2. Benchmark Specifications

2.1 Geometry Data

The geometry is typical of a U.S. PWR assembly and is shown in Figure 1. As this figure shows, the lattice consists of a 1717 array with 24 guide types containing water or burnable poison rods and 1 instrumentation tube. The geometric specifications are presented in Tables 1 and 2. The basic geometry description was taken from Ref. 1.

2.2 Material Data

The material data presented below were obtained from Ref. 2 and 3. Atom densities derived from the following data using SCALE 4.3 are presented in Appendix A.

2.2.1 Zircaloy-4

For simplicity, a typical zircaloy composition is assumed.
 

Density                 6.44 g/cm³
Composition          Zr    97.91 wt. %
                            Sn      1.59 wt. %
                            Fe        0.5 wt. %

 

Parameter	Value
Lattice	17x17
Number of fuel pins	264
Number of guide tubes	24
Number of instrumentation tubes	1
Assembly pitch	21.41728 cm
Pin pitch	1.25984 cm
Fuel rod
Pellet diameter	0.81915 cm
Clad inside diameter	0.83566 cm
Clad outside diameter	0.94996 cm
Pellet stack density	94.5 %TD
Clad material	Zircaloy-4
Active fuel length	365.76 cm
Guide Tubes
Inside diameter	1.143 cm
Outside diameter	1.224 cm
Material	Zircaloy-4

 

 

Region Number	Material	Outside diameter (cm)
1	Water	0.35
2	Zircaloy-4	0.50
3	Burnable poison (Al2O3-B4C)	0.65
4	Zircaloy-4	0.80
5	Water	1.143
6 (guide tube)	Zircaloy-4	1.224

 
 
 
 
Figure 1. PWR lattice geometry. When present burnable poison rod locations are the same as for the guide tubes.  

2.2.2 Fuel
 

Theoretical Density [1]       11.00 g/cm³
Composition                             PuO₂      4    wt. %
                                                UO₂      96   wt. %
Pu isotopics                              ²³⁹Pu    94   wt. %
                                               ²⁴⁰Pu      5   wt. %
                                               ²⁴¹Pu      1   wt. %
Uranium isotopics                     ²³⁵U     0.2   wt. %
                                               ²³⁸U    99.8  wt. %

 

2.2.3 Coolant/Moderator
 

Light water coolant density is a function of temperature as indicated below. The soluble boron concentration is given in the calculation definitions in Section 4 in terms of ppm of B by weight.
 
 

Density                             1.0       g/cm³ at 300 K
                                        0.7295 g/cm³ at 570 K
Boron Isotopics                 ¹⁰B      18.43 wt. %
                                       ¹¹B      81.57 wt. %
 
2.2.4 Burnable Poison
 

The burnable poison consists of Al₂O₃-B₄C with the following composition:

Density                           1.27 g/cm³
Composition                    Al₂O₃  90 wt. %
                                      B₄C    10 wt. % (natural boron)
 

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Cover | Introduction | Benchmark Specifications | Modeling Instructions | Calculational Definitions and Desired Results | References | Appendix A | Appendix B