Laboratory of Integration System and Technology Advanced (LISTA), Department of Physics, Faculty of Science Dhar Mahraz, University of Sidi Mohamed Ben Abdellah Fez Morocco
Email: abdessamad.didi1@usmba.ac.ma
Received: 21 Jun 2016 Revised and Accepted: 12 Aug 2016
ABSTRACT
Objective: Currently, nuclear medicine is becoming increasingly important, through the discovery of several medical radioisotopes, which are used in diagnosis, treatment, and medical imaging. Among the most important radionuclide which is commonly used is iodine-131, with a half-life of 8.02 d. Iodine-131 is one of the mainly essential elements in nuclear medicine. Since their first use, several studies have been conducted to meet the world need of hospital specialists in nuclear medicine. The purpose of this study was to participate in a lawsuit about the feasibility of producing 131I.
Methods: using neutron activation of the dioxide of tellurium (TeO2) under a neutron flux which varies between 5 1011 and 1013 n/cm²s for 4, 6 and 8 hours** per irradiation cycle during 5 d, and used the Fortron90 Code to calculate the activity of iodine-131.
Results: The result of the activity of iodine-131 found about 4,634 Curie with an irradiation of 4 hours** per day and 9.381 Curie with an activation of 8 hours** per day.
Conclusion: Production of iodine-131 can be very effective if an acceptable capsule is used for different masses of tellurium and a neutron flux in a nuclear reactor.
Keywords: Iodine-131, Tellurium, Neutron activation, Thyroid, Cancer, Nuclear medicine, Becquerel
© 2016 The Authors. Published by Innovare Academic Sciences Pvt Ltd. This is an open access article under the CC BY license (http://creativecommons. org/licenses/by/4. 0/) DOI: http://dx.doi.org/10.22159/ijpps.2016v8i11.13595
INTRODUCTION
Radioisotopes used for many years in many fields of medicine [1-14], industry [15], food and science, [16-17]. Accelerators and nuclear reactors are frequently used for the production of radioisotopes, at the moment, the demand for medical isotopes increases, such as iodine-131, [18-32], but it raises problems of cost and transportation of the producer country to consumer countries, which requires a new strategy for countries who had research reactors to produce iodine-131 [33], Such as Morocco, which has personal skills, researchers and academics in the nuclear field. Furthermore, Morocco is also a well-developed infrastructure which uses the nuclear research reactor TRIGA-MARC II 2-MW installed at the National Centre of Energy and Science and Nuclear Techniques in Rabat (CNESTEN). This facility meets the global regulatory requirements, nuclear safety, radiation protection and environmental protection. At this time, some studies are made to the feasibility of the production 131I, B. El Bakkari [34], A. S. Elom Achoribo [35], O. Yu. Kochnov [36], M. A. El-Absy [37], D. IAEA CDOC[38]. There are two main methods for the production of 131I, the first way is the fission of 235U [36] and the second way is a nuclear reaction (1) of 13 °Te, the last method is the one which attracts my interest.
52130Te + 01n → 52131Te + γ → 53131I + −10e + γ ……. (1)
With t1/2(131Te)= 25 min and t1/2(131I)=8.02 d
Research reactors cannot function for a long time because they should be stopped sporadically to make them cold, so a discontinuous operation is obligatory for the production of iodine-131. We call it cyclical irradiation, [40-42]. It is an irradiation of samples for a moment which can take hours. After the shutdown of the irradiation for some hours; we repeat this method for many cycles until the attainment of our objective.
The main aim of this theoretical study was to search the feasibility of producing 131I. We are interested in a range of neutron flux in the channel of irradiation from 5 1011 to 1013 n/cm²s which is generated by research nuclear reactor and capsulated targets of TeO2, with the mass from 1 g to 150 g. By using an analytical method and the cyclic neutron activation technical, we calculate the following activities of 4, 6 and 8 hours** of irradiation per day to achieve our goal.
METHODS AND MATERIALS
Production of-131
Productions of iodine-131 are generated by the following equation,
With,
σ Cross section microscopic (barn)
φ Neutron fluxes n/cm²s
λ radioactive constant ʎ Radiative constant h-1
At t=0 are found that N(53131I) = N(52131Te) = 0
By integrating equation 1 can give the number of formal’s core in each irradiation cycle which is in Equation 2, [34] [36][43-48].
Or tirrad tirrad: Irradiation time
tdecay: Decay time at the end of irradiation.
Na = 6, 02 1023mol−1 m(130Te)=6.02 1023 mol-1, Avogadro's number;
m(130Te) the weight in grams of tellurium;
M(130Te) the atomic mass of irradiated Telluriem isotope.
We can extract activity of 131I in each irradiation cycle using equation 4
A(53131I) = λ(53131I) N(53131I) ……. Equation 4
With A activity by Curie,
As it was motioned at the beginning of the irradiation (130Te)(52130Te) in the form of a cyclic radiation from each study, with 4, 6 and 8 hours** respectively per day for 5 d, the fig. 1 explains the steps of irradiation in each cycle.
Fig. 1: Evolution of activity with a cyclic irradiation
By accumulation of activity for each cycle is,
For the 1st cycle:
A(cycle 1) = Airrd time of first cycle(53131I) − Adecay (8h to 24h) of first cycle(53131I)
For the 2nd cycle:
A(cycle 2) = A(cycle 1) + Airrd time of second cycle(53131I) − Adecay time of second cycle(53131I)
For the 3rd cycle:
A(cycle 3) = A(cycle 2) + Airrd time of third cycle(53131I) − Adecay time of third cycle(53131I)
For the 4th cycle:
A(cycle 4) = A(cycle 3) + Airrd time of fourth cycle(53131I) − Adecay time of fourth cycle(53131I)
For the 5th cycle:
A(cycle 5) = A(cycle 4) + Airrd time of fifth cycle(53131I) − Adecay time of fifth cycle(53131I)
Finally, we found the global activity of 131I 53131I,
After the final calculation, the results obtained are shown schematically in the form of figures.
RESULTS AND DISCUSSION
From the simulations obtained in five irradiation cycles for each cycle with 4, 6 and 8 hours** of irradiation in a neutron flux 5 1011, 1012, 5 1012 and 1013n/cm²s, we have observed clearly that the activity increases during 4, 6 and 8 hours**.
After the stoppage of the first irradiation, the activity decreases slightly in the hours after (radioactive decay of Iodine-131). When we start the second cycle, the activity increases in the irradiation period and it decreases in the cooling period.
This process continues to increase and decrease until the end of the fifth round to achieve the maximum activity, fig. from 4 to 15 show the variation of the activity of 131I at different target weights (5g, 10g, 30g, 50g, 100g and 150g) and attached to a neutron flux ranges from 5 1011 to 1013 n/cm²s, for irradiation time 4, 6 and 8 hours** in each cycle. This work was well validated with the study of A. S. Elom Achoribo [35] and B. El Bakkari [34].
Fig. 2: Validation of our model, evolution of activity (Bq) in 6h of irradiation in each day with 5 1011 n/cm²s
Fig. 3: Evolution of activity [35]
To validate our results we compared them with the results of AS Elom Achorido [35] (fig. 3). For 1g, 3g and 5g, with a neutron flux of 5 1011n/cm²s, masses of TeO2 irradiated for 6 hours** per day (fig. 2), the results show the validation of our work. In our study, we are interested in 5g, 10g, 30g, 50g, 100g and 150g.
Productions 131I with 4 hours** of irradiation for each cycle
Fig. 4: Theoretical evolution activity (Bq) for I-131 production at a neutron flux of 5 1011 n/cm2s-1 for an irradiation time of 4h during each day
After four hours of irradiation by cycle, the results which are shown in fig. 4, 5, 6 and 7 clarify that the activity increases with irradiation time, then a slight decrease at the end of irradiation, then it begins to increase after the second irradiation. For example, the neutron flux of 5 1011n/cm²s for masses of 5g, 10g, 50g, 100g and 150g this activity is 2.86 109, 5.72 109, 1.71 1010, 2.86 1010, 5.72 1010 and 8.57 1010 Becquerel respectively. if we increase the fluxes to 1013 n/cm²s, and for the same masses, the activity is equal to 3.80 1010, 1.14 1011, 3.43 1011, 5.72 1011, 1.14 1012 and 1.71 1012 Becquerel, respectively.
Fig. 5: Theoretical evolution activity (Bq) for I-131 production at a neutron flux of 10[12] n/cm2s-1 for an irradiation time of 4h during each day
Fig. 6: Theoretical evolution activity (Bq) for I-131 production at a neutron flux of 5 10[12] n/cm2s-1 for an irradiation time of 4h during each day
Fig. 7: Theoretical evolution activity (Bq) for I-131 production at a neutron flux of 1013 n/cm2s-1 for an irradiation time of 4h during each day
Productions 131I with 6 hours** of irradiation for each cycle
Fig. 8: Theoretical evolution activity (Bq) for I-131 production at a neutron flux of 5 1011 n/cm2s-1 for an irradiation time of 6h during each day
Fig. 9: Theoretical evolution activity (Bq) for I-131 production at a neutron flux of 1012 n/cm2s-1 for an irradiation time of 6h during each day
Fig. 10: Theoretical evolution activity (Bq) for I-131 production at a neutron flux of 5 1012 n/cm2s-1 for an irradiation time of 6h during each day
Fig. 11: Theoretical evolution activity (Bq) for I-131 production at a neutron flux of 1013 n/cm2s-1 for an irradiation time of 6h during each day
The schemes illustrated in fig. 8, 9, 10 and 11 explain that the activity clearly related to the level of neutron flux and the mass of samples in addition to the microscopic Cross section of target of tellurium. After the analysis of the evolution of the activity, we noticed that the activity increases every day and every increase of irradiation followed directly with a slight decrease. For example, the neutron flux of 5 1011n/cm²s and masses of 5g, 10g, 30g, 50g, 100g and 150g, activity was 3.08 109, 8.71 109, 2.61 1010, 4.35 1010, 8.71 1010 and 2.61 1011 Becquerel respectively. If we increase the flux to 1013 n/cm²s, and for the same masses, activity equals 8.71 1010, 1.74 1011, 5.23 1011, 8.71 1011, 1.74 1012 and 6.53 1012 Becquerel, respectively.
Productions 131I with 8 hours** of irradiation for each cycle
Fig. 12, 13, 14 and 15 show the evolution of 131I with activation of 8 hours** per day for 5 d. The activity of iodine-131 depends on irradiation time, the neutron flux and the mass of target capsules. For example in fig. 12, the neutron flux equal to 5 1011 n/cm²s, the activity becomes at the end of the cyclic irradiation 5.79 109, 1.16 1010, 3.47 1010, 5.79 1010, 1.16 1010 and 1.74 1011 Becquerel, respectively for 5 g, 10 g, 30 g, 50 g, 100 g et 150 g. Therefore, an increase in the neutron flux to 1013 n/cm²s and for the same masses in fig. 15, the activity increases respectively 1.16 1011, 2.31 1011,6.94 1011,1.16 1012,2.31 1011 and 3.47 1012 Becquerel.
Fig. 12: Theoretical evolution activity (Bq) for I-131 production at a neutron flux of 5 1011 n/cm2s for an irradiation time of 8h during each day
Fig. 13: Theoretical evolution activity (Bq) for I-131 production at a neutron flux of 1012 n/cm2s-1 for an irradiation time of 8h during each day
Fig. 14: Theoretical evolution activity (Bq) for I-131 production at a neutron flux of 5.1012n/cm2s-1 for an irradiation time of 8h during each day
Fig. 15: Theoretical evolution activity (Bq) for I-131 production at a neutron flux of 1013 n/cm2s-1 for an irradiation time of 8h during each day
Profile of activity
Maximum feasible activities have been based on the capsules used; when we increase the mass of TeO2, it causes an increase in the activity. maximum activity in irradiation period 4, 6 and 8 hours** for the mass of 150 g give 2.317 Curie, 3.530 Curie, 4.69 Curie respectively in a flux of 5 1011n/cm²s, if the neutron flux increases to 1012 n/cm²s, for the identical weight (150g) and for the same irradiation period 4, 6 and 8 hours** per day, we note that the activity increases respectively in the following values, 4.6345 Ci, 7.0616 Ci and 9.3818 Curie, fig. 16 and 17.
Fig. 16: Increased activity of Iodine-131 as a function of time of irradiation and the mass of the tellurium-130 target in a neutron flux of 5 1011 n/cm²s
Fig. 17: Increased activity of Iodine-131 as a function of time of irradiation and the mass of the tellurium-130 target in a neutron flux of 1012 n/cm²s
CONCLUSION
A feasibility study of the production of iodine-131 is done by using a neutron flux from 5 1011 to 1013 n/cm². Then the results were that the mass of 150 g and a flux of 5 1011 n/cm²s the activity gives (2.317 Curie in 4 hours** of irradiation and 4.69 Curie in 8 hours** of irradiation), for the same mass of 160 g in a flux of 1012 n/cm²s gives (4.634 Curie in 4 hours** of irradiation and 9.381 Curie in 8 hours** of irradiation). These results are compared with study of B. El Bekkouri [34] and AS Elom Achoribo [35]. We noticed that the neutron standpoint, an acceptable capsule for different masses of tellurium, and an irradiation in a neutron flux in the reactor, approximately in the center, can give continuation to the production of Iodine-131.
CONFLICTS OF INTERESTS
Declared none
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