How about DPA in our case?

Question??


------  dpa by SM reactor in RIAR  ------




Dear Dick,

Are you fine?

We are all well and it becomes a nice season of new green leaves in Japan. 

By the way, I have a question to you.

We referred " [24] E.J. Edwards, F.A. Garner and D.S. Gelles, Journal of Nuclear Materials, 375, (2008) 370-381" in the paper for ICFRM-14 as follows,

 

Mo–41 wt% Re irradiated in the fast flux test facility (FFTF) experienced significant and non-monotonic changes in density due to radiation-induced segregation, leading to non-equilibrium phase separation, and progressive transmutation of Re to Os [24]. Beginning as a single-phase solid solution of Re and Mo, irradiation of Mo–41 wt% Re over a range of temperatures (743-1003 K) to 28–96 dpa produced a high density of thin platelets of a hexagonal close-packed (hcp) phase identified as a solid solution of Re, Os and possibly a small amount of Mo. These hcp precipitates are thought to form in the alloy matrix as a consequence of strong radiation-induced segregation to Frank loops. Grain boundaries are also enriched with Re to form the hcp phase, but the precipitates are much bigger and more equiaxed in shape. Although not formed at a lower dose, continued irradiation at 1003 K leads to the co-formation of late-forming χ-phase, an equilibrium phase that then competes with the pre-existing hcp phase for rhenium.

That is to say, 

I. At very high influences  to 28–96 dpa over a range of temperatures (743-1003 K) by FFTF,  irradiation of Mo–41 wt% Re  produced a high density of thin platelets of a hexagonal close-packed (hcp) phase identified as a solid solution of Re, Os and possibly a small amount of Mo (without χ-phase). 

II. Although not formed at a lower dose, continued irradiation at 1003 K leads to the co-formation of late-forming χ-phase, an equilibrium phase that then competes with the pre-existing hcp phase for rhenium.

We conducted two times of irradiation experiment at LT and HT; at 120-160 C, fluences= 3.6-6.0 x 10(21) n/cm2 and at 750-800 C, fluences= 5.5-7.3 x 10(21) n/cm2. 

I would like to demonstrate that both hcp phase and χ-phase do not occur reasonably in Mo-50%Re alloy or weld. 

I think that dpa in SM reactor in our case is rather low. But I don't know the correct dpa value. 

Please let me know the dpa value of the SM reactor in RIAR, if you calculated such a dpa. 

Regards,