Method of recovering enriched radioactive technetium and system therefor

The present invention relates to a method of recovering enriched radioactive technetium ( 99m Tc) as a radioactive medicine and a raw material for its labeled-compound raw material, and a system therefor.

Tc (technetium) is the transition metal of the atomic number 43 which is situated on the 7th family, the 5th period. Out of the isotopes, 99m Tc radiates only γ-ray with the short half-life (6 hours) which suited a diagnostic imaging and the weak energy (140 keV) which suited an external counting. Moreover, 99m Tc can be generated by the generator (the 99 Mo- 99m Tc generator) which utilizes a radiation equilibrium with 99 Mo and it is used for the nuclear medicine diagnostic imaging. 99m Tc is generally used in the way of obtaining it from 99 Mo (with the half-life of 66 hours) which is the parent nuclide of 99m Tc with a short half-life. Methods for obtaining 99 Mo include the Fission method (the nuclear fission method) in which 99 Mo with very high specific radioactivity is first generated by the method of uranium nuclear fission, and then separated. In this case, a method of obtaining 99m Tc by a milking operation in which the 99 mTc is eluted with a physiological saline using alumina as a 99 Mo adsorbent, is used as the actual manufacturing technology. On the other hand, there is another method of generating 99 Mo using the (n,γ) reaction of the 98 Mo isotope which is contained in 99 Mo, instead of using uranium as the raw material for obtaining 99 Mo. In comparison with the Fission method, this (n,γ) method enables a specific radioactivity of 99 Mo to be lowered to about 1/10,000. Therefore, for the practical application of the (n,γ) method, a small amount of 99 Tc must be separated, purified and recovered as the daughter nuclide generated from a small amount of 99 Mo which is contained in a large amount of Mo. So far, a sol-gel method, MEK method, or a sublimation method are known as the investigated and practically useful (n,γ) method. The inventors of this application have separately proposed PZC method as the (n,γ) method.

JP 2008-102078 A discloses the method and the equipment, in which radioactive molybdenum 99 Mo as the parent nuclide of technetium is generated by the 98 Mo(n,γ) reaction in a nuclear reactor.

JP 08-309182 A discloses Mo adsorbent for the 99 Mo- 99m Tc generator. And, it is described that this Mo adsorbent is formed by the zirconium-based inorganic polymer which has a high Mo adsorption ability and a high Tc elution performance. This Mo adsorbent is insoluble in water, adsorbs only Mo (including 99 Mo) from a water solution which contains Mo (including 99 Mo), and elutes 99m Tc generated from the radioisotope of 99 Mo. Furthermore, this patent literature discloses that a gel of ZrO 99 MoO 4 .xH 2 O is synthesized by reacting Na 2 Mo( 99 Mo)O 4 obtained by dissolution of Mo( 99 MoO 3 ) in the (n, γ) method with ZrOCl 2 or ZrO(NO 3 ) 2 , dried, pulverized and packed into a column, and that 99m Tc can be eluted from the packed column by a milking operation.

JP 02-54732 A discloses that technetium is eluted from activated carbon which adsorbs and separates technetium from a solution which contains technetium, such as a high radioactive-effluent, or a spent nuclear fuel solution which is generated by reprocessing of a spent nuclear fuel. Technetium in this case is not directed to 99m Tc (technetium- 99 m) with the short half-life for the nuclear medicine diagnostic imaging, but to 99 Tc with a very long half-life (technetium 99: the half-life of 21 ten thousand years), which causes a problem of remaining in the nuclear waste.

{Patent Literature 1} Japanese Patent Application Laid-Open No. 2008-102027

{Patent Literature 2} Japanese Patent Application Laid-Open Hei No. 08-309182

{Patent Literature 3} Japanese Patent Application Laid-Open Hei No. 02-54732

The conventional method has several problems such as a low performance stability, an operational complexity, an occurrence of radiation damage or a difficulty peculiar to the (n, γ) method in operation of a large amount of Mo, which does not reach the establishment of the practical technique which is equal to the Fission method.

To apply 99m Tc Mo generated as the daughter nuclide of 99 Mo by the (n, γ) method to the raw material for the radioactive medicine, the purification and recovery of a very small amount of 99m Tc in high concentration Mo which contains the radioactive molybdenum ( 99 Mo) must be made with high yield without contamination of 99 Mo. Therefore, the (n,γ) method demands a use of the adsorbent which adsorbs a very small amount of 99m Tc in high concentration Mo which contains a very small amount of 99 Mo, and further a recovery processing for elution and recovery with high yield of 99m Tc which is adsorbed to the adsorbent.

As for the conventional technology, 99 Tc is eluted from a solid-like or gelatinous adsorbent of Mo( 99 Mo) to which Mo (including 99 Mo) is adsorbed. Aforementioned JP 02-54732 A discloses that technetium is separated by adsorption to activated carbon, which indicates that the activated carbon has a performance of adsorbing and separating technetium. However, the invention of JP 02-54732 A is directed to 99 Tc (Technetium) of the long half-life which is contained in the high radioactive-effluent of the strong nitric acid acidity which is generated by the reprocessing of the spent nuclear fuel, and there is no disclosure about the method of purifying and recovering a very small amount of 99mTc when producing a raw material for a radioactive medicine.

The present invention is devised to use Tc as a raw material for a radioactive medicine in view of the above point, and has the purpose of providing a method and a system of purifying and recovering a very small amount of 99m Tc with high yield (95% and more) without contamination of Mo ( 99 Mo) from a large amount of Mo which contains a small amount of 99 Mo, together with reduction of waste fluid and wastes, using radioactive Mo generated by the (n, γ) method.

According to the study of the present invention, it is found that 99m Tc enriched to the required concentration as the radioactive medicine and the raw material for its labeled compound can be obtained by forming the high concentration Na 2 Mo( 99 Mo)O 4 solution of neutral pH in which a large amount of Mo( 99 Mo)O 3 is dissolved with alkaline (NaOH), getting a small amount of 99m Tc generated in the high concentration Mo solution adsorbed to activated carbon selectively, making 99m Tc stay behind the activated carbon by desorption of the Mo (including 99 Mo) remaining in its holes from it, and recovering a trace of the remained 99m Tc.

The present invention provides a method of highly enriching, and eluting, purifying and recovering 99m Tc as a raw material for a radioactive medicine, characterized by the steps of:

forming a high concentration Mo solution which contains radioactive molybdenum ( 99 Mo) as the parent nuclide of 99m Tc as a radioactive medicine and a raw material for its labeled compound;

feeding the Mo( 99 Mo) solution to an adsorption column which has an activated carbon from the high concentration Mo solution which contains radionuclides 99 Mo and 99m Tc which is generated as the daughter nuclide of 99 Mo, getting 99m Tc in the high concentration Mo( 99 Mo) adsorbed to the activated carbon selectively, then getting Mo( 99 Mo) remaining in holes of the activated carbon desorbed with a desorbent, undergoing desorption treatment of a small amount of 99m Tc which adsorbs to and stays behind the activated carbon with a desorbent of 99m Tc from the activated carbon, and recovering 99m Tc;

making secondary purification to remove Mo( 99 Mo) remaining a little in the recovered 99m Tc by a alumina column method; and

recirculating and recovering the high concentration Na 2 Mo( 99 Mo)O 4 solution after desorption treatment of 99m Tc to recover 99m Tc again after 24 hours when 99m Tc is re-formed.

The present invention also provides a method of highly enriching, and eluting, purifying and recovering 99m Tc directly from the high concentration Na 2 Mo( 99 Mo)O 4 solution of neutral pH which is formed by dissolving Mo( 99 Mo)O 3 containing radionuclide 99 Mo with an alkaline solution.

The present invention also provides a method of highly enriching, and eluting, purifying and recovering 99m Tc, characterized by the steps of: removing Mo( 99 Mo) remaining in activated carbon by washing the activated carbon adsorbing 99m Tc with dilute alkaline solution; and then further undergoing desorption treatment of 99m Tc with a high concentration alkaline solution, when recovering 99m Tc by the desorption treatment from the activated carbon adsorbing 99m Tc.

The present invention also provides a method of highly enriching, and eluting, purifying and recovering 99m Tc, characterized by the steps of eluting and recovering 99m Tc by treating the activated carbon with the NaOH solution of 0.05 mole (M) and more at 100° C. and more and at 5 atm and more.

The present invention also provides a method of highly enriching, and eluting, purifying and recovering 99m Tc, characterized by the step of undergoing electrochemical treatment of the activated carbon adsorbing 99m Tc by using the activated carbon as a cathode, when recovering 99m Tc by the desorption treatment of 99m Tc.

The present invention also provides a method of highly enriching, and eluting, purifying and recovering 99m Tc, characterized by the step of undergoing reduction treatment of the activated carbon adsorbing 99m Tc by a reductant, when recovering 99m Tc by the desorption treatment of 99m Tc.

The present invention also provides a method of highly enriching, and eluting, purifying and recovering 99m Tc, characterized by the step of recovering 99m Tc in combination of the treatment with the high concentration alkaline, the electrochemical treatment and the reduction treatment with the reductant. And, in this case, the step can combine the secondary purification to remove Mo ( 99 Mo) remaining a little in the recovered 99m Tc by the alumina column method,

The present invention provides a system of highly enriching, and eluting, purifying and recovering 99m Tc as a raw material for a radioactive medicine, comprising the steps of:

forming a high-concentration Mo solution of neutral pH which contains 99 Mo as the parent nuclide of 99m Tc used for a radioactive medicine and its raw material;

preparing a high concentration Mo( 99 Mo) solution which contains 99m Tc by generating 99m Tc to a radiation-equilibrium state in this high concentration Mo( 99 Mo) solution;

getting a small amount of 99m Tc in the high concentration Mo( 99 Mo) solution adsorbed to the activated carbon selectively by feeding the formed high-concentration Mo( 99 Mo) solution to an adsorption column which has activated carbon, and washing and removing Mo( 99 Mo) remaining in said activated carbon to which 99m Tc is adsorbed, with a Mo desorbent;

adsorbing, desorbing, and recovering and purifying 99m Tc by undergoing desorption treatment of 99m Tc with a 99m Tc desorbent from the activated carbon to which 99m Tc is adsorbed, after washing and removing Mo( 99 Mo) remaining in the activated carbon to which 99m Tc is adsorbed, with a Mo adsorbent;

making secondary purification to remove Mo( 99 Mo) remaining a little in the recovered 99m Tc by the alumina column method; and

recirculating and recovering the high-concentration Mo( 99 Mo) solution by circulating and recovering to reuse the high concentration Mo( 99 Mo) solution after the desorption treatment of 99m Tc, generating 99m Tc to a radiation-equilibrium condition, and re-forming high concentration Mo solution containing radionuclides 99 Mo and 99m Tc.

The present invention provides a system of highly enriching, and eluting, purifying and recovering 99m Tc as a raw material for a radioactive medicine, comprising the steps of:

forming a high concentration Mo solution of neutral pH by dissolving MoO 3 which contains 99 Mo irradiated with neutron in a nuclear reactor, with an alkaline solution, as a method for forming a high-concentration Mo solution which contains 99 Mo as the parent nuclide of 99m Tc used as a radioactive medicine and its raw material;

forming the high concentration Mo solution which contains radionuclides 99 Mo and 99m Tc which is genarated to a radiation-equilibrium state so as to be the daughter nuclide of 99Mo, in the high concentration Mo( 99 Mo) solution;

getting 99m Tc in the high-concentration Mo( 99 Mo) solution adsorbed to the activated carbon selectively by feeding the high-concentration Mo( 99 Mo) solution which contains 99m Tc generated to a radiation-equilibrium, to an adsorption column which has said activated carbon, and desorbing the Mo( 99 Mo) by washing the Mo( 99 Mo) remaining at the activated carbon with a Mo desorbent;

desorbing, and purifying and recovering 99m Tc to recover 99m Tc by undergoing desorption treatment of 99m Tc with a 99m Tc desorbent from the activated carbon to which 99m Tc is adsorbed after the desorption treatment of Mo( 99 Mo);

circulating and recovering the high-concentration Mo( 99 Mo) by circulating and recovering to reuse the high concentration Mo( 99 Mo) solution after the desorption and recovery treatment of 99m Tc, generating 99m Tc to a radiation-equilibrium condition and re-forming the high-concentration Mo solution containing radionuclides 99 Mo and 99m Tc; and

making secondary purification to remove Mo( 99 Mo) remaining a little in the recovered 99m Tc by the alumina column method.

The present invention employs the method of preparing Na 2 Mo( 99 Mo)O 4 solution condition in which 99m Tc of the radiation-equilibrium state is generated from 99 Mo and is mixed by leaving the high concentration Mo (including radioactive 99 Mo) solution formed in the above mentioned method for about 24 hours, and feeding the Na 2 Mo( 99 Mo)O 4 solution containing 99m Tc to the activated carbon. According to the present invention, only a small amount of 99m Tc in the high concentration Mo( 99 Mo) solution is selectively adsorbed to activated carbon and 99m Tc is desorbed after removing Mo( 99 Mo) which remains in the activated carbon, which results in a sufficient performance of the activated carbon for recovery of 99m Tc, and a high yield (of 95% and more) in the purification and recovery of a small amount of 99m Tc in the high concentration Mo solution. The present invention can also purify and recover 99m Tc with high purity without contamination of 99 Mo by feeding the recovered solution of 99m Tc to the alumina column, although Mo( 99 Mo) remaining a little in activated carbon is eluviated simultaneously with 99m Tc in the adsorption treatment of 99m Tc.

FIG. 1 illustrates the system configuration of one embodiment of the present invention.

FIG. 2 illustrates the processing procedures and method of one embodiment of the present invention.

FIG. 3 illustrates the process of one embodiment of the present invention.

FIG. 4 shows Tc dynamic adsorption efficiency of the AC (activated carbon) absorption column.

FIG. 5 shows the operation efficiency of Mo washout in Tc absorption column.

FIG. 6 shows the alk-PLE efficiency in Tc recovery from the Tc absorption column.

FIG. 7 shows the 99 Mo dynamic adsorption efficiency in the purification and recovery of 99m Tc as the evaluated result of an alumina column performance.

FIG. 8 shows the 99m Tc yield in alumina column separation.

FIG. 9 shows the required process time, the material balance, and the amount of occurred waste by 99m Tc collection process with 99 Mo 500 i scale ( 99m Tc master milker process).

The following will explain preferred modes of implementing the present invention referring to attached drawings. Hereinafter, 99m Tc and radionuclide 99 Mo are sometimes described as technetium or merely Tc and merely 99 Mo, respectively.

FIG. 1 illustrates the system concept for highly enriching, and eluting and recovering 99m TC (hereinafter, it is called a main system, and the method implemented by this system is called a main system way) which is one embodiment of the present invention. The system for highly enriching, and eluting and recovering 99m TC can be equipped with the purification and separation procedure.

In FIG. 1 , main system 100 is installed in a hot-cell 1 which shields radiation emitted from 99 Mo and 99m Tc. The main system 100 is equipped with Mo container ( 1 ) 2 , Mo container ( 2 ) 3 and a control tank 4 . A plurality of Mo containers may be equipped. The Na 2 99 MoO 4 solution, which is formed by dissolving MoO 3 which contains 99 Mo generated by neutron irradiation in a nuclear reactor with an alkaline (NaOH) solution, is supplied to Mo container ( 1 ) 2 and Mo container ( 2 ) 3 . That is, the Mo solution which contains radionuclide 99 Mo as the raw material for the radioactive-medicine is supplied to Mo container ( 1 ) 2 and Mo container ( 2 ) 3 . When 99 MoO 3 is dissolved with an alkaline solution, the Na 2 99 MoO 4 solution of neutral pH is formed as shown in the figure.

This example corresponds to the FIG. 3 shown later. On the occasion of generation, the Mo solution containing radioactive 99 Mo means a high concentration Mo solution which contains 500 g of Mo in 2 L of the Mo solution, for example. Hereinafter, this solution is called the high concentration Mo solution. Here, the high concentration means the concentration for the high concentration Mo solution containing 500 g of Mo in above-mentioned 2 L to become necessary to obtain the requirement of 99m Tc, for example, to an extent of 500 i per once.

Plumbing pipes land 8 equipped with three-way valves 5 and 6 is provided for the bottom of Mo container ( 1 ) 2 and Mo container ( 2 ) 3 , respectively. Moreover, Mo container ( 1 ) 2 and Mo container ( 2 ) 3 are connected to the bottom of the control tank 4 through three-way valves 5 and 6 and plumbing pipes 7 and 8 , and moreover the other plumbing pipes 9 and 10 . The termination of plumbing pipes 7 and 8 is equipped with a three-way valve 13 . The control tank 4 has a function of the level adjustment mechanism. The bottom of control tank 4 is connected to the one end (the top face in FIG. 1 ) of the Tc enrichment, purification and recovery-system 16 through a three-way valve 15 which is set up in a plumbing pipe 14 . This Tc enrichment, purification and recovery-system is equipped with the absorption column which has the activated carbon.

A plumbing pipe 17 and a three-way valve 18 set up therein, are prepared for the other edge (the lower edge in FIG. 1 ) of the Tc enrichment, purification and recovery-system 16 , and connected to the three way valve 13 which is set up in the termination of plumbing pipes 7 and 8 . 99m Tc is generated as the daughter nuclide of 99 Mo in the high concentration Mo solution of Mo container ( 1 ) 2 and Mo container ( 2 ) 3 , and the high concentration Mo solution which contains radionuclides 99 Mo and 99m Tc is formed. The new high concentration Mo solution which contains 99 Mo is alternately replaced and supplied to either Mo container ( 1 ) 2 or Mo container ( 2 ) 3 , for example every two weeks.

Although technetium-99 ( 99m Tc) emitting γ-ray (radiation) with weak energy is used for a medical diagnosis like SPECT, the amount of radioactivity of technetium-99 ( 99m Tc) decreases to 1/16 in one day due to its half-life of 6 hours. To compensate for this, 99 Mo which is the parent radionuclide of 99m Tc is kept, and 99m Tc generated by occurrence of beta-minus decay of 99 Mo is separated and utilized. Thus, the way of obtaining the daughter nuclide using the radiation-equilibrium relation between the parent-nuclide and the daughter nuclide is called the milking method.

Here, the method of obtaining the daughter nuclide using the radioactive equilibrium relationship between the mother-nuclide and the daughter nuclide is designated the milking. Also, to perform the milking is named the milking treatment, and the solution which contains the daughter nuclide is named the milking solution. Accordingly, the high concentration Mo solution which contains 99 Mo here means the solution which contains 99 Mo used to obtain the requirement of 99m Tc by utilizing the radioactive equilibrium relationship, as mentioned above.

The high concentration Mo( 99 Mo) solution is introduced into the Tc purification and recovery system 16 by adsorption, which has an activated carbon column from the lower part of the Tc purification and recovery system 16 through plumbing pipe 7 and plumbing pipe 8 , three-way valve 13 , and plumbing pipe 17 . Because Tc purification and recovery system 16 is equipped with the adsorption column which has the activated carbon, 99m Tc can be adsorbed selectively by feeding the high concentration Mo( 99 Mo) solution which contains the requirement of 99m Tc in this activated carbon. The purification and enrichment of 99m Tc are accomplished in this process. Here, relations of 99 Mo amount and 99m Tc amount to Mo amount (being 500 g here) in the high concentration Mo solution are indicated as follows:

The half-life of 99 Mo.65.94 h, The half-life of 99m Tc: 6.01 h

The 99 Mo quantity in 500 Ci=1.04 mg (1/500,000 to 500 g of Mo).

The 99m Tc quantity in 500 Ci=0.095 mg (1/5,000,000 to 500 g of Mo).

99 Mo in case of 5×10 4 Bq or less, the 99 Mo amount is 6×10 15 or less to 500 g of Mo.

99m Tc in case of 6×10 4 Bq or less, the 99m Mc amount is 6×10 −16 or less to 500 g of Mo.

Thus, 99m Tc can be adsorbed by the activated carbon, even when there exists only a little amount of 99m Tc in the high concentration Mo solution.

A large amount of Mo containing 99 Mo which is not adsorbed in the Tc enrichment, purification and recovery-system 16 , are returned to the control tank 4 through the three-way valve 15 and the plumbing pipe 14 , and further to either Mo container ( 1 ) 2 or Mo container ( 2 ) 3 . In this way, using the Mo solution which is contained in either of two Mo containers, 99m Tc adsorption treatment is undergone every 24 hours everyday for total about 2 weeks and the Mo solution that 99m Tc is recovered is returned to the original Mo container (either of Mo container ( 1 ) 2 and (2) 3 ). After this process, 99m Tc which is enriched, purified and recovered in Tc enrichment, purification and the recovery-system 16 is transferred to the desorption process.

Thus, the high concentration Mo solution which contains 99 Mo, is formed as the high solution Mo solution which contains radionuclide 99 Mo by directly dissolving the Mo compound (MoO 3 ) irradiated with neutron in a nuclear reactor with an alkaline solution, and supplied to a plurality of Mo containers. Tc is adsorbed and enriched by alternately feeding the high concentration Mo( 99 Mo) solution stored in these plural Mo containers to the adsorption column which has the above-mentioned activated carbon, and then the Tc elution, purification and recovery is accomplished.

Feed system 22 is connected to a three-way valve 18 through a plumbing pipe 20 and a three-way valve 21 . The washing solution, the Tc eluent and the others for desorption of Mo( 99 Mo), which remains in Tc enrichment purification and recovery-system 16 (the activated carbon column), are distributed from this feed system 22 , and introduced to the Tc enrichment purification and recovery-system 16 .

First, in the desorption process, Mo( 99 Mo) is desorbed by introducing the 99 Mo desorbent from the feed system 22 , and this solution is thrown as 99 Mo washing waste fluid to a liquid waste tank 32 . Then, Mo( 99 Mo) desorption process is stopped and transferred to Tc desorption process in which the Tc desorbent is introduced from the feed system 22 and Tc adsorbed to the activated carbon is desorbed.

Tc enrichment, purification and recovery-system 16 is connected to humoral regulation system 25 through the three-way valve 15 , and further through a plumbing pipe 23 and a three-way valve 24 set up therein. Desorbed Tc is introduced into the humoral regulation system 25 together with the desorbent. The humoral regulation is carried out by adding a reagent for humoral regulation 34 in this humoral regulation system, and is connected to second purification system 27 through a plumbing pipe 26 and further with Tc recovery equipment 29 through a plumbing pipe 28 .

This system 100 is equipped with waste fluid systems after using 99 Mo 30 and 31 and washing waste fluid system 32 , and each system is properly regulated by control system 33 , as shown in FIG. 1 .

FIG. 2 illustrates the method and the process for purifying and recovering Tc by the treatments using this modal system which is illustrated in FIG. 1 . In FIG. 2 , the system for highly enriching, purifying and separating, and eluting and recovering 99mTc of this embodiment, comprises forming procedure of (n,γ) 99 Mo 41 , forming procedure of high concentration Mo( 99 Mo) solution 42 , Tc generation processing procedures 43 and 44 , procedure of adsorption, elution, purification and recovery of 99m Tc 49 , secondary purification procedure for humoral regulation of 99m TC 50 , procedure for obtaining 99m Tc 51 and recirculating procedure of high concentration Mo solution 52 .

99 Mo is necessary to utilize 99m Tc. To produce 99 Mo in large quantity, (n,γ) 99 Mo is formed using the forming procedure of Mo pellet by the (n,γ) method in which natural Mo is irradiated in the nuclear reactor. In this embodiment, for example, a pellet formed by the (n,γ) method is used. Mo may be a powder. The Mo pellet which generates 99 Mo in this way, is directly dissolved with an alkaline solution by introducing the alkaline solution using the forming procedure of the high concentration Mo solution. The alkaline can use NaOH. Tc is generated using Tc generation processing procedures 43 and 44 . In generation of this Tc, system 1 ( 43 ) and system 2 ( 44 ) are used. These systems ( 1 ) and system ( 2 ), respectively, correspond to Mo container ( 1 ) 2 and Mo container ( 2 ) 3 in FIG. 1 .

The high concentration Na 2 Mo( 99 Mo)O 4 solution is formed when dissolving the Mo pellet irradiated with neutron in the nuclear reactor with a NaOH solution. The high concentration Mo( 99 Mo) solution which contains radionuclides 99 Mo and 99m Tc, is formed by generating 99m Tc as the daughter nuclide of 99 Mo using the high concentration 99 Mo solution. Thus, according to this method, the Na 2 Mo( 99 Mo)O 4 solution obtained by dissolving MoO 3 target irradiated in the nuclear reactor with the alkaline (NaOH) solution is alternately put into either of system 1 and system 2 once every week (last week and this week, respectively). Then, either of both Mo( 99 Mo) solutions is alternately introduced into the procedure of adsorption, elution, purification and recovery procedure of 99m Tc 49 which composes Tc purification and recovery-system by adsorption 16 ( FIG. 1 ), and fed to Tc adsorption column 53 .

The adsorption column 53 has activated carbon 54 . 99m Tc adsorption procedure is composed of the Tc adsorption column 53 which has activated carbon 54 . 99m Tc in high concentration Na 2 Mo( 99 Mo)O 4 solution of either of systems 1 and 2 or the both is adsorbed by feeding the high concentration Na 2 Mo( 99 Mo)O 4 solution to activated carbon 54 in this way. The activated carbon 54 adsorbs 99m Tc selectively. The amount of adsorbed 99m Tc increases along with alternate adsorptions of a small amount of 99m Tc in this way. 99m Tc concentration can be enriched to, for example, 40 times and more, compared with 99mTc concentration in the high concentration Na 2 Mo( 99 Mo)O 4 solution by combining this activated carbon adsorption method with latter desorption method. This enables 99m Tc to be enriched to the proper concentration as the raw material for the radioactive medicine. Incidentally, according to the present invention, 99m Tc can be enriched in an optional enrichment factor.

In this embodiment, the high concentration alkaline solution is used as a Tc desorbent used for desorption of Tc which is adsorbed to activated carbon 54 . Next, 99m TC is recovered by desorption treatment of 99m Tc with the desorbent by 99m Tc recovery procedure from the activated carbon to which 99m Tc is adsorbed. The absorption, desorption by elution and purification, and purification and recovery of 99m Tc are performed by these procedures.

The high concentration Na 2 Mo( 99 Mo)O 4 solution in which 99m Tc is adsorbed and recovered, is returned to system 1 or system 2 by the circulation means of high concentration Mo( 99 Mo) solution 52 , and recovered and reused as the high concentration Na 2 Mo( 99 Mo)O 4 solution.

A part of Mo( 99 Mo) which is adsorbed to the activated carbon, is removed from the activated carbon by the Mo( 99 Mo) washing process.

The secondary purification of the recovered Tc is made by removing the remained 99 Mo by the alumina column method after 99m Tc humoral generation by the secondary purification procedure of 99mTc humoral regulation, and 99m Tc is collected and recovered by the procedure for obtaining 99m Tc 51 .

As above-mentioned, the high concentration Mo solution is circulated to systems 1 and 2 by the circulation means of high Mo solution 52 to reuse the high concentration Mo( 99 Mo) solution after 99mTc adsorption. That is, high concentration Mo( 99 Mo) solution is returned to system 1 or system 2 and is reused, and then 99m Tc is newly generated by 99m Tc generation processing in these systems. Thus, the high concentration Mo( 99 Mo) solution is circulated and reused.

In this way, the system for highly enriching, purifying and separating, and eluting and recovering 99m Tc, and the recovery method are established as the 99Mo solution-type Tc master milker for using of the high concentration Mo( 99 Mo) solution, which enables to obtain an enriched 99m Tc solution based on the physiological saline. This solution is used for medical diagnosis as the raw material of the radioactive medicine.

FIG. 3 illustrates a process of highly enriching, purifying and separating, and eluting and recovering 99m Tc.

In FIG. 3 this process comprises formation of Mo( 99 Mo)O 3 S 1 , a dissolving process of Mo( 99 Mo) S 2 , a generation process of 99m Tc formation S 3 , a purification process by adsorption of 99m Tc to activated carbon S 4 , a removal process of Mo by water and weak alkaline of 0.01 mole of NaOH S 5 , a 99m Tc elution and recovery process S 6 , 99m Tc humoral regulation process S 7 , purification process of 99m Tc for recovering and purifying 99m Tc by washing and removing the remained Mo( 99 Mo) using the alumina column method S 8 , and a process for obtaining 99m Tc with high concentration and high purification S 9 .

The whole operation is as follows:

(1) dissolving of the irradiated Mo( 99 Mo) 3 pellet→(2) formation of Na 2 Mo( 99 MO)O 4 solution→(3) Tc adsorption and recovery (total recovery of the high concentration Mo solution used as an undiluted solution of 99 Mo for Tc adsorption and recovery (returning to the original tank and reusing 24 hours later))→(4) washing and removal of Mo( 99 Mo) which adheres to and remains in activated carbon→(5) Tc elution, purification and recovery→(6) regulation of pH and NaCl concentration of Tc recovered solution→(7) Tc secondary purification by the alumina column method (final purification)→(8) collection of Tc recovered solution (Tc≧1 Ci/mL, a physiological saline base, the neutral pH, containing no 99 Mo).

The present invention is composed of the eight processes mentioned above.

As the elution and recovery method of 99m Tc adsorbed to the activated carbon after high enrichment and adsorption of 99m Tc in the high concentration 99m Tc solution using the activated carbon, the remained Mo( 99 Mo) is removed by washing the activated carbon with a dilute alkaline solution, and further 99m Tc in the high concentration Mo( 99 Mo) solution can be highly enriched, purified and separated, and eluted and recovered by efficiently eluting, purifying and recovering 99m Tc by treatment with a high concentration alkaline solution.

As the elution and recovery method of 99m Tc adsorbed to the activated carbon after high enrichment and adsorption of 99m Tc in the high concentration 99m Tc solution using the activated carbon, the remained Mo( 99 Mo) is removed by washing the activated carbon with a dilute alkaline solution. Furthermore, as the efficient elution and recovery method of 99m Tc by treatment of 99m Tc with the high concentration alkaline solution, 99m Tc in the high concentration Mo( 99 Mo) solution can be highly enriched, purified and separated, and eluted and recovered by treating the activated carbon with NaOH solution of 0.05 mole and more at 100° C. and more and at 10 atoms and more to improve the elution and recovery rate of 99mTc.

As the elution and recovery method of 99m Tc adsorbed to the activated carbon after high enrichment and adsorption of 99m Tc in the high concentration 99mTc solution using the activated carbon, the high enrichment, purification and separation, and elution and recovery of 99m Tc in the high concentration Mo ( 99 Mo) solution can be performed selectively by eluting and recovering 99m Tc electrochemically using the activated carbon as a cathode.

As the elution and recovery method of 99m Tc adsorbed to the activated carbon after the high enrichment and adsorption of 99m Tc in the high concentration 99m Tc solution using the activated carbon, 99m Tc adsorbed to the activated carbon can be eluted and recovered without heating or pressurization by using a hydrazine or thiocyanic acid solution as a reducer of 99m Tc elute, which facilitates the elusion and recovery of 99m Tc.

Incidentally, the Tc milking time is 4 hours per batch in a whole process, and 99m Tc can be recovered at Tc concentration of 1 Ci/mL or more in the physiological saline of about 100 to 150 mL.

FIG. 4 to FIG. 9 shows experimental results.

FIG. 4 shows Tc dynamic adsorption efficiency of AC absorption column. As indicated in the figure, Tc adsorption zone is equal even if SV (the sky pipe speed: 114 to 273 h-1) varies. The pass time of 99 Mo solution in the column layer of AC (5 g) is 4.4 to 11 seconds (the current velocity: 0.5 to 1.3 cm/s) and 99m Tc in high concentration Mo solution is adsorbed and recovered in the efficiency of 98% and more.

FIG. 5 shows Mo washout efficiency in Tc adsorption column 16 . From this figure it is found that there is no movement of Tc adsorption zone even when the operation of Mo washout is undergone. Once 99m Tc is adsorbed to the activated carbon, 99m Tc stays behind it without removal even in washing and removal processing of remained Mo( 99 Mo) therein.

FIG. 6 shows the elution efficiency of 99m Tc in extraction processing of the alkaline pressurized solution (alk-PLE) which is performed as the Tc recovery operation from Tc adsorption column. From this figure, the movement of the 99m Tc adsorption zone is found, wherein 99m Tc is adsorbed to the activated carbon column by the alk-PLE processing. The recovery rate of Tc adsorbed to AC by this alk-PLE processing is 98 to 99%.

FIG. 7 shows 99 Mo dynamic adsorption efficiency in the purification and recovery of 99m Tc as the evaluated result of an alumina column performance. From this figure, even if SV (30 to 60 h-1) varies, 99m Tc can be eluted, purified and recovered in a 100% yield in a trapped state of 99 Mo inside the alumina column due to no change of 99 Mo adsorption zone, which causes 99m Tc to be obtained with high purity.

FIG. 8 shows 99m Tc yield in alumina column separation. The purification and recovery rate of Tc by the alumina column is 100%.

FIG. 9 shows the material balance in 99m Tc collection process with 99 Mo 500 Ci scale.

Since in this system used as the 99 Mo solution-type Tc master milker, no use of a solid-like or gelatinous 99 Mo adsorption support prevents any constituent elements of an adsorbent (Zr, for example) to be elusidated and mixed by the radiation damage of the 99 Mo adsorption support and moreover 99m Tc is in a dissolved state in 99 Mo solution, the concerns to the 99m Tc milking efficiency derived from the 99 Mo absorption support are unnecessary. The activated carbon used in this system can selectively adsorb 99m Tc with high efficiency without adsorption of 99 Mo in the high concentration Mo solution. Furthermore, 99m Tc can be applied in the best condition to the raw material for the radioactive medicine by using the 99m Tc solution based on the physiological saline, in which Tc adsorbed to the activated carbon is eluted. Also, in the highly enriching, purifying and separating, and eluting and recovering process of a very small amount of 99m Tc from the high concentration Mo( 99 Mo) solution, 99m Tc maintains the form of pertechnetic acid ( 99m TcO 4 − ) in all the processes, when recovering 99m Tc using the high concentration alkaline from the activated carbon to which 99m Tc is adsorbed. Incidentally, in 98 Mo(n, γ) reaction of MoO 3 , 92 Mo, 95 Mo and 96 Mo of Mo isotopes which are contained in MoO 3 of the neutron irradiation target for the 99 Mo production, generates 92m Nb, 96 Nb and 96 Nb of radioactive niobiums by each (n, γ) reaction, respectively, but these radioactive niobiums are never adsorbed to the activated carbon when 99m Tc in the high concentration Mo( 99 Mo) solution is adsorbed and recovered using the activated carbon column. Therefore, these radioactive niobiums are never mixed into the 99m Tc recovery solution.

Since this system used as the 99 Mo solution-type Tc master milker has several advantages of not only easy pharmaceutical affairs application and low cost due to no use of 99 Mo adsorption support, but also reduction of the quantity of radioactive waste fluid or solid wastes which are generated in 99m Tc recovery. Furthermore, a very small amount of 99m Tc in the high concentration Mo( 99 Mo) solution can be purified and recovered in a high yield without contamination of 99 Mo.

According to 99 Mo solution method of this embodiment, The product of same 99m Tc ( 99m Tc concentration and fluid volume) as one which is eluted and recovered by the present Fission- 99 Mo alumina column method, can be steadily obtained from (n,γ) 99 Mo solution. Thereby, the technology which can be used as 99m Tc master milker in production lines is established.