- Email: [email protected]
Current status of JAEA-AMS-TONO in the 20th year
Nuclear Inst. and Methods in Physics Research B xxx (xxxx) xxx–xxx
Contents lists available at ScienceDirect
Nuclear Inst. and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb
Current status of JAEA-AMS-TONO in the 20th year Yoko Saito-Kokubua, , N. Fujitaa, M. Miyakea, T. Watanabea, C. Ishizakaa, N. Okabea, T. Ishimarua, A. Matsubarab, A. Nishizawab, T. Nishiob, M. Katob, H. Torazawab, N. Isozakib ⁎
a b
Japan Atomic Energy Agency, Toki, Gifu 509-5102, Japan Pesco Corp., Ltd., Toki, Gifu 509-5123, Japan
ARTICLE INFO
ABSTRACT
Keywords: AMS JAEA-AMS-TONO C-14 Al-26 Be-10 I-129
JAEA-AMS-TONO has been in operation at the Tono Geoscience Center, Japan Atomic Energy Agency since 1998 and 20 years have passed from the beginning of its utilization. The AMS has been used to measure 14C, 10Be and 26 Al. The main use is measurement of 14C in geological samples for dating studies in neotectonics and hydrogeology, in support of the research on geosphere stability applicable to the long-term isolation of high-level radioactive waste. In order to increase the speed of sample preparation, we introduced an automated graphitization equipment and made a gas-strip line to collect dissolved inorganic carbon in groundwater samples. Measurement of 10Be and 26Al has been used for geoscience studies and the detection limit in the measurement of 10Be was improved. Recently optimization of AMS settings for 129I-AMS has been progressed.
1. Introduction The JAEA-AMS-TONO facility at the Tono Geosciences Center (TGC), Japan Atomic Energy Agency (JAEA) installed an accelerator mass spectrometer (AMS) manufactured by National Electrostatics Corporation (US), utilized a Model 15SDH-2 PelletronTM accelerator with a maximum terminal voltage of 5 MV at March 1997 and 20 years have passed from the beginning of its utilization [1]. This AMS has mainly been used to determine the age of geological samples using long half-life cosmogenic nuclides, such as radiocarbon (14C), bellium-10 (10Be) and aluminum-26 (26Al) in studies into long-term geological stability as a basic research and development related to the geological disposal of high-level radioactive waste [1–5]. The studies into longterm geological stability include characterization of past and present geological events of crustal deformations and igneous activities such as fault activity and volcanic eruption. Date of the appearance and speed of the geological events are important information of the studies. The JAEA-AMS-TONO is the main instrument in the TGC because this is the most used instrument for dating in the TGC and JAEA-AMS-TONO has been used to measure 14C since the beginning of the installation of the AMS as radiocarbon dating is a standard method for determination of ages of organic matter such as wood, charcoal, shell, soil and groundwater in the age range of present to 60,000 year. Recently, other dating method using the other long half-life cosmogenic nuclides is increasing demanded. For the sake of estimation of the exposure age of basement rocks and the denudation rate, we started routine 10Be-AMS from the
⁎
Japanese fiscal year (FY) of 2013 and 26Al-AMS from 2015. Thus the AMS is also available to the JAEA’s common-use facility program, which is shared use of the AMS for researchers belonging to other research organizations. Moreover we have developed 129I-AMS for dating groundwater and investigation of the behavior of iodine in the environment. This paper is a status report of the JAEA-AMS-TONO during the past couple of decades and the recent improvements. 1.1. Description of the AMS The AMS is a versatile system based on a 5 MV tandem pelletron type accelerator [1]. The AMS has two ion sources; a 40-target MCSNICS ion source and a 12-target MGF-SNICS. Now the MC-SNICS is only used and the MGF-SNICS was shut down. Other equipment on the beam line except for a detector of a gas ionization chamber have not been changed since the installation of the AMS. The detector consists of cathode electrode, grid and anodes of five ΔE electrodes [6]. The ΔE electrodes determine the specific of energy loss arising in their respective regions. This enables to distinguish the spectrum of desired nuclide from other spectra of interfering particles and has a beneficial effect on discrimination between isobars. Measurement condition of the AMS was shown in Table 1. The AMS of 14C, 10Be and 26Al has already been used for routine measurements and the 129I AMS has been developed. The total measurement time and samples have exceeded 20,000 h and 16,000 samples in March 2017. Fig. 1 shows the annual operation time and number of samples after the
Corresponding author. E-mail address: [email protected] (Y. Saito-Kokubu).
https://doi.org/10.1016/j.nimb.2019.03.015 Received 12 March 2018; Received in revised form 4 October 2018; Accepted 9 March 2019 0168-583X/ © 2019 Elsevier B.V. All rights reserved.
Please cite this article as: Yoko Saito-Kokubu, et al., Nuclear Inst. and Methods in Physics Research B, https://doi.org/10.1016/j.nimb.2019.03.015
Nuclear Inst. and Methods in Physics Research B xxx (xxxx) xxx–xxx
Y. Saito-Kokubu, et al.
Table 1 Summary of measurement condition for the AMS systems. 14
Status Terminal Voltage Target (Ratio by weight) Current Injection Transmission Ionization chamber Count rate (Sample) Measurement Ratio Background (Sample) *1 *2 *3 *4 *5
10
C
Routine 4.5 MV Graphite : Fe powder (1:1) 15 – 20 μA (C-) Sequential 12C: 0.3 ms, 13C: 0.9 ms, 98.6 ms 48 – 58% (12C) ΔE1 – ERes 60 cps (SRM4990C(HOxII)@NIST)
14
C:
14 4+ 12 4+ 13 4+ 12 4+
C / C , C / C < 2 × 10-16 (< 0.03 pMC) (Graphite@ Wako*3)
26
Be
129
Al
I
Routine 4.6 – 4.8 MV BeO : Nb powder (1:4)
Routine 4.3 MV Al2O3 : Ag powder (1:4)
1 – 3 μA (BeO-) Simultaneous (10Be16O, 9 Be17O) ∼ 20% (9Be) ΔE1 – E2 (with gas cell) 45 cps (01–5-1@California Univ.*1) 10 Be3+/17O5+ (for 9Be) < 5 × 10-15 (BeO@ Merck*4)
∼ 0.1 μA (Al-) Sequential 26Al: 98 ms,
Test 3.5 MV AgI : Nb powder (1:4)
27
Al: 1 ms
34 – 39% (27Al) ΔE1 – ERes 15 cps (01–4-1@ California Univ.
*2
)
26
Al3+/27Al3+ < 1 × 10-14 (Al2O3 prepared from the standard solution for AAS*5@Wako*3)
∼ 0.7 μA (I-) Sequential 129I: 99 ms, 127 I: 1 ms ∼ 0.2% (127I) ΔE1 – ERes 50 cps (SRM3230@NIST) 129 5+ 127 5+
I / I Under test measurement
01–5-1: The ICN standard of 01–5-1 reported by Nishiizumi [8]. 01–4-1: The ICN standard of 01–4-1 reported by Nishiizumi [9]. Wako: Wako Pure chemical Industries, Ltd., Japan Merck: Merck Ltd., Germany AAS: Atomic absorption spectrometry
I-129 Al-26
1,500
Be-10 C-14
1,000
500
2016
2015
2014
2013
2012
2011
2010
2009
2008
2007
2006
2005
2004
2003
2002
2001
2000
1999
1998
0 1997
Operation time (h) and samples
2,000
Japanese fiscal year Fig. 1. Annual operation time (open circles) and sample number (bars).
installation. When about 10 years passed, some equipment issues broke down and staffs turned over, which caused that AMS was not operational. However the equipment issues were troubleshot and new staffs have increased the stability of the staff. These leads an operating rate of the AMS becomes steadily increasing and about a thousand samples per a year in 5FY’s past have been measured by the AMS.
the JAEA’s website and some of them were reported in scientific journals [19–22]. Recent measurement quality of the 14C-AMS is shown in Fig. 2. Arithmetic means of the results of reference materials of C6 (sucrose), C5 (wood) and C1 (marble) from International Atomic Energy Agency (IAEA) are 149.8 ± 3.3 (1σ) pMC (percent Modern Carbon), 23.10 ± 0.41 (1σ) pMC and 0.13 ± 0.06 (1σ) pMC, respectively. The results are corresponding to the nominal values [23] and our previous results [5]. In order to increase the speed of sample preparation, an automated graphitization equipment (AGE3, Ionplus, Switzerland) was introduced at 2017. A zeolite carbon dioxide (CO2) trap and reactors of the AGE3 was connected to the existing elemental analyzer (Vario Micro cube, Elementar Analysensysteme GmbH, UK) coupled on to a stable isotope ratio mass spectrometer (IsoPrime100, Isoprime Ltd., UK) [5]. Sample preparation using this equipment has high throughput of 7 samples per 4 h. Table 2 shows pMC of the IAEA standard samples prepared by the equipment. Measured values of the IAEA standard samples are consistent with their reference values. Therefore, we started to use it for graphite production of regular samples, which contain about 1 mg of carbon. Dissolved inorganic carbon (DIC) in groundwater sample is usually collected as carbonate by a chemical precipitation method [ex. 24,25]. In this method, the DIC is precipitated into strontium carbonate or barium carbonate, and then oxidized with phosphoric acid (H3PO4) to extract CO2. However the method is time-consuming and has low
1.2. Carbon-14 AMS The 14C-AMS has been used routinely since the FY of 1998 for measurement of 14C in geological samples for dating studies in neotectonics and hydrogeology. Especially in neotectonics study, 14C dating is one of the most useful dating methods. As geological events such as fault activity, volcanic eruption and generation of tsunami occur with a period of several hundreds or thousands, we have applied to the 14C dating to make accurate estimates of the occurrence time of these geological events; for example, Atera fault [9], Yoro fault [10,11,12], Senya fault [13], Sakurajima volcano [14], climate change [15]. Moreover, we use the 14C-AMS to study soil carbon dynamics by using 14C released from nuclear tests as a tracer for the carbon source [16,17] and to estimate the age of cultural property [18]. The 14C-AMS has also been used for studies under JAEA’s common-use facility program since the program stared at the fiscal year of 2006. We have accepted 39 projects containing 1322 samples until the FY of 2017. These projects cover a wide variety of study fields: geoscience, environment science and archaeology. The project reports were open to the public on 2
Nuclear Inst. and Methods in Physics Research B xxx (xxxx) xxx–xxx
Y. Saito-Kokubu, et al.
(a) C6
(150.61±0.11)
(a) 01-5-1 ((2.709±0.030)×10-11)
(b) 01-5-4 ((2.851±0.031)×10-12)
(b) C5 (23.05±0.02)
(c) BeO
(c) C1
(0.00±0.02)
Fig. 3. 10Be/9Be ratios in standard materials supplied by California University [7] (01–5-1 (a) and 01–5-4 (b)) and BeO (c) prepared from the standard solution for ICP from Merck Ltd. at 2015–2016. Parentheses and lines in (a) and (b) show the nominal values [7].
2016 FY Fig. 2. Percent Modern Carbon (pMC) in the IAEA reference materials C6 (a), C5 (b) and C1 (c) at 2016 FY (April 2016 – March 2017). Parentheses in (a) – (c) and lines in (a) and (b) show the nominal values [18].
1.3. Beryllium-10 AMS The 10Be-AMS has started routinely measurement since the FY of 2013. As beryllium-10 produced in terrestrial quartz make it possible to estimate rate of erosion, weathering, exposure of rocks, we have applied for dating studies in neotectonics. Fujisawa et al. reported denudation rates calculated from 10Be/9Be ratios in sediments of rivers flowing to Lake Biwa [27]. We have also started utilization under the JAEA’s common-use facility program and accepted one study (5 samples) under the JAEA’s common-use facility program from the FY of 2013 to the FY of 2017. Pachri et al. reported relationships between sediments concentrations of 10Be and morphometric aspect in Sangun catchment area, Fukuoka [28]. The measurement quality of the 10Be-AMS is shown in Fig. 3. Arithmetic means of the results of standard materials of 01–5-1 and 01–54 supplied by California University [7] are (2.71 ± 0.03) × 10-11 (1σ) and (2.86 ± 0.05) × 10-12 (1σ), respectively. The results agree with the nominal values [7]. The mean of beryllium oxide (BeO) prepared from the standard solution for ICP from Merck Ltd. is (0.90 ± 0.55) × 10-14 (1σ). This shows that background level has been kept constant and low enough to measure samples in applied studies. Recently, we try to improve detection limit to measure low 10Be/9Be ratio [29]. As 7Be is produced by the reaction 10B(p, α)7Be at the entrance of a gas cell and the distribution of the 7Be in energy spectra overlap that of 10Be, detection limit in the measurement of 10Be was
Table 2 pMC of IAEA standard samples.
C1 C4 C5 C6 C7 C9
(Carbonate) (Wood) (Wood) (Sucrose) (Oxalic acid) (Wood)
N
pMC (%) [Reference value]
3 3 6 6 3 6
0.15 ± 0.02 [0.00 ± 0.02] 0.19 ± 0.04 [0.20–0.44] 23.38 ± 0.13 [23.05 ± 0.02] 152.4 ± 1.5 [150.61 ± 0.11] 49.35 ± 0.22 [49.35 ± 0.12] 0.33 ± 0.02 [0.12–0.21]
reproducibility to collect the precipitation (carbonate) and to measure 14 C concentration. Therefore, we applied a gas-strip method using by a self-built gas-strip line to collect the DIC [26]. This gas-strip line can be attracted on bottles which contains 300, 500 and 1000 ml of water samples. The DIC is extracted as CO2 gas from the water samples on adding H3PO4. After the extraction, bubbling of the water with N2 gas for 5 min encourage to extract CO2 gas. The CO2 gas is collected and purified at traps. Recovery rates of carbon using by this gas-strip line from groundwater were more than 85%. 3
Nuclear Inst. and Methods in Physics Research B xxx (xxxx) xxx–xxx
Y. Saito-Kokubu, et al.
indicated that the data quality of the 26Al-AMS can be accepted for the routinely measurement. Therefore we have started routinely measurement and utilization under the JAEA’s common-use facility program since the FY of 2015. The measurement quality of the 26Al-AMS is shown in Fig. 4. Arithmetic means of the results of standard materials of 01–4-1 and 01–51 supplied by California University [8] and aluminum oxide (Al2O3) prepared from the standard solution for the atomic absorption spectrometry (AAS) from Wako Pure chemical Industries, Ltd. (Wako) are (7.44 ± 0.05) × 10-11, (4.70 ± 0.10) × 10-12 and (0.9 ± 0.6) × 1014 , respectively. The results if the standard materials are consistent with the nominal values [8] and the result of Al2O3 shows background level constant and low enough to measure samples in applied studies.
(a) 01-4-1((7.444 ±0.082)×10-11)
(b) 01-5-1((4.694±0.052)×10-12)
1.5. Iodine-129 Groundwater such as fossil salt water is one of the indicators to assess geological disposal in coastal areas. As the fossil salt water is very old, 129I/127I dating is effective to estimate age of the fossil salt water. The old fossil salt water has low ratio of 129I/127I (10-15 level, [30]), which need that 129I-AMS has low background. The JAEA-AMS-TONO has possibility to measure low ratio of 129I/127I in the fossil salt water because the JAEA-AMS TONO is not contaminated by samples with high ratios which are collected around reprocessing plants and disabled nuclear plants and can have high terminal voltage to 5 MeV. In order to measure 129I/127I ratio for dating of groundwater and for investigation of the behavior of iodine in the environment, a 129I-AMS has been in an early phase of development at JAEA-AMS-TONO. We succeeded detection of 129I ions in the detector of the gas ionization chamber, and then have repeatedly performed test measurements of standard samples. In addition, we are studying about sample preparation method to extract iodine. So routinely measurement will start in the next few years.
(c) Al2O3
2. Summary
improved by 7Be-counting suppression due to gate size reduction on an energy spectrum of the ionization detector and additional processes as mentioned below; cleaning by acetone and dry of high temperature (100 °C × 1 h) of Havar® foil that is used as a window at an inlet of the gas cell in front of the gas ionization chamber, increase of terminal voltage from 4.7 MV to 4.8 MV, reduction of half-length of a cable from the ionization detector to the preamplifier, electromagnetic shield of the cable wrapping with Al foil, change of anodes in the detector from Eres to E2. These processes leaded that the 10Be/9Be ratios in BeO prepared from the standard solution for ICP from Merck Ltd. became 1/3 lower than the values obtained before.
As twenty years has passed since the establishment of the JAEAAMS-TONO, the JAEA-AMS-TONO enables us to be available the multinuclide AMS for cosmogenic nuclides analyses (14C, 10Be, 26Al) to use dating of geological samples for geoscience studies. The AMS setting and some sample preparation equipment have improved to increase efficiency of measurement of samples and reduce background. We will promote development of the multi-nuclide AMS including the addition of 129I-AMS, renovation of the facility, the AMS and the sample preparation equipment and ingenuity of their operation to high throughput of measurement and increase of use of application studies. Though the AMS and the sample preparation equipment become order, daily check will find small defects and eliminate the causes promptly. Moreover the JAEA-AMS-TONO will serve the most important instrument to measure radiometric nuclides in the TGC because the TGC push forward to play a central role in the center of excellence for development of radiometric dating methods for geological sample and human resource in close coordination and cooperation with universes and other research institutes.
1.4. Aluminum-26 AMS
Acknowledgments
To start routinely measurement, the tuning of the AMS and test measurement has been progressed. As results of test measurement using diluted ICN standard samples provided by California University [8] were comparable with the performance of the MALT (Micro Analysis Laboratory, Tandem accelerator), Univ. of Tokyo, Japan, we performed intercomparison test with the MALT as a final test measurement [24]. Aluminum oxide of the ICN standard samples prepared at the JAEAAMS-TONO were measured at the JAEA-AMS-TONO and the MALT and results obtained from both laboratories were consistent. These results
This study was carried out under a contract with Ministry of Economy, Trade and Industry (METI), Japan as part of its R&D supporting program for developing geological disposal technology. The authors thank Prof. Matsuzaki for test measurement of Al.
Fig. 4. 26Al /27Al ratios in standard materials supplied by California University [8] (01–4-1 (a) and 01–5-1 (b)) and Al2O3 (c) prepared from the standard solution for the AAS from Wako Pure chemical Industries, Ltd. at 2014 and 2016. Parentheses and lines in (a) and (b) show the nominal values [8].
References [1] S. Xu, S. Ito, T. Iwatsuki, M. Abe, M. Watanabe, Nucl. Instrum. Methods Phys. Res., Sect. B 172 (2000) 8.
4
Nuclear Inst. and Methods in Physics Research B xxx (xxxx) xxx–xxx
Y. Saito-Kokubu, et al. [2] S. Itoh, M. Abe, M. Watanabe, S. Nakai, H. Touyama, S. Xu, Nucl. Instrum. Methods Phys. Res. Sect. B 223–224 (2004) 100. [3] Y. Saito-Kokubu, A. Nishizawa, M. Suzuki, Y. Ohwaki, T. Nishio, A. Matsubara, T. Saito, T. Ishimaru, K. Umeda, T. Hanaki, Nucl. Instrum. Methods Phys. Res., Sect. B 294 (2013) 43. [4] A. Matsubara, Y. Saito-Kokubu, A. Nishizawa, M. Miyake, T. Ishimaru, K. Umeda, in: Geochronology - Methods and Case Studies, Nils-Axel Morner, ed. InTech, 2014, p. 3. [5] Y. Saito-Kokubu, A. Matsubara, M. Miyake, A. Nishizawa, Y. Ohwaki, T. Nishio, K. Sanada, T. Hanaki, Nucl. Instrum. Methods Phys. Res., Sect. B 361 (2015) 48. [6] C. Maden, P.A.F. Anastasi, A. Dougans, S.P.H.T. Freeman, R. Kitchen, G. Klody, C. Schnabel, M. Sundquist, K. Vanner, S. Xu, Nucl. Instrum. Methods Phys. Res., Sect. B 259 (2007) 131. [7] K. Nishiizumi, M. Imanura, M.W. Caffee, J.R. Southon, R.C. Finkel, J. McAninch, Nucl. Instrum. Methods Phys. Res., Sect. B 258 (2007) 403. [8] K. Nishiizumi, Nucl. Instrum. Methods Phys. Res., Sect. B 223–224 (2004) 388. [9] R. Doke, K. Yasue, D. Hirouchi, Y. Saito-Kokubu, A. Matsubara, Active Fault Res. 40 (2014) 43. [10] Y. Niwa, T. Sugai, T. Ogami, M. Tajikara, K. Yasue, T. Saito, O. Fujiwara, Quatern. Res. 48 (2009) 339. [11] Y. Niwa, T. Sugai, T. Ogami, M. Tajikara, K. Yasue, O. Fujiwara, J. Geogr. 119 (2010) 668. [12] Y. Niwa, T. Sugai, K. Yasue, Y. Saito-Kokubu, Trans., Jpn. Geomorphol. Union 32 (2011) 201. [13] T. Imaizumi, K. Kagohara, K. Otuki, A. Miwa, H. Kosaka, T. Nohara, Active Fault Res. 26 (2006) 71 (in Japanese). [14] M. Ikuta, M. Niwa, T. Danhara, T. Yamashita, S. Maruyama, T. Kamataki, T. Kobayashi, H. Kurosawa, Y. Saito-Kokubu, T. Hirata, J. Geol. Soc. Japan 122 (2016) 89. [15] T. Sasaki, T. Sugai, M. Yanagida, Y. Morita, A. Furusawa, O. Fujiwara, T. Moriya, T. Nakagawa, T. Miyagi, Quatern. Res. 45 (2006) 275 (in Japanese). [16] T. Nakanishi, M. Atarashi-Andoh, J. Koarashi, Y. Saito-Kokubu, K. Hirai, Eur. J. Soil Sci. 63 (2012) 495.
[17] T. Nakanishi, M. Atarashi-Andoh, J. Koarashi, Y. Saito-Kokubu, K. Hirai, J. Environ. Radioact. 128 (2014) 27. [18] Y. Saito-Kokubu, A. Matsubara, T. Ishimaru, M. Miyake, A. Nishizawa, Y. Ohwaki, T. Nishio, Archaeological reports in Toki city at the fiscal year of 2013 (Toki-city education committee, 2014), pp. 28–30. [19] M. Okuno, T. Torii, H. Naruo, Y. Saito-Kokubu, T. Kobayashi, Radiocarbon 54 (2012) 351. [20] M. Okuno, T. Nakamura, N. Geshi, K. Kimura, Y. Saito-Kokubu, T. Kobayashi, Nucl. Instrum. Methods Phys. Res., Sect. B 294 (2013) 602. [21] Ma.H.T. Mirabueno, M. Torii, E. P. Laguerta, P.J. Delosreyes, E.B. Bariso, M. Okuno, T. Nakamura, T. Danhara, Y. Saito-Kokubu, T. Fujiki, T. Kobayashi, J. Geogr., accepted. [22] M. Okuno, S. Nagaoka, Y. Saito-Kokubu, T. Nakamura, T. Kobayashi, Radiocarbon 59 (2017) 483. [23] Reference sheet for quality control materials, IAEA-C1 to IAEA-C9. Rev. 01, International atomic energy agency (2014). [24] T.W. Linick, Radiocarbon 22 (1980) 599. [25] IAEA, Guidebook on Nuclear Techniques in Hydrology, Tech Rep Ser. 91, p. 456, IAEA, Vienna (1983). [26] T. Kato, T. Iwatsuki, T. Nishio, Gas-strip methods of dissolved inorganic carbon in groundwater for radiocarbon analysis, JAEA-Technology 2017–009, JAEA, Ibaraki, 2017, p. 30. [27] J. Fujisawa, M. Minami, Y. Saito-Kokubu, Proceedings of the 18th Japanese symposium on accelerator mass spectrometry, The Japan Society for AMS Research, Tokyo, 2016, pp. 141–145. [28] H. Pachri, Y. Mitani, H. Ikemi, R. Nakanishi, Y. Saito-Kokubu, J. Geol. Resour. Eng. 3 (2015) 163. [29] A. Matsubara, M. Miyake, A. Nishizawa, N. Fujita, Y. Saito-Kokubu, Proceedings of the 18th Japanese Symposium on Accelerator Mass Spectrometry, The Japan Society for AMS Research, Tokyo, 2016, pp. 107–113. [30] K. Nakata, T. Hasegawa, T. Oyama, E. Ishii, K. Miyakawa, H. Sasamoto, Geofluids, 2018 (2018) Article ID 7823195.
5
Contents lists available at ScienceDirect
Nuclear Inst. and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb
Current status of JAEA-AMS-TONO in the 20th year Yoko Saito-Kokubua, , N. Fujitaa, M. Miyakea, T. Watanabea, C. Ishizakaa, N. Okabea, T. Ishimarua, A. Matsubarab, A. Nishizawab, T. Nishiob, M. Katob, H. Torazawab, N. Isozakib ⁎
a b
Japan Atomic Energy Agency, Toki, Gifu 509-5102, Japan Pesco Corp., Ltd., Toki, Gifu 509-5123, Japan
ARTICLE INFO
ABSTRACT
Keywords: AMS JAEA-AMS-TONO C-14 Al-26 Be-10 I-129
JAEA-AMS-TONO has been in operation at the Tono Geoscience Center, Japan Atomic Energy Agency since 1998 and 20 years have passed from the beginning of its utilization. The AMS has been used to measure 14C, 10Be and 26 Al. The main use is measurement of 14C in geological samples for dating studies in neotectonics and hydrogeology, in support of the research on geosphere stability applicable to the long-term isolation of high-level radioactive waste. In order to increase the speed of sample preparation, we introduced an automated graphitization equipment and made a gas-strip line to collect dissolved inorganic carbon in groundwater samples. Measurement of 10Be and 26Al has been used for geoscience studies and the detection limit in the measurement of 10Be was improved. Recently optimization of AMS settings for 129I-AMS has been progressed.
1. Introduction The JAEA-AMS-TONO facility at the Tono Geosciences Center (TGC), Japan Atomic Energy Agency (JAEA) installed an accelerator mass spectrometer (AMS) manufactured by National Electrostatics Corporation (US), utilized a Model 15SDH-2 PelletronTM accelerator with a maximum terminal voltage of 5 MV at March 1997 and 20 years have passed from the beginning of its utilization [1]. This AMS has mainly been used to determine the age of geological samples using long half-life cosmogenic nuclides, such as radiocarbon (14C), bellium-10 (10Be) and aluminum-26 (26Al) in studies into long-term geological stability as a basic research and development related to the geological disposal of high-level radioactive waste [1–5]. The studies into longterm geological stability include characterization of past and present geological events of crustal deformations and igneous activities such as fault activity and volcanic eruption. Date of the appearance and speed of the geological events are important information of the studies. The JAEA-AMS-TONO is the main instrument in the TGC because this is the most used instrument for dating in the TGC and JAEA-AMS-TONO has been used to measure 14C since the beginning of the installation of the AMS as radiocarbon dating is a standard method for determination of ages of organic matter such as wood, charcoal, shell, soil and groundwater in the age range of present to 60,000 year. Recently, other dating method using the other long half-life cosmogenic nuclides is increasing demanded. For the sake of estimation of the exposure age of basement rocks and the denudation rate, we started routine 10Be-AMS from the
⁎
Japanese fiscal year (FY) of 2013 and 26Al-AMS from 2015. Thus the AMS is also available to the JAEA’s common-use facility program, which is shared use of the AMS for researchers belonging to other research organizations. Moreover we have developed 129I-AMS for dating groundwater and investigation of the behavior of iodine in the environment. This paper is a status report of the JAEA-AMS-TONO during the past couple of decades and the recent improvements. 1.1. Description of the AMS The AMS is a versatile system based on a 5 MV tandem pelletron type accelerator [1]. The AMS has two ion sources; a 40-target MCSNICS ion source and a 12-target MGF-SNICS. Now the MC-SNICS is only used and the MGF-SNICS was shut down. Other equipment on the beam line except for a detector of a gas ionization chamber have not been changed since the installation of the AMS. The detector consists of cathode electrode, grid and anodes of five ΔE electrodes [6]. The ΔE electrodes determine the specific of energy loss arising in their respective regions. This enables to distinguish the spectrum of desired nuclide from other spectra of interfering particles and has a beneficial effect on discrimination between isobars. Measurement condition of the AMS was shown in Table 1. The AMS of 14C, 10Be and 26Al has already been used for routine measurements and the 129I AMS has been developed. The total measurement time and samples have exceeded 20,000 h and 16,000 samples in March 2017. Fig. 1 shows the annual operation time and number of samples after the
Corresponding author. E-mail address: [email protected] (Y. Saito-Kokubu).
https://doi.org/10.1016/j.nimb.2019.03.015 Received 12 March 2018; Received in revised form 4 October 2018; Accepted 9 March 2019 0168-583X/ © 2019 Elsevier B.V. All rights reserved.
Please cite this article as: Yoko Saito-Kokubu, et al., Nuclear Inst. and Methods in Physics Research B, https://doi.org/10.1016/j.nimb.2019.03.015
Nuclear Inst. and Methods in Physics Research B xxx (xxxx) xxx–xxx
Y. Saito-Kokubu, et al.
Table 1 Summary of measurement condition for the AMS systems. 14
Status Terminal Voltage Target (Ratio by weight) Current Injection Transmission Ionization chamber Count rate (Sample) Measurement Ratio Background (Sample) *1 *2 *3 *4 *5
10
C
Routine 4.5 MV Graphite : Fe powder (1:1) 15 – 20 μA (C-) Sequential 12C: 0.3 ms, 13C: 0.9 ms, 98.6 ms 48 – 58% (12C) ΔE1 – ERes 60 cps (SRM4990C(HOxII)@NIST)
14
C:
14 4+ 12 4+ 13 4+ 12 4+
C / C , C / C < 2 × 10-16 (< 0.03 pMC) (Graphite@ Wako*3)
26
Be
129
Al
I
Routine 4.6 – 4.8 MV BeO : Nb powder (1:4)
Routine 4.3 MV Al2O3 : Ag powder (1:4)
1 – 3 μA (BeO-) Simultaneous (10Be16O, 9 Be17O) ∼ 20% (9Be) ΔE1 – E2 (with gas cell) 45 cps (01–5-1@California Univ.*1) 10 Be3+/17O5+ (for 9Be) < 5 × 10-15 (BeO@ Merck*4)
∼ 0.1 μA (Al-) Sequential 26Al: 98 ms,
Test 3.5 MV AgI : Nb powder (1:4)
27
Al: 1 ms
34 – 39% (27Al) ΔE1 – ERes 15 cps (01–4-1@ California Univ.
*2
)
26
Al3+/27Al3+ < 1 × 10-14 (Al2O3 prepared from the standard solution for AAS*5@Wako*3)
∼ 0.7 μA (I-) Sequential 129I: 99 ms, 127 I: 1 ms ∼ 0.2% (127I) ΔE1 – ERes 50 cps (SRM3230@NIST) 129 5+ 127 5+
I / I Under test measurement
01–5-1: The ICN standard of 01–5-1 reported by Nishiizumi [8]. 01–4-1: The ICN standard of 01–4-1 reported by Nishiizumi [9]. Wako: Wako Pure chemical Industries, Ltd., Japan Merck: Merck Ltd., Germany AAS: Atomic absorption spectrometry
I-129 Al-26
1,500
Be-10 C-14
1,000
500
2016
2015
2014
2013
2012
2011
2010
2009
2008
2007
2006
2005
2004
2003
2002
2001
2000
1999
1998
0 1997
Operation time (h) and samples
2,000
Japanese fiscal year Fig. 1. Annual operation time (open circles) and sample number (bars).
installation. When about 10 years passed, some equipment issues broke down and staffs turned over, which caused that AMS was not operational. However the equipment issues were troubleshot and new staffs have increased the stability of the staff. These leads an operating rate of the AMS becomes steadily increasing and about a thousand samples per a year in 5FY’s past have been measured by the AMS.
the JAEA’s website and some of them were reported in scientific journals [19–22]. Recent measurement quality of the 14C-AMS is shown in Fig. 2. Arithmetic means of the results of reference materials of C6 (sucrose), C5 (wood) and C1 (marble) from International Atomic Energy Agency (IAEA) are 149.8 ± 3.3 (1σ) pMC (percent Modern Carbon), 23.10 ± 0.41 (1σ) pMC and 0.13 ± 0.06 (1σ) pMC, respectively. The results are corresponding to the nominal values [23] and our previous results [5]. In order to increase the speed of sample preparation, an automated graphitization equipment (AGE3, Ionplus, Switzerland) was introduced at 2017. A zeolite carbon dioxide (CO2) trap and reactors of the AGE3 was connected to the existing elemental analyzer (Vario Micro cube, Elementar Analysensysteme GmbH, UK) coupled on to a stable isotope ratio mass spectrometer (IsoPrime100, Isoprime Ltd., UK) [5]. Sample preparation using this equipment has high throughput of 7 samples per 4 h. Table 2 shows pMC of the IAEA standard samples prepared by the equipment. Measured values of the IAEA standard samples are consistent with their reference values. Therefore, we started to use it for graphite production of regular samples, which contain about 1 mg of carbon. Dissolved inorganic carbon (DIC) in groundwater sample is usually collected as carbonate by a chemical precipitation method [ex. 24,25]. In this method, the DIC is precipitated into strontium carbonate or barium carbonate, and then oxidized with phosphoric acid (H3PO4) to extract CO2. However the method is time-consuming and has low
1.2. Carbon-14 AMS The 14C-AMS has been used routinely since the FY of 1998 for measurement of 14C in geological samples for dating studies in neotectonics and hydrogeology. Especially in neotectonics study, 14C dating is one of the most useful dating methods. As geological events such as fault activity, volcanic eruption and generation of tsunami occur with a period of several hundreds or thousands, we have applied to the 14C dating to make accurate estimates of the occurrence time of these geological events; for example, Atera fault [9], Yoro fault [10,11,12], Senya fault [13], Sakurajima volcano [14], climate change [15]. Moreover, we use the 14C-AMS to study soil carbon dynamics by using 14C released from nuclear tests as a tracer for the carbon source [16,17] and to estimate the age of cultural property [18]. The 14C-AMS has also been used for studies under JAEA’s common-use facility program since the program stared at the fiscal year of 2006. We have accepted 39 projects containing 1322 samples until the FY of 2017. These projects cover a wide variety of study fields: geoscience, environment science and archaeology. The project reports were open to the public on 2
Nuclear Inst. and Methods in Physics Research B xxx (xxxx) xxx–xxx
Y. Saito-Kokubu, et al.
(a) C6
(150.61±0.11)
(a) 01-5-1 ((2.709±0.030)×10-11)
(b) 01-5-4 ((2.851±0.031)×10-12)
(b) C5 (23.05±0.02)
(c) BeO
(c) C1
(0.00±0.02)
Fig. 3. 10Be/9Be ratios in standard materials supplied by California University [7] (01–5-1 (a) and 01–5-4 (b)) and BeO (c) prepared from the standard solution for ICP from Merck Ltd. at 2015–2016. Parentheses and lines in (a) and (b) show the nominal values [7].
2016 FY Fig. 2. Percent Modern Carbon (pMC) in the IAEA reference materials C6 (a), C5 (b) and C1 (c) at 2016 FY (April 2016 – March 2017). Parentheses in (a) – (c) and lines in (a) and (b) show the nominal values [18].
1.3. Beryllium-10 AMS The 10Be-AMS has started routinely measurement since the FY of 2013. As beryllium-10 produced in terrestrial quartz make it possible to estimate rate of erosion, weathering, exposure of rocks, we have applied for dating studies in neotectonics. Fujisawa et al. reported denudation rates calculated from 10Be/9Be ratios in sediments of rivers flowing to Lake Biwa [27]. We have also started utilization under the JAEA’s common-use facility program and accepted one study (5 samples) under the JAEA’s common-use facility program from the FY of 2013 to the FY of 2017. Pachri et al. reported relationships between sediments concentrations of 10Be and morphometric aspect in Sangun catchment area, Fukuoka [28]. The measurement quality of the 10Be-AMS is shown in Fig. 3. Arithmetic means of the results of standard materials of 01–5-1 and 01–54 supplied by California University [7] are (2.71 ± 0.03) × 10-11 (1σ) and (2.86 ± 0.05) × 10-12 (1σ), respectively. The results agree with the nominal values [7]. The mean of beryllium oxide (BeO) prepared from the standard solution for ICP from Merck Ltd. is (0.90 ± 0.55) × 10-14 (1σ). This shows that background level has been kept constant and low enough to measure samples in applied studies. Recently, we try to improve detection limit to measure low 10Be/9Be ratio [29]. As 7Be is produced by the reaction 10B(p, α)7Be at the entrance of a gas cell and the distribution of the 7Be in energy spectra overlap that of 10Be, detection limit in the measurement of 10Be was
Table 2 pMC of IAEA standard samples.
C1 C4 C5 C6 C7 C9
(Carbonate) (Wood) (Wood) (Sucrose) (Oxalic acid) (Wood)
N
pMC (%) [Reference value]
3 3 6 6 3 6
0.15 ± 0.02 [0.00 ± 0.02] 0.19 ± 0.04 [0.20–0.44] 23.38 ± 0.13 [23.05 ± 0.02] 152.4 ± 1.5 [150.61 ± 0.11] 49.35 ± 0.22 [49.35 ± 0.12] 0.33 ± 0.02 [0.12–0.21]
reproducibility to collect the precipitation (carbonate) and to measure 14 C concentration. Therefore, we applied a gas-strip method using by a self-built gas-strip line to collect the DIC [26]. This gas-strip line can be attracted on bottles which contains 300, 500 and 1000 ml of water samples. The DIC is extracted as CO2 gas from the water samples on adding H3PO4. After the extraction, bubbling of the water with N2 gas for 5 min encourage to extract CO2 gas. The CO2 gas is collected and purified at traps. Recovery rates of carbon using by this gas-strip line from groundwater were more than 85%. 3
Nuclear Inst. and Methods in Physics Research B xxx (xxxx) xxx–xxx
Y. Saito-Kokubu, et al.
indicated that the data quality of the 26Al-AMS can be accepted for the routinely measurement. Therefore we have started routinely measurement and utilization under the JAEA’s common-use facility program since the FY of 2015. The measurement quality of the 26Al-AMS is shown in Fig. 4. Arithmetic means of the results of standard materials of 01–4-1 and 01–51 supplied by California University [8] and aluminum oxide (Al2O3) prepared from the standard solution for the atomic absorption spectrometry (AAS) from Wako Pure chemical Industries, Ltd. (Wako) are (7.44 ± 0.05) × 10-11, (4.70 ± 0.10) × 10-12 and (0.9 ± 0.6) × 1014 , respectively. The results if the standard materials are consistent with the nominal values [8] and the result of Al2O3 shows background level constant and low enough to measure samples in applied studies.
(a) 01-4-1((7.444 ±0.082)×10-11)
(b) 01-5-1((4.694±0.052)×10-12)
1.5. Iodine-129 Groundwater such as fossil salt water is one of the indicators to assess geological disposal in coastal areas. As the fossil salt water is very old, 129I/127I dating is effective to estimate age of the fossil salt water. The old fossil salt water has low ratio of 129I/127I (10-15 level, [30]), which need that 129I-AMS has low background. The JAEA-AMS-TONO has possibility to measure low ratio of 129I/127I in the fossil salt water because the JAEA-AMS TONO is not contaminated by samples with high ratios which are collected around reprocessing plants and disabled nuclear plants and can have high terminal voltage to 5 MeV. In order to measure 129I/127I ratio for dating of groundwater and for investigation of the behavior of iodine in the environment, a 129I-AMS has been in an early phase of development at JAEA-AMS-TONO. We succeeded detection of 129I ions in the detector of the gas ionization chamber, and then have repeatedly performed test measurements of standard samples. In addition, we are studying about sample preparation method to extract iodine. So routinely measurement will start in the next few years.
(c) Al2O3
2. Summary
improved by 7Be-counting suppression due to gate size reduction on an energy spectrum of the ionization detector and additional processes as mentioned below; cleaning by acetone and dry of high temperature (100 °C × 1 h) of Havar® foil that is used as a window at an inlet of the gas cell in front of the gas ionization chamber, increase of terminal voltage from 4.7 MV to 4.8 MV, reduction of half-length of a cable from the ionization detector to the preamplifier, electromagnetic shield of the cable wrapping with Al foil, change of anodes in the detector from Eres to E2. These processes leaded that the 10Be/9Be ratios in BeO prepared from the standard solution for ICP from Merck Ltd. became 1/3 lower than the values obtained before.
As twenty years has passed since the establishment of the JAEAAMS-TONO, the JAEA-AMS-TONO enables us to be available the multinuclide AMS for cosmogenic nuclides analyses (14C, 10Be, 26Al) to use dating of geological samples for geoscience studies. The AMS setting and some sample preparation equipment have improved to increase efficiency of measurement of samples and reduce background. We will promote development of the multi-nuclide AMS including the addition of 129I-AMS, renovation of the facility, the AMS and the sample preparation equipment and ingenuity of their operation to high throughput of measurement and increase of use of application studies. Though the AMS and the sample preparation equipment become order, daily check will find small defects and eliminate the causes promptly. Moreover the JAEA-AMS-TONO will serve the most important instrument to measure radiometric nuclides in the TGC because the TGC push forward to play a central role in the center of excellence for development of radiometric dating methods for geological sample and human resource in close coordination and cooperation with universes and other research institutes.
1.4. Aluminum-26 AMS
Acknowledgments
To start routinely measurement, the tuning of the AMS and test measurement has been progressed. As results of test measurement using diluted ICN standard samples provided by California University [8] were comparable with the performance of the MALT (Micro Analysis Laboratory, Tandem accelerator), Univ. of Tokyo, Japan, we performed intercomparison test with the MALT as a final test measurement [24]. Aluminum oxide of the ICN standard samples prepared at the JAEAAMS-TONO were measured at the JAEA-AMS-TONO and the MALT and results obtained from both laboratories were consistent. These results
This study was carried out under a contract with Ministry of Economy, Trade and Industry (METI), Japan as part of its R&D supporting program for developing geological disposal technology. The authors thank Prof. Matsuzaki for test measurement of Al.
Fig. 4. 26Al /27Al ratios in standard materials supplied by California University [8] (01–4-1 (a) and 01–5-1 (b)) and Al2O3 (c) prepared from the standard solution for the AAS from Wako Pure chemical Industries, Ltd. at 2014 and 2016. Parentheses and lines in (a) and (b) show the nominal values [8].
References [1] S. Xu, S. Ito, T. Iwatsuki, M. Abe, M. Watanabe, Nucl. Instrum. Methods Phys. Res., Sect. B 172 (2000) 8.
4
Nuclear Inst. and Methods in Physics Research B xxx (xxxx) xxx–xxx
Y. Saito-Kokubu, et al. [2] S. Itoh, M. Abe, M. Watanabe, S. Nakai, H. Touyama, S. Xu, Nucl. Instrum. Methods Phys. Res. Sect. B 223–224 (2004) 100. [3] Y. Saito-Kokubu, A. Nishizawa, M. Suzuki, Y. Ohwaki, T. Nishio, A. Matsubara, T. Saito, T. Ishimaru, K. Umeda, T. Hanaki, Nucl. Instrum. Methods Phys. Res., Sect. B 294 (2013) 43. [4] A. Matsubara, Y. Saito-Kokubu, A. Nishizawa, M. Miyake, T. Ishimaru, K. Umeda, in: Geochronology - Methods and Case Studies, Nils-Axel Morner, ed. InTech, 2014, p. 3. [5] Y. Saito-Kokubu, A. Matsubara, M. Miyake, A. Nishizawa, Y. Ohwaki, T. Nishio, K. Sanada, T. Hanaki, Nucl. Instrum. Methods Phys. Res., Sect. B 361 (2015) 48. [6] C. Maden, P.A.F. Anastasi, A. Dougans, S.P.H.T. Freeman, R. Kitchen, G. Klody, C. Schnabel, M. Sundquist, K. Vanner, S. Xu, Nucl. Instrum. Methods Phys. Res., Sect. B 259 (2007) 131. [7] K. Nishiizumi, M. Imanura, M.W. Caffee, J.R. Southon, R.C. Finkel, J. McAninch, Nucl. Instrum. Methods Phys. Res., Sect. B 258 (2007) 403. [8] K. Nishiizumi, Nucl. Instrum. Methods Phys. Res., Sect. B 223–224 (2004) 388. [9] R. Doke, K. Yasue, D. Hirouchi, Y. Saito-Kokubu, A. Matsubara, Active Fault Res. 40 (2014) 43. [10] Y. Niwa, T. Sugai, T. Ogami, M. Tajikara, K. Yasue, T. Saito, O. Fujiwara, Quatern. Res. 48 (2009) 339. [11] Y. Niwa, T. Sugai, T. Ogami, M. Tajikara, K. Yasue, O. Fujiwara, J. Geogr. 119 (2010) 668. [12] Y. Niwa, T. Sugai, K. Yasue, Y. Saito-Kokubu, Trans., Jpn. Geomorphol. Union 32 (2011) 201. [13] T. Imaizumi, K. Kagohara, K. Otuki, A. Miwa, H. Kosaka, T. Nohara, Active Fault Res. 26 (2006) 71 (in Japanese). [14] M. Ikuta, M. Niwa, T. Danhara, T. Yamashita, S. Maruyama, T. Kamataki, T. Kobayashi, H. Kurosawa, Y. Saito-Kokubu, T. Hirata, J. Geol. Soc. Japan 122 (2016) 89. [15] T. Sasaki, T. Sugai, M. Yanagida, Y. Morita, A. Furusawa, O. Fujiwara, T. Moriya, T. Nakagawa, T. Miyagi, Quatern. Res. 45 (2006) 275 (in Japanese). [16] T. Nakanishi, M. Atarashi-Andoh, J. Koarashi, Y. Saito-Kokubu, K. Hirai, Eur. J. Soil Sci. 63 (2012) 495.
[17] T. Nakanishi, M. Atarashi-Andoh, J. Koarashi, Y. Saito-Kokubu, K. Hirai, J. Environ. Radioact. 128 (2014) 27. [18] Y. Saito-Kokubu, A. Matsubara, T. Ishimaru, M. Miyake, A. Nishizawa, Y. Ohwaki, T. Nishio, Archaeological reports in Toki city at the fiscal year of 2013 (Toki-city education committee, 2014), pp. 28–30. [19] M. Okuno, T. Torii, H. Naruo, Y. Saito-Kokubu, T. Kobayashi, Radiocarbon 54 (2012) 351. [20] M. Okuno, T. Nakamura, N. Geshi, K. Kimura, Y. Saito-Kokubu, T. Kobayashi, Nucl. Instrum. Methods Phys. Res., Sect. B 294 (2013) 602. [21] Ma.H.T. Mirabueno, M. Torii, E. P. Laguerta, P.J. Delosreyes, E.B. Bariso, M. Okuno, T. Nakamura, T. Danhara, Y. Saito-Kokubu, T. Fujiki, T. Kobayashi, J. Geogr., accepted. [22] M. Okuno, S. Nagaoka, Y. Saito-Kokubu, T. Nakamura, T. Kobayashi, Radiocarbon 59 (2017) 483. [23] Reference sheet for quality control materials, IAEA-C1 to IAEA-C9. Rev. 01, International atomic energy agency (2014). [24] T.W. Linick, Radiocarbon 22 (1980) 599. [25] IAEA, Guidebook on Nuclear Techniques in Hydrology, Tech Rep Ser. 91, p. 456, IAEA, Vienna (1983). [26] T. Kato, T. Iwatsuki, T. Nishio, Gas-strip methods of dissolved inorganic carbon in groundwater for radiocarbon analysis, JAEA-Technology 2017–009, JAEA, Ibaraki, 2017, p. 30. [27] J. Fujisawa, M. Minami, Y. Saito-Kokubu, Proceedings of the 18th Japanese symposium on accelerator mass spectrometry, The Japan Society for AMS Research, Tokyo, 2016, pp. 141–145. [28] H. Pachri, Y. Mitani, H. Ikemi, R. Nakanishi, Y. Saito-Kokubu, J. Geol. Resour. Eng. 3 (2015) 163. [29] A. Matsubara, M. Miyake, A. Nishizawa, N. Fujita, Y. Saito-Kokubu, Proceedings of the 18th Japanese Symposium on Accelerator Mass Spectrometry, The Japan Society for AMS Research, Tokyo, 2016, pp. 107–113. [30] K. Nakata, T. Hasegawa, T. Oyama, E. Ishii, K. Miyakawa, H. Sasamoto, Geofluids, 2018 (2018) Article ID 7823195.
5