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MODERN
POWER STATION PRACTICE
Third Edition
Incorporating Modern Power System Practice
British Electricity International, London
Volume A
Station Planning and Design
®
PERGAMON PRESS
Member of Maxwell Macmillan Pergamon Publishing Corporation
OXFORD - NEW YORK - BEIJING - FRANKFURT
‘SAO PAULO - SYDNEY - TOKYO - TORONTO UK
usa
PEOPLE'S REPUBLIC
‘OF CHINA
FEDERAL REPUBLIC
OF GERMANY
eRAZIL
AUSTRALIA
JAPAN
CANADA
Pergamon Press ple, Headington Hill Hall,
(Oxlord OX3 OBW, England
Porgamon Press, ine., Maxwell Houte, Fairview Park,
Elmsford, New York 10623, U.S.A.
Pergamon Press, Room 4037, Olanmen Hotel, Bejing,
People's Repubiic of China
Pergarmon Press GmbH, Hammerweg 6
6202 Kronberg, Federal Repubic of Germany
Pergamon Editora Ltda, Rus Es de Queiros, 348,
CEP 04011, Pereizo, S80 Paulo, Brat!
Pergamon Press (Australi) Pry Ltd, P.O. Box 544,
Potts Point, NSW. 201%, Australia
Pergamon Press, Sth Floor, Matsuoia Central Building,
1-7-1 Nishishinjuku, Shinjuia-ku, Tekye 180, Jazan
Pargamon Press Canads Ltd, Suite No. 271,
253 College Strest, Toronto, Ontarie, Canada MST 195
Copyright © 1991 British Electricity Internationa! Lec
All Rights Reserved. No pert of this publication may be
‘reproduced, stored in 2 retrieval system oF transmitted
in any form of by any means: electronic, electrostatic,
‘magnetic tape, mechanical, photocopying, recording or
‘thenwise, without permission in writing rom the copy-
right holder
First edition 1963
‘Second edition 1971
‘Third edition 1892
Library of Congress Cataloging in Publication Date
Modern power station practice: incorporating modarn
ower system practice/Brtish Electicity Internetion:
Sed ed. p. om
includes index.
1. Electric powerplants. |. British Electricity Intor
national
TRIISTMdS 1390
2.3921 — e290 90-43748,
British Library Cataloguing in Publication Date
Briish Electricity Internation.
Modern power station practice ~Srd, ed.
1, Blectne power-plants, Design ard construction
L. Tile. I.” Cencrat Electricity Generating Board
éar3i21
ISBN 0-08-040511-8 (Volume A}
ISBN 0.08-040510-X (Set)
Printed in the Republic of Singapore by Singapore National Printers Lid MODERN
POWER STATION PRACTICE
Third Edition
{in 12 volumes)
Incorporating Modern Power System Practice Main Editorial Panel
D. J. Littler, BSc, PhD, ARCS, CPhys, FinstP, CEng, FIEE (Chairman)
Professor E. J. Davies, DSc, PhD, CEng, FIEE
H. E. Johnson
F. Kirkby, BSc, CEng, MIMechE, AMIEE
P. B. Myerscough, CEng, FiMechE, FINucE.
W. Wright, MSc, ARCST, CEng, FIEE, FiMechE, Finst€, FBIM
Volume Advisory Editors
P. C. Martin, BSc, DMS, CEng, MIMechE {Chapters 1 and 2)
|. W. Hannah, BSc(Tech), CEng, FICE, HonFRIBA (Chapter 3)
Authors
Chapters 1 and 2
M. J. Brindle, BTech, CEng, MIMechE
|. Cresswell, BSc, CEng, MIMechE
J.C, Greenslade, BSc, CEng, MIMechE
‘A. R. Jones, BEng(Mech}(hons}, MIMechE
K. Jones
P.C. Martin, BSc, DMS, CEng, MiMechE
A. R. Smith, BSc, CEng, MIMeché
Stagg, BEngthons)
Chapter 3
4. D. Blackhall, BSothons), CEng, MICE
P. D. Davis, MSc, MICE
P.M. Emberson, BA, DipLD, ALI
E. J. Forsey, CEng, MiMechE
R. Hawkridge, HNC(Civils)
M.F.F. Hynes, BSc, CEng, MICE
J. Irving, BSc, CEng, FICE
D. J. Mallard, MSc, MICE, FGS
P. A. Moulding, CEng, MICE
R. A. Pope, BSc, CEng, MICE
©. H. Trent, DRTC, CEng, MICE
R.A. Vevers, CEng, MICE
Series Production
Managing Ecitor P.M, Reynolds
Production Editor H. E. Johnson
Resources and TA. Dolling
Co-ordination J. R. Jackson Contents
CoLour PLATES ~
ForeworD
PREFACE
ConTENTS OF ALL VOLUMES
Chapter 1 Power station siting and site layout
Chapter 2 Station design and layout
Chapter 3 Civil engineering and building works
INDEX
vi
vii
xi
59
178
305 2
6.
Fis.
Fos.
Fis.
Fis.
Re.
Fe.
2.8
Fic.
Re.
Fee.
Feo.
Fis,
Frc,
Fee.
Fic,
Fe.
Fe.
gee 7 BR
19
Lu
a
1s
119
1.20
1.33
2
22
23
24
25
26
27
2d
Fis,
2.26
267
2.80
3
32
33
34
36
3.30
3.5
3.60
371
Colour Plates
(between pp 66 and 67)
Satelite imagery of thermal discharges from power stations
‘Transport of heavy or abnormal Toads
Ash disposal site
Cooling towers at Drax power station
‘Hidden power: Dinorwig pumped storage power station
‘View of Drex power station nesting completion
Didcot coal-fired station landscape
Drax 6 x 660 MW coal-fired station
Littlebrook D 3 % 660 MW oilfired station
Kingsnorth 4 x $00 MW dual-fited station
Oldbury 2 x 313 MW magnox station
Heysham 2.2 x 660 MW AGR station
Ffestiniog 4 x 9 MW pumped storage station
Kielder 1 x 5.5 MW hydro station
Cowes 2 x 70 MW gas-turbine station
Leicester 2 x 70 MW gas-turbine station
Wind turbines at Carmarthen Bay site
‘Turbine island concept
‘View of pumphouse and intake screens — Littlebrook D
Bucket wheel stocking-out reclaiming machine
(between pp 242 and 243)
Light cable tool boring rig
Large rotary drilling rig
Detail of rotary drilling
Rotary core drilling of an upwartly-inclined borehole in an existing dan
Interior of electric static cone penetrometer truck showing data processing equipment
Reclaim hopper under construction
West Thurrock coal-fired station
Lower stressing gallery for AGR pressure vessei
Precipicators Foreword
G. A, W. Blackman, CBE, FEng
Chairman, Central Electricity Generating Board
and Chairman, British Electricity International Ltd
Fok OVER THIRTY YEARS, since its formation in 1958, the Central Electricity Generating
Bourd (CEGB) has been at the forefront of technological advances in the design,
construction. operation, and maintenance of power plant and transmission systems. During
this time capacity increased almost fivefold, involving the introduction of thermal and
nuclear generating units of 500 MW and 660 MW, to supply one of the largest integrated
power systems in the world. In fulfilling its statutory responsibility to ensure continuity of a
safe and economic supply of electricity, the CEGB built up a powerful engineering and
scientific capability, and accumulated a wealth of experience in the operation and
maintenance of power plant and systems. With the privatisation of the CEGB this
experience and capability is being carried forward by its four successor companies —
National Power, PowerGen, Nuclear Electric and National Grid.
‘At the heart of the CEGB’s success has been an awareness of the need to sustain and
improve the skills and knowledge of its engineering and technical staff. This was achieved
through formal and on-job training, aided by a series of textbooks covering the theory and
practice for the whole range of technology to be found on « modern power station. A
second edition of the series, known as Modern Power Station Practice, was produced in the
early 1970s, and it was sold throughout the world to provide electricity undert
engineers aad students with an account of the CEGB's practices aad hard-won experience.
‘The edition had substantial worldwide sales and achieved recognition as the authoritative
reference work on power generation.
‘A completely revised and enlarged (third) edition has now been produced which updates
the relevant information in the ealier edition together with a comprehensive account of the
solutions to the many engineering and environmental challenges encountered, and which
puts on record the achievements of the CEGB during its lifetime as one of the world’s
leading public electricity utilities.
In producing this third edition, the opportunity has been taken to restructure the
information in the original eight volumes to provide a more logical and detailed exposition
of the technical content. The series has also been extended to include three new volumes on.
‘Station Commissioning’, ‘EHV Transmission’ and ‘System Operation’, Each of the eleven
subject volumes had an Advisory Editor for the technical validation of the many
contributions by individual authors, all of whom are recognised as authorities in their
particular field of technology.
‘All subject volumes carry their own index and a twelfth volume provides @ consolidated
index for the series overall. Particular attention has been paid to the production of draft
material, with text refined through a number of technical and language editorial stages and
complemented by a large number of high quality illustrations. The result is a high standard
of presentation designed to appeal to a wide international readership.
It is with much pleasure therefore that I introduce this new series, which has been
attributed to British Electricity International on behalf of the CEGB and its successor
companies. i have been closely associeted with its production and have no doubt that it will
be invaluable to engineers worldwide who are engaged in the design, construction,
‘commissioning, operation and maintenance of modern power stations and systems.
on Aint Preface
Chapters 1 and 2
‘The planning and design development of new power station proposals at first sight appears
straightforward, but experience has shown that such a process can involve complex
interaction between not only the various engineering disciplines which contribute to the
process but also environmental, planning, economical, political and social pressures.
In this third edition, the opportunity has been taken to restructure the information and
CEGB experience to provide a logical review of the investigations and engineering design
activities which are required to underwrite power station development.
‘The Engineering studies are outlined in some detail together with examples showing how
such activities need to be brought together to fully define the project parameters, Engincers
by nature and iraining prefer to make decisions on factual information but in reality
judgement is often required. A sound basis for exercising this need is not only experience
bbut also knowledge, and the revised text attempts to illustrate how the progressive and
interactive nature of investigations allows for project evolution from initial conception
through {0 commitment to consiruct
The implications of the more intangible ‘non-engincering’ factors are reviewed and their
potential influence on the development process discussed in general terms, but for any
particular proposal these aspects will have varying degrees of relevance. It will be the
responsibility of the development manager in his own particular circumstances to judge the
influence of these factors and the implications they may have for the cost and programme
of his project.
There is always so much that is of relevance in preparing a text that the engineers
responsible for this chapter have trad to be responsible for choosing those aspects which
they consider most important. If the material they have chosen is found to be of benefit to
the reader and helps to pass on the experience and ‘know how’ of the CEGB engineers
working in this field, then the authors will no doubt draw some satisfaction from their
efforts.
PC. Magny
Advisory Editor — Chapters 1 and 2 Preface
Chapter 3
Civil engineering anc building in. the power industry may initially be seen, in simplistic
terms, as the provision of weatherproof containment over the mechanical and electrical
plant and the necessary foundations to support it, In this edition of Modern Power Station
Practice my contributors and I have tried to illustrate that this truism leaves much unsaid.
The civil engineer and the architect are main contributors in every sense throughout the
design and construction on any new power station, From the earliest planning and site
selection studies through to the final landscaping both these disciplines together with the
support of colleagues in estimating, finance and quantity surveying, are fully involved.
Indeed the start of a project presents the civil engineer with perhaps his greatest
challenge. Unavoidably he is unable to proceed with his design work until the weights and
loads of the plant and their locations are known with some certainty. This late start must
then be compensated by design and conteact to allow the construction phase to go ahead.
‘Under these circumstances the civil engineer must accept the soil conditions as found, since.
the proximity of cooling water, fuel supplies and transmission connections are likely to
‘outweigh the poorest ground strata in the overall planning considerations.
Setting up his own ‘factory’ on the site and providing good access and working facilities
for the mechanical and electrical contractors presents its own unique set of problems for the
civil engineer. Doing so with a labour force that is mainly recruited locally, or itinerant, and
assembled specifically for the project, requices considerable man management skills
The timely and successful completion of the civil works isthe key factor without which no
power station project can mect its overall criteria of quality, programme and cost. These
seemingly supplementary items to the boiler and turbine plant — the roads, drains,
culverts, cooling towers, chimneys, building and structures are likely to represent at least
25% of the total cost of a fossil-fired or nuclear station and up to 66% of a hydro or pumped
storage station.
Beyond cost, the potential for cumulative delay is massively enhanced if the civil
‘engineering and building works run late and hence delay the erection of the largely factory-
produced mechanical and electrical plant.
Equally the final stage on site — the landscaping — has its own importance. Hard and
soft landscape treatments are essential in leaving a completed station which reflects credit,
on its designers and builders, inspires pride and dedication in its operators and shows the
public and planning authorities that the promises made at the outset have been fully kept.
T hope that this civil engineering chapter of the Station Planning and Design volume
is able to convey to the reader a litte of the technical skills, imagination, excitement,
perseverance and devotion that are always present in any successful civil engineering and
architectural team working on a power station project. If it also conveys any sense of the
innate satisfaction and fun that so often helps motivate that team, our purpose will have
been well served.
LW. Hawwant
Advisory Editor — Chapter 3 Contents of All Volumes
Volume A — Station Planning and Design
Power station siting and site layout
Station design and layout
Civil engineering and building works
Volume B — Boilers and Ancillary Plant
Furnace design, gas side characteristics and combustion equipment
Boiler unit — thermal and pressure parts design
Ancillary plant and fittings
Dust extraction, draught systems and flue gas desulphurisation
Volume C — Turbines, Generators and Associated Plant
The steam turbine
‘Turbine plant systems
Feedwater heating systems
Condensers, pumps and cooling water systems
Hydraulic turbines
The generator
Volume D — Ebectrical Systems and Equipment
Electrical system design
Electrical system analysis
‘Transformers
Generator main connections
‘Switchgear and control gear
Cabling
Motors
Telecommunications
Emergency supply equipment
Mechanical plant electrical services
Protection
Synchronising
Volume E — Chemistry and Metallurgy
Chemistry
Fuel and oi!
Corrosion: feed and boiler water
Water treatment plant and cooling water systems
Plant cleaning and inspection
Metallurgy
Introduction to metallurgy
Materials behaviour
Non-ferrous metals and alloys
Non-metallic materials
Materials selection Contents of All Volumes
Welding processes
Nondestructive testing
Defect analysis and life assessment
Environmental effects
‘Volume F — Control and Instrumentation
Introduction
‘Automatic control
‘Automation, protection interlocks and manual comtrols
Boiler and turbine instrumentation and actuators
Electrical instruments and metering
Central control rooms
Ondine computer systems
Control and instrumentation system considerations.
Volume G — Station Operation and Maintenance
Introduction
Power plant operation
Performance and operation of generators
The planning and management of work
Power plant maintenance
Safety
Station thermal efficiency
‘Volume H — Station Commissioning
Introduction
Principles of commissioning
‘Common equipment and station plant commissioning
Boiler pre-steam to set commissioning
‘Turbine-generatorifeedheating systems pre-steam to set commissioning
Unit commissioning and post-commissioning activities
Volume J — Nuclear Power Generation
Nuclear physics and basic technology
‘Nuclear power station design
Nuclear power station operation
Nuclear safety
‘Volume K — EHV Transmission
Transmission planning and development
‘Transmission network design
‘Overhead line design
Cable design
‘Switching station design and equipment
Transformer and reactor design
Reactive compensation plant
HVDC transmission plant design
Insulation co-ordination and surge protection
Interference
Power system protection and automatic switching
Telecommunications for power system management
‘Transmission operation and maintenance Contents of All Volumes.
‘Volume L — System Operation
System operation in England and Wales
Operational planning — demand and generation
Operational planning — power system
Operational procedures — philosophy, principles and outline contents
Control in real time
System control structure, supporting services and staffing
‘Volume M — Index
‘Complete contents of all volumes
‘Cumulative index
xl CHAPTER 1
Power station siting and site layout
1. Planning for new power stations
1.1 introduetion
42. Capecity con
15 System planning studies
18 Authority to bulld @ new power station
2. Site selection and investigation
24. Basie site requicems
22. Area of search for initial sie selection
23. Detailed site invastigation
23.3. Preliminary station layout
23.2 Land requirements
233 Gooling water
23.4 Trensmission
235 Geolosy
236 ‘Site and station levels,
12. Ash and dust disposal
3.10 Fiue gas desulphurisation byproducts
2311 Detailed favestgations related to nuclear safery
24) Environmental considerations
24.1. Ecological eHtects
24.2 Amenity considerations
243 Sociceconomie effects,
24.4 Communication with local people
245 _Assesemont of environment affects
25° Site selection
9 Site layout — thermal power stations
34. General
32 Foundations
2
23.8 Weter supplies for make-up and domestic purposes
23,
2
23. Ske and station levels
3.4 Main buildings and oriencation
35 Ancifery buildings
as coess and on-site roads
37. Stator operation constserations
38 Cooling water systom
3.8.1 Direct cooled sysiem
382 Closed cooling tower water system
38° Fuel supplies and storage
38.1 Coal plant
3.82 Fuel oll plant
310 Ash and dust disposal
3.11 Flue gas desulphurisation plant materials
3.12 Transmission requirements
3.13. Construction requirements
3:44 Amenity considerations
315 Typical site layouts
4 Pumped storage
41 fntroduetion
42 Suttabie topology
43. Ground conditions
44 Site capacity
45. Systom one transmission requirements
48 Hydraulic system requirements
47 Heavy load access
48 Avaitablity of construction labour
43. Environmental impact,
5 Gas turbines
5.1. Introduction
5.2 The role of gas turbines
52.1 Auxiliary power generation
8.22 Peak load generation
1 Planning for new power stations
1.1 Introduction
The construction of a major new power station takes
typically about five to six years from the decision to
build the station to the commissioning of the first unit,
‘The CEGB's annual plans therefore include the pro-
vision for specific new generating stations that are
planned for commissioning in the period seven to aine
‘years ahead of need (referred to as the planning years).
Before it can embark on the ordering of a new power
station the CEGB must have received the Secretary of
State's consent required under Section 2 of the Electric
Lighting Act 1909. together with any related consent
and licences, and must separately have received finan-
ial sanction from the Government.
‘The CEGB has to evaluate the need for power
stations in the light of its statutory duties. It considers
whether there is a need for new capacity in order to
maintain an adequate security of supply, or to give
greater economy, or to improve the security of fuel
supply by allowing the types ard sources of fucl or
primary energy to be diversified. In addition, it may be
justifiable to build a new form of generating capacity in
order to develop the ground for a possible future
benefit
1.2 Capacity considerations
Capacity requirement is determined by the need to
meet the peak demand of the year. The first step in
estimating generating capacity requirement is therefore
1 Power station siting and site layout
Chapter 4
to forecast the peak demand for each future winter up
to the planning years. The forecast presumes that the
peak is most likely to occur on working weekdays in
December to February during a spell ot cold weather of
average severity and is thus described as the average
cold spell (ACS) winter peak demand. ACS conditions
are determined by a statistical analysis of past weather
data and the variation in demand caused by weather
variations.
Each year the Electricity Supply Industry prepares
new estimates of the unrestricted ACS winter peak
demand, the corresponding values of restricted peak
demand after allowing for the expected reduction in
peak demand by load management, and the total
number of units of electricity (unit requirements) to be
produced by the CEGB or purchased from external
suppliers. The unit requirement therefore equals the
sum of the CEGB sales of electricity to Area Boards
and to its direct consumers and the transmission losses
on the CEGB system.
After consideration of the various forecasts, recom-
mendations are made to the Electricity Council as to
estimates of demand and unit requirement up to the
planning years. The Electricity Council then formally
adopts these forecasts, together with provisional esti-
mates for the subsequent two years, on behalf of the
Electricity Supply Industry in England and Wales.
In order to meet the statutory requirement to pro-
vide a continuous supply of electricity except in cases
‘of emergency, the industry has over many years aimed
to provide sufficient generating capacity to meet the
future demand with a high degree of security. Since itis
impracticable to ensure 100% security of supply there
will, on occasions, be insufficient generating capacity
to meet demand even after the application of load
management. In such circumstances, the first action
would be to reduce the voltage and/or frequency within
permissible statutory limits. This has the effect of
reducing the magnitude of demands which are sensitive
to voltage or frequency while maintaining continuity of
supply to all consumers. In this way the overall demand
can be reduced by up to 7.5%, but if the remaining
demand still exceeds the generation available. then
some consumers must be disconnected.
It is the CEGB’s function to ensure that sufficient
generating capacity is provided to meet the generation
standard and it achieves this by planning @ rescrve
margin of generating capacity called the planning
‘margin. This is defined as — the percentage margin of
additional generating plant planned to be in service in
the planning years over and above that needed to meet
the peak demand.
‘The CEGB and Electricity Council make estimates
of the expected average availability and of the expected
magnitude of variabilities of availability and forecast
demand. A simple statistical calculation then gives the
size of planning margin that meets, or approximately
meets, the security standard.
2
1.3. Economic considerations
The provision of new capacity to meet the forecast
demand is not the only reason which might justify the
construction of new generating plant. New construction
‘might also be justified on economic grounds and might
allow the retirement of some existing capacity, In
principle, a plants retained in service until it becomes
‘more economic to replace it with new capacity. Evalua-
tions are made for certain economic indicators for
cxisting stations and for the potential new stations that
might be built:
© For existing stations, the anmual avoidable cost is
evaluated on a year-by-year basis of retaining certain
stations or parts of stations in an operable condition
This cost is calied the net avoidable cost (NAC)
expressed in units of /kWpa
© For new generating station options for commis-
sioning by the planning years, the CEGB calculates
‘the net effect on total system costs of building and
operating the station over its lifetime and converts
this into an average annual cost, in units of £/kWpa,
called the net affective cost (NEC).
‘These indicators allow two economic comparisons to be
‘made. Firstly, the comparison of NEC for alternative
new generating plant allows, for given assumptions of
input parameter values, the indication of the most
economic option, namely the one with the lowest NEC
Secondly, for that option, it is possible to test whether
it is economic to instal! the new plant and decommi
sion existing capacity.
‘When making an economic appraisal of alternative
‘new generating station options, itis necessary to assess
the probable cost of installing and runing each station
and its impact on other system operating costs, and to
censure that there is likely to be sufficient fuel available
at an acceptable price throughout its expected operat-
ing life. Some generating plant options may have a
relatively short construction time and have the poten-
tial of being economic after a short period of gener-
ation. However, the plaaner must consider all options,
including ones with a construction lead-time of five to
six years and operating life of up to 40 years, Hence the
planner needs to take a view of electricity demand, fuel
availability and fuel price many years ahead
Figure 1.1 shows @ possible future plant mix as
envisaged by CEGB in 1985,
1.4 Future requirement predictions
The interrelationship between estimates of economic
activity. fuel prices, energy supply and demand, elect
city demand and the implications for electricity supply
have been more fully examined through the develop-
‘ment of economic scenarios (j,e., imagined sequence of
future events) Planning for new power stations
carsriom
oF Bg
2
‘assume nucLean evEonMeNT
se
aay
ay
Fic. 1.1 Possible @xure CEGB plant nix
The scenarios set cut @ spectrum of possible future
developments which can be used in a variety of plan-
ning studies. More specifically:
© They form a valuable aid to the judgement of the
range of plausible outcomes that should be allowed
for in planning, especially with regard to the furure
extent and composition of economic activity, energy
supply and demand, energy conservation, fuel prices
and availabilities, and electricity demand.
‘# The relative economic merits of alternative generat-
ing plant types for each scenario are evaluated.
‘* The implications for economic operation and sccur-
ity of fuel supplies of alternative generating plant
development options within each scenario are con-
sidered,
‘The scenario approach does not require the CEGB
Xo estimate specific probabilities of occurrence of the
alternative scenarios, but provides a background
against which planning judgements can be made for a
highly uncertain future, However, each scenario is
considered with care when it has been fully developed
and is judged whether or not it still appears to be
plausible and with a significant prospect of occurrence
in real life. Provided the scenarios individually pass this
test, the CEGB aims ideally to ptan so as to be able to
respond to any one of these plausible outcomes. In
practice, some reasonable latitude would be accept-
able; for example, in the case of a scenario entailing
rapid growth of electricity demand, it might be prac-
tically necessary to accept a moderately lower standard
of security of supply for some interim period before
generating capacity could be fully adjusted to the
requirement. However, it is planned to avoid a really
serious failure to achieve a secure and economic supply
for any plausibie scenario.
‘The scenarios allow the CEGB to examine the risks
attached to alternative generating plant options which
arise, in particular, from variations in future electricity
demand or fuel prices. In addition, the analysis of risk
covers uncertainties which attach to the alternative
3 Power station siting and site layout
Chapter 1
‘options, especially with regard to capital cost, perform-
ance factors, lifetime and construction time. The wider
strategic aspects are also considered, of which two are
worth particular mention, namely the security of fuel
supplies and making provision for future investment
options.
Figure 1.2 shows the effect of particular scenarios on
the estimation of system demand up to the end of the
century, using 1979/80 as the base year.
In order to assess the economic merits of different
types of generating plant it is necessary to make
estimates of capital cost, construction period, station
efficiency, lifetime and availability in service, all of
which are relevant to the overall value of the plant. The
construction period and the incidence of expenditure
over that period are important in relation to the total
capital investment and the time when a return may be
expected on that investment; the lifetime and avail-
ability (together with the estimated fuel and running
costs) determine what that cetumn will be. Endeavours
are made to ensure that, as far as possible, these
estimates are central ones (i.e., those which are as
likely to be high as they are to be low) and the sensi-
tivity of the results of the economic appraisals to
changes either way in the estimated values is examined.
‘As the economic appraisal must represent the per-
formance of a new station over its lifetime, it must take
account of the other generating plant which may be on
the system over that period. It is therefore necessary to
make assumptions about the types of generating plant
which might be installed in the future and their cost and
availability. For this purpose it has been assumed that
‘the values of capital cost, construction period, lifetime
and availability for later stations would be the same as
for the stations being appraised unless there is justifica-
tion for doing otherwise.
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soganio 4 wie chown
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1.8 System planning studies
Early planning work begins with the examination of
system load flows and the identification of future gen-
eration and transmission needs. This process shoves
regional requirements and notional locations of gener-
ation sites. One important factor which is taken into
account is a CEGB policy to develop existing sites
wherever possible, if this satisfies the system require=
ments. By developing such sites to their full capacity, as
determined by any technical and environmental limits,
advantage can be taken of existing facilities, such as
transmission outlet, improved local roads and minimi-
sing the amount of new works.
‘At an early stage the type and size of power station
are selected. An initial technical appraisal, capital cost
and construction programme can be produced for each
site. At the completion of this review, a list of
alternative generation sites will have been compiled
and they can be ranked in preferred order for develop
ment. Detailed siting studies can then be carried out —
as described in Section 2 of this chapter,
1.6 Authority to buiid a new power
station
Station design and siting studies are carried out, to the
point where an application is made for Government
consent 10 develop 4 site. This procedure, a statutory
obligation, is a request to the Secretary of State, under
the provision of Section 2 of the 1909 Electric Lighting
Act, to build a power station,
In addition to Section 2 Consent, the CEGB requires
planning permission under the Town and Country
Planning Act of 1971. Part of this Act empowers the
Sceretary of State to direct that planning permission
Fio, 1.2 fects of scensrios on demand Site selection and investigation
is granted at the same time as Section 2 Consent
However, the Secretary of State may attach conditions,
as he thinks appropriate, in regard to the planning
sanction, the CEGB proceeds with the design and con-
struction of the project. Figure 1.3 shows the typical
timescale for power station planning and carly con-
struction.
‘An important part of the investigation programme is
consultation with Ministerial and Local Authorities and
other statutory bodies such as Water Authorities. As
part of the procedure for ensuring that all parties are
fully aware of agreements which have been negotiated
and which must be observed during the station design
and construction period, a document called ‘Station
Development Particulars’ is issued, which records all
discussions and agreements with parties and also con-
tains @ schedule of statutory consents which must be
obtained,
‘The Station Devetopment Particulars also contain a
technical section dealing with the transmission connec-
tions and parameters of the main plant, particularly
the generator transformer, so that they are properly
matched to the transmission system. The details cover
matters such as power factor, synchronous impedance,
frequency regulation, the dynamic response of the unit
to change in load demand and guidelines on the elec-
trical auxiliary system to ensure that this is a reliable
network
2. Site selection and investigation
2.1. Basic site requirements
A power station is simply a factory for the conversion
of the energy stored in the fuel into electrical energy.
The basic requirements for a power station are, there-
fore, similar to those of any other factory
A supply of raw material at a competitive cost
(fuel).
@ Access to the markets for its products (transmis.
sion)
© A labour force of the size and quality required.
© Means of disposal for any trade effluent or by-
product.
* Land for construction and operation.
‘The raw material from which electricity is made in s
thermal power station can be coal, oil, uranium or
‘natural gas. Electricity, the main product, has its own
‘access to centres of consumption through the transmis-
sion and distribution system. By-products are ash or
irradiated uranium fuel elements and the economic
disposal of the former is often a major consideration.
The trade effluents are the large quantities of heat, the
disposal of which generally requires very large quanti-
ties of water which, for cost reasons, must be available
close to the site. The products of combustion, in the
ar Meee wxgiheere
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Fic. 1.3 ‘Typical timescale for power station planning Power station siting and site layout
form of large volumes of flue gases, must also be
dispersed without contravening the national clean air
policy or causing atmospheric pollution.
‘The main techaical requirements of sites for nuclear
and coal-fired stations of the size being considered
currently are summarised in Table 1.1.
Chapter 1
2.2 Area of search for initial
site selection
In densely-developed countries like England and
Wales, suitable power station sites are difficult to find.
Many of the best sites have already been used for one
Taste Lt
Technleat ste requirements
NUCLEAR STATION (1200)
PARAMETER CCOAL-FIRED STATION 20044)
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whaticent cea Site selection and investigation
purpose or another and more and more of the undevel-
‘oped areas are being conserved. In fact some 12% is
built on, while over 40% is given statutory protection;
‘on the coast, the respective figures art 25% and 60%
(sce Fig 1.4), Nevertheless the CEGB must be able to
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meet the need for new stations as foreseen by its
estimates of future demand,
The considerable length of time’ that is required to
plan and construct a station and the regular revision of
future demand estimates means that it is wise for the
fo, 13 Protected land apd major eomurbations as at 1984 Power station siting and site layout
Chapter 1
CEGB to maintain a ‘pool’ of potential sites from
which suitable candidates can be chosen a8 necessary.
This pool is made up of the following three types of
sit
‘© Existing power station sites capable of further
development,
© Pieces of land already purchased by the CEGB for
future development.
* Pieces of land not owned by the CEGB, but that
have been identified as potential sites.
‘The identification and investigation of potential sites is
usually divided into two phases: area of search and
detailed investigation.
Although the Supergrid allows the transfer of large
amounts of electricity from one part of the country to
another, its capacity to do so is limited by both
technical and economic constraints. Therefore, when
the need for new generation is foreseen, transmission
considerations combined with other factors, such as
fuel sources, usually indicate in which part of the
country it would be best to locate the station. The type
of station required (nuclear, coal or oil) is dictated by
such factors as the relative costs, the desired overail
balance between fuels, and environmental considera-
tions.
Having identified the need for new generation in a
certain region, a large area, perhaps covering several
hundred square kilometres, is studied to find out its
potential. Any known sites are also reviewed. Govern
ment Departments arc invited to draw attention to any
places of special concern to them. Bodies such as The
Countryside Commission and the Nature Conservancy
Council, who have responsibility for preserving areas of
natural beauty or of scientific value, are also notified
and discussions are held with officers of the Local
Planning Authority.
Information is gathered and analysed on technical
matters such as water resources, geology, population
distribution, road and rail system; as well as on
environmental aspects such as areas of scientific
interest or of outstanding natural beauty, historic
features and recreational areas. Much of this informa-
tion can be obtained from ordnance and geological
survey maps, local and county plans, aetial photo-
graphs, Admiralty charts and other published material.
‘These studies may take upwards of a year before a
shortlist of sites thought worthy of detailed investiga-
tion can be prepared.
2.3. Detailed site investigation
Prospective sites may be ideatified through the area of
search work or because changes in land-use give new
opportunities, ¢... the closure of defence installations,
Before detailed site investigations are started, the
bodies previously consulted arc notified, the owners
8
and occupiers are approached, and announcements are
made in national and local newspapers.
It can take over two years to carry out the necessary
detailed studies to prove the viability and determine the
‘optimum capacity of each of the alternative sites being
considered. During this period consultations take place
with the authorities concemed with planning, environ-
mental protection, transport, water supply, flood pro-
tection, fisheries, safety and other relevant subjects.
A careful study is made of the technical and amenity
aspects of power station siting, The main topics covered
for @ typical nuclear power station site are shown on
Fig 1.5. The major aspects of the studies are described
as follows,
2.3.1. Preliminary station layout
In order to assess the suitability of a particular site for
the type of power station being considered, it is
necessary t0 establish the initial basic station design.
‘This includes the disposition of the major plant or
{groups of plant in the main station buildings, leading up
to the determination of the shape and size of the build-
ings and then the grouping of the various individual
buildings, and external plant items to produce a co-
‘ordinated station design which achieves the lowest
capital cost, ease of construction and efficient oper-
ation and maintenance of the power station
The preliminary station layout enables the on-site
geological work to proceed and assessments to be
carried out on the proposed site level, disposition of
construction contractors’ plant and storage areas and
environmental aspects.
The station layout would be developed during the
study period to take the fullest possible advantage of
the available site area and of the recommendations
of the architectural and landscape consultants. ‘The
principles used in the development of the station layout
are described in Chapter 2 of this Volume.
23.2 Land requirements
Sufficient land will be required not only for the station
when it is in operation, but also to provide adequate
arcas during the construction period.
The area occupied by an 1800 MW tower cooled,
coal-fired station may be up to £00 ha (exciuding ash
disposal arcas). The station buildings will take only a
portion of the site. The remainder depends on the
needs of the coal store and railway sidings.
‘A 1200 MW nuclear power station will require 16-20
ha for operational purposes
‘A considerable area will be required during the
construction of both coal-fired and nuclear power
stations. Typically 28-34 ha would be required to
provide adequate working and storage arcas for the
contractors and for the construction car and bus parks.
In addition, storage space will be required for topsoil
removed during excavations (the area required would depend on the particular site) and for excavated
materiel required for backfill
‘Most of the temporary construction areas for a coal-
fired station could probably be accommodated on the
‘coal store area, although some extra land may also be
required. Extra land would be required temporarily for
nuclear stations. Therefore a suitable site for a coal-
fired station would require about 100 ha and for a
nuclear station about 60 ha. Some further off-site land
may also be required to provide areas for planting or
landscaping (0 screen the station.
Site selection and investig
Figure 1.6 shows the typical land requirements for a
pressurised water reactor (PWR) station location next
to an existing nuclear station
2.3.3 Cooling water
‘The total cooling water (CW) requited depends on the
ultimate station capacity planned. Typically for a coal-
fired station a 900 MW turbine requires a main CW
flow rate of about 24 ms. For a PWR station a
(600 MW turbine requires about 23 ms. Allowing for
Fic, 15 Typiesl site investigation programme for a nuclear power station ion siting and site layout
Chapter 1
-RESLAMED AREA SRONTING TEMPO WORKS AREAS
ectamen area enokeing new Staion St
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PROPOSED NEW BOUNDARY
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fie. 1.6 Typical land requirements for a PWR station next to an existing auslear station
other cooling water requirements this means that an
1800 MW coal-fired station would require about 52 mvs
and a 1200 MW PWR station about 50 m/s.
As the cooling water flows through the condenser
tubes, its temperature is raised and this could typically
vary between 8°C and 12°C. This warmed water mast
then be cooled using cooling towers or, in the case of
direct cooied stations, by discharge to the water source
and be dispersed in such a manner as t minimise its
recirculation back into the cooling water intake with
attendant loss of steam cycle efficiency.
The use of cooling towers requires that 2 suitabie
make-up water supply b¢ identified which would typi-
cally amount to 2% to 3% of the total cooling water
flow. Whilst the actual flow would be influenced by the
10
site-specific water quality aspects, it is usual for about
‘wo-thirds of this abstraction to be retuned to the water
source as purge to maintain the concentration factor
‘within the cooling system. This water would be about
WC warmer than the ambient water temperature.
If such a water supply is to be obtained from a river,
then studies are required to identify minimum Hows
and the consequences of the water abstraction and
return on the environmental well-being of the river
system. In the UK, water authorities often hold long
term records of water flows and details of licensed
abs:ractions. A seasonally variable ‘minimam pre
scribed flow” is often applied to rivers, which prohibits
abstractions if the actual river flow falls to the specified
level Site selection and investigation
‘The preferred location for a power station from the
cooling water viewpoint, is near a large tiver, estuary or
sea coast to obtain the large volume flows at lowest
temperatures. One of the key problems facing the
cooling water system designer is therefore to provide
the optimum location and separation between the
cooling water intake point and the outfall. Another
important requirement is to design a system which
has the minimum effect on marine ecology. In this con-
nection it is necessary to ensure that warm water
is adequately dispersed to avoid harmful effects on
marine life. The acquisition of information on currents
and water temperatures over a large area is necessary
for these cooling water studies.
With a direct cooled system abstracting from and
Gischarging to the sea or estuary, the eventual loss of
heat to the atmosphere is 2 lengthy process, and in the
intervening period the dispersion of warm water dis-
charged from a station outfall can be identified in a
number of separate stages. The first, or near-field
stage, is represented by the immediate mixing of newly
discharged warmed water into the ambient sea
Alter a brief transitory period, a second or midfield
stage is represented by a buoyant plume of warm water
lifting towards the surface and spreading outwards at a
rate determined by gravity currents, momentum effects
and the action of the tidal stream. A midfield plume
can eventually reach several hundred metres in width
and can extend in length for 1 km to 2 km in the
direction of the tidal stream (see Fig 1.7).
The normal practice is to minimise recirculation by
physical separation of the intake and outfall structures.
Civil tunnelling costs may limit the degree of protection
that can be afforded by this practice, but additional
protection can be sought by designing the intake
structure to minimise drawdown from an overhead
plume, to ensure maximum possibie depth of water
over the period of coverage, and to minimise the period
of coverage,
CEGB surveys have identified a third stage in the
heat dispersion process at a number of sites. During
periods of calm weather conditions it has been
observed that sequential flood and ebb movements of
the midfield plume alongshore over a period of several
Fic. 17 Midielé plume surface contours stout 30 minutes before low water slack at Sizewell
Ww Power station siting and site layout
Chapter 1
days can develop a far larger pool of warm water; Fig
1.8 shows this condition at Sizewell on the Suffolk
‘coast. It can be seen that the spatial spread extended
full tidal excursion alongshore and several kilometres
offshore. This far field plume is also moved alongshore
by the reversing tidal stream and an amount of secon-
dary recirculation cannot be avoided, in the example
shown, as the cost of separating the intake and dutfall
structures exceeds the recirculation penalty. It has been
found that a far field phume is quickly dissipated with
increasing wind strengths.
Tt is important that survey operations should be
conducted over a long period to ensure that the
eventual design of the cooling water offshore works is
founded upon a data base that sufficiently represents
the variable meteorological and tidal current conditions
local to the site. Tt is equally important that the survey
period should include the calmer and warmer condi-
tions of the summer months when the natural and
artificial thermal fields are most likely to reach a
combined maximum temperature.
Some hydrographical information will be avaitable
for proposed sites near to an existing power station.
However, the increase in size of new developments, the
need to place the new offshore works in correct juxta-
position to existing structures, and the need to ensure
that eventual combined discharges will not adversely
affect local ecology, will still require additional survey
operations.
zai ean
Fic. 18
2
A survey will comprise an array of moored instru-
mentation to record continuous data of flow patterns
and water temperature changes throughout the survey
period, and a number of individual operations gen-
erally limited in time to a single tidal excursion, The
‘moored array can include current meters, tide gauges
and thermistor stringers which, together with an on-
shore aotomatic meteorological station, provide an
overall record of data to improve understanding of the
results from individual survey operations. These indivi-
dual operations can include float tracking, infra red
photography from helicopters or satellites, dye release,
thermal plume profiling, and temperatureicurrent
salinity profiling. Alongside these activities, which are
mainly designed to assist in evaluating thermal plume
behaviour, the survey will contain the necessary echo
sounding, side scan sonar, seismic work, seabed
sediment sampling and wave recording to supply the
information required by civil engineers for designing
the station structures. The data is also used for asses-
sing the movement of materials on the sea bed and
beach under the influence of winds and tides.
‘Thermal images of offshore coastal waters or estuaries
can be obtained using infrared cameras on satellites
Contours of temperature may be marked by different
grey tones for cach temperature band step on black and
white image presentations, Alternatively, a colour
sliced image may be obtained, as shown in Fig 1.9, by
the choice of individual colours for each contour.
ware ie
Summer far Geld at end of flood tide Site selection and investigation
DUNGENESS
Fis, 19. Saclte imagery of thermal discharges trom power stations
{see alse colour photograph between pp 66 and pp 67) Power station siting and site layout
Chapter 1
Improvements in survey operations and measuring
‘equipments have been paralleled by development of
mathematical modelling techniques. Experience how-
‘ever has clearly demonstrated the complex problems
involved in both modelling the separate temperature
fields that make up the thermal structure of a body of
water, and of estimating the relative contributions of
these temperature fields at different sites and under