Cell Calculation
The fuel assembly design is similar to the Westinghouse 17×17 XL Robust Fuel Assembly design and AP1000 fuel assembly design[Ref.3]. Cell homogenization calculation to get the group constants is carried out by using SRAC code. Once we have the group constants, then k-eff for a single calculational cell can be calculated as follow,
Where for finite cylinder, the geometrical buckling is formulated as,
The neutron energy is divided into 4 groups, and because this is a thermal reactor, so I arranged it as 1 fast group and 3 thermal groups, shown in the table below,
Energy Group Structure
| Fast 1 |
1.00000E+07 – 2.38240E+00 eV |
| Thermal 1 |
2.38240E+00 – 4.13990E-01 eV |
| Thermal 2 |
4.13990E-01 – 1.09630E-01 eV |
| Thermal 3 |
1.09630E-01 – 1.00000E-05 eV |
Some results of cell calculation are as follow.
Figures below depict k-eff for a single calculational cell under geometrical buckling 4.51658E-4 cm-2
Core Calculation
The summary of the reference design is shown below[Ref.4],
Reference Design
| Nominal reload strategy |
Two-batch (partial reload) |
| Number of fresh fuel assemblies |
40–45 |
| Actual number of batches |
1.98–2.22 |
| Fuel assemblies with 4.95% 235U enrichment |
40–45 |
| Fuel assemblies with reduced 235U enrichment |
- |
| Cycle length (Years) |
3.0–3.5 |
| Average discharge burnup (MWd/tU) |
48–53,000 |
| Lead rod average burnup (MWd/tU) |
< 62,000 |
And here is the schematic cross sectional view of the reactor core[Ref.3]:
For SRAC-CITATION calculation purpose, the core geometry is approximated as multi-region concentric cylinders, as follow,
Core geometrical approximation for SRAC-CITATION calculation
The reference core employs two-batch partial reload, which means that at the end of each cycle (3 – 3.5 years), about half of the fuel assemblies (40 – 45 FAs) are replaced with fresh fuels. By employing such reloading strategy in a 3 year cycle, the result is shown in the figure below,
The in-core power distribution of cycles after the first cycle depends on the fuel reloading pattern, which means the positioning strategy for fresh FAs. One possible option is to divide the active core radially into 2 equi-volume regions, and then replace the FAs in the outer region with fresh FAs, as illustrated in the figure below,
For the reloading pattern as explained above, the in-core power distributions are as follow,
Or another option is to divide the active core radially into 4 equi-volume regions, as illustrated in the following figure,
In that case, the power profile will become as follow,
References
- Duderstadt, James J. and Louis J. Hamilton. (1976), Nuclear Reactor Analysis, John Wiley & Sons, Inc, New York.
- Carelli, 2003 M.D. Carelli, IRIS, a global approach to nuclear power renaissance, Nuclear News 46 (10) (2003), pp. 32–42.
- Carelli et al., 2004 M.D. Carelli et al., The design and safety features of the IRIS reactor, Nuclear Engineering and Design 230 (2004), pp. 151–167.
- Carelli, 2009 M.D. Carelli, The exciting journey of designing an advanced reactor, Nuclear Engineering and Design 239 (2009), pp. 880–887.
