**2. Laboratory description**

Neutron activation analysis is a multielemental chemical analytical technique based on neutrons generated by the nuclear reactor to create radioactive isotopes from stable isotopes in a sample material. The technique relies on excitation by neutrons so that the treated sample emits gamma-rays, and this radiation is then analyzed enabling the user to detect, identify and measure the presence of radioactivity in natural or man-made sources. The main use for the laboratory is to complement the conventional analytical techniques adopted in the institute, especially for those elements whose routine determination may require costly procedures with high environmental impact due to their nature and complexity. This type of analysis is used for the elaboration of a national geochemical map, which is essential for mineral exploration in the territory.

In 2009, not long after restarting the IAN-R1 Research Reactor, the laboratory was re-established at the Colombian Geological Survey, serving the country once again as a key player in the determination of elemental composition in geological matrices. Samples are irradiated under appropriate safety conditions following national regulations, which are lined up to the International Atomic Energy Agency (IAEA) and International Commission on Radiation Protection (ICRP) guides and scientific publications.

**2.3. Gamma spectrometry rooms 1 and 2**

**Figure 11.** Shielded port for sample transfer.

**Figure 10.** Gas extraction cabin.

multichannel module are located in the first room.

The Gamma Spectrometry Systems used in the detection and quantification of the gammarays emitted by the activated samples after irradiation are located in two different rooms. A HPGe Canberra GC-1020 detector, a Canberra 2002CSL pre-amplifier and the InSpector 2000

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From 2016 to 2017, the delayed neutron counting technique was re-established for the determination of uranium and thorium in resource exploration projects due to the sensitivity of the technique, which is lower than 1 μg/kg and can be used to analyze materials with high uranium content (including U3 O8 ) and enrichment of 235U [15].

The scientific staff are qualified and trained with several years of experience and extensive operational knowledge in the management of radioactive material, radiation protection, qualitative and quantitative chemical analysis, waste management, isotope applications and nuclear energy applications.

A brief description of the rooms that make up the CNAAL is given in the following sections.

## **2.1. Sample preparation room**

This room has the necessary infrastructure and equipment for the preparation and adaptation of samples. A Niton XL3t GOLDD portable X-ray fluorescence analyzer, which is used for the preliminary characterization of the samples, a homogenizer mill, three analytical balances, a tablet press and a bag sealer. Reference materials and standards are properly stored under controlled conditions in this room.

## **2.2. Neutron activation analysis room**

This room is where the samples are sent into and out of the core if the pneumatic transfer system is to be used. The systems console and Port No. 1 are located here. There is a gas and vapor extraction cabin with a 1.5 cm thick shielded port used to receive irradiated material from the reactor, and there is also a leaded glass which protects the staff from radiation exposure from the samples (**Figures 10** and **11**). Verification sources used for radiation monitors and calibration of gamma spectrometers are also stored in this room.

Colombian Neutron Activation Analysis Laboratory (CNAAL): Applications and Development… http://dx.doi.org/10.5772/intechopen.74395 37

**Figure 10.** Gas extraction cabin.

**2. Laboratory description**

36 Advanced Technologies and Applications of Neutron Activation Analysis

eral exploration in the territory.

uranium content (including U3

nuclear energy applications.

**2.1. Sample preparation room**

controlled conditions in this room.

**2.2. Neutron activation analysis room**

Protection (ICRP) guides and scientific publications.

O8

Neutron activation analysis is a multielemental chemical analytical technique based on neutrons generated by the nuclear reactor to create radioactive isotopes from stable isotopes in a sample material. The technique relies on excitation by neutrons so that the treated sample emits gamma-rays, and this radiation is then analyzed enabling the user to detect, identify and measure the presence of radioactivity in natural or man-made sources. The main use for the laboratory is to complement the conventional analytical techniques adopted in the institute, especially for those elements whose routine determination may require costly procedures with high environmental impact due to their nature and complexity. This type of analysis is used for the elaboration of a national geochemical map, which is essential for min-

In 2009, not long after restarting the IAN-R1 Research Reactor, the laboratory was re-established at the Colombian Geological Survey, serving the country once again as a key player in the determination of elemental composition in geological matrices. Samples are irradiated under appropriate safety conditions following national regulations, which are lined up to the International Atomic Energy Agency (IAEA) and International Commission on Radiation

From 2016 to 2017, the delayed neutron counting technique was re-established for the determination of uranium and thorium in resource exploration projects due to the sensitivity of the technique, which is lower than 1 μg/kg and can be used to analyze materials with high

) and enrichment of 235U [15]. The scientific staff are qualified and trained with several years of experience and extensive operational knowledge in the management of radioactive material, radiation protection, qualitative and quantitative chemical analysis, waste management, isotope applications and

A brief description of the rooms that make up the CNAAL is given in the following sections.

This room has the necessary infrastructure and equipment for the preparation and adaptation of samples. A Niton XL3t GOLDD portable X-ray fluorescence analyzer, which is used for the preliminary characterization of the samples, a homogenizer mill, three analytical balances, a tablet press and a bag sealer. Reference materials and standards are properly stored under

This room is where the samples are sent into and out of the core if the pneumatic transfer system is to be used. The systems console and Port No. 1 are located here. There is a gas and vapor extraction cabin with a 1.5 cm thick shielded port used to receive irradiated material from the reactor, and there is also a leaded glass which protects the staff from radiation exposure from the samples (**Figures 10** and **11**). Verification sources used for radiation monitors

and calibration of gamma spectrometers are also stored in this room.

#### **2.3. Gamma spectrometry rooms 1 and 2**

The Gamma Spectrometry Systems used in the detection and quantification of the gammarays emitted by the activated samples after irradiation are located in two different rooms. A HPGe Canberra GC-1020 detector, a Canberra 2002CSL pre-amplifier and the InSpector 2000 multichannel module are located in the first room.

**Figure 11.** Shielded port for sample transfer.

**2.5. Decay room**

**2.6. Pneumatic transfer system**

against the system ports.

radioactive gas by the operators.

**Figure 14.** Concrete shielding in decay room.

in the safety of the sample positioning system.

The radioactive material decay room is a space with lead and concrete shields needed to store activated samples for decay. It has two cylindrical lead containers with 6 cm thick walls for the storage of radioactive waste and two compartments made out of 15 cm thick concrete blocks for the storage of samples according to their half-life (**Figure 14**). Activated samples are

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The pneumatic transfer system allows for the rapid exchange of samples between the neutron activation room, the delayed neutron counting room and the nuclear reactor. Its master control is located in the Reactor's console room and without authorization from the reactor's personnel, it is not possible to send samples for irradiation, and this results in a redundancy

This system consists of two compressors: flow diverters, two controls to send and receive samples (**Figure 15**) and a high-density polyethylene duct. The samples enter directly into one of the two aluminum terminals located in the core (positions D3 and C4), where the highest neutron flux can be found. It has the advantage to transfer activated samples to different areas speeds of 15 m/s, being an important aspect in the radiological protection of the personnel. This system is equipped with "air cushion" braking mechanisms to avoid violent crashes

The systems control unit includes a digital counter which can be set up for times between 30 s and 4 h. This unit controls the automatic valves to open and cut the air pressure at the right time. Since it is a complex pneumatic system with two receiving stations and two in-core terminal positions, there are diverters operated remotely from the control unit, which allows for the selection of irradiation positions and terminal stations where samples are received.

Due to the production of Ar41 during activation, terminal ports in the laboratory rooms are located inside extraction cabins with filters for radionuclides, preventing the inhalation of the

temporarily stored in this room until the exemption levels are reached [16].

**Figure 12.** Gamma spectrometry – Room 2.

The second room (**Figure 12**) has four HPGe detectors. Two Canberra GC-3018 detectors with 30% efficiency and energy resolution of 1.8 keV at 1.33 MeV at full-width at half-maximum (FWHM), and two GC-7020 units with 70% efficiency and energy resolution of 2.0 keV at 1.33 MeV (FWHM); each detector comes with its respective shielding, a LYNX® digital signal analyzer and is controlled by the Canberra's Genie2000 v.3.3 software. There is also an automated positioning system that uses a robotic arm to automatically place the samples in each of the four HPGe detectors and reads the gamma spectra during the time it is programmed; this system was designed for radiological protection purposes.

#### **2.4. Delayed neutron counting room**

he room assigned for delayed neutron counting consists of a console and Port No. 2 of the pneumatic transfer system, one ton of paraffin shield which sits on top of 20 cm thick concrete blocks, a geometric arrangement of eight proportional BF3 counters and its associated electronic instrumentation for neutron counting and determination of uranium and thorium in geological, environmental and forensic matrices. There is a central hole in the paraffin shield were samples are placed for reading, and there is also a manual mechanism for sample extraction once readings are done (**Figure 13**).

**Figure 13.** Delayed neutron instrumentation.

#### **2.5. Decay room**

The second room (**Figure 12**) has four HPGe detectors. Two Canberra GC-3018 detectors with 30% efficiency and energy resolution of 1.8 keV at 1.33 MeV at full-width at half-maximum (FWHM), and two GC-7020 units with 70% efficiency and energy resolution of 2.0 keV at 1.33 MeV (FWHM); each detector comes with its respective shielding, a LYNX® digital signal analyzer and is controlled by the Canberra's Genie2000 v.3.3 software. There is also an automated positioning system that uses a robotic arm to automatically place the samples in each of the four HPGe detectors and reads the gamma spectra during the time it is programmed;

he room assigned for delayed neutron counting consists of a console and Port No. 2 of the pneumatic transfer system, one ton of paraffin shield which sits on top of 20 cm thick concrete

tronic instrumentation for neutron counting and determination of uranium and thorium in geological, environmental and forensic matrices. There is a central hole in the paraffin shield were samples are placed for reading, and there is also a manual mechanism for sample extrac-

counters and its associated elec-

this system was designed for radiological protection purposes.

blocks, a geometric arrangement of eight proportional BF3

**2.4. Delayed neutron counting room**

**Figure 12.** Gamma spectrometry – Room 2.

38 Advanced Technologies and Applications of Neutron Activation Analysis

tion once readings are done (**Figure 13**).

**Figure 13.** Delayed neutron instrumentation.

The radioactive material decay room is a space with lead and concrete shields needed to store activated samples for decay. It has two cylindrical lead containers with 6 cm thick walls for the storage of radioactive waste and two compartments made out of 15 cm thick concrete blocks for the storage of samples according to their half-life (**Figure 14**). Activated samples are temporarily stored in this room until the exemption levels are reached [16].

## **2.6. Pneumatic transfer system**

The pneumatic transfer system allows for the rapid exchange of samples between the neutron activation room, the delayed neutron counting room and the nuclear reactor. Its master control is located in the Reactor's console room and without authorization from the reactor's personnel, it is not possible to send samples for irradiation, and this results in a redundancy in the safety of the sample positioning system.

This system consists of two compressors: flow diverters, two controls to send and receive samples (**Figure 15**) and a high-density polyethylene duct. The samples enter directly into one of the two aluminum terminals located in the core (positions D3 and C4), where the highest neutron flux can be found. It has the advantage to transfer activated samples to different areas speeds of 15 m/s, being an important aspect in the radiological protection of the personnel. This system is equipped with "air cushion" braking mechanisms to avoid violent crashes against the system ports.

The systems control unit includes a digital counter which can be set up for times between 30 s and 4 h. This unit controls the automatic valves to open and cut the air pressure at the right time. Since it is a complex pneumatic system with two receiving stations and two in-core terminal positions, there are diverters operated remotely from the control unit, which allows for the selection of irradiation positions and terminal stations where samples are received.

Due to the production of Ar41 during activation, terminal ports in the laboratory rooms are located inside extraction cabins with filters for radionuclides, preventing the inhalation of the radioactive gas by the operators.

**Figure 14.** Concrete shielding in decay room.

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

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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 18**).

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