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diff --git a/doc/IGE335/Section3.05_uss.tex b/doc/IGE335/Section3.05_uss.tex new file mode 100644 index 0000000..4961bf6 --- /dev/null +++ b/doc/IGE335/Section3.05_uss.tex @@ -0,0 +1,240 @@ +\subsection{The {\tt USS:} module}\label{sect:USSData} + +The universal self-shielding module in DRAGON, called {\tt USS:}, allows the +correction of the microscopic cross sections to take into account the +self-shielding effects related to the resonant isotopes. These isotopes are +identified as such by the \dusa{inrs} +parameter, as defined in \Sect{LIBData}. The universal +self-shielding module is based on the following models: + +\begin{itemize} +\item The Livolant-Jeanpierre flux factorization and approximations are used to +uncouple the self-shielding treatment from the main flux calculation; +\item The resonant cross sections are represented using probability +tables computed in the \moc{LIB:} module (the keyword \moc{SUBG} or \moc{PTSL} {\sl must} be +used). Two approaches can be used to compute the probability tables: +\begin{enumerate} +\item Physical probability tables can be computed using a RMS approach similar +to the one used in Wims-7 and Helios.\cite{subg} In this case, the slowing-down operator of +each resonant isotope is represented as a pure ST\cite{st}, ST/IR or ST/WR approximation; +\item Mathematical probability tables\cite{pt} and slowing-down correlated weight matrices +can be computed in selected energy groups using the {\sl Ribon extended} approach.\cite{nse2004} In this case, +an elastic slowing-down model is used and a mutual self-shielding model is +available. +\end{enumerate} +\item The resonant fluxes are computed for each band of the probability tables +using a subgroup method if \moc{SUBG}, \moc{PT}, \moc{PTMC} or \moc{PTSL} keyword is set in module \moc{LIB:}; +\item The resonance spectrum expansion (RSE) method is used if \moc{RSE} keyword is set in module \moc{LIB:}; +\item The flux can be solved using collision probabilities, or using {\sl any} +flux solution technique for which a tracking module is available; +\item The resonant isotopes are computed one-a-time, starting from the isotopes +with the lower values of index \dusa{inrs}, as defined in \Sect{LIBData}; If +many isotopes have the same value of \dusa{inrs}, the isotope with the greatest +number of resonant nuclides is self-shielded first. One or many outer iterations +can be performed; +\item The distributed self-shielded effect is automatically taken into account +if different mixture indices are assigned to different regions inside the +resonant part of the cell. The rim effect can be computed by dividing the fuel +into "onion rings" and by assigning different mixture indices to them. +\item A SPH (superhomog\'en\'eisation) equivalence is performed to correct the +self-shielded cross sections from the non-linear effects related to the +heterogeneity of the geometry. +\end{itemize} + +\vskip 0.2cm + +The general format of the data for this module is: + +\begin{DataStructure}{Structure \dstr{USS:}} +\dusa{MICLIB} \moc{:=} \moc{USS:} \dusa{MICLIB\_SG} $[$ \dusa{MICLIB} $]$ +\dusa{TRKNAM} $[$ \dusa{TRKFIL} $]$ \moc{::} \dstr{descuss} +\end{DataStructure} + +\noindent +where + +\begin{ListeDeDescription}{mmmmmmmm} + +\item[\dusa{MICLIB}] {\tt character*12} name of the \dds{microlib} that will +contain the microscopic and macroscopic cross sections updated by the +self-shielding module. If +\dusa{MICLIB} appears on both LHS and RHS, it is updated; otherwise, +\dusa{MICLIB} is created. + +\item[\dusa{MICLIB\_SG}] {\tt character*12} name of the \dds{microlib} builded +by module \moc{LIB:} and containing probability table information (the keyword \moc{SUBG} {\sl must} be +used in module {\tt LIB:}). + +\item[\dusa{TRKNAM}] {\tt character*12} name of the required \dds{tracking} +data structure. + +\item[\dusa{TRKFIL}] {\tt character*12} name of the sequential binary tracking +file used to store the tracks lengths. This file is given if and only if it was +required in the previous tracking module call (see \Sect{TRKData}). + +\item[\dstr{descuss}] structure describing the self-shielding options. + +\end{ListeDeDescription} + +Each time the \moc{USS:} module is called, a sub-directory is updated in the +\dds{microlib} data structure to hold the last values defined in the +\dstr{descuss} structure. The next time this module is called, +these values will be used as floating defaults. + +\subsubsection{Data input for module {\tt USS:}}\label{sect:descuss} + +\begin{DataStructure}{Structure \dstr{descuss}} +$[$ \moc{EDIT} \dusa{iprint} $]$ \\ +$[$ \moc{GRMIN} \dusa{lgrmin} $]~~[$ \moc{GRMAX} \dusa{lgrmax} $]$~~ +$[$ \moc{PASS} \dusa{ipass} $]~~[$ \moc{NOCO} $]~~[$ \moc{NOSP} $]$~~$[$ $\{$ \moc{TRAN} $|$ +\moc{NOTR} $\}$ $]$ \\ +$[$ $\{$ \moc{PIJ} $|$ \moc{ARM} $\}$ $]$ \\ +$[$ \moc{MAXST} \dusa{imax} $]~[$ \moc{FLAT} $]$ \\ +$[$ \moc{CALC} \\ +~~~~$[[$ \moc{REGI} \dusa{suffix} $[[$ \dusa{isot} $\{$ \moc{ALL} $|$ +(\dusa{imix}(i),i=1,\dusa{nmix}) $\}$ $]]$ \\ +~~~~$]]$ \\ +\moc{ENDC} $]$ \\ +{\tt ;} +\end{DataStructure} + +\noindent where + +\begin{ListeDeDescription}{mmmmmmmm} + +\item[\moc{EDIT}] keyword used to modify the print level \dusa{iprint}. + +\item[\dusa{iprint}] index used to control the printing of this module. The +amount of output produced by this tracking module will vary substantially +depending on the print level specified. + +\item[\moc{GRMIN}] keyword to specify the minimum group number considered +during the self-shielding process. + +\item[\dusa{lgrmin}] first group number considered during the +self-shielding process. By default, \dusa{lgrmin} is set to the first group +number containing self-shielding data in the library. + +\item[\moc{GRMAX}] keyword to specify the maximum group number considered +during the self-shielding process. + +\item[\dusa{lgrmax}] last group number considered during the self-shielding +process. By default, \dusa{lgrmax} is set is set to the last group +number containing self-shielding data in the library. + +\item[\moc{PASS}] keyword to specify the number of outer iterations during +the self-shielding process. + +\item[\dusa{ipass}] the number of iterations. The default is +\dusa{ipass} $=2$ if \dusa{MICLIB} is created. + +\item[\moc{NOCO}] keyword to ignore the directives set by {\tt LIB} concerning +the mutual resonance shielding model. This keyword has the effect to replace the +mutual resonance shielding model in the subgroup projection method (SPM) by a full +correlation approximation similar +to the technique used in the ECCO code. This keyword can be used to avoid the message +\begin{verbatim} +USSIST: UNABLE TO FIND CORRELATED ISOTOPE ************. +\end{verbatim} +\noindent that appears with the SPM if the correlated weights matrices are missing in +the microlib. + +\item[\moc{NOSP}] keyword to deactivate the SPH equivalence scheme which +modifies the self-shielded averaged neutron fluxes in +heterogeneous geometries. The default option is to perform SPH equivalence. + +\item[\moc{TRAN}] keyword to activate the transport correction option for +self-shielding calculations (see \moc{CTRA} in \Sectand{MACData}{LIBData}). This +is the default option. + +\item[\moc{NOTR}] keyword to deactivate the transport correction option for +self-shielding calculations (see \moc{CTRA} in \Sectand{MACData}{LIBData}). + +\item[\moc{PIJ}] keyword to specify the use of complete collision +probabilities in the subgroup and SPH equivalence calculations of {\tt USS:}. +This is the default option for \moc{EXCELT:} and \moc{SYBILT:} trackings. +This option is not available for \moc{MCCGT:} trackings. + +\item[\moc{ARM}] keyword to specify the use of iterative flux techniques +in the subgroup and SPH equivalence calculations of {\tt USS:}. +This is the default option for \moc{MCCGT:} trackings. + +\item[\moc{MAXST}] keyword to set the maximum number of fixed point iterations +for the ST scattering source convergence. + +\item[\dusa{imax}] the maximum number of ST iterations. The default is +\dusa{imax} $=50$ ($=20$ with the RSE method). A non-iterative response matrix approach is available with +the subgroup projection method (SPM) by setting \dusa{imax} $=0$. + +\item[\moc{FLAT}] keyword to force the flat-flux initialization of subgroup fluxes if \dusa{MICLIB} +is open in modification mode. + +\item[\moc{CALC}] keyword to activate the simplified self-shielding +approximation in which a single self-shielded isotope is shared by many +resonant mixtures. + +\item[\moc{REGI}] keyword to specify a set of isotopes and mixtures that +will be self-shielded together. All the self-shielded isotopes in this group +will share the same 4--digit suffix. + +\item[\dusa{suffix}] {\tt character*4} suffix for the isotope names in this +group + +\item[\dusa{isot}] {\tt character*8} alias name of a self-shielded isotope in this +group + +\item[\moc{ALL}] keyword to specify that a unique self-shielded isotope will be +made for the complete domain + +\item[\dusa{imix}] list of mixture indices that will share the same self-shielded +isotope + +\item[\dusa{nmix}] number of mixtures that will share the same self-shielded +isotope + +\item[\moc{ENDC}] end of \moc{CALC} data keyword + +\end{ListeDeDescription} + +\vskip 0.15cm + +Here is an example of the data structure corresponding to a production case where +only $^{238}$U is assumed to show distributed self-shielding effects: + +\begin{verbatim} +LIBRARY2 := USS: LIBRARY TRACK :: + CALC REGI W1 PU239 ALL + REGI W1 PU241 ALL + REGI W1 PU240 ALL + REGI W1 PU242 ALL + REGI W1 U235 ALL + REGI W1 U236 ALL + REGI W1 PU238 ALL + REGI W1 U234 ALL + REGI W1 AM241 ALL + REGI W1 NP237 ALL + REGI W1 ZRNAT ALL + REGI W1 U238 <<COMB0101>> <<COMB0201>> <<COMB0301>> + <<COMB0401>> <<COMB0501>> + REGI W2 U238 <<COMB0102>> <<COMB0202>> <<COMB0302>> + <<COMB0402>> <<COMB0502>> + REGI W3 U238 <<COMB0103>> <<COMB0203>> <<COMB0303>> + <<COMB0403>> <<COMB0503>> + REGI W4 U238 <<COMB0104>> <<COMB0204>> <<COMB0304>> + <<COMB0404>> <<COMB0504>> + REGI W5 U238 <<COMB0105>> <<COMB0205>> <<COMB0305>> + <<COMB0405>> <<COMB0505>> + REGI W6 U238 <<COMB0106>> <<COMB0206>> <<COMB0306>> + <<COMB0406>> <<COMB0506>> + ENDC ; +\end{verbatim} + +\vskip 0.15cm + +In this case, $^{238}$U is self-shielded within six distributed regions (labeled +{\tt W1} to {\tt W6}) and each of these regions are merging volumes belonging +to five different fuel rods. The mixture indices of the 30 resonant volumes belonging +to the fuel are CLE-2000 variables labeled {\tt <<COMB0101>>} to {\tt <<COMB0506>>}. + +\eject + |