gwzp_a_trans_ini.html

Tran/ini mode analysis of case a

Zero power case

gwzp_a_ini.dat (download) is the case a input.dat file, adapted for trans/ini mode.
The combination dsec=1, beg=.001 is adequate for obtaining fast convergence to rog= -3.3583E-03 in 4 iterations, as illustrated on gwzp_a_ini_wrt.pl0.

If the reference lstg/data set is supposed to be critical, it would mean that the residual reactivity deviation of about 3e-3 is due to thermal group correction effect?
gwzp_ini_ch1 comparing f2ci(1:32) vs ref shows little deviation and exhibits the same spectral transients at configuration interfaces, but the effect is smoother than for the anl benchmark because the reactivity differences between the core configurations are also lower

Case a transient

gwzp_a_trans.dat (download)
Case a transient application is now repeated after trans/ini initialization .
Under Lstci we simply enter the file name "f2ci.dat" containing the f2ci distribution gwzp_a_f2ci.dat (download) saved from trans/ini run
Under &Lstg, we add the core eigen reactivity r0g= -3.3583E-03 obtained from the trans/ini run, and let swsknug= f (default).

These are the only changes from the normal input deck.
chart 2 indicates that, for this case, at least, the effect of initialization mode on the subsequent power and reactivity transients is not significant. This result was expected, considering the weak deviations observed on the f2ci profiles.

Initialization at nominal power

cf gwzp_a1_ini.dat (download)
At nominal power, the physical feedbacks have a direct effect on the solution.
In Lstau, we set dsec_au= 1000 to disable over-power protection.
The combination (dsec=5, beg=.002) provides fast convergence gwzp_a1_ini_wrt.pl0
to r0g= -2.5297E-02 after 13 iterations. Here, the longer dsec needed may be linked to the time necessary for reach a converged radial temperature distribution in the pellets. This effect could be investigated by reducing the pellet and clad thermal capacity coefficients.
Notice also the large f2c floating before reaching the convergence. Observe the perfect stabilizatioin of q2c toward f0c after a rapid transient and the stabilization of u2c (effective) and u2ac (average) fluel temeperature, as the following the power profile stabilization.
hsc is of course unaffected by the power profile deformation.
Compare also (chart 3) the fci profiles withe zero power case and observe the effect of physical feedbacks on the fci profile.

Checking stationnarity

gwzp_a1_ini_check.dat (download) run confirms gwzp_a1_ini_check_wrt.pl0 the perfect stationnarity of the trans/ini solution at nominal power
The trans/ini procedure could easily be expanded for calculating as well all the reactivity coefficients (vs density, power, boron, rod displacement, ) and allowing specification of reactor vessel average water temperature instead of inlet enthalpy

Note to conlude that the ini/trans and subsequent transient runs could be linked as a single application