Preparation method of Mo-100 target

Abstract

The invention discloses a preparation method of a Mo-100 target piece, which belongs to the technical field of nuclide production, and comprises the following steps: tabletting: uniformly grinding elemental molybdenum powder, weighing, pouring into a mold of a tablet press, and tabletting to obtain a molybdenum target piece; the molybdenum target sheet is put into a muffle furnace to be sintered, and the temperature control process of the muffle furnace is as follows: in the first stage, the temperature ranges from the room temperature to 1000-1650 DEG C, and the time ranges from 60 min to 300 min; in the second stage, the holding time is more than 120 minutes at the temperature of 1000-1650 DEG C; in the third stage, the temperature is reduced to the room temperature, and the time is 100-300 min; and after sintering is completed, the obtained silver-white molybdenum target piece is the Mo-100 target piece. The process is simple and easy to operate, the raw material utilization rate is extremely high, the production cost is reduced, the obtained target material is sufficient in thickness, the hardness and radiation of the target material meet the application requirements through the specific sintering process, the product quality and the production efficiency are improved, the conditions needed by nuclide production are met, meanwhile, environmental pollution is reduced, and batch production is facilitated.

Description

Technical Field

[0001] The present invention belongs to the technical field of radionuclide production, and particularly relates to a preparation method of a Mo-100 target for the production of Tc-99m (i.e., the nuclear isomer of technetium-99). Background Art

[0002] Technetium-99m, as a nuclear isomer (half-life 6.01 h) produced by the decay of molybdenum-99 (Mo-99), has become the most core radioactive tracer in single photon emission computed tomography (SPECT) due to its excellent physical properties (moderate γ-ray energy, no β radiation) and short half-life characteristics. Currently, 80% of the world's Tc-99m depends on the decay chain production method of irradiating highly enriched uranium-235 (U-235) in a reactor to prepare Mo-99 (half-life 65.94 h), but this technology has inherent defects such as the risk of nuclear proliferation and complex radioactive waste treatment.

[0003] In recent years, the direct production technology route based on accelerators has received high attention. Its core is to directly generate Tc-99m through the (p, 2n) nuclear reaction by bombarding enriched Mo-100 (natural abundance 9.74%) target materials with protons. This method not only avoids the sensitivity problems of the nuclear fuel cycle but also enables on-demand production and regional supply, and is regarded as the strategic direction for the next-generation production of Tc-99m. However, the industrial application of this technology is still restricted by the maturity of the key link, namely the preparation process of Mo-100 target materials.

[0004] The preparation process of Mo-100 target parts is directly related to the product quality, production cost, and production efficiency, and is of crucial significance. The quality of the target parts is closely related to the irradiation and dissolution processes and has a direct impact on the subsequent separation and purification processes.

[0005] There are some problems in the traditional production methods of Mo-100 target parts, such as low raw material utilization rate, high production cost (Mo-100 is expensive as a target material raw material), and poor target material stability. For example, the traditional electroplating method faces the dilemmas of insufficient target material thickness and low product quality; the molybdenum metal foil method relies on rolling high-purity molybdenum ingots, with high process energy consumption and a target material forming qualification rate of less than 60%; while the direct encapsulation of molybdenum powder method is feasible, but it has high requirements for the target material raw materials and is difficult to effectively control properties such as porosity.

[0006] Although the pressing and sintering processes are commonly used in target material production, there is currently no successful case of applying a reasonably designed pressing and sintering process to the production of Mo-100 target parts. The traditional pressing and sintering processes are difficult to meet the quality requirements of Mo-100 target parts and still need further optimization and innovation. Summary of the Invention

[0007] The object of the present invention is to provide a preparation method of a Mo-100 target with good quality, low cost and high efficiency in order to solve the above problems.

[0008] The present invention realizes the above object through the following technical solutions:

[0009] A preparation method of a Mo-100 target includes the following steps:

[0010] Step 1, tablet pressing: First, put elemental molybdenum powder into a mortar and grind it evenly, then weigh 300-500 mg of the ground elemental molybdenum powder, pour it into the mold of a tablet press for tablet pressing, the pressure of the tablet press is greater than 5 T, the tablet pressing time is ≥10 min, and after demolding, a molybdenum target sheet with a metallic luster on the surface and in a sheet shape is obtained;

[0011] Step 2, sintering: Put the molybdenum target sheet into a muffle furnace for sintering. After evacuating the muffle furnace, introduce argon or a hydrogen-argon mixture with a flow rate of 0.06-0.6 m 3 / h, and the temperature control process of the muffle furnace is as follows:

[0012] The first stage: from room temperature to 1000-1650 °C, the time is 60-300 min;

[0013] The second stage: keep at 1000-1650 °C for a time >120 min;

[0014] The third stage: cool down to room temperature, the time is 100-300 min;

[0015] The silver-white molybdenum target sheet obtained after sintering is the Mo-100 target.

[0016] Preferably, in step 1, the elemental molybdenum powder is prepared by reducing molybdenum trioxide, and the specific preparation method is as follows: Spread the molybdenum trioxide powder containing Mo-100 with an abundance >95% evenly on the bottom of the crucible, put the crucible into the muffle furnace, evacuate in the muffle furnace, and then introduce a hydrogen-argon mixture with a hydrogen content >4% and a flow rate of 0.06-0.6 m 3 / h, and the temperature control process of the muffle furnace is as follows: The first stage: from room temperature to 500-600 °C, the time is 30-150 min; The second stage: from 500-600 °C to 1000-1100 °C, the time is 30-150 min; The third stage: keep at 1000-1100 °C for a time >300 min; The fourth stage: cool down to room temperature, the time is 100-300 min.

[0017] Preferably, in step 1, the mold of the tablet press is a circular mold with a diameter of 11-13 mm.

[0018] The beneficial effects of the present invention are as follows:

[0019] The present invention makes a sheet-shaped Mo-100 target by pressing and sintering elemental molybdenum powder. The process is simple and easy to operate, with extremely high raw material utilization rate (close to 100%), reducing production costs. The obtained product target has sufficient thickness, and through a specific sintering process, its hardness and radiation meet the application requirements, improving product quality and production efficiency, meeting the conditions required for radionuclide production, while reducing environmental pollution and facilitating mass production; preparing elemental molybdenum powder by high-temperature reduction of molybdenum trioxide through a specific reduction process not only reduces the requirements for raw materials but also reduces production costs, facilitating the continuous production of Mo-100 targets to meet the continuous production demand of Tc-99m. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic flow chart of the preparation method of the Mo-100 target described in the present invention;

[0021] Figure 2 is a top view schematic diagram of the Mo-100 target obtained in Example 1 of the present invention.

[0022] Figure 3 is a top view schematic diagram of the Mo-100 target obtained in Example 2 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] The present invention will be further described below with reference to the drawings and embodiments:

[0024] As Figure 1 shown, the preparation method of the Mo-100 target described in the present invention includes the following steps:

[0025] Step 1: First, prepare elemental molybdenum powder by reducing molybdenum trioxide. The specific preparation method is as follows: evenly spread molybdenum trioxide powder containing Mo-100 with an abundance > 95% on the bottom of a quartz crucible, place the quartz crucible in a muffle furnace, evacuate the air in the muffle furnace, and then introduce a hydrogen-argon mixture with a hydrogen content > 4% and a flow rate of 0.06 - 0.6 m 3 / h. The temperature control process of the muffle furnace is as follows: The first stage: from room temperature to 500 - 600 °C, for 30 - 150 min; The second stage: from 500 - 600 °C to 1000 - 1100 °C, for 30 - 150 min; The third stage: maintain at 1000 - 1100 °C for a time > 300 min; The fourth stage: cool down to room temperature, for 100 - 300 min;

[0026] Next, press the single - element molybdenum powder tablets: First, put the single - element molybdenum powder into an agate mortar and grind it evenly. Then weigh 300 - 500 mg of the ground single - element molybdenum powder, pour it into a circular mold with a diameter of 11 - 13 mm in a tablet press for pressing. The pressure of the tablet press is greater than 5 T, and the pressing time is ≥10 min. After demolding, a molybdenum target sheet with a metallic luster on the surface and in a flake shape is obtained;

[0027] Step 2, sintering: Put the molybdenum target sheet into a muffle furnace for sintering. After evacuating the muffle furnace, introduce argon or a hydrogen - argon mixture with a flow rate of 0.06 - 0.6 m 3 / h. The temperature control process of the muffle furnace is as follows:

[0028] The first stage: from room temperature to 1000 - 1650 °C, the time is 60 - 300 min;

[0029] The second stage: maintain at 1000 - 1650 °C for a time > 120 min;

[0030] The third stage: cool down to room temperature, the time is 100 - 300 min;

[0031] The silver - white molybdenum target sheet obtained after sintering is the Mo - 100 target piece.

[0032] The following uses two examples to illustrate the specific preparation methods under different process parameters:

[0033] Example 1:

[0034] Step 1, first prepare single - element molybdenum powder by reducing molybdenum trioxide. The specific preparation method is as follows: Use an electronic balance to weigh 2 g of molybdenum trioxide powder containing Mo - 100 with an abundance > 95%, and spread it evenly in a quartz crucible with an area of 30 cm 2 and a height of 3 cm; Place the quartz crucible in a muffle furnace, evacuate the muffle furnace, and then introduce a hydrogen - argon mixture with a hydrogen content of 5% and a flow rate of 0.3 m 3 / h. The temperature control process of the muffle furnace is as follows: The first stage: from room temperature to 600 °C, the time is 60 min; The second stage: from 600 °C to 1050 °C, the time is 100 min; The third stage: maintain at 1050 °C for a time of 500 min; The fourth stage: cool down to room temperature, the time is 200 min; Obtain 1.4 g of single - element molybdenum powder;

[0035] Next, press the single - element molybdenum powder tablets: First, put the single - element molybdenum powder into an agate mortar and grind it for 5 min. After grinding evenly, weigh 400 mg of the ground single - element molybdenum powder, pour it into a circular mold with a diameter of 12 mm in a tablet press for pressing. The pressure of the tablet press is 8 T, and the pressing time is 10 min. After demolding, a molybdenum target sheet with a metallic luster on the surface and in a circular flake shape is obtained;

[0036] Step 2, Sintering: Place the molybdenum target sheet in a magnesia crucible and put them together in a muffle furnace for sintering. After evacuating the muffle furnace, introduce a hydrogen-argon mixture with a hydrogen content of 5% and a flow rate of 0.3 m 3 / h. The temperature control process of the muffle furnace is as follows:

[0037] The first stage: from room temperature to 1100 °C, for 180 min;

[0038] The second stage: hold at 1100 °C for 300 min;

[0039] The third stage: cool down to room temperature, for 200 min;

[0040] After sintering, a silver-white molybdenum target sheet with a mass of 398 mg, a thickness of 0.46 mm, and a diameter of 11.84 mm as shown in Figure 2 is obtained, which is the Mo-100 target piece.

[0041] Example 2:

[0042] Step 1, First, prepare elemental molybdenum powder by reducing molybdenum trioxide. The specific preparation method is as follows: Weigh 2 g of molybdenum trioxide powder containing Mo-100 with an abundance > 95% using an electronic balance and spread it evenly in a quartz crucible with an area of 30 cm 2 and a height of 3 cm; Place the quartz crucible in a muffle furnace, evacuate the muffle furnace, and then introduce a hydrogen-argon mixture with a hydrogen content of 5% and a flow rate of 0.3 m 3 / h. The temperature control process of the muffle furnace is as follows: The first stage: from room temperature to 600 °C, for 60 min; The second stage: from 600 °C to 1000 °C, for 100 min; The third stage: hold at 1000 °C for 600 min; The fourth stage: cool down to room temperature, for 200 min; Obtain 1.4 g of elemental molybdenum powder;

[0043] Then press the elemental molybdenum powder: First, put the elemental molybdenum powder into an agate mortar and grind it for 5 min. After grinding evenly, weigh 400 mg of the ground elemental molybdenum powder and pour it into a circular mold with a diameter of 12 mm of a tablet press for pressing. The pressure of the tablet press is 9 T, and the pressing time is 10 min. After demolding, a molybdenum target sheet with a metallic luster on the surface and in a circular sheet shape is obtained;

[0044] Step 2, Sintering: Place the molybdenum target sheet in a magnesia crucible and put them together in a muffle furnace for sintering. After evacuating the muffle furnace, introduce a hydrogen-argon mixture with a hydrogen content of 5% and a flow rate of 0.3 m 3 / h. The temperature control process of the muffle furnace is as follows:

[0045] The first stage: from room temperature to 1650 °C, for 300 min;

[0046] Paragraph 2: The holding time at 1650 °C is 150 min;

[0047] Paragraph 3: Cool down to room temperature, and the time is 300 min;

[0048] After sintering is completed, a silver-white molybdenum target piece with a mass of 397 mg, a thickness of 0.45 mm, and a diameter of 11.24 mm as shown in Figure 3 the figure is the Mo-100 target piece, and its whiteness is a little larger than that of the Mo-100 target piece in Example 1.

[0049] The above embodiments are only preferred embodiments of the present invention and do not limit the technical solutions of the present invention. Any technical solutions that can be achieved on the basis of the above embodiments without creative labor shall be regarded as falling within the scope of the patent rights of the present invention.

Claims

1. A method for preparing a Mo-100 target, characterized in that: The following steps are involved: Step 1, tableting: firstly, the elemental molybdenum powder is put into a mortar and ground evenly, then 300-500 mg of the ground elemental molybdenum powder is weighed and poured into the mold of a tablet press for tableting. The pressure of the tablet press is greater than 5T, and the tableting time is ≥10min. After demolding, a molybdenum target sheet with a metallic luster and a flake shape is obtained; Step 2: Sintering: Place the molybdenum target into a muffle furnace for sintering. After the muffle furnace is evacuated, the flow rate is 0.06-0.6m 3 / h argon or hydrogen-argon mixture, the temperature control process of the muffle furnace is as follows: Stage 1: room temperature to 1000-1650°C, time 60-300min; Section 2: 1000-1650℃ holding time>120min; Stage 3: Cooling to room temperature, time is 100-300 minutes; The silvery white molybdenum target sheet obtained after sintering is the Mo-100 target.

2. The method for preparing a Mo-100 target according to claim 1, characterized in that: In step 1, the elemental molybdenum powder is prepared by reducing molybdenum trioxide. The specific preparation method is as follows: molybdenum trioxide powder containing Mo-100 with an abundance of more than 95% is evenly spread on the bottom of a crucible, the crucible is placed in a muffle furnace, vacuum extraction is performed in the muffle furnace, and then hydrogen with a content of more than 4% and a flow rate of 0.06-0.6m 3 / h of hydrogen-argon mixed gas, the temperature control process of the muffle furnace is as follows: Section 1: room temperature to 500-600℃, time is 30-150min; Section 2: 500-600℃ to 1000-1100℃, time is 30-150min; Section 3: 1000-1100℃ holding time>300min; Section 4: cooling to room temperature, time is 100-300min.

3. The method for preparing a Mo-100 target according to claim 1 or 2, characterized in that: In the step 1, the mold of the tablet press is a circular mold with a diameter of 11-13 mm.

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