26.08.2015   NUCLEAR REACTORS 2

Solution irradiation method

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, y) 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 irradiation method:

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 the irradiation target is an aqueous solution.

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

99Mo production methods

Items

Fission method ((n, f) method)

Neutron capture method ((n, у) method)

Solid irradiation method

Solution irradiation method

<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 container>

Rabbit (30 cm3)

Rabbit (30 cm3)

Capsule (1,663 cm3)

<Irradiation>

•Pre-process of irradiation

•Adjustment of target and enclosing with container

•Adjustment of target and enclosing with container

•Adjustment of target

•Reaction

•235U (n, f)

•98Mo (n, у) 99Mo

•98Mo (n, у) 99Mo

of 99Mo production

•Irradiation time

• 5-7 days

•5-7 days

•5-7 days

•Collection of target

•Batch collection

•Batch collection

• Continuous or batch collection

•Post-process of irradiation

•Isolation in hot lab. (Complex)

•Dissolution in hot lab. (Relatively simple)

•No special treatment

Generated 99Mo

•Specific activity

•370 TBq/g-Mo

•37-74 GBq/g-Mo

•37-74 GBq/g-Mo

•Activation by-product

•Quite many

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

•92mNb

•92mNb, 14C, 42K, etc. (depending on a target solution)

<Mo adsorbent>

Alumina

(2 mg-Mo/g-AhO3)

PZC

(250 mg-Mo/g-PZC)

PZC

(250 mg-Mo/g-PZC)

<Radioactive waste>

Rabbits with FPs and Pu (Generation every one irradiation)

Rabbits

(Generation every one irradiation)

Capsule

(Lifetime: about 15 operation cycles)

<Production in Japan>

Difficult

Possible

Possible

Table 1. Comparison between three 99Mo production methods

In this new method, efficient and low-cost 99Mo production compared with the conventional 99Mo production can be realized by using the (n, y) reaction and PZC. This new method aims to provide 100% of the 99Mo imported into Japan.