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[.]
Trang 1Tiểu 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
XÁC ĐỊNH HỆ SỐ k 0 CỦA 110 Ag VÀ 46m Sc CHO PHƯƠNG PHÁP PHÂN TÍCH
KÍCH HOẠT NEUTRON
DETERMINATION OF K 0 FACTOR OF 110 AG AND 46M SC FOR NEUTRON ACTIVATION ANALYSIS METHOD
DOANH-VAN HO 1 , MANH-DUNG HO 1 , VAN-GIAP PHAM 3 , TRUONG-SON TRUONG 4 AND VAN-CUONG TRINH 2
1
Center for Nuclear Technologies, 217 Nguyen Trai street, 70000, Vietnam
2
Dalat Nuclear Research Institute, 01 Nguyen Tu Luc street, 67000, Vietnam
3
Xuan Loc high school, Dong Nai province, 76000, Vietnam
4
HCMC University of Education, 280 An Duong Vuong street, 70000, Vietnam
*E-mail: hovandoanh@gmail.com
Tóm tắt: Một thiết lập thí nghiệm trên hệ chiếu mới đã từng được thực hiện cho việc xác định hệ số k 0 của các hạt nhân sống ngắn Trong đó, hệ chiếu ngắn và đo nhanh đã được hiệu chuẩn một cách cẩn thận và được mô tả chi tiết Sau đó, qui
trình được áp dụng vào việc xác định hệ số k 0 của 110 Ag (T 1/2 = 24 s) và 46m Sc (T 1/2 = 18,75 s) như là trường hợp điển hình
Kết quả của hệ số k 0 được xác định là 0,037 ± 0,002 đối với 110 Ag và 0,220 ± 0,005 đối với 46mSc Trong khi đó, hệ số k 0
của 110 Ag hiện tại đang được sử dụng trong phần mềm k0-DALAT là 0,0306 Giá trị này có sự khác biệt khoảng 20% so
với kết quả đo được trong nghiên cứu này Đối với kết quả đo hệ số k 0 của 46m Sc thì hoàn toàn phù hợp với các giá trị của các nghiên cứu trước đó của các tác giả khác Số liệu này sẽ được xem xét cho việc cập nhật vào phần mềm k0-DALAT để xác định nguyên tố Scandi thông qua hạt nhân sống ngắn 46m Sc
Từ khóa: hệ số k 0 , k 0 -NAA, Lò phản ứng Đà Lạt
Abstract: In this study, an experimental setup on new short irradiation system has been performed for determination of the
k 0 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 k 0 factor of 110 Ag (T 1/2 = 24 s) and 46m Sc (T 1/2 =
18.75 s) as a case in point The k 0 factor of were 0.037 ± 0.002 for 110 Ag and 0.220 ± 0.005 for 46mSc The k 0 factor of 110 Ag
currently used in k0-DALAT software is 0.0306 However, the k 0 factor of 110 Ag determined in this study is 0.037 with
significantly difference of 20% The k 0 factor of 46m Sc 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: k 0 factor, k 0 -NAA, Dalat research reactor
1 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 k 0 factor [1] Recently, the nuclear database of k 0 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 k 0 standardization in neutron activation analysis has been researched and applied to the Dalat research reactor (DRR) since 1984 [3]
Although the k 0 factor of short-lived nuclides have been determined by thermal neutron activation
technique since 1991 [4] However, k 0 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 k 0 factors are
necessary for recent applications and updating database for k0-DALAT sofware
In the k 0 standardization of NAA, the concentration of an analyte “a” is obtained by the equation [1, 2]:
(𝑁 𝑃 /𝑤𝑡 𝑚 𝑆𝐷𝐶) 𝐴𝑢× 1
𝑘 0,𝐴𝑢 (𝑎)×𝑓+𝑄0,𝐴𝑢(𝛼)
𝑓+𝑄 0,𝑎 (𝛼) ×𝜀𝑃,𝐴𝑢
Where “Au” refer to the co-irradiated gold monitor 197Au(n,γ)198Au, Eγ = 411.8 keV
k 0,Au(a) – k0 factor of monitor “m” (commonly Au) for analyte “a”
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Proceedings of Vietnam conference on nuclear science and technology VINANST-14
k0 factor is defined 𝑘0,𝐴𝑢(𝑎) = 𝑀𝐴𝑢 𝜃𝑎𝜎0,𝑎𝐼𝛾,𝑎
𝑀𝑎𝜃𝐴𝑢𝜎0,𝐴𝑢𝐼𝛾,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 k 0 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 k 0,m (a)
= k 0,Au (a) / k 0,Au (m)
The k 0 factor is experimentally measured according to the equation:
(𝑁 𝑃 /𝑤𝑡 𝑚 𝑆𝐷𝐶) 𝐴𝑢×𝑓+𝑄0,𝐴𝑢(𝛼)
𝑓+𝑄 0,𝑎 (𝛼) ×𝜀𝑃,𝐴𝑢
𝜀 𝑃,𝑎 (2)
Where N p is the net number of counts in the full energy peak (corrected for pulse losses), w is mass
of element, t m is measuring time, S = 1 – exp(-ti), is the decay constant, t i is the irradiation time, D =
exp(-td), td is the decay time, C = (1 – exp(-tm))/ tm , t m is the measurement time, f is the thermal to epithermal neutron flux ratio, Q 0 = I0/0 (resonance integral to 2200 ms-1 cross-section ratio), α is the measure for epithermal neutron flux distribution, approximated by 1/E 1+α dependence and p is the full-energy peak detection efficiency
3 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 1 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 4 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 1 Diagram of the auto-pneumatic transfer system installed at DRR
Absolute efficiency curves of GMX-4076 detector were used for calculation in Table 1 [7]:
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Section B: Nuclear physics, Nuclear data, Nuclear analysis and Accelerator
Table 1: The coefficients of fitting efficiency curves for calculation of k 0 factor
Table 2 The results of neutron spectrum parameters for calculation of k 0 factor [7]
To determine k0 factors, the Ag, Sc and Au monitors were irradiated and measured (repetition of 3 times for each monitor) The experimental parameters were presented in Table 3 and Table 4 The Sc minotors were measured at 10 cm The Ag monitors were measured at 5 cm Au monitors were measured at
5 cm and 10 cm The irradiation time and decay time are correct in 0.01 s
Table 3 The information of the monitors in the experiment
(mm)
Thickness (mm)
Length (mm)
Weight (mg)
Density (g/cm3)
Table 4 The irradiation, decay and measurement time for the k 0 factor determination
Distance from sample to
detector (mm)
46m
110
4 RESULTS AND DISCUSSION
Table 5 presents the experimental result for determination of k 0 factors for 110Ag and 46mSc nuclides
The k 0 factor of 110Ag nuclide determined in this study is 0.037 ± 0.002 The k 0 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 k 0 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)
46mSc 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
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Proceedings of Vietnam conference on nuclear science and technology VINANST-14
Table 5: The result of k 0 factor of this study and comparison with the other research
Nucl T1/2 (s) E (keV) kThis work,
0,Au (%RSD) Literature-k0,Au (%RSD)
Bias (%)
110Ag 24.56 657.5 4.5 0.0368 (3.2) 0.0374(2.0)
(P Z Hien, 1991) [4]
-1.6 0.0306 (0.4)
(Van Lierde S, 1999) [8]
20.0 0.03627 (1.7)
(Szentmikiosi L, 2006) [9]
1.4 0.0352 (1.7)
(Acharya R, 2012) [10]
4.5
46mSc 18.75 142.5 62 0.220 (2.2) 0.225 (2.4)
(Szentmikiosi L, 2006) [9]
-2.0 0.223 (5.4)
(Acharya R, 2010) [11]
-1.1
0.222 (2.5) (Acharya R, 2012) [10]
-0.7
5 CONCLUSION
Technical procedure for determination of k 0 factor was established for short-lived nuclides The
facility for experimental procedure was calibrated carefully for k 0 further measurements The k 0 factor of
110
Ag (T1/2 = 24 s) and 46mSc (T1/2 = 18.75 s) were determined in this work The k 0 factor of 46mSc is entirely
consistent with earlier research of other authors However, the k 0 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
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