraded during 2012 and 2013 (**Figure 19**) by National Institute of Nuclear Research (ININ, México), in 2016 a new automated pneumatic transfer system (**Figure 20**) was installed, replacing the original system installed in 1997. This system opened up two irradiation positions inside the core, remotely

**Figure 19.** Nuclear research reactor IAN-R1.

**Figure 20.** Rack with samples for irradiation.

controlled from ports 1 and 2 located in the neutron activation and delayed neutron counting rooms, respectively.

Additionally, there is a peripheral pneumatic transfer system that was part of the original design (1965) and is used to irradiate samples in a position adjacent to the core (Position A6). This old system was used from 1968 to 1992 for radioisotope production (24Na, <sup>32</sup>P, <sup>82</sup>Br, <sup>198</sup>Au and 99Mo) [17].

The rack containing the flux monitors and samples is positioned in the middle of the frontal face of the core, irradiated during 4 h at 30 kW (**Figure 20**) and subjected to a thermal neutron flux of around 2.3 × 1011 neutrons cm−2 s−1.

**Table 1** presents a summary of the experimental conditions used for the analysis of short-, medium- and long-lived elements.


**Table 1.** Experimental irradiation conditions.

Sample irradiation in these rabbits ranges from 40 s at 5 kW for the analysis of uranium and thorium using delayed neutron counting techniques and up to 5 min at 30 kW for the analysis

The IAN-R1 nuclear reactor was built by the Lockheed Western Export Company and was commissioned in 1965 as a graphite-reflected pool-type research reactor, cooled by natural convection with light water. The current core consists of 50 fuel elements made of U-ZrH1.6 enriched up to 19.75%. The reactor is licensed by the Ministry of Mines and Energy (Nuclear Regulatory Body) to operate at the maximum steady-state power of 30 kW, and it is located inside a cylindrical tank made of carbon steel 6 × 10−3 m thick, 5.25 m tall and 2 m in diameter

The nuclear reactor's instrumentation and control systems were fully upgraded during 2012 and 2013 (**Figure 19**) by National Institute of Nuclear Research (ININ, México), in 2016 a new automated pneumatic transfer system (**Figure 20**) was installed, replacing the original system installed in 1997. This system opened up two irradiation positions inside the core, remotely

of short-lived elements (Al, Ca, Mg, Ti, V, Dy, Mn, K and Na).

42 Advanced Technologies and Applications of Neutron Activation Analysis

of water.

with capacity to store up to 16 m3

**Figure 19.** Nuclear research reactor IAN-R1.

**Figure 20.** Rack with samples for irradiation.
