efit (pb) - design and preliminary ulof(ss) analysis m. schikorr, d. struwe (fzk)

Forschungszentrum KarlsruheTechnik und Umwelt

IRS /FzK W.M.SchikorrEUROTRANS WP1.5 Safety Meeting : Lyon, Oct 11-12. 2006 1

EFIT (PB) - Design and EFIT (PB) - Design and Preliminary ULOF(ss) AnalysisPreliminary ULOF(ss) Analysis

M. Schikorr, D. Struwe (FzK)M. Schikorr, D. Struwe (FzK)

EUROTRANS: DM1 WP1.5 : “Safety”

Lyon , 10-11 October 2006



1. Design Criteria for EFIT (Pb)

2. EFIT (Pb) design Data for Transient Analysis

3. Some EFIT (Pb) results to the ULOF transient

Topics:



1. Use MgO as fuel matrix for the MA-based fuel

2. Assure an optimal MA burning rate

3. Operate the system as a sub-critical system (k_eff ~ 0.95 - 0.97)

4. Account for the relatively low fuel temperatures allowable

T_fuel_max < 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)

1. Some important thermohydraulic EFIT Design Criteria:



Assure a sufficiently large natural convection flow rate ( > 25 % nominal flow) under ULOF conditions.

This implies :

1. keep pressure drop across the core „low“ (~< 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 <~ 0.8 bar

3. assure a height differential between the core midplane and the heat sink midplane of ~ 3.7 m

EFIT ULOF Design Criteria requires :



Option 1 :

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 :

Several EFIT design iterations were performed :



EFIT (Pb) Design Data used: Inner Core Zone CZ1, Fuel 62.5% MgO

Fuel Bundle and Pin Design

Dimensions UnitsNumber of pins 169Number of anchoring SS pins per SA 1Active Fuel Heights 90.0 cmPitch to Diameter Ratio 1.563Pin diameter 8.72 mmPitch 13.63 mmAnnulus diameter 0.0 mmNumber of Pin rows in SA 7Clad Thickness 0.6 mmCold Gap between clad and fuel 0.155 mmPellet diameter 7.210 mmAvailable inter-pin gap for spacers 7.7 mmSpace pin - inner wrapper 2.0150 mmWidth over inner flats 178.00 mmThickness Wrapper 4.00 mmGap between SA´s 5.00 mmWidth over outer flats (wrapper) 186.00 mmWidth over unit cell (includes Sgap) 191.00 mm

Number Fuel Subassemblies 48Number of SA spallation zone 19Number Grid Spacers 6

Thermal power 104.9 MW

Average Linear Power 144.5 W/cm

Axial Form Factor f_ax 1.143Radial Form Factor f_rad_hot_SA 1.29

f_peak_pin 1f_rad_tot 1.290f_tot_hot_SA 1.474f_tot_peak_pin 1.474

Peak Burn Up 100 MWd/kgiHM

62.5% MgO - 37.5% MOX Fuel BOC EOC

Porosity of MgO 10% 10%Porosity of Fuel 10% 10%O/M 1.88 1.88

T_in 400 °CT_out 480 °CMass Flow Rate 8980 kg/s

Heights difference core / heat sink 3.70 m



EFIT (Pb) Design Data used: Outer Core Zone CZ2, Fuel 50% MgO

Fuel Bundle and Pin Design

Dimensions UnitsNumber of pins 169Number of anchoring SS pins per SA 1Active Fuel Heights 90.0 cmPitch to Diameter Ratio 1.563Pin diameter 8.720 mmPitch 13.63 mmAnnulus diameter 0.0 mmNumber of Pin rows in SA 7Clad Thickness 0.6 mmCold Gap between clad and fuel 0.155 mmPellet diameter 7.210 mmAvailable inter-pin gap for spacers 7.7 mmSpace pin - inner wrapper 2.0150 mmWidth over inner flats 178.00 mmThickness Wrapper 4.00 mmGap between SA´s 5.00 mmWidth over outer flats (wrapper) 186.00 mmWidth over unit cell (includes Sgap) 191.00 mm

Number Fuel Subassemblies 174Number of SA spallation zone 19Number Grid Spacers 6

Thermal power 290 MW

Average Linear Power 110.2 W/cm

Axial Form Factor f_ax 1.133Radial Form Factor f_rad_hot_SA 1.45

f_peak_pin 1.00f_rad_tot 1.450f_tot_hot_SA 1.643f_tot_peak_pin 1.643

Peak Burn Up 100 MWd/kgiHM

50% MgO - 50% MOX Fuel BOC EOC

Porosity of MgO 10% 10%Porosity of Fuel 10% 10%O/M 1.88 1.88

T_in 400 °CT_out 480 °CMass Flow Rate 24825 kg/s



EFIT (Pb) Fuel Design: Inner and Outer Core Zones

Source : D1.6 Draft Sept.2006Source : V. Sobolev Sep. 2006 Source : D1.6 Draft Sept.2006



Calc. Pressure Drops:Spacers 0.042 barCore Inlet/Outlet - Core zone gagged 0.105 barFriction 0.183 barTotal Core 0.330 barTotal Prim. System 0.495 bar

Assumed Ratio System/Core Pressure Drop

1.500

EFIT (Pb) Data : Inner Core Zone CZ1

Fuel Thermal Cond. Poly Coeffs W/mK W/mKkfuel_k1 34.70 12.610kfuel_k2 -7.05E-02 -1.37E-02kfuel_k3 6.04E-05 4.81E-06kfuel_k4 -2.377E-08 2.259E-10kfuel_k5 3.707E-12 -1.595E-13

EFIT (Pb) Data : Outer Core Zone CZ2

Fuel Thermal Cond. Poly Coeffs W/mK W/mKkfuel_k1 25.66 9.754kfuel_k2 -5.09E-02 -1.01E-02kfuel_k3 4.33E-05 3.42E-06kfuel_k4 -1.694E-08 2.531E-10kfuel_k5 2.643E-12 -1.284E-13

Calc. Pressure Drops:Spacers 0.025 barCore Inlet/Outlet - Core zone gagged 0.190 barFriction 0.114 barTotal Core 0.329 barTotal Prim. System 0.493 bar

Assumed Ratio System/Core Pressure Drop

1.500



Nominal Conditions Inner Core Zone at BOC : EFIT (Pb) Axial Temperature Profile, PbBi-cooled Average Pin 145 W/cm

472

440480

503

1020

871933

723756

1111

300

400

500

600

700

800

900

1000

1100

1200

-45 -35 -25 -15 -5 5 15 25 35 45

Axial Core Position [cm]

Te

mp

era

ture

s [

°C]

Cladding

Coolant

Center Fuel

Surf Fuel

Avg

Axial Temperature Profile, PbBi-cooled Hot SA - avg Pin 186 W/cm

493

452503

533

1200

9931067

786 825

1310

300

500

700

900

1100

1300

1500

-45 -35 -25 -15 -5 5 15 25 35 45


Te

mp

era

ture

s [

°C]

Cladding

Coolant

Center Fuel

Surf Fuel

Avg Fuel

Source : D1.6 Draft Sept.2006



Nominal Conditions Outer Core Zone at BOC : EFIT (Pb)

Source : D1.6 Draft Sept.2006

Axial Temperature Profile, PbBi-cooled Average Pin 110 W/cm

468

440480

500

928

801852

674703

1002

300

400

500

600

700

800

900

1000

1100

-45 -35 -25 -15 -5 5 15 25 35 45


Te

mp

era

ture

s [

°C]

Cladding

Coolant

Center Fuel

Surf Fuel

Avg

Axial Temperature Profile, PbBi-cooled Hot SA avg Pin 160 W/cm

498

458516

545

1173

9671035

761 798

1274

300

500

700

900

1100

1300

1500

-45 -35 -25 -15 -5 5 15 25 35 45


Te

mp

era

ture

s [

°C]

Cladding

Coolant

Center Fuel

Surf Fuel

Avg Fuel



Nominal Conditions Inner Core Zone at EOL : EFIT (Pb) Axial Temperature Profile, PbBi-cooled Average Pin 146 W/cm

472

440480

503

775

639680

502528

840

300

400

500

600

700

800

900

-45 -35 -25 -15 -5 5 15 25 35 45


Te

mp

era

ture

s [

°C]

Cladding

Coolant

Center Fuel

Surf Fuel

Avg

Axial Temperature Profile, PbBi-cooled Hot SA - avg Pin 186 W/cm

493

452503

533

915

723780

531564

1008

300

400

500

600

700

800

900

1000

1100

-45 -35 -25 -15 -5 5 15 25 35 45


Tem

per

atu

res

[°C

]

Cladding

Coolant

Center Fuel

Surf Fuel

Avg Fuel

Note that peak clad temperatures exceed 500 °C requiring „coating“ of the T91 clad material.



Nominal Conditions Outer Core Zone at EOL : EFIT (Pb) Axial Temperature Profile, PbBi-cooled Average Pin 110 W/cm

468

440480

500

736

613648

491518

789

300

400

500

600

700

800

900

-45 -35 -25 -15 -5 5 15 25 35 45


Te

mp

era

ture

s [

°C]

Cladding

Coolant

Center Fuel

Surf Fuel

Avg Fuel

Axial Temperature Profile, PbBi-cooled Hot SA avg. Pin 159 W/cm

498

458516

545

926

729784

531570

1014

300

400

500

600

700

800

900

1000

1100

-45 -35 -25 -15 -5 5 15 25 35 45


Te

mp

era

ture

s [

°C]

Cladding

Coolant

Center Fuel

Surf Fuel

Avg Fuel

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



ULOF (ss) Inner / Outer Core Zone at BOC and EOL :

1. Natural Convection flow rate of EFIT under ULOFss conditions ~ 43 % !!

(much higher than the ~ 25% for XT-ADS)

1. This leads to lower T91 cladding temperatures ( < 700 °C ) for EFIT (Pb) in comparison to XT-ADS ULOFss temperatures ( 790 – 800 °C )



ULOF (ss) Inner / Outer Core Zone at BOC :EFIT (Pb) Inner Core Zone Hot SA avg Pin ULOF 187 W/cm

576

520

642

681

1303

10881174

874935

1420

300

500

700

900

1100

1300

1500

-45 -35 -25 -15 -5 5 15 25 35 45


Te

mp

era

ture

s [

°C]

Cladding surf

Coolant

Center Fuel

Surf Fuel

Avg Fuel

EFIT (Pb) Outer Core Zone Hot SA avg Pin ULOF 160 W/cm

579

528

657

693

1272

10581141

845909

1383

300

500

700

900

1100

1300

1500

-45 -35 -25 -15 -5 5 15 25 35 45


Te

mp

era

ture

s [

°C]

Cladding surf

Coolant

Center Fuel

Surf Fuel

Avg Fuel

Time to Failure [hr] of T91 Cladding

4.1E+04

1.E-01

1.E+01

1.E+03

1.E+05

1.E+07

1.E+09

1.E+11

1.E+13

1.E+15

400 450 500 550 600 650 700 750 800 850 900

Cladding Temperature [°C]

Tim

e t

o F

ailu

re [

hr]

BOL : Pgas = 10 bar

EOL Design: Pgas = 50 bar

Pgas = 100 bar

EFIT peak pin

30 min Failure Limit


1.4E+04

1.E-01

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

1.E+10

1.E+11

1.E+12

1.E+13

400 450 500 550 600 650 700 750 800 850 900


Tim

e t

o F

ailu

re [

hr]

BOL : Pgas = 10 bar


Pgas = 100 bar

EFIT peak pin


Clad failure not an issue at these clad temps.

Pgas =~10 bar

Pgas =~10 bar



ULOF (ss) Inner / Outer Core Zone at EOL :EFIT (Pb) Inner Core Hot SA avg Pin ULOF 187 W/cm

576

520

642

681

1034

824915

613

1159

300

400

500

600

700

800

900

1000

1100

1200

1300

-45 -35 -25 -15 -5 5 15 25 35 45


Te

mp

era

ture

s [

°C]

Cladding surf

Coolant

Center Fuel

Surf Fuel

Avg Fuel

EFIT Outer Core Zone Hot SA avg Pin ULOF 160 W/cm

579

528

657

693

1038

825

918

611

1159

300

400

500

600

700

800

900

1000

1100

1200

1300

-45 -35 -25 -15 -5 5 15 25 35 45


Tem

per

atu

res

[°C

]

Cladding surf

Coolant

Center Fuel

Surf Fuel

Avg Fuel

Clad failure not an issue at these clad temps.

Pgas = 178 bar tent.

Pgas = 178 bar tent.


1.1E+01

1.E-01

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

1.E+10

1.E+11

1.E+12

1.E+13

400 450 500 550 600 650 700 750 800 850 900


Tim

e to

Fai

lure

[hr]

BOL : Pgas = 10 bar


Pgas = 100 bar

EFIT peak pin



5.3E+00

1.E-01

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

1.E+10

1.E+11

1.E+12

1.E+13

400 450 500 550 600 650 700 750 800 850 900


Tim

e t

o F

ailu

re [

hr]

BOL : Pgas = 10 bar


Pgas = 100 bar

EFIT peak pin




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.



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 < 500 mbar )

5.) The ULOF transient behavior of the design still needs to be analysed in detail

efit (pb) - design and preliminary ulof(ss) analysis m. schikorr, d. struwe (fzk)

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