MINISTRY OF EDUCATION AND MINISTRY OF SCIENCE AND TRAINING TECHNOLOGY VIETNAM ATOMIC ENERGY INSTITUTE Phonesavanh Lathdavong EXPERIMENTAL VALIDATION OF NUCLEAR DATA IN THE k0-STANDARDIZED NEUTRON ACTIVATION ANALYSIS USING THE DALAT RESEARCH REACTOR Dissertation for the Doctor Degree of Atomic and Nuclear Physics Ho Chi Minh City, Vietnam – 2023 MINISTRY OF EDUCATION AND MINISTRY OF SCIENCE AND TRAINING TECHNOLOGY VIETNAM ATOMIC ENERGY INSTITUTE Phonesavanh Lathdavong EXPERIMENTAL VALIDATION OF NUCLEAR DATA IN THE k0-STANDARDIZED NEUTRON ACTIVATION ANALYSIS USING THE DALAT RESEARCH REACTOR Majors: Atomic and nuclear physics Code: 9. Ho Manh Dung 2. Hoang Sy Minh Tuan Ho Chi Minh City, Vietnam – 2023 Dedication I dedicate my dissertation work to my parents, brother, and sister, as well as to my love, whose words of encouragement and constant support have been with me throughout the entire challenging years of my doctorate program. Their unwavering love and care have always been beside me, and I am forever grateful for their support.
Ho Chi Minh City, … December 2023. Phonesavanh LATHDAVONG i Acknowledgments First of all, I would like to express my sincere gratitude to my supervisors, Assoc. Ho Manh Dung and Dr. Hoang Sy Minh Tuan, for their invaluable guidance and support throughout my studies.
Their practical insights and advice were instrumental in leading me through my dissertation thesis, and they provided numerous beneficial incentives for my future professional activities. I would also like to thank the Nuclear Training Center, which is belonging to Vietnam Atomic Energy Institute (VINATOM) for their excellent facilitation of all arrangements and documentation. Furthermore, I extend my gratitude to the Dalat Nuclear Research Reactor (DNRR) and the Center for Nuclear Technologies (CNT) in Ho Chi Minh City, particularly Dr. Ho Van Doanh, for their collaboration and accommodations during my Ph.
I am grateful to the International Atomic Energy Agency (IAEA) for their partial financial support and encouragement towards achieving my Ph. I would also like to acknowledge the generosity of my committee members for their expertise and precious time. Finally, I wish to express my heartfelt thanks to my beloved parents, siblings, colleagues, and institutional fellows for nurturing and establishing a conducive environment for my education. ii Contents Pages Dedication.
iii List of Symbols. vii Greek Alphabet. ix List of Abbreviations. xi List of Figures.
xii List of Tables .3 Chapter 1 The Overview of Neutron Activation Analysis .2 Neutron activation analysis as a trace element analytical method. Advantages of Neutron Activation Analysis. Disadvantages of Neutron Activation Analysis .5 Introduction to k0-NAA.6 Introduction to Q0 factor .7 Determination of k0,Au factors.8 Determination of Q0 factors .9 Determination of α, ƒ, 𝜙th .10 QA and QC for k0-NAA .11 The reference materials .12 The reason to conduct the experiment of this dissertation.13 Purpose of the dissertation .25 Chapter 2 Theoretical methods of neutron activation analysis .1 Theoretical aspects of neutron activation analysis .1 Types of neutron activation analysis .3 Derivation of computational equations .2 Standardization methods of neutron activation analysis.1 Absolute standardization method .2 Relative standardization method .3 Single-comparator standardization method .4 The k0 standardization method .1 The k0-NAA in different approaches .2 The k0 factor for complex decay .3 The k0 factors for threshold reactions .4 The k0 and Westcott formalization .3 The implementation of k0-standardization on DNRR .1 Calibration of HPGe detector.2 Full-energy peak detection efficiency .3 Peak-to-total ratio calibration .4 Neutron spectrum parameter determination .3 Comparator Fc and thermal neutron fluence rate determination .5 Validation of method .1 Determinaiton of k0 factors .2 Determinaiton of Q0 factors .58 Chapter 3 Experimental in Dalat nuclear research reactor .1 Designation of the DNRR .2 Introduction to Irradiation system for k0-NAA on DNRR .1 The Channel 7-1 as sample irradiation system in the DNRR .2 The k0-NAA in Dalat nuclear research reactor .3 Practical Experiment in Dalat nuclear research reactor .3 Measurement of monitors .4 The use of specialized program k0-IAEA .5 Sample irradiation of the seven short-lived radionuclides.6 Calibration of neutron spectra in Channel 7-1 .72 Chapter 4 Results and discussion .3 Conclusions and future work .2 New points of discussion .88 Papers published using for the dissertation .90 vii List of Symbols Symbols Meaning A Activity Asp Specific activity A0 Activity created at the end of irradiation C Correction for decay during counting c Concentration COI Correction factor for true-coincidence effects E Neutron energy E0 (Maxwellian) neutron energy (0.025 eV) ECd Effective Cd cut-off energy (0.55 eV in 1 mm Cd) Er Effective resonance energy f Thermal to epithermal neutron flux ratio fF Ratio of thermal neutron flux to fast neutron flux Gth Correction factor for thermal neutron self-shielding Ge Correction factor for epithermal neutron self-shielding I0 Resonance integral M Mass number NA Avogadro number Np Number of counts in full-energy peak corrected for pulse losses N0 Number of target nuclei n(v) neutron density per unit of velocity at neutron velocity v Q0 Resonance integral (1/E) to 2200 m·s-1 cross-section ratio Q0(α) Resonance integral (1/E1+α) to 2200 m·s-1 cross-section ratio R Reaction rate per nucleus capturing a neutron RCd Cadmium ratio viii Re Epicadmium reaction rate per nucleus capturing a neutron S Saturation factor Tn The temperature of the neutrons (or ambient temperature) T1/2 Half-life td Decay time ti Irradiation time tm Measurement time v Neutron velocity vCd Neutron velocity at cadmium cut-off point ECd vo Most probable neutron velocity at 20˚C (2 200 m.s-1) W Mass of elemental sample ix Greek Alphabet Symbols Meaning Epithermal neutron flux distribution parameter, approximated by a 1/E1+α distribution γ Gamma-emission probability ε Photopeak efficiency εp Full-energy peak detection efficiency Total resonance width 𝛾 Radiative resonance width n Neutron resonance width Decay constant σ Thermal neutron cross-section σ0 Thermal neutron cross-section at 2200 m.s-1 r Average cross-section of the fission neutron spectrum 235U Isotopic abundance Neutron flux th Thermal neutron flux epi Epithermal neutron flux f Fast neutron g (Tn ) Westcott coefficient x List of Abbreviations CSC Compton Suppression Counting DNRR Dalat Nuclear Research Reactor ENAA Epithermal Neutron Activation Analysis FNAA Fast Neutron Activation Analysis HPGe High Purity Germanium detector IAEA International Atomic Energy Agency INAA Instrumental Neutron Activation Analysis k0-IAEA IAEA software for k0-NAA method k0-NAA Neutron Activation Analysis based on k0 method k0-INAA Instrumental neutron activation analysis based on k0 method NAA Neutron Activation Analysis SMELS Synthetic multi-element standards SRMs Standard Reference Materials TNAA Thermal Neutron Activation Analysis. xi The List of Figures Pages Fig.1 The (n, ) reaction schematically.
The principle of self-verification. The elements available for determination by k0-NAA .3 The element for medium-lived radionuclides (T1/2 = 5 h – 10 days) .4 The element detection limits of NAA in environmental sample .5 The element for short-lived radionuclides (T1/2 = 12s - 5 h) .6 The element for long-lived radionuclides (T1/2 >10 days). A typical neutron flux scheme in a nuclear fission reactor .1 Diagram of neutron activation analysis types .2 The distribution of neutrons according to their energy in the nuclear reactor .3 Dependence of cross-section on the neutron energy .4 The calibration of necessary spectrum corrections for P/T.1 The layout of the reactor and its main components in vertical .2 The layout of the reactor and its main components in horizontal .3 DNRR cross-section .4 Diagram of PTS system for irradiation of sample .5 PTS system uses sample containers and sample carrying containers .6 Conduct sample screening.7 The pneumatic sample transfer machine for the channel 7-1 .8 HPGe detector GMX-30190 in DNRR .9 Efficiency calibration curve obtained from the height 136 mm to GMX30190 HPGe detector by using 152Eu .10 Efficiency calibration curve obtained from the heigh 51 mm to GMX30190 HPGe detector by using 152Eu .1 k0 values of this work compared to other references .2 k0 data of this work for 52V compared to other references .3 k0 data of this work for 66Cu compared to other references .4 k0 data of this work for 2167.4 Cl compared to other references .5 k0 data of this work for 1642.7Cl compared to other references .6 k0 data of this work for 134m Cs compared to other references.7 k0 data of this work for 128I-442.9 compared to other references .8 k0 data of this work for 140La-328 compared to other references .9 k0 data of this work for 140La-1596 compared to other references .10 k0 data of this work for 140La-487 compared to other references .11 k0 data of this work for 56Mn-1810.7 compared to other references .12 k0 data of this work for 56Mn-846.8 compared to other references .82 xiii The List of Tables Pages Table 1.1 Assigned values with the estimated expanded uncertainty U with a coverage factor of 2, corresponding to a level of confidence of about 95% [32] .1 The specification of the Dalat Nuclear Research Reactor.2 Description of sample preparation conditions under the k0-IAEA program .3 Neutron spectral parameters of sample in channel 7-1 in the thermal column [41].5 The irradiation, decay and counting times for determination of k0 factor .6 SRMs and comparator information .7 Irradiation channel neutron spectral parameter .8 Nuclear parameters condition for k0-NAA .1 Experimental k0, Au -factors of the short- and medium-lived radionuclides compared to the k0 reference using Channel 7-1 facility at DNRR.2 Relative standard uncertainties of parameters in the k0-NAA standardization .3 Values of k0,Au determined by this work and the other authors .4 The comparison of analysis results based on the experimented and referenced k0,Au factors. 85 xiv Tóm tắt Luận án với tên đề tài: “Phê chuẩn thực nghiệm các số liệu hạt nhân trong phân tích kích hoạt neutron dựa trên phương pháp chuẩn hóa k0 sử dụng Lò phản ứng hạt nhân Đà Lạt” tập trung vào việc tiến hành thực nghiệm đánh giá các số liệu hạt nhân được yêu cầu bởi phương pháp phân tích kích hoạt neutron theo chuẩn k0 (ký hiệu là k0-NAA): các hệ số k0 – tổ hợp các hằng số hạt nhân (khối lượng nguyên tử, M; độ phổ biến đồng vị, ; hiệu suất phát gamma, ; và tiết diện bắt neutron nhiệt, 0).
Nghiên cứu nhằm đánh giá các hệ số k0 của 7 hạt nhân phóng xạ có thời gian sống ngắn (cỡ phút) và trung bình (cỡ vài giờ), bao gồm: 66Cu, 52V, 38Cl, 134mCs, 128I, 140La và 56Mn, được xác định bằng thực nghiệm tại Lò phản ứng hạt nhân Đà Lạt (DNRR). Phê chuẩn thực nghiệm là quá trình đánh giá bằng thực nghiệm các hệ số k0 phù hợp với mục đính sử dụng trong phương pháp k0-NAA. Tiến hành thực hiện k0-NAA sử dụng bộ số liệu k0 mới để xác định hàm lượng các nguyên tố trong mẫu chuẩn so với giá trị hàm lượng đã được xác nhận. Độ lệch giữa kết quả thực nghiệm xác định các hệ số k0 mới với giá trị tham khảo nhỏ hơn 7%.
Từ đó, áp dụng các hệ số k0 mới trong phương pháp k0-NAA tại DNRR cho kết quả hàm lượng các nguyên tố trong mẫu chuẩn so với giá trị xác nhận nằm trong khoảng 7-11%. Luận án cũng thảo luận về phương pháp thực nghiệm tại DNRR, bao gồm việc xác định đặc trưng của kênh chiếu xạ neutron 7-1; hiệu chuẩn hệ phổ kế gamma dùng đầu dò bán dẫn siêu tinh khiết HPGe; và xử lý số liệu mà phương pháp k0-NAA yêu cầu đối với các thông số thực nghiệm (thông số trường neutron, hiệu suất detector, các hiệu chính, v. Nghiên cứu này lần đầu tiên áp dụng phương pháp “tự đặc trưng hóa” cho Kênh 7-1 tại DNRR sử dụng các mẫu chuẩn đa nguyên tố tổng hợp (SMELS). Phương pháp “tự đặc trưng hóa” được đánh giá là đơn giản và thuận tiện về mặt thực nghiệm cho kết quả phù hợp với phương pháp truyền thống sử dụng các lá dò độc lập.