Tiểu ban B Vật lý hạt nhân, Số liệu hạt nhân, Phân tích hạt nhân và Máy gia tốc Section B Nuclear physics, Nuclear data, Nuclear analysis and Accelerator 179 XÁC ĐỊNH HỆ SỐ k0 CỦA 110Ag VÀ 46mSc CHO P[.]
Tiểu ban B: Vật lý hạt nhân, Số liệu hạt nhân, Phân tích hạt nhân Máy gia tốc Section B: Nuclear physics, Nuclear data, Nuclear analysis and Accelerator XÁC ĐỊNH HỆ SỐ k0 CỦA 110Ag VÀ 46mSc CHO PHƯƠNG PHÁP PHÂN TÍCH KÍCH HOẠT NEUTRON DETERMINATION OF K0 FACTOR OF 110AG AND 46MSC FOR NEUTRON ACTIVATION ANALYSIS METHOD DOANH-VAN HO1, MANH-DUNG HO1, VAN-GIAP PHAM3, TRUONG-SON TRUONG4 AND VAN-CUONG TRINH2 Center for Nuclear Technologies, 217 Nguyen Trai street, 70000, Vietnam Dalat Nuclear Research Institute, 01 Nguyen Tu Luc street, 67000, Vietnam Xuan Loc high school, Dong Nai province, 76000, Vietnam HCMC University of Education, 280 An Duong Vuong street, 70000, Vietnam *E-mail: hovandoanh@gmail.com Tóm tắt: Một thiết lập thí nghiệm hệ chiếu thực cho việc xác định hệ số k0 hạt nhân sống ngắn Trong đó, hệ chiếu ngắn đo nhanh hiệu chuẩn cách cẩn thận mơ tả chi tiết Sau đó, qui trình áp dụng vào việc xác định hệ số k0 110Ag (T1/2 = 24 s) 46mSc (T1/2 = 18,75 s) trường hợp điển hình Kết hệ số k0 xác định 0,037 ± 0,002 110Ag 0,220 ± 0,005 46mSc Trong đó, hệ số k0 110Ag sử dụng phần mềm k0-DALAT 0,0306 Giá trị có khác biệt khoảng 20% so với kết đo nghiên cứu Đối với kết đo hệ số k0 46mSc hồn tồn phù hợp với giá trị nghiên cứu trước tác giả khác Số liệu xem xét cho việc cập nhật vào phần mềm k0-DALAT để xác định nguyên tố Scandi thông qua hạt nhân sống ngắn 46mSc Từ khóa: hệ số k0, k0-NAA, Lị phản ứng Đà Lạt Abstract: In this study, an experimental setup on new short irradiation system has been performed for determination of the k0 factor of short-lived nuclides The system for short irradiation and rapid measurement were calibrated carefully and described in detail Moreover, this work focused on determination of the k0 factor of 110Ag (T1/2 = 24 s) and 46mSc (T1/2 = 18.75 s) as a case in point The k0 factor of were 0.037 ± 0.002 for 110Ag and 0.220 ± 0.005 for 46mSc The k0 factor of 110Ag currently used in k0-DALAT software is 0.0306 However, the k0 factor of 110Ag determined in this study is 0.037 with significantly difference of 20% The k0 factor of 46mSc is entirely consistent with earlier research of other authors These results in this work will be evaluated for updating database of k0-DALAT software Keywords: k0 factor, k0-NAA, Dalat research reactor INTRODUCTION The k0-NAA standardization was a reliable and sensitive method that applied for determination of the quality and quantity of elemental concentration in the various samples The accuracy of the k0-NAA method directly depends on the k0 factor [1] Recently, the nuclear database of k0 factor has been updated for 2003, 2012 and 2015 [2] However, there are some data that have not been updated or were measured by the one laboratory Thereby it does not have much credibility The k0 standardization in neutron activation analysis has been researched and applied to the Dalat research reactor (DRR) since 1984 [3] Although the k0 factor of short-lived nuclides have been determined by thermal neutron activation technique since 1991 [4] However, k0 factor of some very short-lived nuclides were determined since 30 years and some of them were not approval Therefore, re-determination and re-valuation of k0 factors are necessary for recent applications and updating database for k0-DALAT sofware THE DEFINITION OF K0 FACTOR In the k0 standardization of NAA, the concentration of an analyte “a” is obtained by the equation [1, 2]: (𝑁 /𝑊𝑡 𝑆𝐷𝐶) 𝜌𝑎 = (𝑁 𝑃/𝑤𝑡 𝑚𝑆𝐷𝐶) 𝑎 × 𝑘 𝑃 𝑚 𝐴𝑢 0,𝐴𝑢 × (𝑎) 𝑓+𝑄0,𝐴𝑢 (𝛼) 𝑓+𝑄0,𝑎 (𝛼) × 𝜀𝑃,𝐴𝑢 𝜀𝑃,𝑎 (1) Where “Au” refer to the co-irradiated gold monitor 197Au(n,γ)198Au, Eγ = 411.8 keV k0,Au(a) – k0 factor of monitor “m” (commonly Au) for analyte “a” 179 Tuyển tập báo cáo Hội nghị Khoa học Cơng nghệ hạt nhân tồn quốc lần thứ 14 Proceedings of Vietnam conference on nuclear science and technology VINANST-14 k0 factor is defined 𝑘0,𝐴𝑢 (𝑎) = 𝑀𝐴𝑢 𝜃𝑎 𝜎0,𝑎 𝐼𝛾,𝑎 𝑀𝑎 𝜃𝐴𝑢 𝜎0,𝐴𝑢 𝐼𝛾,𝐴𝑢 where M is the atomic weight, is the isotopic abundance, 0 is the 2200ms-1 (n,γ) cross-section, and γ is the absolute gamma-ray intensity (emission probability) Although the k0 factors are defined versus Au (co-irradiated with the sample to be analyzed), the gold monitor can be replaced by any monitor ‘‘m’’ for which a k0,Au factor is available, because k0,m (a) = k0,Au (a) / k0,Au (m) The k0 factor is experimentally measured according to the equation: (𝑁 /𝑤𝑡 𝑆𝐷𝐶) 𝑘0,𝐴𝑢 = (𝑁 𝑃/𝑤𝑡 𝑚𝑆𝐷𝐶) 𝑎 × 𝑃 𝑚 𝐴𝑢 𝑓+𝑄0,𝐴𝑢 (𝛼) 𝑓+𝑄0,𝑎 (𝛼) × 𝜀𝑃,𝐴𝑢 𝜀𝑃,𝑎 (2) Where Np is the net number of counts in the full energy peak (corrected for pulse losses), w is mass of element, tm is measuring time, S = – exp(-ti), is the decay constant, ti is the irradiation time, D = exp(-td), td is the decay time, C = (1 – exp(-tm))/ tm, tm is the measurement time, f is the thermal to epithermal neutron flux ratio, Q0 = I0/0 (resonance integral to 2200 ms-1 cross-section ratio), α is the measure for epithermal neutron flux distribution, approximated by 1/E1+α dependence and p is the fullenergy peak detection efficiency EXPERIMENTAL The experiment was carried out using a short irradiation and rapid measurement system, connected to irradiation position of thermal column with the thermal neutron flux of (1.2 0.1) 1011 cm-2 s-1 [5] The transfer time of sample from irradiation position to detector (Ttrans) was 3.165 ± 0.002 s (including both Ttrans and the time required to start the detector) Timing information for both irradiation and counting would be instantly delivered to the workstation Characterizations of this system has been reported elsewhere and thus will not be described here [6] The operating principle of the PTS 13-2/TC is as shown in Figure The sample is loaded in loading sample (LS1) unit through sample changer (SE1) unit Then the sample is transferred to irradiation position by fresh air from valve 11 At the end of irradiation time, the sample is ejected by fresh air from valve 12 or valve 13 Next, sample passes relief unit (RU) to separation unit (SU) before going to counting chamber (CC) Sensor is used to initiate the measurement After the measurement, the sample is taken out through D4 V11, V12, V13, V14, V15 and V16 are the clean air valves to push the sample Figure Diagram of the auto-pneumatic transfer system installed at DRR Absolute efficiency curves of GMX-4076 detector were used for calculation in Table [7]: logε𝑝 =a0 +a1logE+a2 (logE)2 +a3 (logE)3+a4 (logE)4 (3) 180 Tiểu ban B: Vật lý hạt nhân, Số liệu hạt nhân, Phân tích hạt nhân Máy gia tốc Section B: Nuclear physics, Nuclear data, Nuclear analysis and Accelerator Table 1: The coefficients of fitting efficiency curves for calculation of k0 factor Distance a0 a1 a2 a3 a4 cm 10 cm 15 cm 18 cm -22,993 -8,297 -15,632 -23,032 34,146 9,502 21,836 32,912 -19,822 -4,943 -12,964 -19,232 5,008 1,059 3,352 4,915 -0,475 -0,085 -0,328 -0,473 Table The results of neutron spectrum parameters for calculation of k0 factor [7] Irradiation position 𝜑𝑡ℎ (n/cm2/s) 𝛼 𝑓 13-2 channel (4.2 0.1) x 1012 -0.038 ± 0.006 10.7 2.4 (1.24 0.03) x 10 0.092 0.035 195 Thermal column 11 To determine k0 factors, the Ag, Sc and Au monitors were irradiated and measured (repetition of times for each monitor) The experimental parameters were presented in Table and Table The Sc minotors were measured at 10 cm The Ag monitors were measured at cm Au monitors were measured at cm and 10 cm The irradiation time and decay time are correct in 0.01 s Table The information of the monitors in the experiment Monitor Shaping Al-0.1%Au 99.9%Sc 1%Ag-Al Foil Foil Wire Radius (mm) 5.44 2.21 1.00 Thickness (mm) 0.100 0.127 - Length (mm) 1.397 Weight (mg) 6.268 1.448 2.960 Density (g/cm3) 2.7 3.0 2.7 Table The irradiation, decay and measurement time for the k0 factor determination Nuclide 46m 110 Sc Ag ti (s) td (s) tm (s) 10 20 69 10 30 Distance from sample to detector (mm) 10 cm cm RESULTS AND DISCUSSION Table presents the experimental result for determination of k0 factors for 110Ag and 46mSc nuclides The k0 factor of 110Ag nuclide determined in this study is 0.037 ± 0.002 The k0 factor of 110Ag is entirely consistent with our earlier research on Dalat research reactor [4], (Szentmikiosi L, 2006) and (Acharya R, 2012) authors Howeve, there is significantly difference of 20% with (Van Lierde S, 1999) author The k0 factor of 46mSc nuclide determined in this study is 0.037 ± 0.002 This value is consistent with the results of other authors (Szentmikiosi L, 2006; Acharya R, 2012) There are some reasons for that: (1) 46m Sc emits only one gamma-ray with high emission probability; (2) Sc monitor have the purity of 99.9%, not mixed with Al Therefore, it is insignificantly affacted by Compton background from Al; (3) Sc is light element used in its purity form, it absorbs insignificantly gamma-rays The efficiency is also not much affected by the monitor geometry 181 Tuyển tập báo cáo Hội nghị Khoa học Công nghệ hạt nhân toàn quốc lần thứ 14 Proceedings of Vietnam conference on nuclear science and technology VINANST-14 Table 5: The result of k0 factor of this study and comparison with the other research Nucl 110 Ag 46m Sc T1/2 (s) E (keV) 24.56 657.5 4.5 18.75 142.5 62 This work, k0,Au (%RSD) 0.0368 (3.2) 0.220 (2.2) Literature-k0,Au (%RSD) 0.0374(2.0) (P Z Hien, 1991) [4] 0.0306 (0.4) (Van Lierde S, 1999) [8] 0.03627 (1.7) (Szentmikiosi L, 2006) [9] 0.0352 (1.7) (Acharya R, 2012) [10] 0.225 (2.4) (Szentmikiosi L, 2006) [9] 0.223 (5.4) (Acharya R, 2010) [11] 0.222 (2.5) (Acharya R, 2012) [10] Bias (%) -1.6 20.0 1.4 4.5 -2.0 -1.1 -0.7 CONCLUSION Technical procedure for determination of k0 factor was established for short-lived nuclides The facility for experimental procedure was calibrated carefully for k0 further measurements The k0 factor of 110 Ag (T1/2 = 24 s) and 46mSc (T1/2 = 18.75 s) were determined in this work The k0 factor of 46mSc is entirely consistent with earlier research of other authors However, the k0 factor of 110Ag determined in this work is significantly difference with current using value in k0-DALAT sofware Therefore, these results in this work will be evaluated for updating database of k0-DALAT software ACKNOWLEDGEMENTS This research is funded by the Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 103.04-2017.75 REFERENCES [1] Corte, F.D., The k0 standardization method - a move to the optimization of NAA, Habilitation Thesis University of Gent, Gent, 1987 [2] Corte, F.D and A Simonits, Recommended nuclear data for use in the k0 standardization of neutron activation analysis Atomic Data and Nuclear Data Tables, 2003 [3] Dung, H.M and P.D Hien, The application and development of k0-standardization method of neutron activation analysis at Dalat research reactor J Radioanal Nucl Chem, 2003 [4] Hien, P.Z., et al., Determination of k0 factors of short-lived nuclides by thermal neutron activation technique J Radioanal Nucl Chem, 1991 [5] Doanh HV, e.a., A new rapid neutron activation analysis system at Dalat nuclear research reactor Vietnam Nucl Sci Tech, 2014 [6] Doanh, H.V and H.M Dung, The upgrading of the cyclic neutron activation analysis facility at the Dalat research reactor J Radioanal Nucl Chem, 2018 [7] Giap, P.V., Xác định hệ số k0 Q0 số hạt nhân phóng xạ sống ngắn có chu kỳ bán rã nhỏ 100 giây Trường Đại học khoa học tự nhiên, Đại học quốc gia TP.HCM, 2017 [8] Lierde, S.V., et al., Determination of k0 and related nuclear data for short-lived radionuclides to be used in KAYZERO-NAA at DSM research Nuclear Instruments and Methods in Physics A, 1999 [9] Szentmiklosi, R.v Zs., and B T., Measurement of partial g-ray production cross-sections and k0 factors for radionuclides with chopped-beam PGAA Nuclear Instruments and Methods in Physics Research A, 2006 [10] Acharya, R., J Holzbecher, and A Chatt, Determination of k0-factors of short-lived nuclides and application of k0NAA to selected trace element Nuclear Instruments and Methods in Physics Research A, 2012 [11] Acharya, R., et al., Determination of k0-factors and validation of k0-INAA for short-lived nuclides J Radioanal Nucl Chem, 2010 182 ... experimental result for determination of k0 factors for 110Ag and 46mSc nuclides The k0 factor of 110Ag nuclide determined in this study is 0.037 ± 0.002 The k0 factor of 110Ag is entirely consistent... procedure for determination of k0 factor was established for short-lived nuclides The facility for experimental procedure was calibrated carefully for k0 further measurements The k0 factor of 110... (T1/2 = 24 s) and 46mSc (T1/2 = 18.75 s) were determined in this work The k0 factor of 46mSc is entirely consistent with earlier research of other authors However, the k0 factor of 110Ag determined