**5. Designs of the NAS components for ITER**

measurement from the upper and divertor position, when the displacement range is within ±20 cm vertically and radially. The equatorial port position can be used for backup when the

The effect of neutron source broadening (**Figure 9**) on the measurement, which cannot be estimated during the in-vessel calibration, was evaluated. The result also indicates that the upper port is the best position because it has the lowest effect from the neutron source broadening, and shows good characteristic of depending only on the vertical broadening. It is interesting to note that the equatorial port position shows symmetric measurement with the upper port position. Therefore, the simultaneous measurements from the upper and equatorial port position are expected to provide the total neutron production with the broadening error of ~1% without compensation from other diagnostics, when the profile peaking factor is in the range of 3 < α < 7. The calculations show that with the combination of the measurements from the upper port, equatorial port, and divertor region can provide relatively good evaluation of the total neutron production in the plasma. In spite of the low reliability of the measurement from the inboard midplain position, it is reasonable to keep this irradiation ends, as they are the only ones capable of providing the absolute value of the neutron flux coming to the inboard side.

data are compensated from other diagnostics.

78 Advanced Technologies and Applications of Neutron Activation Analysis

**Figure 8.** Evaluation of the effect of neutron source position.

**Figure 9.** Evaluation of the effect of neutron source broadening.

Thermal analysis has made significant impact on the design of the NAS front-end components (**Figure 10**). All NAS components installed inside the vacuum vessel shall follow the design guideline SDC-IC (Structural Design Criteria for ITER In-vessel Components), which requires the maximum temperature of the components to be less than about 500°C.According to the simple thermal analysis on the irradiation end in the upper port, the temperature of the irradiation end is found to exceed 500°C when the irradiation end protrudes only by 6 cm from the actively cooled diagnostic shield module (DSM) inside (but not touching) the diagnostic first wall (DFW) that has a full depth of 60 cm. Similarly, all in-vessel irradiation ends located inboard side of the vacuum vessel are found to exceed 500°C, when there is no active cooling of the irradiation end structures. The temperature could be below 500°C only when the forced circulation of He gas with the velocity higher than 10 m/s is provided for the in-vessel transfer line during the plasma operation, which can be problematic when the gas blowing with such velocity fails, for example, when the capsule touches the irradiation location and plugs the hole for the gas circulation. In order to resolve the thermal issue, the design is updated to cool down all in-port irradiation ends by attaching the cooling jacket around the irradiation end structure, where coolant can be supplied from the in-port coolant manifold.

Port plug irradiation ends mainly consist of two transfer lines which are composed of coaxial or parallel tubes (**Figure 11**). Most components will be fabricated with SS316L except the capsule monitoring cabling, which consists of MgO mineral insulated (MI) cables and Al2 O3 based electrical feedthrough. The front part of the irradiation end is enclosed with the coolant housing, which is connected with the coolant tubing. Two guiding rings are attached on the outside of the coolant housing for the smooth insertion of the irradiation end into the DSM. The feedthroughs will be welded on the closure plate of the port plugs.

**Figure 10.** Calculated temperature of NAS irradiation ends.

**Figure 11.** Port plug transfer line in EP11.

Transfer station consists of many moving components such as a servo-motor, linear actuators and many solenoid or gas-driven valves. Pneumatic properties of the transfer system for transferring capsule are as below:


Samples will be transferred to the designated position by the action of distribution machine 'carousel' (**Figure 12**). Rotating platter inside the carousel will transfer sample to the loading position which are connected to the designated position. When the samples are ready, the valves behind are opened to shoot them to the designated positions. Before arriving at the designated position, the speed of them will be slowed down to prevent breakage. A Programmable Logic Controller (PLC) will control the operation of the transfer system. Figure 9.4.2 is a current design of the carousel.

ones for neutron activation analysis, but other types of detector can be also considered. Appropriate detectors will be chosen for the proper operation of ITER NAS considering

Neutron Activation System for ITER Tokamak http://dx.doi.org/10.5772/intechopen.75966 81

The NAS system has been designed for determining the total neutron yield during the DT operation. The system must provide also time-resolved measurements of the global neutron source strength and evaluation of the fusion power. Measurement of absolutely calibrated

state of the art.

**6. Performance assessment**

neutron flux and fusion power will be performed.

**Figure 12.** Design of sample distribution machine 'carousel'.

Counting station measures gamma-rays from the activated samples. It consists of gammaray detector, signal processing electronics such as high voltage supply, preamplifier, amplifier, and multichannel analyzer, and data analyzing software. Many gamma-ray detectors such as gas chambers, scintillators, and semiconductor detectors are commercially available. Among these detectors, NaI detectors and HPGe detectors are the most commonly used

**Figure 12.** Design of sample distribution machine 'carousel'.

ones for neutron activation analysis, but other types of detector can be also considered. Appropriate detectors will be chosen for the proper operation of ITER NAS considering state of the art.

#### **6. Performance assessment**

Transfer station consists of many moving components such as a servo-motor, linear actuators and many solenoid or gas-driven valves. Pneumatic properties of the transfer system for

Samples will be transferred to the designated position by the action of distribution machine 'carousel' (**Figure 12**). Rotating platter inside the carousel will transfer sample to the loading position which are connected to the designated position. When the samples are ready, the valves behind are opened to shoot them to the designated positions. Before arriving at the designated position, the speed of them will be slowed down to prevent breakage. A Programmable Logic Controller (PLC) will control the operation of the transfer system.

Counting station measures gamma-rays from the activated samples. It consists of gammaray detector, signal processing electronics such as high voltage supply, preamplifier, amplifier, and multichannel analyzer, and data analyzing software. Many gamma-ray detectors such as gas chambers, scintillators, and semiconductor detectors are commercially available. Among these detectors, NaI detectors and HPGe detectors are the most commonly used

transferring capsule are as below:

**Figure 11.** Port plug transfer line in EP11.

• Pressure of driving gas: 1–8 bars

• OD of sample transfer tube: 12.7 mm

• OD of retrieving gas tube: 12.7 mm

• Diameter of capsule: ~8 mm • Length of capsule: ~20 mm

• Pressure of gas in reservoir: ~8 bars max.

80 Advanced Technologies and Applications of Neutron Activation Analysis

• Thickness of sample transfer tube: 1.25 mm

• Thickness of retrieving gas tube: 1.25 mm

Figure 9.4.2 is a current design of the carousel.

The NAS system has been designed for determining the total neutron yield during the DT operation. The system must provide also time-resolved measurements of the global neutron source strength and evaluation of the fusion power. Measurement of absolutely calibrated neutron flux and fusion power will be performed.

Various tools are used for carrying out the analysis:


An irradiation location at midplane inboard region is selected for the calculation of neutron flux and spectrum with MCNP code. The flux of this location is the second strongest among seven poloidal irradiation locations. Two tallies are designated for the irradiation ends, one is very close to the first wall, and the other is behind the blanket module very close to the

vacuum vessel wall. Both are located at the cross point of horizontal and vertical gap centers of four blanket modules. Tally 15 is located near the inner VV wall whereas Tally 25 is facing the plasma. **Figure 13** shows two tally locations. Si, Al, Ti, Fe, Nb, and Cu have been selected as sample materials for the investigation [6]. Samples are assumed to be a foil type with the

Neutron Activation System for ITER Tokamak http://dx.doi.org/10.5772/intechopen.75966 83

**Figure 14** shows the calculated neutron spectra at two tallies. Total neutron fluxes at tally 15 and tally 25 are 5.45 × 1013 and 5.9 × 1014 s−1 cm−2 respectively, assuming 500 MW of fusion power. In spite of the heavy blanket modules structure in front of the irradiation end, the spectrum of tally 15 shows clear 14 MeV neutron peak. This is due to the blanket modules acting as a collimator that absorbs scattered neutrons. Calculated neutron flux and spectrum

As one of the requirements of the ITER NAS is to measure time-integrated neutron fluence to the first wall for all discharge duration, it is desirable for samples to be irradiated as long as possible time within the discharge time. Thus, the activities of various samples are calculated with the irradiation of 1000 s, and the result is shown in **Figure 15** D-T fusion power of

Another requirement is to provide supplementary neutron flux data with a crude temporal resolution of about 10 s, when necessary for a backup or calibration of other flux measurement systems, such as Microfission Chambers (MFC) and neutron flux monitors (NFM). Thus, the activities of various samples are calculated with the irradiation of 10 s, and the result

are used for input data of FISPACT for the calculation of the sample activity.

diameter of 7 mm and the thickness of 0.1 mm.

500 MW is assumed for the flux calculation.

**Figure 14.** Neutron spectra at tally 15 and tally 25.

is shown in **Figure 16**.

**Figure 13.** Tally locations in the Alite model.

vacuum vessel wall. Both are located at the cross point of horizontal and vertical gap centers of four blanket modules. Tally 15 is located near the inner VV wall whereas Tally 25 is facing the plasma. **Figure 13** shows two tally locations. Si, Al, Ti, Fe, Nb, and Cu have been selected as sample materials for the investigation [6]. Samples are assumed to be a foil type with the diameter of 7 mm and the thickness of 0.1 mm.

**Figure 14** shows the calculated neutron spectra at two tallies. Total neutron fluxes at tally 15 and tally 25 are 5.45 × 1013 and 5.9 × 1014 s−1 cm−2 respectively, assuming 500 MW of fusion power. In spite of the heavy blanket modules structure in front of the irradiation end, the spectrum of tally 15 shows clear 14 MeV neutron peak. This is due to the blanket modules acting as a collimator that absorbs scattered neutrons. Calculated neutron flux and spectrum are used for input data of FISPACT for the calculation of the sample activity.

As one of the requirements of the ITER NAS is to measure time-integrated neutron fluence to the first wall for all discharge duration, it is desirable for samples to be irradiated as long as possible time within the discharge time. Thus, the activities of various samples are calculated with the irradiation of 1000 s, and the result is shown in **Figure 15** D-T fusion power of 500 MW is assumed for the flux calculation.

Another requirement is to provide supplementary neutron flux data with a crude temporal resolution of about 10 s, when necessary for a backup or calibration of other flux measurement systems, such as Microfission Chambers (MFC) and neutron flux monitors (NFM). Thus, the activities of various samples are calculated with the irradiation of 10 s, and the result is shown in **Figure 16**.

**Figure 14.** Neutron spectra at tally 15 and tally 25.

**Figure 13.** Tally locations in the Alite model.

Various tools are used for carrying out the analysis:

82 Advanced Technologies and Applications of Neutron Activation Analysis

ma neutron source is used for the MCNP calculation.

the MCNP calculation

materials.

FISPACT-2007

• MCNP v.5 (Monte Carlo N-Particle) transport code is used for the calculation of neutron

• FENDL-2.1 (Fusion Evaluated Nuclear Data Library) is used as the material database for

• FISPACT-2007 is used for the inventory of neutron induced activation of the sample

• EAF-2007 (European Activation File) is used for the source of cross-section data for

• Lite series (A-lite, B-lite, and C-lite) 40° sector ITER geometrical model with a fusion plas-

An irradiation location at midplane inboard region is selected for the calculation of neutron flux and spectrum with MCNP code. The flux of this location is the second strongest among seven poloidal irradiation locations. Two tallies are designated for the irradiation ends, one is very close to the first wall, and the other is behind the blanket module very close to the

fluxes and neutron energy spectra at the designated locations for the irradiation.

The activation desired for a sample should be similar to that provided by a standard source used for absolute calibration of the gamma-ray detectors. A typical maximum value for modestly safe handling would be 100 μCi. **Figure 17** shows the fusion power needed to create 100 μCi samples assuming 10-s irradiation and 20-s cooling at a irradiation location D.

Assuming the mass of samples to be from a few milligrams to a few grams, the fusion power that NAS can cover ranges from a few hundred watts to gigawatts by using various sample materials at different irradiation end locations. This measurement range satisfies the required measurement range both of the neutron flux and the fusion power.

**Figure 18** shows the fusion power needed to create 100 μCi samples assuming 1000-s irradiation and 1000-s cooling at an irradiation location D. This result also shows that the NAS can measure neutron fluence in a long pulse operation condition of ITER. Si is not an appropriate sample material for the long time irradiation because the activity of Si saturates when the irradiation is much longer than the half-life of Si.

**Figure 16.** Activity by irradiation of 10 s (a) tally 15, (b) tally 25.

(right) at tally 25.

**Figure 17.** Fusion power needed to create 100 μCi samples by the 10-s irradiation and 20-s cooling (left) at tally 15, and

Neutron Activation System for ITER Tokamak http://dx.doi.org/10.5772/intechopen.75966 85

**Figure 15.** Activation by irradiation of 1000 s (a) tally 15, (b) tally 25.

**Figure 16.** Activity by irradiation of 10 s (a) tally 15, (b) tally 25.

The activation desired for a sample should be similar to that provided by a standard source used for absolute calibration of the gamma-ray detectors. A typical maximum value for modestly safe handling would be 100 μCi. **Figure 17** shows the fusion power needed to create 100 μCi samples assuming 10-s irradiation and 20-s cooling at a irradiation location D.

Assuming the mass of samples to be from a few milligrams to a few grams, the fusion power that NAS can cover ranges from a few hundred watts to gigawatts by using various sample materials at different irradiation end locations. This measurement range satisfies the required

**Figure 18** shows the fusion power needed to create 100 μCi samples assuming 1000-s irradiation and 1000-s cooling at an irradiation location D. This result also shows that the NAS can measure neutron fluence in a long pulse operation condition of ITER. Si is not an appropriate sample material for the long time irradiation because the activity of Si saturates when the

measurement range both of the neutron flux and the fusion power.

irradiation is much longer than the half-life of Si.

84 Advanced Technologies and Applications of Neutron Activation Analysis

**Figure 15.** Activation by irradiation of 1000 s (a) tally 15, (b) tally 25.

**Figure 17.** Fusion power needed to create 100 μCi samples by the 10-s irradiation and 20-s cooling (left) at tally 15, and (right) at tally 25.

[3] Cheon MS, Seon CR, Pak S, Lee HG, Bertalot L. Development of the prototype pneumatic transfer system for ITER neutron activation system. Review of Scientific Instruments.

Neutron Activation System for ITER Tokamak http://dx.doi.org/10.5772/intechopen.75966 87

[4] Barnes CW, Loughlin MJ, Nishitani T. Neutron activation for ITER. The Review of

[5] Encheva A, Bertalot L, Macklin B, Vayakis G, Walker C. Integration of ITER in-vessel diagnostic components in the vacuum vessel. Fusion Engineering and Design.

[6] Lee Y, Dang J, Jo J, Chun K, Hwang Y, Cheon M, Lee H, Bertalot L. Preliminary study on capsule material for ITER neutron activation system. Fusion Engineering and Design.

[7] Vayakis G, Hodgson ER, Voitsenya V. Chapter 12: Generic diagnostic issues for a burn-

ing plasma experiment. Fusion Science and Technology. 2008;**53**:699-750

2012;**83**(10):10D303. DOI: 10.1063/1.4729673

2009;**84**:736-742

2014;**89**(9-10):1894-1898

Scientific Instruments. 1997;**68**:1-577. DOI: 10.1063/1.1147657

**Figure 18.** Fusion power needed to create 100 μCi samples by the 1000-s irradiation and 1000-s cooling (left) at tally 15, and (right) at tally 25.

#### **7. Summary**

The ITER neutron activation system that has been briefly presented in the earlier sections is under development by the Korean Domestic Agency of ITER. Despite the challenges driven by ITER's unprecedented thermal, electromagnetic and nuclear loads, those driven by high activation in full-power operation leading to very limited personnel access and the highest safety and reliability requirements [7], despite all these aspects, the presented NAS design proves to be suitable to satisfy ITER's measurement requirements.

## **Author details**


### **References**


**7. Summary**

and (right) at tally 25.

**Author details**

**References**

Vitaly Krasilnikov1,3\*, MunSeong Cheon2

3 Tokamak Energy Ltd, Abingdon, UK

2005;**45**:1503-1509

10.1063/1.2990857

The ITER neutron activation system that has been briefly presented in the earlier sections is under development by the Korean Domestic Agency of ITER. Despite the challenges driven by ITER's unprecedented thermal, electromagnetic and nuclear loads, those driven by high activation in full-power operation leading to very limited personnel access and the highest safety and reliability requirements [7], despite all these aspects, the presented NAS design

**Figure 18.** Fusion power needed to create 100 μCi samples by the 1000-s irradiation and 1000-s cooling (left) at tally 15,

and Luciano Bertalot1

[1] Krasilnikov A et al. Status of ITER neutron diagnostic development. Nuclear Fusion.

[2] Cheon MS, Pak S, Lee HG, Bertalot L, Walker C. In-vessel design of ITER diagnostic neutron activation system. Review of scientific instruments. 2008;**79**(10):10E505. DOI:

proves to be suitable to satisfy ITER's measurement requirements.

\*Address all correspondence to: vitaly.krasilnikov@iter.org

2 National Fusion Research Institute, Daejeon, Republic of Korea

1 ITER Organization, St. Paul-lez-Durance, France

86 Advanced Technologies and Applications of Neutron Activation Analysis

**Chapter 6**

Provisional chapter

0-Instrumental Neutron

**An Overview of the Establishment of Methodology to**

DOI: 10.5772/intechopen.83812

An Overview of the Establishment of Methodology to

**Analyse up to 5g-Sample by** *k***0-Instrumental Neutron**

The team of the Laboratory for Neutron Activation Analysis, Brazil, has been continuously improving the k0-instrumental neutron activation analysis, the k0-INAA method, having Jožef Stefan Institute, Slovenia, as partner researcher of the neutron activation technique. The group aims at answering the analytical requests of customers and the needs of the researches developed by the lab. The latest improvement was to establish a methodology to analyse up to 5 g-samples. The usual procedure in neutron activation analysis is to determine elemental concentrations in small samples of about 200 mg, a geometrical point source. The reason why these samples are used is that this geometry brings about a number of simplifications during irradiation and gamma spectrometry. This paper describes the steps carried out in the development of the large sample methodology that has already been published elsewhere and has been applied successfully. The results of some reference materials and samples are displayed. It is important to mention that this research has confirmed that any other laboratory applying k0-INAA is able to establish this methodology without having to modify its facilities, since the neutron self-shielding, gamma attenuation, and

Keywords: k0-instrumental neutron activation analysis, large sample, detector efficiency,

When an analytical result is available, several tasks had been accomplished before such as the routine procedure establishment, calibration of instruments, quality assurance and quality

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited.

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

k

**Activation Analysis, at CDTN, Brazil**

Activation Analysis, at CDTN, Brazil

Additional information is available at the end of the chapter

detector efficiency over the volume source are established.

neutron self-shielding, gamma-ray attenuation

Additional information is available at the end of the chapter

Maria Ângela de B.C. Menezes and

Maria Ângela de B.C. Menezes and

Analyse up to 5g-Sample by

http://dx.doi.org/10.5772/intechopen.83812

Radojko Jaćimović

Abstract

1. Introduction

Radojko Jaćimović

#### **An Overview of the Establishment of Methodology to Analyse up to 5g-Sample by** *k***0-Instrumental Neutron Activation Analysis, at CDTN, Brazil** An Overview of the Establishment of Methodology to Analyse up to 5g-Sample by k0-Instrumental Neutron Activation Analysis, at CDTN, Brazil

DOI: 10.5772/intechopen.83812

Maria Ângela de B.C. Menezes and Radojko Jaćimović Maria Ângela de B.C. Menezes and Radojko Jaćimović

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.83812

#### Abstract

The team of the Laboratory for Neutron Activation Analysis, Brazil, has been continuously improving the k0-instrumental neutron activation analysis, the k0-INAA method, having Jožef Stefan Institute, Slovenia, as partner researcher of the neutron activation technique. The group aims at answering the analytical requests of customers and the needs of the researches developed by the lab. The latest improvement was to establish a methodology to analyse up to 5 g-samples. The usual procedure in neutron activation analysis is to determine elemental concentrations in small samples of about 200 mg, a geometrical point source. The reason why these samples are used is that this geometry brings about a number of simplifications during irradiation and gamma spectrometry. This paper describes the steps carried out in the development of the large sample methodology that has already been published elsewhere and has been applied successfully. The results of some reference materials and samples are displayed. It is important to mention that this research has confirmed that any other laboratory applying k0-INAA is able to establish this methodology without having to modify its facilities, since the neutron self-shielding, gamma attenuation, and detector efficiency over the volume source are established.

Keywords: k0-instrumental neutron activation analysis, large sample, detector efficiency, neutron self-shielding, gamma-ray attenuation

## 1. Introduction

When an analytical result is available, several tasks had been accomplished before such as the routine procedure establishment, calibration of instruments, quality assurance and quality

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited. © 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

control (QA/QC), training of technical group, good laboratory practice and others. All of these requirements are needed to meet the demand for analytical values that are even increasing in all fields, contributing to environmental monitoring, individual and population health and economical decisions. According to the development of human knowledge, the requirements for quality have been diversified and increasing in several fields. Therefore, the demand for analytical data with smaller uncertainties and lower detection limits is expanding and more requirements are necessary to meet the quality required by the clients.

aliquot for analysis, for example, of archaeological ceramics. In addition, the low neutron flux of a low-power reactor can be compensated by increasing the amount of sample to be exposed

An Overview of the Establishment of Methodology to Analyse up to 5g-Sample…

http://dx.doi.org/10.5772/intechopen.83812

91

A possibility to overcome these problems is to analyse larger samples—samples of more than 0.5 g [25–32]. In order to obtain reliable analysis results, some parameters should be determined: (i) detector efficiency evaluation over the volume source, (ii) neutron flux depression due to absorption and scattering and (iii) the relative attenuation of gamma rays originating

During the irradiation, the neutron field is perturbed during absorption and scattering inside the sample. It is called neutron self-shielding. This can be overcome by experimentally determining the neutron flux distribution in real samples in a defined volume for a matrix [6, 33, 34]. The degree of gamma self-attenuation depends on a number of factors such as sample geometry, linear attenuation coefficient, material density, sample composition and photon energy [35].

The laboratories that have been applying the neutron activation to large samples (LS-INAA) analyse samples in a range of kilogrammes, and for this procedure, special facilities are required, for the activation as well as for the detection. For instance, in Delft, The Netherlands,

The LNAA determines chemical elemental concentrations following the usual procedure small cylindrical samples. The irradiations are carried out in the carousel facility of the TRIGA MARK I IPR-R1 reactor that operates at 100 kW with an average thermal neutron

clients' request, analysing several kinds of samples. It is often necessary to overcome the difficulties due to low neutron fluency, inhomogeneity of unknown sample and time consumption of analysis. For that reason, to analyse larger samples would be an attractive possibility. However, it is not allowed to change the infrastructure of irradiation; therefore, a study was developed to verify the possibility to analyse 5 g-samples, maximum mass content in the irradiation vial, 25 times larger than usual samples analysed. The k0-method of neutron activation analysis [21] would be applied and the current infrastructure for irradiation and gamma spectrometry facilities would be used. To develop this study, the mass of the small sample analysed was around 200 mg and the larger cylindrical sample,

Aiming at solving the main limitations when dealing with small samples and exploring a new possibility of analysis, a methodology of analysing larger samples or cylindrical samples was established in LNAA at CDTN [16, 36, 37]. All experiments were developed in geological matrix. The reason was that matrix is the one most used in routine elemental analysis at CDTN. All irradiations were performed in the carousel facility of the 100 kW TRIGA MARK I

IPR-R1 reactor under an average thermal neutron flux of 6.3 <sup>10</sup><sup>11</sup> cm<sup>2</sup> <sup>s</sup>

. The laboratory has a high demand of analysis, answering the

<sup>1</sup> and average

a facility was built to irradiate and measure samples from 2 to 50 kg [3, 26–31].

3. Development of the methodology applied at CDTN

1

to irradiation.

flux of 6.3<sup>10</sup><sup>11</sup> cm<sup>2</sup> <sup>s</sup>

around 5 g.

from different positions within the sample.

The nuclear analytical technique, NAA [1, 2], fulfils several requirements. It is well-known that NAA requires a non-chemical preparation—a non-destructive technique—and analyses a large number of elements simultaneously. Besides, it is a traceable technique [3, 4]. It presents sensitivity, multi-element ability, selectivity and versatility and determines chemical elements with precision and accuracy [5, 6]. That is why it is a powerful technique.

The technique is well established at the Laboratory for Neutron Activation Analysis, LNAA, located at the Nuclear Technology Development Centre (CDTN) sponsored by the Brazilian Commission for Nuclear Energy (CNEN), in Belo Horizonte, capital of the Brazilian state of Minas Gerais. The nuclear research reactor, the 100 kW TRIGA MARK I IPR-R1, has enabled the NAA to be applied determining the elemental concentration of different samples, such as soil, sediment, plants, food, medicines and biological tissues of humans and animals, among others [7–20]. The NAA has been applied through relative and parametric methods and has been applied meeting requests of customers both of CDTN and at industries, universities and other institutions. The technique has also been applied in researches of the LNAA. The standardised k0-method [21] was established in 1995, being the most efficient form of application of this nuclear analytical technique [8, 9]. The k0-method has been continuously improving along its nuclear data [22, 23], which can be found in the form of an Excel file, the k0-database 2015 [24].
