Benchmarking
ANSI/ANS 6.6.1 Benchmark I.1
This benchmark is described in ANSI/ANS 6.6.1-1979, “American National Standard for Calculation and Measurement of Direct and Scattered Gamma Radiation from LWR Nuclear Power Plants”.
The benchmark models a 1 photon/sec point source of 6.2 MeV photons immersed in an air environment. Doses are calculated at locations 57 feet below the point source and at horizontal distances ranging from 200 ft to 5,000 ft. Air is modeled with a density of 0.00122 g/cm3. Results are provided in the following table.
Distance
(feet)
|
ANS 6.6.1
(mR/hr)
|
Microshield 7
(mR/hr)
|
ZapMeNot
(mR/hr)
|
MCNP5
(mR/hr)
|
|---|---|---|---|---|
200 |
1.04E-11 to
1.56E-11
|
1.194E-11 |
1.20E-11 |
1.2067E-11
+/- 0.02%
|
1,000 |
2.6E-13 to
3.91E-13
|
3.332E-13 |
3.30E-13 |
3.3980E-13
+/- 0.06%
|
3,000 |
5.86E-15 to
9.77E-15
|
9.096E-15 |
9.15E-15 |
9.4131E-15
+/- 0.2%
|
5,000 |
4.56E-16 to
7.55E-16
|
6.997E-16 |
6.99E-16 |
7.2265E-16
+/- 0.44%
|
ANSI/ANS 6.6.1 Benchmark II.1
This benchmark is also described in ANSI/ANS 6.6.1-1979. The source is a cylinder of water containing a uniformly distributed source of 0.8 MeV photons with a source strength of 30 MeV/sec/cm3. The cylinder is 12 feet in diameter and 35 feed high. Water density is 1 g/cm3 and the air density is 0.00122 g/cm3. Dose rates are determined at points with a height of 3 feet above the bottom of the cylinder and and radial distances from the cylinder centerline ranging from 20 feet to 500 feet. Results are provided in the following table.
Distance
(feet)
|
ANS 6.6.1
(mR/hr)
|
Microshield 7
(mR/hr)
|
ZapMeNot
(mR/hr)
|
MCNP5
(mR/hr)
|
|---|---|---|---|---|
20 |
7.81E-02 to
1.56E-01
|
9.213E-02 |
9.13E-02 |
7.9002E-02
+/- 0.2%
|
50 |
1.56E-02 to
2.86E-02
|
2.051E-02 |
2.06E-02 |
1.8210E-02
+/- 1.15%
|
200 |
9.77E-04 to
1.95E-03
|
1.178E-03 |
1.19E-03 |
1.1819E-03
+/- 1.92%
|
500 |
7.03E-05 to
1.56E-04
|
1.259E-04 |
1.26E-04 |
1.3537E-04
+/- 2.73%
|
ESIS Benchmark Problem 1
The ESIS benchmarks were originally documented in “Specification for gamma ray shielding benchmark applicable to a nuclear radwaste facility.” Newsletter #37, European Shielding Information Service. The benchmarks have been use in evaluations of both Microshield and VISIPLAN.
Problem 1 is a cylindrical water-filled steel tank surrounded by a concrete wall. It will be modeled in ZapMeNot as a cylindrical water source, an annular steel shield, and an slab concrete shield. The material densities are 0.00122 g/cm3, 1.0 g/cm3, 7.8 g/cm3, and 2.4 g/cm3 for air, water, steel, and concrete, respectively.
The source cylinder is 108.3 cm tall with a diameter of 308 cm. The steel shield has a radial thickness of 2.54 cm. The concrete slab shield is 220 from the centerline of the source cylinder and has a thickness of 91 cm. The dose rates are calculated on the inside of the concrete wall at a height of 50.15 cm and on the outside of the concrete wall at a height of 54.15 cm.
The source is defined in the following table.
Energy
(MeV)
|
Source
(photons/sec/cm3)
|
|
|---|---|---|
0.4 |
4.0E+6 |
|
0.8 |
7.0E+6 |
|
1.3 |
2.8E+6 |
|
1.7 |
8.2E+6 |
|
2.2 |
4.0E+4 |
|
2.5 |
3.0E+4 |
|
3.5 |
1.2E+1 |
|
Results are provided in the following table.
Radial
Location
|
ESIS Results
(mR/hr)
|
Microshield 7
(mR/hr)
|
ZapMeNot
(mR/hr)
|
|---|---|---|---|
Inside Wall |
4.54E+04 to
8.01E+04
|
6.29E+04 |
6.22E+04 |
Outside Wall |
4.9E-01 to
2.46E+00
|
1.89E+00 |
1.88E+00 |
ESIS Benchmark Problem 2
Problem 2 is similar to EIS Benchmark Problem 1. However, the source is a square tank 273 cm wide by 479.9 cm high. The tank wall remains at 2.54 cm thick and is surrounded by a concrete wall. The inside surface of the wall is 228.6 cm from the tank centerline. The thickness of the wall is 91.4. It will be modeled in ZapMeNot as a box water source, a slab steel shield, and an slab concrete shield. The material densities continue to be 0.00122 g/cm3, 1.0 g/cm3, 7.8 g/cm3, and 2.4 g/cm3 for air, water, steel, and concrete, respectively.
The dose rates are calculated on the inside and outside of the concrete wall at a height of 240.0 cm. Results are provided in the following table.
Radial
Location
|
ESIS Results
(mR/hr)
|
Microshield 7
(mR/hr)
|
ZapMeNot
(mR/hr)
|
|---|---|---|---|
Inside Wall |
1.49E+05 |
1.33E+05 |
1.32E+05 |
Outside Wall |
3.15E+00 |
3.01E+00 |
3.00E+00 |
Sphere Benchmark Problem
This is an analytic benchmark designed to evaluate a the ability to model a spherical source inside a shell acting as a shield.
The spherical source is an air medium with a radius of 70 ft and a density of 0.00122 g/cm3. The shell surrounding the spherical source region has a thickness of 30 inches and is composed of concrete with a density of 2.3 g/cm3. The dose point is located 302 ft, 7 in from the center of the sphere. The source is uniformly distributed within the air sphere with an energy of 1 MeV and a total activity of 1E17 photons/sec. The region surrounding the spherical shell is air with a density of 0.00122 g/cm3. The buildup material is concrete.
The following table contains the resulting dose rates calculated using ZapMeNot and Microshield7. ZapMeNot and Microshield7 were compared with both (10, 10, 10) and (30, 30, 30) intervals for the R, Theta, Phi quadrature and the dose point on the X axis (i.e. coplanar with the “equator” of the sphere). The results agree well, with ZapMeNot showing slightly more sensitvity to the quadrature used. An additional case was run using a (10, 10, 10) quadrature, but rotating the dose point such that It is on the Z axis of the sphere. This configuration eleminates the quadrature sensitivity. The results demonstrate that the quadrature used by ZapMeNot results in a non-uniform source quadrature. However, the impact of the quadrature is slight compared to the uncertainties introduced by the point-kernel model and can be compensated by increasing the quadrature used.
(10,10,10) Quadrature
7.331
7.384
(30,30,30) Quadrature
7.331
7.333
Dose Point on the Z Axis
N/A
7.333
Synthetic Benchmark Problem
This is an analytic benchmark designed to evaluate a number of features:
the use of multiple shields
older vs modern cross sections
photon energy group structure
This benchmark includes a point source composed of the following radioactive materials in the following table. Additionally, Ba-137m is assumed to be in secular equilibrium with Cs-137.
Isotope |
uCi |
|---|---|
Co-58 |
22.5 |
Co-60 |
32.4 |
Cs-137 |
150 |
Mn-54 |
12.5 |
Sb-125 |
11.3 |
The point source is centered in an annular iron shield with an inner radius of 3 feet and a thickness of 3 inches. A concentric annular concrete shield has an inner radius of 4 feet and a thickness of 18 inches. The material densities are 0.00122 g/cm3, 7.874 g/cm3, and 2.34 g/cm3 for air, steel, and concrete, respectively.
The following tables contain the resulting dose rates calculated using ZapMeNot, Microshield7, and MCNP5. Note that the Microshield results were generated using the “linear” energy group option. The default energy group option resulted in an additional 10% to 15% bias.
The first table contains dose rates determined at the outer surface of the concrete shield at varying axial distances above the point source.
The second table contains dose rates determined at the outer surface of the iron shield at varying axial distances above the point source.
Z
(cm)
|
MCNP
(mR/hr)
|
ZapMeNot
(mR/hr)
|
Microshield 7
(mR/hr)
|
|---|---|---|---|
0 |
1.87E-05 |
2.64E-05 |
2.64E-05 |
6 |
1.84E-05 |
2.62E-05 |
2.62E-05 |
20 |
1.73E-05 |
2.45E-05 |
2.45E-05 |
40 |
1.42E-05 |
1.97E-05 |
1.97E-05 |
60 |
1.01E-05 |
1.39E-05 |
1.39E-05 |
80.7 |
6.24E-06 |
8.54E-06 |
8.53E-06 |
Z
(cm)
|
MCNP
(mR/hr)
|
ZapMeNot
(mR/hr)
|
Microshield 7
(mR/hr)
|
|---|---|---|---|
0 |
1.08E-02 |
1.30E-02 |
1.30E-02 |
6 |
1.07E-02 |
1.29E-02 |
1.29E-02 |
20 |
9.89E-03 |
1.18E-02 |
1.18E-02 |
40 |
7.61E-03 |
9.03E-03 |
9.05E-03 |
60 |
5.14E-03 |
5.99E-03 |
6.01E-03 |
80.7 |
3.11E-03 |
3.52E-03 |
3.54E-03 |