PWR Heat Transfer & Fluid Flow

6 April 2011

Presentation to

ANSYS Info Day

Presented by

Chris Fry/Serco Technical Consultancy Services

What is the connection between Serco and ANSYS?

Who are Serco?

Why have they been invited to give a presentation by ANSYS?

Need to look at history

Serco Public

In the beginning things were simple

UKAEA

Developed reactor

concepts

NNC

Built reactors

CEGB

Operated

reactors

BNFL

Produced and

reprocessed fuel

Serco Public

concepts reactors reprocessed fuel

Then Privatisation came along

UKAEA NNC CEGB BNFL

AEA Technology Nuclear

ElectricSellafield Ltd

Serco Public

AMEC

Electric

British

Energy

EDF

Energy

NNL

Then Privatisation came along

UKAEA NNC CEGB BNFL

AEA Technology Nuclear

ElectricSellafield Ltd

Serco Public

AMEC

Electric

British

Energy

EDF

Energy

NNL

ANSYS

SERCO

CFDConsultants

Introduction Heat transfer and fluid flow innuclear reactors

In a nuclear reactor the nuclear

reaction generates heat

Thereafter the engineering can be

considered as conventional

The removal of heat from the fuel is

vital for both operation and safety

Serco Public

vital for both operation and safety

Generation of heat continues even

after the reactor is shut down

The ability to reliably model heat

transfer and fluid flow is therefore

vitally important to the design and

safety justification of a nuclear

reactor

CFD should therefore have a central

place

Introduction

In a nuclear reactor the nuclear

reaction generates heat

Thereafter the engineering can be

considered as conventional

The removal of heat from the fuel is

vital for both operation and safety

Serco Public

vital for both operation and safety

Generation of heat continues even

after the reactor is shut down

The ability to reliably model heat

transfer and fluid flow is therefore

vitally important to the design and

safety justification of a nuclear

reactor

CFD should therefore have a central

place

In practice it is not as central as you

might expect!

The Current Role of CFD in Civil Nuclear Power

To understand the current role one has to look at the history of civil

nuclear power in the UK

Serco Public

1st generation Magnox

11 reactors built in UK

Commissioned between 1956 and

1971

No CFD used in design or safety

case!

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Fluid flow and heat transfer

calculations performed using:

1st generation Magnox

11 reactors built in UK

Commissioned between 1956 and

1971

No CFD used in design or safety

case!

Serco Public

Fluid flow and heat transfer

calculations performed using:

Slide Rule!

2nd Generation - AGR

7 reactors built in UK

Commissioned between 1976 and

1988

Fluid flow and heat transfer

calculations performed using:

Serco Public

2nd Generation - AGR

7 reactors built in UK

Commissioned between 1976 and

1988

Fluid flow and heat transfer

calculations performed using:

Computers!

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Computers!

But not CFD!

3rd Generation - PWR

PWRs are the dominant reactor type

worldwide

First reactor (Shippingport US),

commissioned in 1957

Only 1 PWR in UK

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Sizewell B commissioned in 1995

Established Westinghouse design

(with UK modifications)

Only limited amount of fluid flow

assessment therefore performed in

UK

Thermal hydraulics analysis of PWRs

Original designs developed using slide rules and mainframe computers

Network computer codes developed to perform thermal hydraulic

calculations:

RELAP5

TRACE

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TRACE

CONTAIN

MELCOR

Based on engineering correlations for heat transfer and fluid flow

derived from experiments

Single phase

Two phase

Example of network code model

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Where is CFD being applied?

Where mixing occurs

Where the geometry is non standard

Where the flow pattern is complex:

e.g. counter-current flow

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To support, rather than replace, the network codes

3 examples will be given

Example 1 Boron Dilution

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ISP 43 A CFD code benchmark

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ISP-43 Test results

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ISP-43 Serco Results

60

70

80

Temperature (C)

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20

30

40

50

0 100 200 300 400 500 600

Total Flow (l)

Temperature (C)

CFX-4 calculation

Nominal test

Repeat test

Repeat test

Repeat test

Repeat test

Data from one repeat test

not available

ISP-43 all CFD results

level 4 average

55

60

65

70

75

temperature (deg. C)

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25

30

35

40

45

50

10 15 20 25 30 35 40 45 50 55 60time (s)

temperature (deg. C)

test B AEAT

CEAkeps CEAnut0

CEAnut0p IVO

NRI NUPEC

NRC Vattenfall

ensemble B viz

Example 2 Temperature of a boiler bifurcation

Hot gas

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Steam

Boiler tube CFD model

Hot gas

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Steam

Boiler tube results external flow and HTC

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Boiler tube results internal flow and HTC

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Boiler tube results tube temperature

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Example 3 hydrogen control in a VVER-440

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Hydrogen control CFD model

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Hydrogen control hydrogen concentration

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Hydrogen control amount of hydrogen recombined

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Hydrogen control effect of condensation

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Without pool wall condensation With pool wall condensation

Other Issues

Two phase CFD

Use of best practice guidelines

CFD4NRS

Collaboration in international exercises

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Mistrust of CFD

Use of CFD for assessing PWR thermal hydraulics the future

An important (but not dominant) role

Increased use of passive safety features (e.g. natural convection)

Integration with network codes

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Conclusions

The current role of CFD in assessing heat transfer and fluid flow in

Pressurised Water (and other) Reactors has been described.

Flow analysis dominated by network codes

However CFD still has an important (and slowly growing) contribution

to make

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to make