- Email: [email protected]
T2 and CO under high pressure
Journal of Hazardous Materials 378 (2019) 120720
Contents lists available at ScienceDirect
Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat
Radiochemical reaction of DT/ T2 and CO under high pressure Song Jiangfeng a b
a,b
a,⁎
a
a
a
a
a
, Xiong Yifu , Liu Lang , Shi Yan , Ba Jingwen , Jing Wenyong , He Mingming
T
Institute of Materials, China Academy of Engineering Physics, P.O. Box 9071, Jiangyou, 621907, Sichuan, PR China Institute of Atomic and Molecular Physics, Sichuan University, PR China
ARTICLE INFO
ABSTRACT
Keywords: Reaction Tritium CO DT Fusion
For both fuel cycle design and safety evolution of tritium (T) in fusion reactor, it is important to study irradiation-induced reactions between T2 and various molecular species produced from nuclear-fusion fuel cleanup systems. The radiochemical reactions between deuterium-tritium/tritium and carbon monoxide of different concentrations under 1.0 MPa were elucidated in this work. The products and the process of radiochemical reactions of T2/CO and D2-T2/CO mixed system with different tritium concentrations were analyzed by mass spectrometry and gas chromatography. The evolution of the product composition in 300 min. was monitored at room temperature with a rapid decrease of tritium concentration and pressure. It was found that, in T2/CO and D2-T2/CO mixed system, only tritium was involved in the reaction of CO. Under the β irradiation of tritium, the reaction products were mainly composed of tritiated formaldehyde (CT2O) and tiny amount of CO2, C(DT)4, C3(DT)8. The concentration of products rose with the increase of CO concentration in reaction system.
1. Introduction Tritium, which is an important fuel for controlled nuclear fusion, would be handled for fuel cycle in fusion reactors including the International Thermonuclear Experimental Reactor (ITER) and China Fusion Experiment Test Reactor (CFETR). As a radioactive material, tritium in substances can produce chemically active phase due to the production of ions and free radicals produced by β decay. Therefore, in order to implement tritium recycling and purification, it is necessary to investigate the reactions between impurities and the tritium distribution under β irradiation. CO is one of the gaseous species considered to exist in plasma exhaust. In addition, when ‘oxygen baking’ of carbon codeposited layer and dust in the vacuum vessel is carried out, CO is also supposed to be generated [1–4]. Hence, for both fuel cycle design and safety evolution of tritium in fusion reactors, it is important to study irradiation-induced reactions between T2 and various molecular species produced from nuclear-fusion fuel cleanup systems. Early studies have investigated the reactions between equimolar tritium (93.7% tritium, 3.5% hydrogen, 2.8% helium) with CO (purity 99.9%). The products were analyzed by fourier infrared spectrometer and mass spectrometry. The results showed that, in the mixed system after 450 h, the reaction products were carboxylic acids, aldehydes, and alcohols in condensed phase as well as methane, carbon monoxide, and tritiated water in gaseous phase [5]. Karlsruhe research laboratory investigated the reaction products
⁎
and mechanism of the equimolar tritium-deuterium gas mixture and CO (purity 99.97%) under atmospheric pressure, using fourier IR spectrometer [6]. The results showed that the reaction rate constant was directly proportional to the initial pressure of the mixed gas. After 36 days, the reaction products were mainly composed of tritium, tritium oxide, CO2, tritium ethylene, higher hydrocarbon, etc. With the methods of laser raman, fourier transform infrared (FT-IR) and mass spectrometry, W.M. Shu et al. investigated the reactions in a N2-balanced system of tritium oxides (T2O and possible T2O2) with carbon monoxide (CO). It was found that the main products after the reactions at 290 K are carbon dioxide (CO2) and tritiated water (T2O). Tritiated acids as found in T2−CO system had not been detected in the reactions between T2O/T2O2 and CO at the same detection limit, which indicated that the presence of N2 and O2 may restrain the formation of erosive substances like NT3 and NOx [7]. In this work, the radiochemical reactions between deuterium-tritium/tritium and carbon monoxide of different concentrations under 1.0 MPa is studied. The composition of the reaction productions was analyzed online by mass spectrometry and gas chromatography. 2. Experimental The schematic of experimental apparatus is shown in Fig.1. The experiments were carried out in a 50 cm3 stainless steel reactor in a glovebox filled with Ar. Through gas chromatography (HP 7890), the
Corresponding author. E-mail address: [email protected] (Y. Xiong).
https://doi.org/10.1016/j.jhazmat.2019.05.113 Received 4 December 2018; Received in revised form 30 May 2019; Accepted 31 May 2019 Available online 31 May 2019 0304-3894/ © 2019 Elsevier B.V. All rights reserved.
Journal of Hazardous Materials 378 (2019) 120720
J. Song, et al.
Fig. 1. Scheme of the experiment.
in T2−CO system. Formaldehyde (CT2O) were found to be the major products with trace amount of CO2, CQ4 and C3Q8, where Q refers to D or T. CO almost disappeared after 300 min. It should be noted that DT and HT could be observed, which was supposed to be produced by isotope exchange induced by tritium beta and D2 in initial tritium. Besides, it also can be seen from Fig. 3. that the concentration of products went up with the increase of CO concentration in T2/CO reaction system. The time evolution of pressure tested by mass spectrum is depicted in Fig. 4. It can be seen that with the initial pressure of 1.0 MPa, the final pressure decreases with the increase of CO concentration in this reaction system. In the initial stage (25 min), the main process is the process of β-ray irradiation to induce tritium to react directly with CO to produce intermediate products, which is a molecular reaction process. Therefore, the change of tritium is faster. Subsequently, under the catalysis of β ion, subsequent reactions occur, resulting in CT2O, etc., so the decline becomes slower.
Table 1 Isotopic composition of the feed gas. Feed gas
H2%
D2%
T2%
Pure tritium Deuterium-tritium mixture gas
0.1 0.3
0.2 39.8
99.7 59.9
3.2. D2-T2/CO reaction The time evolution of tritium and deuterium concentration and the time evolution of D2/T2 molar ratio in different CO concentration reaction system are shown in Fig. 5. As shown in Fig. 5a–c, corresponding to T2/CO reaction system, tritium concentration decreased with the increase of reaction time in all three reaction systems with CO concentration varied from 0.3% to 0.5% and deuterium concentration almost unchanged. In addition, as shown in Fig. 5d, all the initial D2/T2 molar ratio of three reaction system is 1.505:1. However, after the 300 min reaction, the D2/T2 molar ratio of DT + 0.3% CO, 0.4% CO, 0.5% CO reaction system is1.552,1.559 and 1.594, respectively. This result indicated that only tritium was involved in irradiation reaction with CO, and deuterium exchanges with tritium and hydrogen. Fig. 6 shows the relationship between the product composition and the reaction time in in DT−CO system. It can be found that the major products are CT2O and with trace CO2, CQ4 and C3Q8, and its generation rate rose with the increase of CO concentration in the reaction system. The time evolution of total pressure is shown in Fig. 7. It can be seen that with the initial pressure of 1.0 MPa, the final pressure is decreased with the increase of CO concentration, and under the same CO concentration, the final pressure of T2/CO system is lower than that of D2-T2/CO. In the case of the same instrument error, the main difference between them is reflected in the difference of partial pressure of T2. The reaction rate is related to partial pressure of T2. At the same total pressure, the partial pressure of pure tritium is higher, so the reaction rate is faster. On the contrary, the partial pressure of tritium in mixed gas is relatively low, so the reaction rate is slower.
Fig. 2. Time evolution of tritium concentration for three systems with different CO concentrations.
isotopic composition of the feed gas was found to be 0.1% H2, 0.2% D2, and 99.7% T2 (Table 1). In D2-T2/CO reaction system, the molar ratio of deuterium–tritium mixture was 1.505:1. Carbon monoxide with a purity of 99.97% (balance Ar) was used in the test. The deterium-tritium/tritium was supplied by a uranium getter bed, and then pressurized to 1.0 MPa by LaNi5 bed. After that, CO with concentrations of 0.3%, 0.4%, and 0.5% were introduced into the reactor. The total pressure was monitored on line by pressure sensor at room temperature while the composition and concentration of reaction products were analyzed online by a Finnigan MAT 271 mass spectrometer and an Agilent HP 7890 gas chromatograph. The effect of reaction time and CO concentration were also studied. 3. Results and discussion 3.1. T2/CO reaction Time evolution of tritium concentration in different CO concentration reaction systems is shown in Fig. 2. It is obvious that the tritium concentration decreases with the increase of reaction time in three reaction systems. Meanwhile, there is an abrupt change in tritium concentration slope coincident with CO depletion in the first 20 min, indicating the fast reaction rate in the beginning of reaction. Fig. 3 shows the relationship between the product composition and the reaction time
3.3. Reaction mechanism discussion Mass spectrometry analysis indicated a marked peak in 34 amu, which demonstrate that the basic product is CT2O. The reaction 2
Journal of Hazardous Materials 378 (2019) 120720
J. Song, et al.
Fig. 3. Time evolution of concentrations of major components after reaction.
T2
-decay 3
[ HeT]+ + e
T+ + 3 He+e
(1)
Meanwhile, under the β-ray irradiation, T2 and CO is ionized.
T2 + e
T+2 + 2e
(2)
CO+e
CO+
(3)
+ 2e
Then, the reaction enthalpy between CO and T2 is calculated based on the density functional theory at the m-GGA/TTSP level by applying Dmol3 module to evaluate the possibility of reactions between CO and T2
T2+CO
trans -TCOT H = +181.08 kJ/mol
(4)
T2+CO
cis-TCOT H = +199.93 kJ/mol
(5)
T2+CO
CT2 O H = -46.28 kJ/mol
(6)
Where trans-TCOT and cis-TCOT are the isomerides of CT2O. According to the calculation result, the formations of trans-TCOT and cis-TCOT both are endothermic reactions, while the formation of CT2O is an exothermic reaction. In addition, the T2+ and CO+ can also react with CO and T2 and the reaction enthalpy is calculated.
Fig. 4. Time evolution of total pressure for three systems with different CO concentrations.
mechanism is mainly ion and molecular reaction, because it has a relatively high reaction rate constant. These following reactions take place. First, due to the β decay of tritium molecule, free T+ ions are formed.
3
T+2 +CO
CO+ + T2 H = -274.15 kJ/mol
T2+CO+
trans
T2+CO+
cis
TCOT+ H = -319.38 kJ/mol TCOT+ H = -303.37 kJ/mol
(7) (8) (9)
Journal of Hazardous Materials 378 (2019) 120720
J. Song, et al.
Fig. 5. Time evolution of tritium/deuterium concentration for three systems with different CO concentrations：(a) CO, 0.3%; (b) CO, 0.4%; (c) CO, 0.5%; (d) D2/T2 molar ratio in different CO concentration reaction system.
T2+CO+
CT2 O+ H = -351.97 kJ/mol
(10)
CO2 + T+ 3
+
The above four reactions are all exothermic reactions, so the CT2O and its isomerides (trans-TCOT+ and cis-TCOT+) can be formed spontaneously. Moreover, as shown above, with the ionization of T2 and CO, the reaction enthalpy released is more so that the reaction is more likely to take place. The formation of CT2O+ releases the most reaction enthalpy, which indicates the the CT2O+ possess a stable structure. In addition, since CO can be is changed into CO2 after β-ray irradiation [5], some other reactions happens, too. First CO2 is ionized into CO2+ with the β-ray irradiation.
CO2 + e
CO+2 + 2e +
Then free T
T2 +
T+
CO2 + T+
T+3 +CO2
TOCO+
CT3 O++TCTO
T+ 3 +T
CT3O+2
(16)
C2 T2 O+ + C2 T3O+ + C2 T5O+
(17)
In summary, under the β irradiation of tritium, the main category of reaction between tritium and CO is ion-molecule. The reactants are T2 and CO, while the resultants were tritiated water vapor, methane, and CO2 in gaseous phase as well as aldehyde (RCTO), alcohols (ROT), and acids (RCOOT) in condensed phase.
(11)
4. Conclusions
(12)
In this work, the radiochemical reactions between deuterium-tritium/tritium and carbon monoxide of different concentrations under 1.0 MPa were elucidated, and some quantitative data had been obtained. Two main conclusions are summarized as follows: (1) Mass spectrometry was applied to study the products and the process of T2/CO and D2-T2/CO, only tritium was involved in the reaction of CO, and the reaction rate was in direct proportion to tritium concentration in the reaction system. (2) CT2O are major products under β irradiation of tritium, HT and
(13)
And T2+ can also react with T2.
T2 + T+2
transcis
(15)
The molecular ions generated by above reactions could further react with each other to form even bigger organic molecules:
ions react with CO2 and T2.
T+ 3
CO+T3 O+
(14)
Then, based on the density functional theory at the B3LYP/ 6–311 G(d, p) level by applying Gaussian 03 module, the reaction paths of TOCO++ T2 and T3++ CO2 is calculated to get the possible reactions which can take place under room temperature.
4
Journal of Hazardous Materials 378 (2019) 120720
J. Song, et al.
Fig. 6. Time evolution of concentrations of major components after reaction.
Acknowledgments The authors express their thanks to the support of china national key research and development program (No. 2017YFE0301502). The authors also express thanks to the help of Dr. Deng Shunjie and Dr. Feng Xingwen for English polish. References [1] R.D. Penzhorn, U. Berndt, C. Caldwell-Nichols, et al., Radiochemistry of an equimolar deuterium-tritium mixture or of T2 with CO[J], Fusion Eng. Des. 49 (2000) 927–937, https://doi.org/10.1016/S0920-3796(00)00343-4. [2] S. O’hira, H. Nakamura, K. Okuno, et al., Beta-decay induced reaction studies of tritium by laser raman Spectroscopy—T2-CO system—[J], Fusion Technol. 28 (3P2) (1995) 1239–1243, https://doi.org/10.13182/FST95-A30579. [3] D.L. Douglas, Tritium-carbon monoxide reaction[J], J. Chem. Phys. 23 (8) (1955) 1558–1559, https://doi.org/10.1063/1.1742371. [4] G. Federici, R.A. Anderl, P. Andrew, et al., In-vessel tritium retention and removal in ITER [J], J. Nucl. Mater. 266 (1999) 14–29 https://doi.org/ 10.1016/S0022-3115(98)00876-9. [5] S. O’hira, K. Isobe, T. Suzuki, et al., Beta induced reaction study on T2–CO system[J], Fusion Eng. Des. 49 (2000) 905–914, https://doi.org/10.1016/S0920-3796(00)00334-3. [6] R.H. Sherman, D.J. Taylor, K.G. Honnell, et al., Radiochemical reactions between tritium and humid air[C]//17th IEEE/NPSS symposium fusion engineering (Cat. No. 97CH36131), IEEE 1 (1997) 313–316 https://doi.org/10.1109/FUSION.1997.687045. [7] W.M. Shu, S. O’hira, T. Suzuki, et al., Radiochemical reactions between tritium oxides and carbon monoxide[J], Fusion Eng. Des. 70 (2) (2004) 123–129 https://doi.org/ 10.1016/ j.fusengdes.2003.09.001.
Fig. 7. Time evolution of total pressure for three systems. with different CO concentrations.
DT are produced by isotope exchange, the concentration of products went up with the increase of CO concentration in reaction system.
5
Contents lists available at ScienceDirect
Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat
Radiochemical reaction of DT/ T2 and CO under high pressure Song Jiangfeng a b
a,b
a,⁎
a
a
a
a
a
, Xiong Yifu , Liu Lang , Shi Yan , Ba Jingwen , Jing Wenyong , He Mingming
T
Institute of Materials, China Academy of Engineering Physics, P.O. Box 9071, Jiangyou, 621907, Sichuan, PR China Institute of Atomic and Molecular Physics, Sichuan University, PR China
ARTICLE INFO
ABSTRACT
Keywords: Reaction Tritium CO DT Fusion
For both fuel cycle design and safety evolution of tritium (T) in fusion reactor, it is important to study irradiation-induced reactions between T2 and various molecular species produced from nuclear-fusion fuel cleanup systems. The radiochemical reactions between deuterium-tritium/tritium and carbon monoxide of different concentrations under 1.0 MPa were elucidated in this work. The products and the process of radiochemical reactions of T2/CO and D2-T2/CO mixed system with different tritium concentrations were analyzed by mass spectrometry and gas chromatography. The evolution of the product composition in 300 min. was monitored at room temperature with a rapid decrease of tritium concentration and pressure. It was found that, in T2/CO and D2-T2/CO mixed system, only tritium was involved in the reaction of CO. Under the β irradiation of tritium, the reaction products were mainly composed of tritiated formaldehyde (CT2O) and tiny amount of CO2, C(DT)4, C3(DT)8. The concentration of products rose with the increase of CO concentration in reaction system.
1. Introduction Tritium, which is an important fuel for controlled nuclear fusion, would be handled for fuel cycle in fusion reactors including the International Thermonuclear Experimental Reactor (ITER) and China Fusion Experiment Test Reactor (CFETR). As a radioactive material, tritium in substances can produce chemically active phase due to the production of ions and free radicals produced by β decay. Therefore, in order to implement tritium recycling and purification, it is necessary to investigate the reactions between impurities and the tritium distribution under β irradiation. CO is one of the gaseous species considered to exist in plasma exhaust. In addition, when ‘oxygen baking’ of carbon codeposited layer and dust in the vacuum vessel is carried out, CO is also supposed to be generated [1–4]. Hence, for both fuel cycle design and safety evolution of tritium in fusion reactors, it is important to study irradiation-induced reactions between T2 and various molecular species produced from nuclear-fusion fuel cleanup systems. Early studies have investigated the reactions between equimolar tritium (93.7% tritium, 3.5% hydrogen, 2.8% helium) with CO (purity 99.9%). The products were analyzed by fourier infrared spectrometer and mass spectrometry. The results showed that, in the mixed system after 450 h, the reaction products were carboxylic acids, aldehydes, and alcohols in condensed phase as well as methane, carbon monoxide, and tritiated water in gaseous phase [5]. Karlsruhe research laboratory investigated the reaction products
⁎
and mechanism of the equimolar tritium-deuterium gas mixture and CO (purity 99.97%) under atmospheric pressure, using fourier IR spectrometer [6]. The results showed that the reaction rate constant was directly proportional to the initial pressure of the mixed gas. After 36 days, the reaction products were mainly composed of tritium, tritium oxide, CO2, tritium ethylene, higher hydrocarbon, etc. With the methods of laser raman, fourier transform infrared (FT-IR) and mass spectrometry, W.M. Shu et al. investigated the reactions in a N2-balanced system of tritium oxides (T2O and possible T2O2) with carbon monoxide (CO). It was found that the main products after the reactions at 290 K are carbon dioxide (CO2) and tritiated water (T2O). Tritiated acids as found in T2−CO system had not been detected in the reactions between T2O/T2O2 and CO at the same detection limit, which indicated that the presence of N2 and O2 may restrain the formation of erosive substances like NT3 and NOx [7]. In this work, the radiochemical reactions between deuterium-tritium/tritium and carbon monoxide of different concentrations under 1.0 MPa is studied. The composition of the reaction productions was analyzed online by mass spectrometry and gas chromatography. 2. Experimental The schematic of experimental apparatus is shown in Fig.1. The experiments were carried out in a 50 cm3 stainless steel reactor in a glovebox filled with Ar. Through gas chromatography (HP 7890), the
Corresponding author. E-mail address: [email protected] (Y. Xiong).
https://doi.org/10.1016/j.jhazmat.2019.05.113 Received 4 December 2018; Received in revised form 30 May 2019; Accepted 31 May 2019 Available online 31 May 2019 0304-3894/ © 2019 Elsevier B.V. All rights reserved.
Journal of Hazardous Materials 378 (2019) 120720
J. Song, et al.
Fig. 1. Scheme of the experiment.
in T2−CO system. Formaldehyde (CT2O) were found to be the major products with trace amount of CO2, CQ4 and C3Q8, where Q refers to D or T. CO almost disappeared after 300 min. It should be noted that DT and HT could be observed, which was supposed to be produced by isotope exchange induced by tritium beta and D2 in initial tritium. Besides, it also can be seen from Fig. 3. that the concentration of products went up with the increase of CO concentration in T2/CO reaction system. The time evolution of pressure tested by mass spectrum is depicted in Fig. 4. It can be seen that with the initial pressure of 1.0 MPa, the final pressure decreases with the increase of CO concentration in this reaction system. In the initial stage (25 min), the main process is the process of β-ray irradiation to induce tritium to react directly with CO to produce intermediate products, which is a molecular reaction process. Therefore, the change of tritium is faster. Subsequently, under the catalysis of β ion, subsequent reactions occur, resulting in CT2O, etc., so the decline becomes slower.
Table 1 Isotopic composition of the feed gas. Feed gas
H2%
D2%
T2%
Pure tritium Deuterium-tritium mixture gas
0.1 0.3
0.2 39.8
99.7 59.9
3.2. D2-T2/CO reaction The time evolution of tritium and deuterium concentration and the time evolution of D2/T2 molar ratio in different CO concentration reaction system are shown in Fig. 5. As shown in Fig. 5a–c, corresponding to T2/CO reaction system, tritium concentration decreased with the increase of reaction time in all three reaction systems with CO concentration varied from 0.3% to 0.5% and deuterium concentration almost unchanged. In addition, as shown in Fig. 5d, all the initial D2/T2 molar ratio of three reaction system is 1.505:1. However, after the 300 min reaction, the D2/T2 molar ratio of DT + 0.3% CO, 0.4% CO, 0.5% CO reaction system is1.552,1.559 and 1.594, respectively. This result indicated that only tritium was involved in irradiation reaction with CO, and deuterium exchanges with tritium and hydrogen. Fig. 6 shows the relationship between the product composition and the reaction time in in DT−CO system. It can be found that the major products are CT2O and with trace CO2, CQ4 and C3Q8, and its generation rate rose with the increase of CO concentration in the reaction system. The time evolution of total pressure is shown in Fig. 7. It can be seen that with the initial pressure of 1.0 MPa, the final pressure is decreased with the increase of CO concentration, and under the same CO concentration, the final pressure of T2/CO system is lower than that of D2-T2/CO. In the case of the same instrument error, the main difference between them is reflected in the difference of partial pressure of T2. The reaction rate is related to partial pressure of T2. At the same total pressure, the partial pressure of pure tritium is higher, so the reaction rate is faster. On the contrary, the partial pressure of tritium in mixed gas is relatively low, so the reaction rate is slower.
Fig. 2. Time evolution of tritium concentration for three systems with different CO concentrations.
isotopic composition of the feed gas was found to be 0.1% H2, 0.2% D2, and 99.7% T2 (Table 1). In D2-T2/CO reaction system, the molar ratio of deuterium–tritium mixture was 1.505:1. Carbon monoxide with a purity of 99.97% (balance Ar) was used in the test. The deterium-tritium/tritium was supplied by a uranium getter bed, and then pressurized to 1.0 MPa by LaNi5 bed. After that, CO with concentrations of 0.3%, 0.4%, and 0.5% were introduced into the reactor. The total pressure was monitored on line by pressure sensor at room temperature while the composition and concentration of reaction products were analyzed online by a Finnigan MAT 271 mass spectrometer and an Agilent HP 7890 gas chromatograph. The effect of reaction time and CO concentration were also studied. 3. Results and discussion 3.1. T2/CO reaction Time evolution of tritium concentration in different CO concentration reaction systems is shown in Fig. 2. It is obvious that the tritium concentration decreases with the increase of reaction time in three reaction systems. Meanwhile, there is an abrupt change in tritium concentration slope coincident with CO depletion in the first 20 min, indicating the fast reaction rate in the beginning of reaction. Fig. 3 shows the relationship between the product composition and the reaction time
3.3. Reaction mechanism discussion Mass spectrometry analysis indicated a marked peak in 34 amu, which demonstrate that the basic product is CT2O. The reaction 2
Journal of Hazardous Materials 378 (2019) 120720
J. Song, et al.
Fig. 3. Time evolution of concentrations of major components after reaction.
T2
-decay 3
[ HeT]+ + e
T+ + 3 He+e
(1)
Meanwhile, under the β-ray irradiation, T2 and CO is ionized.
T2 + e
T+2 + 2e
(2)
CO+e
CO+
(3)
+ 2e
Then, the reaction enthalpy between CO and T2 is calculated based on the density functional theory at the m-GGA/TTSP level by applying Dmol3 module to evaluate the possibility of reactions between CO and T2
T2+CO
trans -TCOT H = +181.08 kJ/mol
(4)
T2+CO
cis-TCOT H = +199.93 kJ/mol
(5)
T2+CO
CT2 O H = -46.28 kJ/mol
(6)
Where trans-TCOT and cis-TCOT are the isomerides of CT2O. According to the calculation result, the formations of trans-TCOT and cis-TCOT both are endothermic reactions, while the formation of CT2O is an exothermic reaction. In addition, the T2+ and CO+ can also react with CO and T2 and the reaction enthalpy is calculated.
Fig. 4. Time evolution of total pressure for three systems with different CO concentrations.
mechanism is mainly ion and molecular reaction, because it has a relatively high reaction rate constant. These following reactions take place. First, due to the β decay of tritium molecule, free T+ ions are formed.
3
T+2 +CO
CO+ + T2 H = -274.15 kJ/mol
T2+CO+
trans
T2+CO+
cis
TCOT+ H = -319.38 kJ/mol TCOT+ H = -303.37 kJ/mol
(7) (8) (9)
Journal of Hazardous Materials 378 (2019) 120720
J. Song, et al.
Fig. 5. Time evolution of tritium/deuterium concentration for three systems with different CO concentrations：(a) CO, 0.3%; (b) CO, 0.4%; (c) CO, 0.5%; (d) D2/T2 molar ratio in different CO concentration reaction system.
T2+CO+
CT2 O+ H = -351.97 kJ/mol
(10)
CO2 + T+ 3
+
The above four reactions are all exothermic reactions, so the CT2O and its isomerides (trans-TCOT+ and cis-TCOT+) can be formed spontaneously. Moreover, as shown above, with the ionization of T2 and CO, the reaction enthalpy released is more so that the reaction is more likely to take place. The formation of CT2O+ releases the most reaction enthalpy, which indicates the the CT2O+ possess a stable structure. In addition, since CO can be is changed into CO2 after β-ray irradiation [5], some other reactions happens, too. First CO2 is ionized into CO2+ with the β-ray irradiation.
CO2 + e
CO+2 + 2e +
Then free T
T2 +
T+
CO2 + T+
T+3 +CO2
TOCO+
CT3 O++TCTO
T+ 3 +T
CT3O+2
(16)
C2 T2 O+ + C2 T3O+ + C2 T5O+
(17)
In summary, under the β irradiation of tritium, the main category of reaction between tritium and CO is ion-molecule. The reactants are T2 and CO, while the resultants were tritiated water vapor, methane, and CO2 in gaseous phase as well as aldehyde (RCTO), alcohols (ROT), and acids (RCOOT) in condensed phase.
(11)
4. Conclusions
(12)
In this work, the radiochemical reactions between deuterium-tritium/tritium and carbon monoxide of different concentrations under 1.0 MPa were elucidated, and some quantitative data had been obtained. Two main conclusions are summarized as follows: (1) Mass spectrometry was applied to study the products and the process of T2/CO and D2-T2/CO, only tritium was involved in the reaction of CO, and the reaction rate was in direct proportion to tritium concentration in the reaction system. (2) CT2O are major products under β irradiation of tritium, HT and
(13)
And T2+ can also react with T2.
T2 + T+2
transcis
(15)
The molecular ions generated by above reactions could further react with each other to form even bigger organic molecules:
ions react with CO2 and T2.
T+ 3
CO+T3 O+
(14)
Then, based on the density functional theory at the B3LYP/ 6–311 G(d, p) level by applying Gaussian 03 module, the reaction paths of TOCO++ T2 and T3++ CO2 is calculated to get the possible reactions which can take place under room temperature.
4
Journal of Hazardous Materials 378 (2019) 120720
J. Song, et al.
Fig. 6. Time evolution of concentrations of major components after reaction.
Acknowledgments The authors express their thanks to the support of china national key research and development program (No. 2017YFE0301502). The authors also express thanks to the help of Dr. Deng Shunjie and Dr. Feng Xingwen for English polish. References [1] R.D. Penzhorn, U. Berndt, C. Caldwell-Nichols, et al., Radiochemistry of an equimolar deuterium-tritium mixture or of T2 with CO[J], Fusion Eng. Des. 49 (2000) 927–937, https://doi.org/10.1016/S0920-3796(00)00343-4. [2] S. O’hira, H. Nakamura, K. Okuno, et al., Beta-decay induced reaction studies of tritium by laser raman Spectroscopy—T2-CO system—[J], Fusion Technol. 28 (3P2) (1995) 1239–1243, https://doi.org/10.13182/FST95-A30579. [3] D.L. Douglas, Tritium-carbon monoxide reaction[J], J. Chem. Phys. 23 (8) (1955) 1558–1559, https://doi.org/10.1063/1.1742371. [4] G. Federici, R.A. Anderl, P. Andrew, et al., In-vessel tritium retention and removal in ITER [J], J. Nucl. Mater. 266 (1999) 14–29 https://doi.org/ 10.1016/S0022-3115(98)00876-9. [5] S. O’hira, K. Isobe, T. Suzuki, et al., Beta induced reaction study on T2–CO system[J], Fusion Eng. Des. 49 (2000) 905–914, https://doi.org/10.1016/S0920-3796(00)00334-3. [6] R.H. Sherman, D.J. Taylor, K.G. Honnell, et al., Radiochemical reactions between tritium and humid air[C]//17th IEEE/NPSS symposium fusion engineering (Cat. No. 97CH36131), IEEE 1 (1997) 313–316 https://doi.org/10.1109/FUSION.1997.687045. [7] W.M. Shu, S. O’hira, T. Suzuki, et al., Radiochemical reactions between tritium oxides and carbon monoxide[J], Fusion Eng. Des. 70 (2) (2004) 123–129 https://doi.org/ 10.1016/ j.fusengdes.2003.09.001.
Fig. 7. Time evolution of total pressure for three systems. with different CO concentrations.
DT are produced by isotope exchange, the concentration of products went up with the increase of CO concentration in reaction system.
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