Forschungszentrum Karlsruhe Technik und Umwelt IRS /FzK W.M.SchikorrEUROTRANS WP1.5 Safety Meeting :...

Forschungszentrum KarlsruheTechnik und Umwelt

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

Temperature Limits for XT-ADS Temperature Limits for XT-ADS Clad Material T-91Clad Material T-91

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

EUROTRANS: DM1 WP1.5 : “Safety”

Lyon , 10-11 October 2006



1. Lower Temperature Limits of T-91 Clad Material under Nominal Conditions

2. Upper Temperature Limits of T-91 Clad Material under Nominal Conditions

3. Temperature Limits of T-91 Clad Material under Transient Conditions

Topics:



1. There appears to be a lower temperature limit due to EMBRITTLEMT isssues

2. There are recommendations to keep T-91 > 325 °C

1. Lower Temperature Limit of T-91 under nominal plant conditions:

See DEMETRA presentation to this issue by Janne Wallenius

DEMETRA recommendation:

Del 4.1: Tinlet = 350 °C

Tcore = 80 °C



1. To avoid CORROSION of T-91 one should keep the upper clad temperature < 500 °C

2. FeAl alloy COATING by GESA treatment will improve corrosion resistance and the upper temperature limit increased to about 550°C (L. Mansani).

3. No „coating“ requires that the nominal maximum cladding temperature of the peak pin should be below ~ 490 °C to provide margin to account for hot-spot analyses results.

2. Upper Temperature Limit of T-91 under nominal plant conditions:



1. Accepting the SPIRE and DEMETRA recommendations leads the core inlet temperature to be : T_in ~ 330 °C

2. No „coating“ requires that the maximum cladding temperature of the peak pin should be T_clad_peak ~ 480 °C.

3. Allowing for a temperature drop of ~ 23 °C between cladding and coolant for the peak pin at the core outlet (peak clad temp), and

4. Using a radial form factor of 1.375 for the XT-ADS requires that the heat up of coolant across the core is limited to:

T_core = (480 - 23 – 330) / 1.375 = 92.4 °C

We have select : T_core = 90 °C

Implications on the XT-ADS Design : Nominal Conditions



1. Under nominal conditions abide by the temperature limits stated above,

2. Assure a sufficiently large natural convection flow rate to „survive“ an unproteced loss of flow transient (ULOF) : minimize pin clad failure

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 / DHRS system such that total system pressure loss <~ 1.0 bar

3. limit the fission pressure gas buildup at EOL to ~ 50 bar to assure pin integrity under ULOF conditions. This implies designing an appropriate fission gas plenum volume.

Contraints on the XT-ADS Design : Nominal and Transient Conditions



1. There are several different modes of pin cladding failure.

2. One of the most important is CLAD CREEP failure.

3. Recent experimental data of unirradiated T-91 material by CIEMAT yielded creep data which indicate that particular attention needs to be paid to this potential clad failure mode under all transient conditions leading to cladding temperatures higher than > 800 °C. This in particular applies to ULOF at EOL conditions when the fuel pins are pressurized by the accumulated released fission gas .

4. For T-91 the clad failure limit is no longer ~ 1000 °C (as we have asssumed in a somewhat generous manner during the PDS-XADS safety study), but it is now in the range ~ 850 °C.

Pin/Cladding Failure Conditions under Transient Conditions (1/2) :



5. The failure time of the cladding due to clad creep is dependent on 3 major parameters, namely:

1. Type of cladding material selected,

2. Hoop_Stress, essentially determined by

a. the fission gas pressure Pgas, and

b. the geometry of the pin design, namely outer pin diameter and cladding thickness,

3. The temperature of the cladding material.

Pin/Cladding Failure Conditions under Transient Conditions (2/2):



Most Current T91-Cladding Creep Data from CIEMAT Experiments

(data distributed by J. Wallenius)

Creep Test (T-91 Material)

Specimen Temperature K

Load Mpa e (s -1)

T-25 723 500 tr: 2.76 h 2.766 P: 18.4 1.22E-04

T-24 723 480 tr: 94 h 94 P:19.50 1.15E-05

T-23 723 450 tr: 2.88h 2.88 P: 18.40 1.71E-04

T-21 773 400 tr: 24h 24 P: 20.39 7.73E-06

T-22 773 380 tr:166 166 P:21.04 1.30E-06

T-3 773 350 tr:953.4 h 953.4 P:21.6 7.65E-09

T-7 773 320 tr: 4730 h 4730 P: 22.17 1.37E-09

T-2 823 280 tr: 42 h 42 P: 21.91 3.93E-07

T-4 823 250 tr: 300 h 300 P:22.6 4.94E-08

T-14 823 240 tr:426.1 h 426.1 P: 22.7 3.22E-08

T-6 823 225 tr:1009.4 h1009.4 P:23

1.60E-08

T-1 823 210 tr:2400 h 2400 P:23,4 4.66E-09

T-8 873 180 tr: 243.1 h 243.1 P: 23.8 8.44E-08T-9 873 170 tr:281.2 h 281.2 P:24 5.38E-08

T-10 873 160 tr: 578 h 578 P:24.24 2.65E-08

T-11 873 150 tr:763.2 h 763.2 P:24.3 1.29E-08

T-12 873 145 tr:1633.4 h1633.4 P: 24.6

6.41E-09

T-15 923 130 tr: 42 h 42 P:24.6 3.89E-07

T-17 923 110 tr: 120.9 h120.9 P: 25

1.14E-07

T-19 923 90 tr: 599.8 h 599.8 P: 25.64 2.09E-08

T-16 973 80 tr:32 h 32 P: 24.5 4.68E-07

T-18 923 70 tr: 3977 h 3977 P:26.4 2.52E-09

T-20 923 60T-13 973 60 tr:320 h 320 P:26.8 2.59E-08

T-5 973 50 tr: 501.76501.76 P:26.95

7.39E-07

P=TK(25+log tR)10-3

P is known as the „Larson-Miller Parameter (LMP)“



T91 Creep Data Analysis

y = -1247.5Ln(x) + 4145

10

100

1000

18 20 22 24 26 28P

Lo

ad

[M

Pa

]

T-91

Logarithmisch (T-91)

y = 27.589e-0.0008x

y = 28.644e-0.0012x

18

20

22

24

26

28

0 200 400 600Load [Mpa]

P

T-91

Equation

Low er_part

Exponentiell (T-91)

Exponentiell (Low er_part)

y = 27.589e-0.0008x

y = 28.644e-0.0012x

23

24

25

26

27

28

29

30

0 50 100 150 200Load [Mpa]

PT-91

Equation

Lower_part

Equation Lower_Part

Exponentiell (T-91)

Exponentiell (Lower_part)

1. Plotting Data from Table :

2. Inverting the plotted Data

3. Curve fitting the data in the critical pressure range

(Two equations)



Creep-Stress Correlations Used in the Analysis

310*25* failTLogTKP

25

10 TK

P

failT

int22

int***2

DD

DDPP

ext

extgas

][

intint

MPapressuregasfissionP

diameterpinernalD

diameterpinexternalD

gas

ext

thicknessClad

DPP gas _

*5.0* int

Another equation providing simliar results (thin cladding ):

][

][

MPaStressHoopP

TimeFailureCladhrT

KeTemperaturCladTK

fail



Issues Needing Attention :

1.) Fission gas plenum pressure and hoop stress is dependant on pin geometry, i.e. pin diameter,clad thickness and volume of fission gas plena made available. This implies that clad failure time is dependant on the particular pin design.

2.) Experimental data on CREEP available only up to 700 °C (973 K). Is extrapolation of data into higher temperature ranges ok ???

3.) Issue of expected fission gas plenum pressure under EOL conditions needs discussion/clarification. Issue : gas release fraction from fuel matrix into gap and plenum,

40, 60, 80, 100% release ??Have decided to be conservative : assume 100% gas release from fuel



T91 Clad Failure Time as Function of Clad Temperature and Fission Gas Pressure for XT-ADS Design : Pin = 6.55mm OD, clad thickness = 0.475mm, 580mm Lower Gas Plenum

1. Design Criteria:

Clad Failure ≥30 min under ULOFss conditions at EOL

2. Adopted :

50 bar (5 Mpa) as design fission gas plenum pressure for peak pin at EOL

3. This implies :

for peak pin :

Tclad_max < 847 °C under ULOFss conditions at EOL

Plenum Gas Pressure [ Mpa] 3 Mpa 4 Mpa 5 Mpa 7 Mpa 10 Mpa

Clad failure time <

10 000 hr 696 688 681 666 643

1 000 hr 731 723 715 699 676

100 hr 768 760 751 735 711

10 hr 808 799 791 774 749

1 hr 851 842 833 816 790

30 min 865 856 847 829 803

2 min 921 912 902 884 856

Expected T-91 Clad Failure Times

(best estimate reference values)

Clad temperature [°C] : mid wall



T91 Clad Failure Time as Function of Clad Temperature and Fission Gas Pressure for XT-ADS Design Variant 1 (Bologna): Pin = 6.55mm OD, 580mm Lower Gas Plenum

Peak Pin, Nominal Conditions, EOL

Time to Failure [hr] of T91 Cladding3.9E+11

1.E-011.E+001.E+011.E+021.E+031.E+041.E+051.E+061.E+071.E+081.E+091.E+101.E+111.E+121.E+13

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

XT-ADS peak pin

30 min Failure Limit

Pgas = 39 bar



XT-ADS :

Pin = 6.55mm OD

T_in = 330 °C

Nominal Conditions at EOL :

Pfriction = 508 mbar

spacers = 97 mbar

Pin_outlet = 123 mbar

Pcore = 729 mbar

Psystem = 1.006 bar

Axial Temperature Profile, PbBi-cooled Avg Pin 146 W/cm

406

375420

438

967

797

913

628689

1138

300

400

500

600

700

800

900

1000

1100

1200

1300

-30 -20 -10 0 10 20 30Axial Core Position [cm]

Te

mp

era

ture

s [

°C]

Cladding surf

Coolant

Center Fuel

Surf Fuel

Avg Fuel

Axial Temperature Profile, PbBi-cooled Peak Pin 201 W/cm

435

392454

478

1227

975

1132

722801

1464

300

500

700

900

1100

1300

1500

1700


Te

mp

era

ture

s [

°C]

Cladding surf

Coolant

Center Fuel

Surf Fuel

Avg Fuel

H_core_HX = 2.0 m

Pgas = 28 bar

Pgas = 39 bar



XT-ADS Variant 1

Bologna Design

Pin = 6.55mm OD

580 mm Gas Plenum

T_in = 330 °C

ULOFss Conditions at EOL, w_nat = 28.7% nom flow

Axial Temperature Profile, PbBi-cooled Peak Pin ULOF 201 W/cm

611

548

769

798

1395

1131

1309

867990

1644

300

500

700

900

1100

1300

1500

1700

1900


Tem

per

atu

res

[°C

]

Cladding surf

Coolant

Center Fuel

Surf Fuel

Avg Fuel

Axial Temperature Profile, PbBi-cooled Hot SA avg Pin 201 W/cm

602

542

756

784

1349

1099

1271

849968

1589

300

500

700

900

1100

1300

1500

1700


Te

mp

era

ture

s [

°C]

Cladding surf

Coolant

Center Fuel

Surf Fuel

Avg Fuel

Pgas = 41.6 bar

Pgas = 39.6 bar



T91 Clad Failure Time as Function of Clad Temperature and Fission Gas Pressure for XT-ADS Design Variant 1 (Bologna): 6.55mm OD Pin, 580mm Lower Gas Plenum

Peak Pin, ULOFss, EOL, nat_conv_flow = 28.7% of nominal (1233 kg/s)

Time to Failure [hr] of T91 Cladding

5.1E+00

1.E-011.E+001.E+011.E+021.E+031.E+041.E+051.E+061.E+071.E+081.E+091.E+101.E+111.E+121.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

XT-ADS peak pin


2. What about

transient conditions ??

Pgas = 42 bar

Under ULOFss steady

state conditions :

5.1 hrs to failure for current designs implying large margin to 30 min limit



XT-ADS

Pin = 6.55mm OD

580 mm Gas Plenum

Time to Clad Failure hot SA avg Pin:

EOC (Pgas=40 bar): 0.64 hrs

ULOFss Conditions at EOL, assume w_nat decreases to 25% nom

Axial Temperature Profile, PbBi-cooled Peak Pin ULOF 201 W/cm

645

581

835

864

1426

1161

1347

896

1035

1680

300

500

700

900

1100

1300

1500

1700

1900


Tem

per

atu

res

[°C

]

Cladding surf

Coolant

Center Fuel

Surf Fuel

Avg Fuel

Axial Temperature Profile, PbBi-cooled Hot SA avg Pin 192 W/cm

631

569

811

840

1376

1125

1304

8731007

1620

300

500

700

900

1100

1300

1500

1700


Te

mp

era

ture

s [

°C]

Cladding surf

Coolant

Center Fuel

Surf Fuel

Avg Fuel

Time to Clad Failure peak pin:

EOC (Pgas=42 bar): 0.17 hrs



T91 Clad Failure Time as Function of Clad Temperature and Fission Gas Pressure for XT-ADS Design Variant 1 (Bologna): 6.55mm OD Pin, 580mm Lower Gas Plenum

Peak Pin, ULOFss, EOL, assume : nat_conv_flow = 25% nominal

Time to Failure [hr] of T91 Cladding

1.7E-011.E-011.E+001.E+011.E+021.E+031.E+041.E+051.E+061.E+071.E+081.E+091.E+101.E+111.E+121.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

XT-ADS peak pin


Clad Failure Time in XT-ADS very sensitive to nat_conv flow rate under ULOFss conditions since nat. convection already relatively low ( ~ 25 % instead of ~ 45% in EFIT and XADS)

Pgas = 42 bar



Potential Uncertainties :

1. Available fission gas plenem volume. Currently calculated to be 17 cm3 per pin. A reduction to ~ 13 cm3 (alternative pin design option) will decrease failure time from 5.1 hrs to 2.9 hrs as it will increase fission gas pressure from 42 bar to 54 bar

2. Uncertainty in the pin fission gas temperature calculation needs to be considered

3. Superimposing two of several uncertainties will decrease failure time to < 1 hr

3. All issues associated with the natural convection flow rate

4. Transient conditions: during the ULOF transient there may be significant over- and under-shoots in clad temperatures (see following presentation).



Conclusions on T-91 Material Property Limits (1/2 ) :

1.) EMBRITTLEMENT makes it advisable to select T_in ~ 330 °C following SPIRE and DEMETRA recommendations.

2.) CORROSION issues require that the maximum clad temperatures of the peak pin are below 500 °C under nominal conditions (unless the clad material is coated thereby increasing the temperature limit to ~ 550 °C) limiting core heat up to 90 °C.

3.) New T91 CREEP Data from CIEMAT should be taken into consideration during all transients especially those leading to clad temperatures > 850 °C.



Conclusions on T-91 Material Property Limits (2/2) :

4.) Under ULOF steady state conditions max. cladding temperatures between

800 °C – 900 °C should be expected.

For T_in = 330 °C, T_clad_max (ULOF) : 800 °C – 865 °C

corresponding clad failure time due to creep ranging from 5 hrs to 0.17 hrs

For the 30 min limit, the maximum temperature of the clad should not exceed 847 °C

6) The issue of high temperature corrosion still needs to be assessed / evaluated in view of experimental data currently assembled (DEMETRA)

5.) The current design (580mm lower gas plenum) is comfortably achieving the 30 min design goal as clad failure time limit under ULOFss and EOL conditions.

Forschungszentrum Karlsruhe Technik und Umwelt IRS /FzK W.M.SchikorrEUROTRANS WP1.5 Safety Meeting :...

Documents

Transcript of Forschungszentrum Karlsruhe Technik und Umwelt IRS /FzK W.M.SchikorrEUROTRANS WP1.5 Safety Meeting :...