Recommendations for the MOX fuel conductivity and heat transfer correlations to be used in the XT-ADS design and safety calculations

1
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)

2
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.
  1990 consistent
• with Del 3.4 Version 1.0 of the AFTRA
  project)

3
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
4
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
5
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
6
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 0.025 2-O/M, 0 at burnup and 5 porosity
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Correlations for the MOX fuel conductivity

• Temperature dependence of green fuel

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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 .

9
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
10
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
11
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.

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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

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Correlations for the MOX fuel conductivity

• Philipponneaus correlation T in K
• Thermal conductivity ? (1/(ABT) CT 3 )
  FP
• A 1.320 v(x0.0093) 0.0911 0.0038 t
• B 2.493 10 -4 m W -1 (constant)
• C 88.4 10 -12 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 t
  burn-up in at

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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

15
Review of heat transfer correlations for HLM
Triangular arraysP/D 1.409
16
Review of heat transfer correlations for HLM
Triangular arraysP/D 1.563
17
Review of heat transfer correlations for HLM

• Experimental investigations to study the heat
  transfer in liquid metals have preferably used
  mercury (Hg) and sodiumpotassium 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.

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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 1975.
• 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.

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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.)

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SAS4A/Ref05R0LBE calculation for XT-ADS hot pin
Peak linear rating 252 W/cm HTF-corr. LBE gt
clad Subbotin/Ushakov Coolant inlet
temperature 300 C Standard calculation corros
ion layer / GESA treatment not taken into
account. Modified calculation Oxide layer
with ? 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.
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XT-ADS Hot Pin Axial profiles of clad and
coolant temperature

22
XT-ADS Hot Pin Axial profiles of the clad
inner temperature(Modified calculation with
different additional oxide layers)