EUROTRANS DESIGN WP 1.5 Meeting May 22nd/23rd 2007 Stockholm, Sweden Recommendations for the MOX fuel conductivity and heat transfer correlations to be used in the XT-ADS design and safety calculations D. Struwe, W. Pfrang Forschungszentrum Karlsruhe Institut für Reaktorsicherheit D. Sruwe, W. Pfrang: “Recommendation for the fuel conductivity of the MOX fuel to be used for the XT-ADS core design” (December 2006) W. Pfrang, D. Struwe:” Assessment of correlations for the heat transfer to the coolant necessary for heavy liquid metal cooled core designs” (May 2007)

EUROTRANS DESIGN WP 1.5 Meeting May 22nd/23rd 2007 Stockholm, Sweden Correlations for the MOX fuel conductivity MOX fuel conductivity is dependent on - temperature, - porosity, - oxygen to metal ratio and - burn-up Correlations of special interest here are the following ones - the Duriez-correlation with the LUCUTA model for burn-up - the Duriez-NFI correlation used in the FRAPCON-3 code, - the mod. Martin correlations used in the CABRI project - the correlations of Philipponneau used in the EFR project. (Fast Reactor Data Manual, issue 1, Nov consistent with Del 3.4 Version 1.0 of the AFTRA project)

EUROTRANS DESIGN WP 1.5 Meeting May 22nd/23rd 2007 Stockholm, Sweden Correlations for the MOX fuel conductivity Burn-up dependence Burn-up correction factor of the fuel thermal conductivity correlations of Lucuta and Duriez-mod NFI mod (FRAPCON) for different temperatures over burn-up qualified for LWR fuels

EUROTRANS DESIGN WP 1.5 Meeting May 22nd/23rd 2007 Stockholm, Sweden Correlations for the MOX fuel conductivity Burn-up dependence Burn-up correction factor of the fuel thermal conductivity correlations of SAS4A mod. Martin and Duriez-mod NFI mod (FRAPCON) for different temperatures over burn-up qualified for fast reactor or LWR fuels respectively

EUROTRANS DESIGN WP 1.5 Meeting May 22nd/23rd 2007 Stockholm, Sweden Correlations for the MOX fuel conductivity Porosity dependence Porosity correction factor of the fuel thermal conductivity correlations SAS4A mod. Martin, Lucuta and Philipponneau over porosity qualified for fast reactor and And LWR fuels respectively

EUROTRANS DESIGN WP 1.5 Meeting May 22nd/23rd 2007 Stockholm, Sweden Correlations for the MOX fuel conductivity Temperature dependence of green fuel Fuel thermal conductivity correlations SAS4A mod. Martin and Duriez-mod NFI mod (FRAPCON) for O/M, 0 at% burnup and 5% porosity

EUROTRANS DESIGN WP 1.5 Meeting May 22nd/23rd 2007 Stockholm, Sweden Correlations for the MOX fuel conductivity Temperature dependence of green fuel

EUROTRANS DESIGN WP 1.5 Meeting May 22nd/23rd 2007 Stockholm, Sweden Correlations for the MOX fuel conductivity Temperature dependence of green fuel In Duriez et.al. it is explicitly stated on basis of experimental data evaluations for green fuel that the behaviour difference between FBR and LWR mixed oxide fuels is to be taken as a fact Equations recommended for the determination of the light water reactor fuels should not be used to calculate the conductivity of hypo- stoichiometric oxide fuels if the Pu- concentration is higher than 15 %.

EUROTRANS DESIGN WP 1.5 Meeting May 22nd/23rd 2007 Stockholm, Sweden Correlations for the MOX fuel conductivity Fuel thermal conductivity correlations of SAS4A mod. Martin and Philipponneau for different 2-O/M-ratios, 0 at% burn-up and 5% porosity

EUROTRANS DESIGN WP 1.5 Meeting May 22nd/23rd 2007 Stockholm, Sweden Correlations for the MOX fuel conductivity Burn-up correction factor of the fuel thermal conductivity of correlations SAS4A mod. Martin and Philipponneau for different temp. over burn-up

EUROTRANS DESIGN WP 1.5 Meeting May 22nd/23rd 2007 Stockholm, Sweden Correlations for the MOX fuel conductivity Theoretical interpretation of the CABRI projects at FZK i.e. pre-test and post test calculations revealed that use of the re- commendations according to mod. Martin led to the relatively best agreement between experimental observations and calculated results especially in case of low power pre- irradiations. The international fuels specialists group of the EFR project came to the conclusion that the recommendations provided by Philipponneau should be taken as reference for the EFR project evaluations. Differences between mod. Martin and Philipponneau are small except for low power operation conditions.

EUROTRANS DESIGN WP 1.5 Meeting May 22nd/23rd 2007 Stockholm, Sweden Correlations for the MOX fuel conductivity Correlations for determination of the influence of burn-up on the fuel conductivity as proposed by Lucuta leads partly to curious results of correction factor dependencies from burn- up which cannot be accepted. The modified approach followed in the FRAPCON-3 code was investigated in view of experimental results obtained within the CABRI – programs. It could be demonstrated that application of this recommendation leads to an over- estimation of the fuel temperatures by up to 350 K especially for high burn-up conditions and thus to erroneous results concerning fission gas release and clad loading in case it is applied to fast reactor fuel pins. To maintain consistency with the EFR project recommendation it is appropriate to apply the set of correlations developed by Philipponeau for the fast reactor fuels of the XT-ADS project

EUROTRANS DESIGN WP 1.5 Meeting May 22nd/23rd 2007 Stockholm, Sweden Correlations for the MOX fuel conductivity Philipponneau’s correlation [T in K] Thermal conductivity: λ = (1/(A+BT) + CT ** 3 )* FP A = √(x ) – τ B = m W -1 (constant) C = W m -1 K -4 (constant) FP – correction factor representing the effect of porosity FP = (1 – P) / (1 + 2P) P – porosity; x – deviation from stoichiometry; τ – burn-up in at%

EUROTRANS DESIGN WP 1.5 Meeting May 22nd/23rd 2007 Stockholm, Sweden Review of heat transfer correlations for HLM Evaluated dependencies: - Correlations for tube flows - Correlations for flows in triangular rod bundles (influence of P/D - ratio) - Correlations for flow in square rod bundles (influence of P/D - ratio) - Influence of spacers and axial power profiles

EUROTRANS DESIGN WP 1.5 Meeting May 22nd/23rd 2007 Stockholm, Sweden Review of heat transfer correlations for HLM Triangular arrays P/D = 1.409

EUROTRANS DESIGN WP 1.5 Meeting May 22nd/23rd 2007 Stockholm, Sweden Review of heat transfer correlations for HLM Triangular arrays P/D = 1.563

EUROTRANS DESIGN WP 1.5 Meeting May 22nd/23rd 2007 Stockholm, Sweden Review of heat transfer correlations for HLM Experimental investigations to study the heat transfer in liquid metals have preferably used mercury (Hg) and sodium–potassium alloy (NaK), sometimes also sodium (Na) and, for tube flows, also a lead-bismuth alloy (LBE) has been used. The Prandtl numbers of lead and LBE are in the same range as those of Hg and NaK. Some developers of correlations assessed experimental data from campaigns using different coolants and none of the respective publications reported on differences which could be attributed to the differences of the fluids. Therefore, correlations considered here, which are not explicitly dependent from the Prandtl number, can be used for lead and LBE without restriction.

EUROTRANS DESIGN WP 1.5 Meeting May 22nd/23rd 2007 Stockholm, Sweden Review of heat transfer correlations for HLM The correlation of Subbotin/Ushakov recommended for P/D ratios between 1.2 and 2.0 appears to be the one with the best experimental qualification The data base for rod bundles with triangular rod arrange- ments, which has been used to adjust the correlations, is relatively extended, but it has to be noted, that the respective experiments for triangular arrays have all been performed before It has been shown that spacers can enhance the heat transfer substantially, especially in the vicinity of the spacer. This has to be kept in mind if spacers are used which alter the local coolant flow considerably.

EUROTRANS DESIGN WP 1.5 Meeting May 22nd/23rd 2007 Stockholm, Sweden Review of heat transfer correlations for HLM The consequences of possible oxide layers on the cladding should not be covered by the Nusselt number correlations but modelled separately in the computer codes. 1 / alpha total = 1 / alpha conv + 1 /alpha cond alpha conv – convective heat transfer alpha cond = lambda / layer thickness lambda - thermal conduction of the layer, f (density, temperature) layer thickness – f (temperature, residence time, etc.)

EUROTRANS DESIGN WP 1.5 Meeting May 22nd/23rd 2007 Stockholm, Sweden SAS4A/Ref05R0LBE calculation for XT-ADS hot pin Peak linear rating:252 W/cm HTF-corr. LBE => clad:Subbotin/Ushakov Coolant inlet temperature:300 °C Standard calculation: corrosion layer / GESA treatment not taken into account. Modified calculation: Oxide layer with λ = 1 W/(mK) and variable thickness added. (Thermal conductivity of steel in the respective temperature range is about 28 W/(mK)). Only thermal aspects considered here.

EUROTRANS DESIGN WP 1.5 Meeting May 22nd/23rd 2007 Stockholm, Sweden XT-ADS Hot Pin: Axial profiles of clad and coolant temperature

EUROTRANS DESIGN WP 1.5 Meeting May 22nd/23rd 2007 Stockholm, Sweden XT-ADS Hot Pin: Axial profiles of the clad inner temperature (Modified calculation with different additional oxide layers)