Number of Isomeric States

[Antonio Guglielmelli]

Dear Users,

how many metastable isotopes are included in the ORIGEN library? In SCALE 6.2.3 manual are reported only examples about  isotopes in the first metastable state.

Thanks in advance,

Antonio Guglielmelli

[Steve Skutnik]

Hello Antonio,

At present, Origen only tracks the first metastable state for nuclides. Future versions may incorporate tracking of additional metastable states (e.g., m2, m3); we are presently developing the infrastructure to support this, but it will also depend on data validation, etc.

Regards,

-Steve
SCALE Support Team

[Antonio Guglielmelli]

Hi Steve,

if I'm not too pushy, I have another question that I submitted in a simplified way yesterday on this Group. 

Shortly I found that the mass activity evaluated as the ratio between activity and mass (Bq/g) with ORIGEN-ARP at a fixed burn-up level of Ce-152, Ce-155, Ce-146 and Ce-157 is not consistent with the values evaluated with the theoretical relationship.

  

were Na is the Avogadro number, M is the atomic mass  and T1/2 is the decay time. In particular, despite for Ce-152 SCALE uses a decay time (1.24 s) equal to that suggested in on line reference [1] that i have used for the theoretical evaluation, the results are different:

Nuclide       SCALE     Theoric1       Theoric2                Ratio                         Ratio 

      (-)           (-)    (T1/2: Wikipedia)   (T/2: SCALE) (Theoric1/SCALE) (Theoric2/SCALE)

Ce-152    3.58E+20   1.96E+21       1.96E+21                 5.48                           5.48

Ce-155    5.10E+21   1.35E+22        5.67E+21         2.64                            1.11

Ce-156    4.49E+21   1.78E+22        7.25E+21         3.97                            1.62

Ce-157   1.24E+22   5.32E+22        1.09E+22         4.29                             0.88

were Theoric1 is the result of a theoric calculation with decay time as reported in wikipedia, while Theoric2 using a decay time reported on SCALE decay file (i.e., origen.rev03.decay). As you can see the Ce-155, Ce-156, Ce-157 results mostly depends on different decay time but, despite I used the same SCALE decay time (Theoric2) the results are still different (10 - 80%). 

Best Regards,

Antonio Guglielmelli

[Steve Skutnik]

Hello Antonio,

I'm not entirely sure I understand how you are getting the "SCALE" result indicated in your post. I ran a simple Origen calculation starting with an initial inventory of 1 gram of Ce-152, Ce-155, Ce-156, and Ce-157 and then printed out the initial inventories in Bq (time t=0); the starting inventories line up with your theoretical values in the "Theoric2" column, which would seem to indicate that SCALE is at least correctly applying the unit conversion correctly; i.e., I am getting the specific activities (in Bq/g) that I would expect to get based on the half-lives used in SCALE.

Unfortunately, the theoretical relationship you posted isn't rendering, so I'm unable to reproduce the calculation you've made.