## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \begin{tabular}{c} **Concentration at** \\ **100 GWd/tHM** \\ **[ppm]** \\ \end{tabular} & \begin{tabular}{c} **Concentration at** \\ **200 GWd/tHM** \\ **[ppm]** \\ \end{tabular} & \begin{tabular}{c} **Concentration at** \\ **300 GWd/tHM** \\ **[ppm]** \\ \end{tabular} & \
\begin{tabular}{c} **POLARIS** \\ **100 GWd/tHM** \\ **[ppm]** \\ \end{tabular} &
\begin{tabular}{c} **Difference at** \\ **100 GWd/tHM** \\ **[ppm]** \\ \end{tabular} \\ \hline Zr & 4151 & 7459 & 10,554 & 4491 & 8\% \\ Mo & 3808 & 7222 & 10,286 & 3890 & 2\% \\ Ru & 2748 & 5967 & 9180 & 2512 & \(-9\%\) \\ Nd & 2988 & 5662 & 8242 & 3122 & 4\% \\ Pd & 1602 & 4543 & 8108 & 1139 & \(-29\%\) \\ Cs & 2998 & 5323 & 6935 & 3061 & 2\% \\ Ba & 1386 & 3424 & 6131 & 1309 & \(-6\%\) \\ Ce & 1976 & 3696 & 5361 & 1944 & \(-2\%\) \\ La & 865 & 1655 & 2396 & 999 & 15\% \\ Sm & 690 & 1495 & 2308 & 663 & \(-4\%\) \\ Pr & 865 & 1587 & 2181 & 904 & 5\% \\ Rh & 724 & 1390 & 1833 & 696 & \(-4\%\) \\ Sr & 926 & 1383 & 1752 & 1067 & 15\% \\ Te & 456 & 953 & 1437 & & \\ Tc & 792 & 1200 & 1330 & 894 & 13\% \\ Y & 518 & 834 & 1102 & 471 & \(-9\%\) \\ Rb & 408 & 661 & 864 & & \\ Cd & 104 & 353 & 811 & & \\ Ag & 110 & 285 & 482 & & \\ Gd & 46 & 180 & 422 & & \\ Sn & 86 & 196 & 313 & & \\ Eu & 63 & 142 & 233 & 53 & \(-16\%\) \\ Se & 74 & 135 & 189 & & \\ Pm & 82 & 89 & 102 & 89 & 9\% \\ Sb & 22 & 38 & 47 & & \\ Dy & 2 & 7 & 23 & & \\ In & 8 & 14 & 20 & & \\ Tb & 2 & 4 & 11 & & \\ Nb & 8 & 8 & 8 & \\ Ge & 1 & 2 & 2 & & \\ As & 0 & 0 & 1 & & \\ Ho & 0 & 0 & 0 & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Fission product elements followed through the HELIOS simulation with the concentrations appearing after different accumulated burnup states of the salt without clean-up and comparison of the results to POLARIS results published in [16]. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & \begin{tabular}{c} **Criticality Change at** \\ **EOL of Reference** \\ **Case [ppm]** \\ \end{tabular} & \begin{tabular}{c} **Achieved Target** \\ **Burnup** \\ **[GWd/tHM]** \\ \end{tabular} & \
\begin{tabular}{c} **Burnup Increase** \\ **Due to Element** \\ **Removal** \\ **[GWd/tHM]** \\ \end{tabular} &
\begin{tabular}{c} **Ranking Based On** \\ **Non-Dynamic** \\ **POLARIS Calc. [16]** \\ \end{tabular} \\ \hline direct & & 75.2 & & \\ ref & & 204.9 & 0.0 & \\
**ref-Ru** & 502 & 245.6 & 40.7 & 1 \\
**ref-Mo** & 444 & 239.7 & 34.9 & 2 \\
**ref-Pd** & 408 & 238.4 & 33.5 & 5 \\
**ref-Cs** & 348 & 231.4 & 26.5 & 3 \\
**ref-Nd** & 335 & 230.3 & 25.5 & 4 \\
**ref-Tc** & 301 & 227.2 & 22.3 & 7 \\ ref-Sm & 294 & 227.0 & 22.1 & 6 \\ ref-Rh & 229 & 221.9 & 17.1 & \\ ref-Zr & 169 & 217.1 & 12.2 & \\ ref-Pr & 57 & 208.9 & 4.0 & \\ ref-Eu & 56 & 208.8 & 4.0 & \\ ref-Ce & 44 & 208.0 & 3.1 & \\ Ref-Ba & 36 & 207.4 & 2.5 \\ ref-Ag & 35 & 207.3 & 2.4 & \\ ref-Pm & 35 & 207.4 & 2.5 \\ ref-La & 28 & 206.8 & 1.9 & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Criticality gain, target burnup, and burnup gain achieved through removal of 5% of the specific fission product in after every 10 GWd/tHM burnup step. The criticality effect of the accumulation of each of the followed-up fission product elements of Table 1 is analysed in Table 2. For this analysis, a direct calculation has been performed without any fission product removal as well as a reference calculation has been performed using the script and the removal of the gaseous and the volatile fission products. The reference calculation has then been re-run, including the removal of 5% of the selected fission product element at the end of each 10 GWd/tHM cycle. The detailed analysis of the criticality effect and the criticality gain at the end of life of the reference case has been evaluated; see the second column. In addition, the cycle simulation was continued until the stopping criterion k < 0.995 was approached.