5.10. PRIMAR-1 Option
PRIMAR-4 contains both a simple PRIMAR-1 type option and the more detailed PRIMAR-4 treatment. The PRIMAR-1 option supplies only the minimum quantities required to drive the subassembly coolant dynamics module. It is often used when the more detailed treatment is not required. The minimum information consists of the inlet and outlet plenum pressures, the subassembly inlet temperatures, and the outlet reentry temperatures. All of these quantities are supplied as a function of time by PRIMAR-1 from user-supplied information, independent of what is happening in the core or in the rest of the primary loop.
There are two available options for determining the inlet pressure.
The first option is based on a normalized pump head and the second option
is based on a normalized flow rate through channel IFLOW.
5.10.1. Defined Pump Head
When IFLOW = 0, the inlet pressure is based on a normalized pump head.
The inlet pressure \(p_{\text{in}} \left( t \right)\) is calculated as
where \(p_{\text{x}}\) is the user-specified exit plenum pressure, PX,
\(p_{\text{gr}}\) is the gravity head, and \(\Delta p_{\text{p}} \left( t \right)\) is the
pump head. The gravity head is calculated as
where \({\rho}_{\text{HOT}}\) is the average steady-state outlet density,
\({\rho}_{\text{COLD}}\) is the average steady-state inlet density,
\(z_{\text{PU}}\) is the reference height at which the outlet plenum
pressure is calculated, ZPLENU, \(z_{\text{PL}}\) is the reference height at which
the inlet plenum pressure is calculated, ZPLENL, and \(z_{\text{IHX}}\) is the
reference height of the thermal center of the intermediate heat
exchanger, ZIHX.
The pump head is calculated as
where \(\Delta p_{\text{o}}\) is the steady-state pump head, taken as
and \(f_{\text{p}} \left( t \right)\) is the user-supplied time dependence of the pump head, which should be normalized so that
There are two options for specifying \(f_{\text{p}} \left( t \right)\). One option is
for the user to supply a table of \(f_{\text{p}}\) as a function of time.
This table is defined in PRETAB and PRETME or a function block,
depending on the value of NPRES.
With this option, the code interpolates linearly between table
entries.
The other option is for the user to supply the three coefficients \(p_{\text{d}}\), \(p_{\text{d}1}\), \(p_{\text{d}2}\) for use in the equation
where
\(p_{\text{d}}\) is defined using PDEC,
\(p_{\text{d}1}\) is defined using PDEC1, and
\(p_{\text{d}2}\) is defined using PDEC2.
This option is selected by setting NPRES = 0.
For both normalized pump head options, the time derivatives of the inlet and exit plenum pressures are calculated as
and
where \(p_{1}\) and \(p_{2}\) are the pump head values at the beginning and end of the time interval \(\Delta t\).
5.10.2. Defined Flow Rate
When IFLOW \(\ne 0\), the inlet pressure is based on flow rate through channel IFLOW.
The inlet pressure \(p_{\text{in}} \left( t \right)\) is calculated as
where
\(I_1\), \(I_2\), \(I_3\), \(I_4\), \(I_5\), \(A_{\text{fr}}\), and \(b_{\text{fr}}\) are the momentum equation contributions, defined in Section 3.9.2, for channel IFLOW,
\(z_{\text{1}}\), and \(z_{\text{MZC}}\) are the elevations at the bottom and top of the fuel channel, and
\(\rho_{\text{HOT}}\), and \(\rho_{\text{COLD}}\) are the coolant density in the upper and lower plenum at time \(t\).
The channel flow rate and its derivative are calculated as
and
where \(w_0\) is the flow rate through channel IFLOW at time \(t=0\),
and \(f\left( t \right)\) is the user-supplied time dependence of the normalized flow rate.
\(f\left( t \right)\) is defined in PRETAB and PRETME or a function block,
depending on the value of NPRES.
The time derivatives of the inlet and exit plenum pressures are calculated as
and
where