During the test term, the aqueous K2MoO4 solution was chemically stable, and the precipitation or the deposit was not generated in the solution. Then the molybdenum concentration of the solution was almost constant before and after the test, and the concentrations before and after the test were 396.2 mg/ml and 384.0 mg/ml respectively. The concentrations were measured with an Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES). The pH of the solution was also almost constant at pH9.5-9.7.

2. Conclusion

In the 99Mo production system with the solution irradiation method, a static or flowing aqueous molybdenum solution in a capsule is irradiated with neutrons in a testing reactor, and 99Mo is produced by the 98Mo (n, y) 99Mo reaction. The system aims to provide 100% of the 99Mo imported into Japan. As a part of the technology development, aqueous (NH4)6Mo7O24 4H2O and K2MoO4 solutions were selected as candidates for the irradiation target of the system, and compatibility between the static two solutions and the structural materials of the capsule and pipes in the system, the chemical stability, the radiolysis and the у heating of the solutions were investigated. As a result, it was found that the solutions are promising as the target. In addition, compatibility between a flowing aqueous K2MoO4 solution, which was the first candidate for the irradiation target in terms of a 99Mo production rate, and the structural material and the chemical stability of the flowing solution were investigated. As a result, it was found that stainless steel SUS304 has good compatibility with a flowing aqueous K2MoO4 solution and that the solution is chemically stable. The fundamental characteristics of the selected aqueous molybdate solutions became clear, and SUS304 can be used as the structural material of the capsule and the pipes.

In the future, a neutron irradiation test will be carried out as an overall test of 99Mo production system with the solution irradiation method, and 99Mo production, the separation of activation by-products, the quantity of radiolysis gas, nuclear heating and so on will be investigated.

Aiming at the domestic production of 99Mo in Japan, the development of 99Mo production with the solution irradiation method is kept going.

3. Acknowledgment

The author would like to thank Dr. Tsuchiya, K. and Mr. Ishida, T. of JAEA and Mr. Ishikawa, K. of KAKEN. Inc. for their valuable comments.

[1]CHF/actual local heat flux

Fig. 22. Critical heat flux as a function of the coolant inlet temperature

The minimum DNBR for IPR-R1 TRIGA (DNBR=8.5) is much larger than other TRIGA reactors. The 2 MW McClellen TRIGA calculated by Jensen and Newell (1998) had a DNBR=2.5 and the 3 MW Bangladesh TRIGA has a DNBR=2.8 (Huda and Rahman, 2004).

[2] Rectangular channel with hydraulic diameter from 2.6 to 6.4 mm.

• Pressure from 1.10 to 1.7 bar.

• Heat flux from 0.66 to 3.4 MW/m2.

• Inlet temperature from 35 to 75°C.

• Velocity from 0.6096 to 9.144 m/s.

[3] Frost(1963)

[4] Cox and Cronenberg (1977)

[5] Lundberg and Hobbins (1992)

[6] at nitrogen pressure > 0.25 MPa

[7] Leitnaker & Godfrey (1967)

[8] UN(s)=U(l)+0.5№(g), Gingerich (1969)

[9] UN(s)=U(g)+0.5№(g), Gingerich (1969)

[10]at 1000°C, Bowman et al.(1965;1966)

[11] Faced-Centered Cubic (FCC)

[12] It might be as high as 850°C.

[13]The views expressed are those of the authors and do not reflect those of any government agency or any part thereof.

[14] Static eigenvalue problem: When the flux does not depend on t, the left hand side is zero, and (4.1) has a nontrivial solution only if the cross-sections are interrelated. To this end, we free keff and the static diffusion equation is put in the form of an eigenvalue problem:

[15] As matrix O is orthogonal, its inverse is just its transpose.

[16] Images of V0 cover V.

[17] We obtain reactions rates also from the Green’s function.

[18] Actually a discretized eigenfunction, i. e. x.

[19] Since keff depends on the entering currents, the problem is non-linear.

[20] After normalization of the row vectors, the П matrices become orthogonal: П+П is the unit matrix.

[21] Here Ent is the integer division.

[22]Mo production in JMTR will start by using the solid irradiation method. JMTR aims to provide 99Mo of 37 TBq/w (1,000 Ci/w), and it will cover about 20% of the 99Mo imported into Japan (Inaba et al., 2011).

[23] The generation and reduction of 99Mo by the neutron capture reaction of 98Mo (n, y) 99Mo and 99Mo (n, у) 100Mo and the radioactive decay of 99Mo are evaluated.

• 99Mo doesn’t exist in the initial stage of the calculation.

• The decay of neutron flux due to the inner and outer tubes of the capsule is considered.

• The circulation of the two irradiation targets is not considered.