efit design and transient analysis m. schikorr, e. bubelis eurotrans: dm1 wp1.5 : “safety”

Forschungszentrum KarlsruheTechnik und Umwelt

IRS /FzK W.M.SchikorrEUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007 1

EFIT Design and Transient EFIT Design and Transient AnalysisAnalysis

M. Schikorr, E. BubelisM. Schikorr, E. Bubelis

EUROTRANS: DM1 WP1.5 : “Safety”

Madrid , 13-14 November 2007



1. Design Criteria for EFIT-Pb

2. EFIT design data for Transient Analysis

3. Some EFIT-Pb results to the ULOF transient

Topics:



1. Use of MgO-based MA-MOX Fuel Mixture

2. Operate EFIT at k_eff ~ 0.95 - 0.97 with flat k_eff burnup characterisitics

3. Adopted 3-Core region design to obtain flat radial power profile (designed by ENEA and ANSALDO)

4. Design core and primary system in such a manner to allow sufficient natural convection flow rate to sustain a ULOF transient for at least 30 minutes without „large number“ of pin failures (via gas blowdown)

5. Account for burn-up and protective oxide layer formation during operation of plant

1. Some important EFIT Design Criteria:



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

This implies :

1. keep pressure drop across the core „low“ (~< 0.75 bar) by selecting an appropriate fuel pin / subassembly design

2. minimize pressure losses throughout the primary / DHR system such that total system pressure loss <~ 1.0 – 1.1

bar

3. assure a height differential between the core midplane and the heat sink midplane of at least > 2.00 m

EFIT ULOF Design Criteria requires :



1. Select an appropriate pin / sub-assembly design by optimizing the pin diameter, pin pitch, wrapper dimensions etc.

2. Minimize the number of grid-spacers and optimise design

3. Keep the length of the fuel pin low

4. Optimize inlet and outlet support structures to keep pressure drops small

Keeping P_core in the XT-ADS Design low:



Most current EFIT Design Data: Inner Core Region, Core Zone 1



Most current EFIT Design Data: Intermediate Core Region, Core Zone 2



Most current EFIT Design Data: Outer Core Region, Core Zone 3



Other EFIT Data Inputs:

854mm lower gas plenum

274mm upper gas plenum

Height difference Core and HX 3.7 m

T_in 400 °CT_out 480 °CFlow Rate 32101 kg/s

P/DEFIT-PB 1.581XT-ADS 1.40

Calc. Prim. System Pressure Drops: 6 Spacers @ 0.50mm thickness 0.181 barCore Inlet/Outlet 0.24 barFlow Friction 0.124 barTotal Core 0.544 barTotal Prim. System 0.751 bar

Assumed Zeta Factor (Ratio of Prim.System/Core Pressure Drop)

1.38

Calc. Prim. System Pressure Drops: 6 Spacers @ 0.25mm thickness 0.05 barCore Inlet/Outlet 0.24 barFlow Friction 0.124 barTotal Core 0.413 barTotal Prim. System 0.569 barAssumed Zeta Factor (Ratio of Prim.System/Core Pressure Drop)

1.38



EFIT-Pb: Avg and Peak Cladding and Fuel Temperatures at Nominal and ULOF-ss Plant Conditions for BOC and EOC

Clad Fuel Clad Fuel Clad Fuel Clad Fuel Clad Fuel Clad FuelNominal Conditions BOC 0 µm 505 1220 530 1399 503 1242 519 1365 497 1133 531 1394

EOC 0 µm 505 824 539 1006 503 842 523 953 497 786 526 933

100 µm 600 1126 580 1058 571 1025

200 µm 677 1241 650 1160 631 1117

300 µm 758 1347 722 1258 695 1206ULOF Conditions BOC 0 µm 675 1475 652 1436 692 1473

EOC 0 µm 689 1149 660 1086 685 1083

EOC 100 µm 743 1259 705 1185 726 1170

EOC 200 µm 797 1361 758 1279 767 1255

EOC 300 µm 868 1457 832 1367 816 1336

Avg Pin Peak Pin

Inner Core Zone CZ1 Intermediate Core Zone CZ2

Avg Pin Peak PinOxide Layer thickness

EFIT - Pb : Peak Fuel and Cladding Temperatures [°C]

Outer Core Zone CZ3

Avg Pin Peak Pin

Avg Pin Peak Pin Avg Pin Peak Pin Avg Pin Peak Pin

Nominal Conditions BOC 0 µm E11 E10 E11 7.0XE10 E11 E10

EOC 0 µm E9 E6 6.8XE8 2.5xE7 6.9xE8 5.2xE6

EOC 100 µm 7.0XE4 1.90E+05 1.1xE5

EOC 200 µm 4.5xE4 1.0xE3 1.2xE3

EOC 300 µm 1.44 9.8 17.4ULOF Conditions BOC 2XE10 5.5xE5 3.0xE4

EOC 0 µm 66.7 371 23.9

EOC 100 µm 2.57 208 2.02

EOC 200 µm 0.14 0.97 0.21

EOC 300 µm 0.3 min 2.0 min 1.0 min

Oxide Layer thickness

Inner Core Zone CZ1Intermediate Core

Zone CZ2Outer Core Zone CZ3

EFIT - Pb : Cladding Failure Times [hrs]

EOC state is defined to be max burnup ~ 100 MWd/kg of MOX-MA fuel



EFIT ULOF Transient Cases Analysed:

1. ULOF: BOC, Peak Pin, 6 Spacer @ 0.50mm thickness

2. ULOF: EOC, Peak Pin, 6 Spacer @ 0.50mm thickness, 100 um oxide



EFIT-Pb : ULOF, BOC, Peak Pin, 6 Spacer @ 0.50mm thickness, no oxide

Conclusion:

For current design EFIT peak pin clad will NOT fail under BOC conditions even though of flow undershoot that is ~ 22 % nom. flow.

Min Clad Failure Time ~ 17 hours

ULOF FzK (SIM-ADS) : Power and Flow Rate

0.00.10.20.30.40.50.60.70.80.91.01.1

0 50 100 150 200Time [sec]

rel.

Un

its

[fr

]

Power_th

Flow_CoolPower

Flow

ULOF FzK (SIM-ADS) : Temperatures

300

500

700

900

1100

1300

1500

1700

0 50 100 150 200

Time [sec]

Te

mp

era

ture

[°C

] Fuel_c_peak

Clad_peak

Cool_out

Cool_in

Fuel

T_clad_max = 810 °C

Coolant

Cladding

ULOF FzK (SIM-ADS) : Clad Failure and Fission Gas Pressure

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

0 50 100 150 200Time [sec]

Cla

d F

ailu

re T

ime

[s

ec

]

5

5

5

5

5

5

5

5

Fis

sio

n G

as

Pre

ss

ure

[b

ar]

Clad Failure Time [sec]

Fission Gas Pressure [bar]

30 min limit

Min. Pin Clad Failure Time = 17 hrs



EFIT-Pb : ULOF, EOC, Peak Pin, 6 Spacer @ 0.50mm thickness, 100um oxide

Conclusion:

For current design EFIT peak pin clad will most likely NOT fail under EOC conditions even though of flow undershoot ~ 22% (min. clad failure time ~ 1000 sec). Peak pin fission gas pressure will be </~ 100 bar.

ULOF FzK (SIM-ADS) : Power and Flow Rate

0.00.10.20.30.40.50.60.70.80.91.01.1

0 50 100 150 200Time [sec]

rel.

Un

its

[fr

]

Power_th

Flow_CoolPower

Flow

ULOF FzK (SIM-ADS) : Temperatures

300

500

700

900

1100

1300

1500

0 50 100 150 200

Time [sec]

Te

mp

era

ture

[°C

] Fuel_c_peak

Clad_peak

Cool_out

Cool_in

Fuel

T_clad_max = 820 °C

Cladding

ULOF FzK (SIM-ADS) : Clad Failure and Fission Gas Pressure

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

0 50 100 150 200Time [sec]

Cla

d F

ailu

re T

ime

[s

ec

]

86

88

90

92

94

96

98

100

Fis

sio

n G

as

Pre

ss

ure

[b

ar]

Clad Failure Time [sec]

Fission Gas Pressure [bar]

30 min Min. Pin Clad Failure Time = 1000

sec



Conclusions on EFIT ULOF Transient :

1.) The ULOF transient is less sensitive in the Pb-cooled EFIT design than to the XT-ADS design because of its better natural convection characterisitcs: (38% of nominal flow for EFIT-Pb compared to ~ 25% nominal flow for the XT-ADS under ULOF-steady state conditions).

2.) The current design of the Pb-cooled EFIT system achieves the design goal of sustaining a ULOF transient for at least 0.5 hours without pin failures.

efit design and transient analysis m. schikorr, e. bubelis eurotrans: dm1 wp1.5 : “safety”

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