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EFIT PB Design and Preliminary ULOFss Analysis

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1. Use MgO as fuel matrix for the MA-based fuel. Assure an optimal MA burning rate ... EFIT (Pb) Design Data used: Outer Core Zone CZ2, Fuel 50% MgO ... – PowerPoint PPT presentation

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Title: EFIT PB Design and Preliminary ULOFss Analysis


1
  • EFIT (PB) - Design and Preliminary ULOF(ss)
    Analysis
  • M. Schikorr, D. Struwe (FzK)
  • EUROTRANS DM1 WP1.5 Safety
  • Lyon , 10-11 October 2006

2
Topics
  • Design Criteria for EFIT (Pb)
  • 2. EFIT (Pb) design Data for Transient Analysis
  • 3. Some EFIT (Pb) results to the ULOF transient

3
1. Some important thermohydraulic EFIT Design
Criteria
  • 1. Use MgO as fuel matrix for the MA-based fuel
  • Assure an optimal MA burning rate
  • Operate the system as a sub-critical system
    (k_eff 0.95 - 0.97)
  • Account for the relatively low fuel temperatures
    allowable
  • T_fuel_max lt 1600 C
  • 5. Also use T91 as clad material (as of now).
  • 6. Design core and primary system in such a
    manner to allow sufficient natural convection
    flow rate to survive a ULOF transient for at
    least 30 minutes without large number of pin
    failures (via gas blowout)

4
EFIT ULOF Design Criteria requires
Assure a sufficiently large natural convection
flow rate ( gt 25 nominal flow) under ULOF
conditions. This implies 1. keep pressure drop
across the core low (lt 0.5 bar) by selecting
an appropriate fuel pin / subassembly
design 2. minimize pressure losses throughout
the primary / DHRS system such that total system
pressure loss lt 0.8 bar 3. assure a height
differential between the core midplane and the
heat sink midplane of 3.7 m
5
Several EFIT design iterations were performed
  • Option 1
  • Assume a constant fuel matrix (i.e. 50 MgO) and
    vary the fuel pin / sub-assembly design in the
    two core zones in order to flatten the power
    profile.
  • Several variations in pin diameters and
    sub-assembly sizes were tried but it was
    difficult to achieve a satisfactory radial power
    distribution without excessive radial form
    factors.
  • Option 2
  • Assume a uniform geometric pin / SA design for
    the two core zones but vary the fuel matrix
    composition.
  • ENEA / ANSALDO decided for Option 2 with the
    following design

6
EFIT (Pb) Design Data used Inner Core Zone CZ1,
Fuel 62.5 MgO
7
EFIT (Pb) Design Data used Outer Core Zone CZ2,
Fuel 50 MgO
8
EFIT (Pb) Fuel Design Inner and Outer Core
Zones
Source D1.6 Draft Sept.2006
Source D1.6 Draft Sept.2006
Source V. Sobolev Sep. 2006
9
EFIT (Pb) Data Inner Core Zone CZ1
EFIT (Pb) Data Outer Core Zone CZ2
10
Nominal Conditions Inner Core Zone at BOC EFIT
(Pb)
Source D1.6 Draft Sept.2006
11
Nominal Conditions Outer Core Zone at BOC EFIT
(Pb)
Source D1.6 Draft Sept.2006
12
Nominal Conditions Inner Core Zone at EOL EFIT
(Pb)
Note that peak clad temperatures exceed 500 C
requiring coating of the T91 clad material.
13
Nominal Conditions Outer Core Zone at EOL EFIT
(Pb)
Note that peak clad temperatures exceed 500 C
requiring coating of the T91 clad
material. There is not much margin to the
temperature limit of coated T91 of 550 C !!
Note Hot spot analysis still pending
14
  • ULOF (ss) Inner / Outer Core Zone at BOC and EOL
  • Natural Convection flow rate of EFIT under ULOFss
    conditions 43 !!
  • (much higher than the 25 for XT-ADS)
  • This leads to lower T91 cladding temperatures ( lt
    700 C ) for EFIT (Pb) in comparison to XT-ADS
    ULOFss temperatures ( 790 800 C )

15
ULOF (ss) Inner / Outer Core Zone at BOC
Pgas 10 bar
Pgas 10 bar
Clad failure not an issue at these clad temps.
16
ULOF (ss) Inner / Outer Core Zone at EOL
Pgas 178 bar tent.
Pgas 178 bar tent.
Clad failure not an issue at these clad temps.
17
Conclusions on current EFIT (Pb) TH design
(1/2)
  • 1.) From the TH point of view the current
    EFIT(PB) design as proposed by ENEA / ANSALDO is
    quite viable assuming the cladding is coated as
    clad temperatures exceed 500 C under nominal
    conditions.
  • 2.) The calculations thus far have not assumed a
    form factor to account for the peak pin within
    the hottest subassembly (f_peak_pin should be
    1.04 instead of 1.0 as has been assumed). This
    will lead to even higher cladding temperatues of
    the peak pin, possibly in excess of 550 C.

18
Conclusions on current EFIT (Pb) TH - design
(2/2)
  • 3.) Under ULOF steady state conditions at EOL
    clad failure times are in excess of 1000 hrs as
    clad temperatures remain below 700 C
  • MgO fuel temperatures also remain below 1430 C
    ( a limit of 1500 C was decided not to be
    exceeded )
  • 4.) The design exhibits excellent natural
    convection characterisitics with w_nat 45
    under ULOF conditions ( low pressure losses lt 500
    mbar )
  • 5.) The ULOF transient behavior of the design
    still needs to be analysed in detail
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