Preliminary Results of Three Dimensional Core Design in JAPAN Information Exchange Meeting on SCWR Development April 29, 2003 Toshiba Corporation The University of Tokyo
Scope of SCWR Core Design (in Short Term) 2 2003/03 Development of Core Simulator Material & Thermalhydraulics Research Plant Design Preliminary Design Improved Design Final Design 2003/09 Design criteria Research 2004/03
Core Simulator Flowchart Nuclear module Thermal hydraulics module 3 Making of base diffusion constant Between bundles low distribution calculation Power correction of diffusion constant The heat balance of each bundle is calculated from the flow and the power distribution. Diffusion calculation Power distribution Water density distribution
Differences of SCWR and BWR Core Simulators Nuclear Module Similar neutron spectra Slightly higher U enrichment for SCWR 50 4 Thermal hydraulics module No boiling phenomenon beyond the critical pressure Large specific heat changes around the pseudo-critical point and its strong temperature dependency Specific heat (kj/kg/k) 40 30 20 0 7 MPa 24 MPa 0 00 200 300 400 500 600 Temperature (ºC)
Improved Thermal Hydraulics Module for SCWR 5 Supercritical water is treated as a single phase fluid The specific volume and the temperatures are calculated from enthalpy The calculation routines have been made based on the steam table by the Japan Society of Mechanical Engineers (JSME Steam Table)
Design Targets 6 High Core Outlet Coolant Temperature Flattening of Radial Power Distribution (Radial power peaking factor less than.25) Small Bundle Power Change during a cycle (Bundle power change less than 30% )
Core Design Conditions (Assumptions) 7 Thermal power : 2273MWt (Electric power : 000MWe) Reactor core flow rate : 57kg/s Average discharge exposure : 45GWd/t Flow distribution are assumed to be unchanged during a cycle (Preliminary) Fuel Bundle 97 bundles reactor core (bundle center)
Fuel Design Conditions 8 Basic configuration : the University of Tokyo design The number of the control rod : 6 Burnable poison : Gd (same as BWR) Worth (%k/k) 40 30 20 0 Uranium fuel Gd fuel Rod Water rod 8 rods 6 rods 36 rods 0 0.0 0.5.0.5 2.0 Rod radius (cm)
Equilibrium Core Design : k 9 Gd concentration and number The shutdown margin, the radial power peaking factor, and the position of the power peak G G G G G G2 High Concentration (0%) Gd Rod Improvement of axial power distribution Partial Length Gd rod G2 24 23 22 2 20 9 8 7 6 5 4 3 2 0 9 8 7 6 5 4 3 2 6.2e 6.2e 0.0G 6.2e.0 6.2e 0.0G 6.20 6.20 G G2 277 20 4
Infinite Multiplication Factors.3 0.2. Lower High Con. Gd k-infinity.0 0.9 0.8 0.7 0.6 Typical design Partial Upper Gd 0 0 20 30 40 50 60 70 Exposure GWd/t
Equilibrium Core Design : Loading Pattern Flattening of radial power distribution The first cycle fuels installed in the most outer The second and the third cycle fuels installed inner Stabilizing the position of radial power peak Monotonous decrease of infinite multiplication factor of fuel assembly Control rod pattern optimization 2nd. cycle fuel 3rd. cycle fuel st. cycle fuel 4th. cycle fuel
Equilibrium Core Characteristics : MLHGR 60 2.6 2 MLHGR(kW/m 50 40 30 20 Maximum linear heat generation rate(mlhgr) Axial Peaking 0 2 3 4 5 6 7 8 9 0 2 3 4 5 Cycle Exposure GWd/t 2.4 2.2 2.0.8.6.4.2.0 Axial Peaking
Moderator Temperature and Radial Peaking 650.8 3 Outlet temperature of moderator( C) 600 550 500 450 Outlet temperature of moderator(highest) Radial peaking.6.4.2.0 Radial peaking 400 0 2 3 4 5 6 7 8 9 0 2 3 4 5 Cycle Exposure GWd/t 0.8
Axial Power Distribution Axial position 24 23 22 2 20 9 8 7 6 5 4 3 2 0 9 8 7 6 5 4 3 2 0.0GWd/t(BOC) 6.6GWd/t(MOC) 4.8GWd/t(EOC) 0.0 0.5.0.5 2.0 2.5 3.0 Relative Power BOC : Bottom peak - partial insertion control rod -water density distribution MOC : Two peaks EOC : Top peak 4
Equilibrium Core Characteristics 5 Radial power peaking factor Power variation of each bundle MLHGR Shutdown margin Moderator outlet temperature.27 or less 30% or less 45kW/m or less.0%k or more 580 o C or less The design condition of BWR was almost satisfied. Radial power distribution is flat enough. Variations of each bundle power is small enough.
Summary 6 The 3-D core simulator for SCWR has been completed by improving the thermal hydraulics module in BWR core simulator. SCWR equilibrium core is feasible, which almost satisfies the design criteria of BWR. The preliminary core design has a flat radial power distribution and small power changes.