**1. Introduction**

322 Nuclear Reactors

L.A. Perez-Maqueda, O.B.Caneo, J. Poyato, J.L. Perez-Rodrguez, "Preparation and

M. Adib, N. Habib, , M. Fathaalla. "Neutron transmission through pyrolytic graphite

M.C. Jimenez De Haro, J.M. Martinez Blanes, J. Poyato, L.A. Perez-Maqueda, A. Lerf, J.L.

S. A. Suvorov and V. V. Skurikhin, "High-Temperature Heat Insulating Materials Based on

S. A. Suvorov and V. V. Skurikhin, "Vermiculite — A Promising Material for High Temperature Heat Insulators", *Refract Ind Ceram+,* 44 (3) (2003) 186-193. S.Agosteo, M. Magistris, A. Mereghetti, M. Silari, Z. Zajacova. "Shielding data for 100–250

T. Korkut, A. Ün, F. Demir, A Karabulut, G. Budak, R. Şahin, M. Oltulu, "Neutron dose

V. É. Peletskii and B. A. Shur, "Experimental Study of the Thermal Conductivity of Heat

V. I. Andronova and P. A. Arifov, "Study of the Material Properties of Micaceous

Y. El Mouzdahir, A. Elmchaouri, R. Mahboub, A. Gil, S.A. Korili, "Synthesis of nano layered vermiculite of low density by thermal treatment", *Powder Technol*, 189 (2009) 2–5.

microporosity of vermiculite", *J Phys Chem Solids*, 65 (2004) 435-439. M.E. Medhat, M. Fayez-Hassan, "Elemental analysis of cement used for radiation shielding by instrumental neutron activation analysis", *Nucl Eng Des,* 241 (2011) 2138 2142. R. Şahin, R. Polat, O. Içelli, C. Çelik, "Determination of transmission factors of concretes

entraining agent", *Ann of Nucl Energy,* 38 (2011) 1505–1511.

Vermiculite", *Refract Ind Ceram+,* 43 (11) (2002) 383-389.

colemanite". *Ann of Nucl Energy,* 37 (2010) 996–998.

crystals". *Ann. of Nucl. En*., 33( 7) (2007), 627-632.

28 (2001) 61-66.

598.

(2007) 356-358.

373 377.

Characterization of Micron and Submicron-sized Vermiculite", *Phys Chem Minerals*,

Perez-Rodriguez, "Effects of mechanical treatment and exchanged cation on the

with different water/cement ratio, curing condition, and dosage of cement and air

MeV proton accelerators: Double differential neutron distributions and attenuation in concrete. " *Nuclear Instruments and Methods in Physics Research B* 265 (2007) 581–

transmission measurements for several new concrete samples including

Insulation Materials Based on Expanded Vermiculite", *Refract Ind Ceram+,* 48 (5)

Vermiculite Minerals of the Tebinbulak Deposit", *Refract Ind Ceram+,* 48(5) (2007)

Technetium-99m (99mTc, half-life: 6.01 hours) is the world's most widely used radiopharmaceutical for exams of cancer, bowel disease, brain faculty and so on, and it is used for more than twenty million exams per year in the world and more than one million exams per year in Japan. The demand for 99mTc is continuously growing up year by year. The features of 99mTc as the radiopharmaceutical are as follows:


The production of the short-lived 99mTc is conducted by extracting from molybdenum-99 (99Mo, half-life: 65.94 hours), which is the parent nuclide of 99mTc. Therefore, the stable production and supply of 99Mo is very important in every country. All of 99Mo used in Japan is imported from foreign countries. However, a problem has emerged that the supply of 99Mo is unstable due to troubles in the import and the aging production facility (Atomic Energy of Canada Limited [AECL], 2007, 2008). In order to solve the problem, the establishment of an efficient and low-cost 99Mo production method and the domestic production of 99Mo are needed in Japan.

As a major 99Mo production method, the fission method ((n, f) method) exists, and as a minor 99Mo production method, the neutron capture method ((n, γ) method) exists. In order to apply to the Japan Materials Testing Reactor (JMTR) of the Japan Atomic Energy Agency (JAEA), two types of 99Mo production methods based on the (n, γ) method have been developed in JAEA (Inaba et al., 2011): one is a solid irradiation method, and the other is a solution irradiation method, which was proposed as a new 99Mo production technique (Ishitsuka & Tatenuma, 2008).

The solution irradiation method aims to realize the efficient and low-cost production and the stable production and supply of 99Mo, and the fundamental research and development for the practical application of the method has been started (Inaba et al., 2009).

Development of 99Mo Production Technology with Solution Irradiation Method 325

In the new solution irradiation method, a solution target including natural molybdenum such as an aqueous solution of a molybdenum compound (aqueous molybdenum solution) is irradiated with neutrons in a testing reactor, and 99Mo is produced by the 98Mo (n, γ) 99Mo reaction. This new method is the improved type of the solid irradiation method, and it is possible to enhance the 99Mo production compared with the solid irradiation method. The solution irradiation method has the following advantages compared with the solid

1. It is easy to increase the irradiated volume by using a capsule with larger volume than that of a rabbit. The rabbit is a small sized (150 mm length) capsule (Inaba et al., 2011). 2. The separation and dissolution processes after the irradiation are not necessary because

3. The amount of generated radioactive waste is smaller than that of the solid irradiation

<Irradiation target> Enriched 235U Natural Mo Natural Mo •Chemical type •U-Al alloy, UO2 •MoO3, metal Mo •Molybdate •Form •Foil, pellet •Powder, pellet, metal •Aqueous solution

•Quality control •Complex •Complex •Simple

•Irradiation time •5-7 days •5-7 days •5-7 days

•Adjustment of target and enclosing with

•Isolation in hot lab. (Complex)

(131I, 103Ru, 89Sr, 90Sr, etc.)

(2 mg-Mo/g-Al2O3)

irradiation)

Table 1. Comparison between three 99Mo production methods

(Generation every one

<Production in Japan> Difficult Possible Possible

container

<Irradiation container> Rabbit (30 cm3) Rabbit (30 cm3) Capsule (1,663 cm3)

•Collection of target •Batch collection •Batch collection •Continuous or batch

•Specific activity •370 TBq/g-Mo •37-74 GBq/g-Mo •37-74 GBq/g-Mo

99Mo production methods Fission method Neutron capture method ((n, f) method) ((n, γ) method)

> Solid irradiation method

•Adjustment of target and enclosing with

•Dissolution in hot lab. (Relatively simple)

(250 mg-Mo/g-PZC)

(Generation every one

container

PZC

Rabbits

irradiation)

•235U (n, f) •98Mo (n, γ) 99Mo •98Mo (n, γ) 99Mo

Solution irradiation method

•Adjustment of target

•No special treatment

 (depending on a target solution)

(250 mg-Mo/g-PZC)

(Lifetime: about 15 operation cycles)

collection

•92mNb •92mNb, 14C, 42K, etc.

PZC

Capsule

**2.2.2 Solution irradiation method** 

the irradiation target is an aqueous solution.

irradiation method:

method.

<Irradiation> •Pre-process of irradiation

•Reaction

•Post-process of irradiation

Generated 99Mo

•Activation by-product •Quite many

<Radioactive waste> Rabbits with FPs and Pu

<Mo adsorbent> Alumina

of 99Mo production

Items

In this paper, a comparison between 99Mo production methods, an overview of the solution irradiation method containing the structure of 99Mo production system with the method and the progress of the development made thus far, estimates of 99Mo production with the method, and the results of a newly conducted test are described.
