JOYO MK-I Core

Overview

MK-I core has been irradiated in the Japanese experimental fast reactor JOYO at 50 MWt and at 75 MWt from 1977 to 1981 (Shimada et al., 1986). JOYO was the first sodium cooled reactor leading the FBR development program in Japan. The MK-I core is composed by a maximum 80 driver assemblies surrounded by stainless steel reflectors.

Test Description

Rod Design Specifications

The fuel specifications for the MK-I core are summarized in Table 1.

Table 1: JOYO MK-I core specifications.

Fuel Rod	Measurement	Unit
Fuel stack height	600	mm
Plenum - fuel ratio	1
Fill gas composition	He
Fill gas pressure	0.3	MPa
Fuel	Measurement	Unit
Material	MOX
U 235 Enrichment	23.0	$var element = document.getElementById("moose-equation-e3426d11-3f11-47df-afca-47d9e5738b72");katex.render("\\%", element, {displayMode:false,throwOnError:false});$
PuO $var element = document.getElementById("moose-equation-9f3d1609-61ea-4ed8-ae06-ee8419731dea");katex.render("_{2}", element, {displayMode:false,throwOnError:false});$ content	18.0	$var element = document.getElementById("moose-equation-de4d33eb-9844-441f-88fa-2e316eb38314");katex.render("\\%", element, {displayMode:false,throwOnError:false});$
Density	93.5	$var element = document.getElementById("moose-equation-910ac269-808d-45a9-9675-4626b3babfc5");katex.render("\\%", element, {displayMode:false,throwOnError:false});$
Outer diameter	5.4	mm
Grain radius	8	$var element = document.getElementById("moose-equation-cf3fa961-9d1b-4ddf-9c0c-11325911a033");katex.render("\\mu", element, {displayMode:false,throwOnError:false});$ m
Cladding	Measurement	Unit
Material	316SS
Outer diameter	6.3	mm
Inner diameter	5.6	mm
Wall thickness	0.35	mm
Pin pitch	7.6	mm

Operating Conditions and Irradiation History

The base irradiation power history is shown in Figure 1 for the the operation at 50MWt and in Figure 2 for the experiment at 75MWt. The axial peak factors profile is shown in Figure 3. The coolant inlet temperature and pressure for the base irradiation is shown in Table 2.

Table 2: Operational input parameters.

	Unit	50 MWt	75 MWt
Coolant inlet temperature	C	370	370
Coolant pressure	MPa	0.101325	0.101325
Primary coolant flow rate	t/h	2200	2200
Linear heat rate	kW/m	21.0	32.0
Max. burnup (pin av.)	GWd/t	25	42

Figure 1: Base irradiation average power history for the 50MWt experiment of MK-I core .

Figure 2: Base irradiation average power history for the 75MWt experiment of MK-I core .

Figure 3: Power peaking factors for MK-I and MK-II cores from (Karahan, 2009).

Model Description

Geometry and Mesh

A generic rod from MK-I core was modeled as a smeared fuel pellet stack. The geometric parameters specified in Table 1 were used to create the meshes for these simulations. The smeared fuel was meshed as a single smeared fuel column with 20 radial elements and 200 axial elements. Figure 4 shows a section of the mesh with a temperature contour plot. This contour plot was made near the end of the run. Actual numbers are irrelevant in this case as this plot is only meant to show the discretization.

Figure 4: A section of the MK-I fuel rod mesh with a temperature contour plot.

Input files

The BISON input and all supporting files (power histories, axial power profile, fast neutron flux history, etc.) for this case are provided with the code distribution at bison/assessment/MOX/JOYO/MK-I/analysis.

Material and Behavioral Models

The following material and behavioral models for MOX fuel were used:

FissionRateMOX: model that takes into account of the pore migration for the fission rate calculations

MAMOXThermal: model for temperature and porosity dependent thermal properties

ComputeFiniteStrainElasticStress: elastic mechanical behavior

MAMOXElasticityTensor: constant values from JAEA are used for the two elastic constants Young's modulus ( $var element = document.getElementById("moose-equation-9d867167-ad63-4e6f-955b-ba65fa1b955c");katex.render("E=2.493\\times10^{11}", element, {displayMode:false,throwOnError:false});$ Pa) and Poisson ratio ( $var element = document.getElementById("moose-equation-b216bcce-7960-4507-8c45-fa5b67d00271");katex.render("\\nu=0.317", element, {displayMode:false,throwOnError:false});$ )

MAMOXThermalExpansionEigenstrain: isotropic thermal expansion's eigenstrain from (Kato et al., 2011) and (Kato et al., 2016)

UO2VolumetricSwellingEigenstrain: volumetric expansion due to solid and gaseous swelling

UO2Sifgrs: fission gas release model used with the gaseous swelling model UO2VolumetricSwellingEigenstrain (Pastore et al., 2015)

The following material and thermal behavior models were used for the cladding:

SS316Thermal: Thermophysical material properties

SS316ElasticityTensor: temperature-dependent Young's modulus and constant Poisson ratio ( $var element = document.getElementById("moose-equation-e7f13018-a6a2-4705-9458-2a9ef7042fb4");katex.render("\\nu=0.31", element, {displayMode:false,throwOnError:false});$ )

SS316ThermalExpansionEigenstrain: eigenstrain due to thermal expansion for Stainless Steel 316 using a function that describes the mean thermal expansion as a function of temperature

SS316CreepUpdate: steady state creep as sum of thermal and irradiation creep, following (Altenbach and Gorash, 2013) and (Garner and Porter, 1988)

Details and references for all of these models listed above can be found on the linked BISON documentation pages.

Results Comparison

Fission Gas Release

The calculated integral fuel rod FGR is compared to the measured data in Figure 5 for the experiment at 50 MWt and in Figure 6 for the 75 MWt experiment. BISON results with the recommended lower limit for the number density of grain boundary bubbles (10 $var element = document.getElementById("moose-equation-5c349c95-20ad-4365-8897-1a40fb198851");katex.render("^{11}", element, {displayMode:false,throwOnError:false});$ bubbles/m $var element = document.getElementById("moose-equation-953e75e4-ace1-452a-9483-cd8194b1dc8a");katex.render("{2}", element, {displayMode:false,throwOnError:false});$ ) for FBR MOX fuels show a good agreement with the experimental data, in line with the intrinsic modeling uncertainties (Pastore et al., 2015).

Figure 5: Fission gas release comparison for the experiment at 50 MWt among MK-I experimental data, BISON simulation using the previous lower limit for the number density of grain boundary bubbles (10 $var element = document.getElementById("moose-equation-e9dec919-4e3a-4040-af9d-b14f6b6d37e3");katex.render("^{10}", element, {displayMode:false,throwOnError:false});$ bubbles/m $var element = document.getElementById("moose-equation-52bfdc40-8110-434e-8e6f-747809939d5e");katex.render("{2}", element, {displayMode:false,throwOnError:false});$ ) used for UO $var element = document.getElementById("moose-equation-a3f0c2e6-4257-4815-9c70-d9029da8ad4c");katex.render("_2", element, {displayMode:false,throwOnError:false});$ and BISON simulation using the recommended lower limit for the number density of grain boundary bubbles (10 $var element = document.getElementById("moose-equation-912a301d-c509-4a88-bb60-c21856a4940f");katex.render("^{11}", element, {displayMode:false,throwOnError:false});$ bubbles/m $var element = document.getElementById("moose-equation-eee6f42d-021d-47d8-82b2-f2de3afae7a9");katex.render("{2}", element, {displayMode:false,throwOnError:false});$ ) for FBR MOX fuels.

Figure 6: Fission gas release comparison for the experiment at 75 MWt among MK-I experimental data, BISON simulation using the previous lower limit for the number density of grain boundary bubbles (10 $var element = document.getElementById("moose-equation-3e2e6039-f154-409b-83c0-963359c6ba74");katex.render("^{10}", element, {displayMode:false,throwOnError:false});$ bubbles/m $var element = document.getElementById("moose-equation-cfc40051-1c9a-47e0-ad43-671190dc1c0d");katex.render("{2}", element, {displayMode:false,throwOnError:false});$ ) used for UO $var element = document.getElementById("moose-equation-155a6d9d-838f-47e8-9447-b7eaad46c2d9");katex.render("_2", element, {displayMode:false,throwOnError:false});$ and BISON simulation using the recommended lower limit for the number density of grain boundary bubbles (10 $var element = document.getElementById("moose-equation-ef42377d-1617-4dd4-b2a6-5163c71c2cb3");katex.render("^{11}", element, {displayMode:false,throwOnError:false});$ bubbles/m $var element = document.getElementById("moose-equation-d32bc97b-8893-4a95-a902-7d29deb83070");katex.render("{2}", element, {displayMode:false,throwOnError:false});$ ) for FBR MOX fuels.

Discussion

For fast MOX fuels, higher temperatures are reached compared to LWR fuels. The associated pronounced bubble growth and coalescence can lead to the attainment of the lower limit for the number density of grain boundary bubbles systematically. Preliminary simulations of FBR MOX irradiations have indicated that a value of $var element = document.getElementById("moose-equation-eb4578a3-20ae-453c-b8fc-19aa4a33ccbf");katex.render("10^{11}", element, {displayMode:false,throwOnError:false});$ $var element = document.getElementById("moose-equation-bd26f6b6-73f3-47d2-b80d-a948b85523e0");katex.render("m^{-2}", element, {displayMode:false,throwOnError:false});$ leads to a more accurate result in terms of both FGR and swelling compared to the default LWR UO $var element = document.getElementById("moose-equation-2fa877c8-1b24-40c1-a2a3-e167cdbb044e");katex.render("_2", element, {displayMode:false,throwOnError:false});$ value. A value of $var element = document.getElementById("moose-equation-ebf6354f-4e1e-43c5-9816-237ea5fd985b");katex.render("10^{11}", element, {displayMode:false,throwOnError:false});$ $var element = document.getElementById("moose-equation-73922884-7069-4968-986b-35f4e3a786d9");katex.render("m^{-2}", element, {displayMode:false,throwOnError:false});$ is compatible with experimental observations, e.g., (White, 2004).

References

Holm Altenbach and Yevgen Gorash. High-temperature inelastic behavior of the austenitic steel aisi type 316. In Advanced Materials Modelling for Structures, pages 17–30. Springer, 2013.

@incollection{altenbach2013,
    author = "Altenbach, Holm and Gorash, Yevgen",
    title = "High-temperature inelastic behavior of the austenitic steel AISI type 316",
    booktitle = "Advanced Materials Modelling for Structures",
    pages = "17-30",
    year = "2013",
    publisher = "Springer"
}

FA Garner and DL Porter. Irradiation creep and swelling of aisi 316 to exposures of 130 dpa at 385-400 c. Journal of Nuclear Materials, 155:1006–1013, 1988.

@article{garner1988,
    author = "Garner, FA and Porter, DL",
    title = "Irradiation creep and swelling of AISI 316 to exposures of 130 dpa at 385-400 C",
    journal = "Journal of Nuclear Materials",
    volume = "155",
    pages = "1006-1013",
    year = "1988",
    publisher = "Elsevier"
}

Aydin Karahan. Modeling of thermo-mechanical and irradiation behavior of metallic and oxide fuels for sodium fast reactors. PhD thesis, Massachusetts Institute of Technology, Jun 2009. URL: https://tinyurl.com/y72vqvbn.

@phdthesis{karahan2009,
    author = "Karahan, Aydin",
    title = "Modeling of thermo-mechanical and irradiation behavior of metallic and oxide fuels for sodium fast reactors",
    school = "Massachusetts Institute of Technology",
    year = "2009",
    month = "Jun",
    url = "https://tinyurl.com/y72vqvbn"
}

M. Kato, Y. c, T. Sunaoshi, A. Nelson, and K. McClellan. Thermal expansion measurement of $(U,Pu)O_2-x$ in oxygen partial pressure-controlled atmosphere. Journal of Nuclear Materials, 469:223–227, 2016.

@article{kato2016,
    author = "Kato, M. and c, Y. and Sunaoshi, T. and Nelson, A. and McClellan, K.",
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}

M. Kato, K. Maeda, T. Ozawa, M. Kashimura, and Y. Kihara. Physical properties and irradiation behavior analysis of Np- and Am-bearing MOX fuels. Journal of Nuclear Science and Technology, 48:646–653, 2011.

@article{kato2011,
    author = "Kato, M. and Maeda, K. and Ozawa, T. and Kashimura, M. and Kihara, Y.",
    title = "Physical properties and Irradiation behavior analysis of {Np-} and {Am}-bearing {MOX} fuels",
    journal = "Journal of Nuclear Science and Technology",
    volume = "48",
    pages = "646-653",
    year = "2011"
}

G. Pastore, L.P. Swiler, J.D. Hales, S.R. Novascone, D.M. Perez, B.W. Spencer, L. Luzzi, P. Van Uffelen, and R.L. Williamson. Uncertainty and sensitivity analysis of fission gas behavior in engineering-scale fuel modeling. Journal of Nuclear Materials, 465:398–408, 2015.

@ARTICLE{pastore_et_al_2015,
    author = "Pastore, G. and Swiler, L.P. and Hales, J.D. and Novascone, S.R. and Perez, D.M. and Spencer, B.W. and Luzzi, L. and Uffelen, P. Van and Williamson, R.L.",
    title = "Uncertainty and sensitivity analysis of fission gas behavior in engineering-scale fuel modeling",
    journal = "Journal of Nuclear Materials",
    year = "2015",
    volume = "465",
    pages = "398-408"
}

Giovanni Pastore, L.P. Swiler, J.D. Hales, S.R. Novascone, D.M. Perez, B.W. Spencer, L. Luzzi, P. Van Uffelen, and R.L. Williamson. Uncertainty and sensitivity analysis of fission gas behavior in engineering-scale fuel modeling. Journal of Nuclear Materials, 456:398–408, 2015. doi:10.1016/j.jnucmat.2014.09.077.

@article{PASTORE2015398,
    author = "Pastore, Giovanni and Swiler, L.P. and Hales, J.D. and Novascone, S.R. and Perez, D.M. and Spencer, B.W. and Luzzi, L. and {Van Uffelen}, P. and Williamson, R.L.",
    title = "Uncertainty and sensitivity analysis of fission gas behavior in engineering-scale fuel modeling",
    journal = "Journal of Nuclear Materials",
    volume = "456",
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    year = "2015",
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    doi = "10.1016/j.jnucmat.2014.09.077"
}

T. Shimada, T. Itaki, Y. Nara, and J. Komatsu. Operational experience of experimental fast reactor joyo driver fuel. International Conference on Reliable Fuels for Liquid Metal Reactors, 1986.

@article{joyo-mk1-mk2,
    Author = "Shimada, T. and Itaki, T. and Nara, Y. and Komatsu, J.",
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    Title = "Operational experience of experimental fast reactor JOYO driver fuel",
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}

R.J. White. The development of grain-face porosity in irradiated oxide fuel. Journal of Nuclear Materials, 325:61–77, 2004.

@ARTICLE{white2004,
    author = "White, R.J.",
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    volume = "325",
    pages = "61-77"
}

Overview
Test Description
Model Description
Input files
Results Comparison
References