the mutual influence of thermal-hydraulics and … of nuclear technology and energy systems the...

Institute of Nuclear Technology

and Energy Systems

The Mutual Influence

of Thermal-hydraulics

and Materials on

Design of SCWR –

Review of Results of

the Project HPLWR

Phase 2

J. Starflinger,

T. Schulenberg,

KIT

• Design Target Data:

• Operational pressure: 25 MPa

• Core mass flow: 1160 kg/s

• Power output: 1000 MWe

• Constraints:

• Average core exit temp.: 500°C

• Max. cladding surface temp.: 625°C

• Max. linear heat rate: 39 kW/m

22/8//2016

University of Stuttgart – Institute of Nuclear Technology and Energy Systems (IKE)

IAEA - Technical Meeting on Heat transfer, Thermal-hydraulics, System Design for SCWR 2

5th Framework Programme of the EU

HPLWR – High Performance Light Water Reactor

AREVA NP, 2005

• „Hot Channel“ by definition is the channel, in which all uncertainties, non-

homogeneities and allowances sum up, leading to the highest enthalpy

rise of the entire core under normal operation conditions!

• Very conservative, provides a very high safety margin

22/8//2016



Definition

„Hot Channel“ Form Factor Analysis of the Core

av

av

h

h

h

hF

max

max

Maximum enthalpy rise in the „Hot Channel“

Average enthalpy rise in the core

• Statistical approaches need a broad validated database (in-pile exp.)

• Statistical approaches are used to reduce the over-conservatism while

keeping the safety margins. Do we really have enough statistical

information to perform such an approach?

22/8//2016



Some thoughts

„Hot Channel“ Form Factor vs. Statistical Approach 95/95

avh

hF

max

• Maximum enthalpy rise

in the „Hot Channel“

• “There is at least a 95%

probability at a 95% confidence

level that …” [NUREG1475]

22/8//2016



Design Targets of Hot Channel Factors

2.01.6Total

Power control, flow control, pressure control, inlet

temperature control

1.15Allowances

Material properties of coolant and claddings,

physical modelling, hydraulic modelling, heat

transfer coefficient, geometry tolerances

1.2Uncertainties

1.6Axial power factor

1.15Local peaking

factor inside FA

1.25Radial peaking

factor

Fuel enrichment and distribution, water density

distribution, reflector design and properties, fuel

and control rod pattern, burn-up, burnable

poisons, …

Form factors for

power profiles

Key ParametersradialaxialHot Channel Factor

2.01.6Total


temperature control

1.15Allowances




1.2Uncertainties


1.15Local peaking

factor inside FA

1.25Radial peaking

factor




poisons, …

Form factors for

power profiles


Schulenberg, KIT, 2010

22/8//2016



One-Pass Core


• Designed for

500°C core

outlet

temperature

• Coolant

average

conditions

Heinecke, AREVA, 2010

Average

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One-Pass Core


• Hot fuel

assembly

(∙ 1.25)


Average

+ Assembly Power

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One-Pass Core


• Hot rod

(∙ 1.25

∙ 1.15

= 1.44 )


Average

+ Assembly Power

+ Rod Power

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One-Pass Core


• Hot rod +

uncertainty

(∙ 1.25

∙ 1.15

∙ 1.2

= 1.73 )

Average

+ Assembly Power

+ Rod Power

+ Uncertainty

22/8//2016



One-Pass Core



• Hot rod + uncertainty + operation (∙ 1.25 ∙ 1.15 ∙ 1.2 ∙ 1.15 = 1.98 )

• Coolant temperature ≈ 1200 °C

Average

+ Assembly Power

+ Rod Power

+ Uncertainty

+ Operation

• Simple „Hot-Channel“ analysis revealed the unfeasibility of single-pass

core design.

• Idea from T. Schulenberg, KIT:

Propose a “Three-pass core” with intermediate mixing in special mixing

chambers.

• One key-issue of a feasible core design is mixing!

• not to overheat the core

• avoid hot streaks from one assembly to another and hot-spots on the

cladding surface

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Consequences


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Three Pass Core Design Proposal for a HPLWR

1000

1500

2000

2500

3000

3500

4000

Evaporator Superheater 1 Superheater 2

En

tha

lpy

[k

J/k

g]

hot channel

average

Strategy to overcome hot-channel issue: Heat-up in steps with Intermediate mixing of the coolant

Mixing

Mixing

Schulenberg, 2006

4 : 2 : 1

Power ratio of the core zones

22/8//2016



Three Pass Core Design Proposal for a HPLWR

200

250

300

350

400

450

500

550

600

650

Evaporator Superheater 1 Superheater 2T

em

pe

ratu

res

[°C

]

cladding

hot channel

average

Schulenberg, 2006

• A 3-Pass coolant flow in the core allows 500°C average core exit

temperature with 625°C cladding temperature

22/8//2016



Core Arrangement

Evaporator:

52 Clusters

Upward Flow

Superheater 1:

52 Clusters

Downward Flow

Superheater 2:

52 Clusters,

Upward Flow

Köhly, 2010

• Cluster of 3x3 assemblies in

square arrangement

• 40 fuel pins with 8mm diameter

• p/d = 1.18

• wire wraps as grid spacers

• assembly box with 3 mm

thickness incl. thermal insulation

• moderator box with 2 mm

thickness incl. thermal insulation

22/8//2016



Details of the Assembly Design Concept

Moderator

box

Assembly

box

Wire wrap

spacers

Himmel, Köhly 2008

22/8//2016



Head and Foot Piece Design of an Assembly Cluster

Control rods

running inside

moderator channels

Inlet orifices

for

moderator

water

Outlets of

moderator

water

New: Rising

moderator water in

gaps between

assemblies

Hofmeister, modified later

Downcomer flow

(50%)

Moderator flow

(50%)

Inlet flow:

280°C

25 MPa

1179 kg/s

Core flow

(100%)

Upper dome

Downcomer

Area


IAEA - Technical Meeting on Heat transfer, Thermal-hydraulics, System Design for SCWR

HPLWR Flow Path

3/11/2016 17

Köhly, 2010

• Analyze the core, whether the power peaking factors will be met

• Neutronics:

• Simulate neutronics (BOC, EOC) for core and assembly-wise power

distribution (input from materials and TH needed)

• Thermal-hydraulics:

• Suitable heat transfer correlation with an uncertainty of less than 25%,

especially for fuel rod bundles with wire wraps as spacers.

• Materials & Water Chemistry

• Identify suitable materials for thick wall and thin wall components, but

especially for cladding.

22/8//2016



Tasks for the HPLWR Partners

Design Support

22/8//2016



Overview CFD validation

Geometry Medium Source/Institute HPLWR partner

Tube SCW Yamagata NRG, USTUTT

Tube SCW Herkenrath NRG

Tube SC CO2 KAERI NRG

Tube

SCW Shitsman KTH/USTUTT

Tube SCW Ornatskii

KTH, USTUTT

Annulus SCW Glushchenko USTUTT

Annulus SC CO2 KAERI NRG/USTUTT

Square annulus SCW Wisconsin univ. USTUTT

Square annulus SCW XTJU USTUTT

22/8//2016



Yamagata tube test, Dh = 3.75 mm

Validation of Tube and Annulus

q/G = 0.18 q/G = 0.37

Laurien 2009

22/8//2016



Ornatskii tube test, Dh = 3 mm, Shitsman tube test, Dh = 8 mm

Validation of Tube and Annulus

q/G = 1.21 q/G = 0.74

Laurien Anglart 2009

• Normal and enhanced heat transfer can be predicted within the 25%

uncertainty as requested.

• Onset of Heat Transfer Deterioration can possibly be predicted, but

maximum temperature is uncertain.

• For use in sub-channel codes, correction factors of a heat transfer

correlation shall be derived.

HTCav = Fgeo x Fwire x HTCbase

Conclusion from CFD calculations:

• Geometry factor Fgeo = 0.6

• Wire factor Fwire = 1.1

22/8//2016



Results of the Heat Transfer investigation

1500 1600 1700 1800 1900 2000 2100 220020000

40000

60000

80000

100000

120000

140000

160000

180000

200000

Bulk enthalpy, kJ/kg

HT

C,

W/m

2

22/8//2016



Example comparison of selected correlations with data

HTC Base correlation

Bishop

Dittus-Boelter

Jackson

Herkenrath

q’’ = 1200 kW/m2

G = 3500 kg/m2.s

p = 24 MPa

d = 10 mm

Anglart 2009

22/8//2016



Bishop (1965) correlation vs. experimental data

Sig.=0.16; bias=0.44

22.8MPa<=p<27.6MPa

N. pts. =236

10 20 30 40 50 60 70 8010

15

20

25

30

35

40

45

Bishop correlation

Exp

eri

me

nt

• Experimental data in

the range of

parameters applicable

to HPLWR upflow and

in range of applicability

of the correlation.

• 236 measurement

points

• Bias is defined as:

mean(HTCBishop/HTCExp)

– 1 = 0.44

+10% -10%

Anglart 2009

Sig.=0.14; bias=0.03

22.8MPa<=p<27.6MPa

N. pts. =236

10 15 20 25 30 35 40 45 50 55 6010

20

30

40

50

60

70

80

90

Jackson correlation

Exp

eri

me

nt

22/8//2016



Jackson, Hall (1979) correlation vs. experimental data upflow

• Experimental data in the

range of parameters

applicable to HPLWR

upflow and in range of

applicability of the

correlation.

• 236 Measurement

Points


mean(HTCJackson/HTCExp)

– 1 = 0.03

+10%

-10%

Anglart 2009

Sig.=0.11; bias=-0.05

22.8MPa<=p<27.6MPa

N. pts. =87

5 10 15 20 25 30 35 40 45 50 550

10

20

30

40

50

60

Jackson correlation

Exp

eri

me

nt

22/8//2016



Jackson, Hall (1979) vs. experimental data downflow

• Experimental data in

the range of

parameters applicable

to HPLWR downflow

and in range of

applicability of the

correlation.

• 87 Measurement Points


mean(HTCJackson/HTCExp)

– 1 = 0.05

+10%

-10%

Anglart 2009

Base correlation HTCbase:

• Look-up tables (e.g. Löwenberg, Groeneveld) will offer best accuracy

and should be considered as first choice (not shown here)

• Jackson correlation is proposed as the second choice, since it offers

best agreement with measured data

• Note: Disadvantage of correlations is that they are not accurate and non-

conservative, especially near the supercritical point.

• Strong interaction between heat transfer and core design

• Validation experiment needed incl. bundle effects and influence wire wrap

spacers on the flow (fuelled loop project).

22/8//2016



HPLWR approach

Heat Transfer Correlation

• Test of 16 materials in autoclaves at different temperatures

• Investigation of general corrosion, stress-corrosion cracking and creep

Main findings:

Thick walled components operating at max. 500°C

• No major structural problems with respect to corrosion (fossil plant

technology)

Thin walled components at above 600°C:

• High corrosion rate with licensed low Ni alloys (especially fuel cladding)

• High impact on core design! Redesign necessary if no suitable

materials will be found.

22/8//2016



Materials

22/8//2016



Influence of high Cr content on oxidation

Materials

after 600h at 650°C

0,1

1

10

100

1000

0 5 10 15 20 25

Cr(%)

Ox

ide

Th

ick

ne

ss

(m

m)

P91

P92

ODS (FZK)

ODS (EU)

PM2000

316NG

1.4970

BGA4

800H

IN 625

Data from VTT, JRC,

UJV Rez,

22/8//2016



Radial Power Profile at BOC, Maraczy et al. 2009

Assessment

1.5

1.3

1.1

0.9

0.7

0.5

0.3

0

Power peaking factors

per heat up step Radial power profile

Local lower

peaking

factor

strongly

scattering

in one

assembly

22/8//2016



Enthalpy Peaking Factors of Assembly

0%

2%

4%

6%

8%

10%

12%

14%

16%

18%

20%

EVA SH1 SH2

Control RodsGd Burn OutPower Gradients

Design Target

The design target

for local coolant

enthalpy peaking

factors inside fuel

assemblies has

been met.

Note:

Factors are not simply

additive.

Control rod effects rather

at BOC.

Gd burn out rather at EOC.

22/8//2016



„Core Zone“ Enthalpy Peaking Factors

Assessment

0

500

1000

1500

2000

2500

3000

3500

4000

EVA SH1 SH2

Pe

ak

En

tha

lpy

[k

J/k

g]

Design Target

BOC

EOC

• Averaged power

peaking factors are

exceeding the design

targets.

• Maximum 14% at

BOC in SH1

• EVA peak coolant

temperature higher

than design target.

• SH1 peak coolant

temperature exceeds

design target.

• SH2 peak coolant

temperatures close to

design target.

• Reason: Clustering of

the fuel assemblies.

22/8//2016



Peak Coolant Temperatures in „Core Zones“

Assessment

0

100

200

300

400

500

600

EVA SH1 SH2

Pe

ak

Co

ola

nt

Te

mp

. [°

C]

Design Target

BOC

EOC

Peak coolant enthalpy

• Assembly bending 2%

• Sub-Channel codes 7%

• Neutron physical modeling 5%

• Local flow blockage 3%

Total sum of variances 9%

• Other uncertainties

• Heat transfer predictions > 20%

• Material properties (corrosion) unknown!

22/8//2016



Summary of Uncertainties

22/8//2016



Simulation from Schlagenhaufer, 2010

Allowances

Temperature control: 10°C

= 2% of total coolant enthalpy rise

Pressure control: 50 kPa

Design Target: 15%

• There is enough margin for measurement errors.

22/8//2016



Design Targets of Hot Channel Factors

2.01.6Total


temperature control

1.15Allowances




1.2Uncertainties


1.15Local peaking

factor inside FA

1.25Radial peaking

factor




poisons, …

Form factors for

power profiles


2.01.6Total


temperature control

1.15Allowances




1.2Uncertainties


1.15Local peaking

factor inside FA

1.25Radial peaking

factor




poisons, …

Form factors for

power profiles


EVA SH1 SH2 Comment

1.42 1.37 1.29 Design value

exceeded

1.13 1.15 1.14 Close to design

value

1.09 1.09 1.09 Heat transfer

and materials

not considered

1.02 1.02 1.02 Simulation

1.79 1.75 1.63

• Enthalpy form factor of the HPLWR zones are met, because of very low

uncertainty and allowances. Radial peeking factor is too high.

• The design target of 500°C core outlet temperature at 630°C maximum

cladding surface temperature can be met.

• The 3x3 assembly cluster is too large for the 3 pass core concept, better

individual smaller assemblies (better shuffling -> redesign)

• Core is complicated to analyze and optimize. Single pass core (EVA), only?

• Uncertainties of heat transfer and material properties still too large.

Materials and heat transfer are to be further investigated!

22/8//2016



Did we meet the design targets?

Assessment

22/8//2016



Mix it, baby!

Advice from A. Schwarzenegger

Thank you!

e-mail

phone +49 (0) 711 685-

fax +49 (0) 711 685-

Universität Stuttgart

Pfaffenwaldring 31 • 70569 Stuttgart • Germany

Prof. Dr.-Ing. Jörg Starflinger

62116

62008

Institute of Nuclear Technology and Energy Systems

[email protected]

Institute of Nuclear Technology

and Energy Systems

22/8//2016



the mutual influence of thermal-hydraulics and … of nuclear technology and energy systems the...

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