Achievements of the Dragon project

~nnals Qf Nuelear E~ergy, Vol.5, pp.305 to 3 2 0 . Pergamon Press Ltd 1978. Printed in Great Britain.

O306-4549/78/iOO1-O305502.00/~

ACHIEVEMENTS OF THE D R A G O N PROJECT C. A. Rennie* Chief Executive, April 1959 - July 1968

A b s t r a c t - - T h e D r a g o n High T e m p e r a t u r e Reactor ( H T R ) Project b e g a n

1 April

1959 u n d e r

OECD auspices.

a l l o w e d the p r o j e c t

to c o n t i n u e

100 m i l l i o n d o l l a r s

under

ment.

The reactor

with double

from

corrosion

from

dimensional

were

easily solved.

to c o a t e d p a r t i c l e

proved

easy

changes

elements

fuel elements

maintenance.

of h e a t e x c h a n g e r s

an d

in the r e f l e c t o r

graphite.

circuit

t h a t k e p t the

steel These

p i p e s an d problems

operation were very

th e s o u n d n e s s of t h e c o n c e p t .

The Dragon

to be a v e r y u s e f u l t e s t b e d f o r a n u m b e r

HTR fuel element

an d c o n t i n -

Some difficulties

stainless

S o m e t e n y e a r s of e x p e r i m e n t a l

s u c c e s s f u l and d e m o n s t r a t e d reactor

purged

manage-

c o o l a n t in a h i g h l y c o n t a m i n a t e d

c o o l a n t a c t i v i t y low and p e r m i t t e d arose

a t a t o t a l c o s t of n e a r l y

evolved from

helium

containment,

17 y e a r s

in t i m e an d b u d g e t

e f f i c i e n t and f l e x i b l e i n t e r n a t i o n a l

design

uously decontaminated

Extensions

of d i f f e r e n t

concepts. INTRODUCTION

The Dragon ture

Reactor

1976.

Project,

or more

three

of e i g h t y e a r s

Present

Address:

formally

b e g a n on 1 A p r i l

The original agreement

y e a r s , but a f t e r period

Project,

years

between

a revised

up to 1967,

Wareham,

the OECD High T e m p e r a -

1959 an d e n d e d on 31 M a r c h the S i g n a t o r i e s

agreement

was

was for five signed for a

w i t h i n a b u d g e t ofo~25 m i l l i o n .

Dorset, 305

England.

306

C. A. Rennie This latter a g r e e m e n t w a s of three years each,

subsequently extended three times for periods

m a k i n g a total of seventeen years and a total

budget of just unda~r¢~49 million (about i00 million dollars). In discussing the a c h i e v e m e n t s to be a n s w e r e d would from

seem

of the Project the m a i n questions

to be whether the Project w a s

a success

the technical point of v i e w and whether the Signatories to the

a g r e e m e n t got value for their m o n e y .

However,

before discussing this

it is relevant to look back to the position of nuclear energy s o m e twenty years ago w h e n

the Project w a s

first proposed.

the climate for nuclear energy projects w a s first nuclear p o w e r

Undoubtedly

very different then.

The

stations had been constructed and s o m e had already

given good p e r f o r m a n c e . future of nuclear p o w e r

There were seemed

difficulties but the c o m m e r c i a l

very bright and there w a s

great en-

t h u s i a s m for exploring different reactor types to find out w h i c h would be the best. In E u r o p e

in particular there w a s

a desire to initiate a joint

project not only because it should be advantageous economically but also because

it w o u l d d e m o n s t r a t e the international nature of nuclear

energy r e s e a r c h and development.

Light water

carbon dioxide cooled reactors w e r e The

already in the c o m m e r c i a l

s o d i u m cooled fast breeder reactor w a s

national basis so that the choice w a s vanced water m o d e r a t e d reactor or a m o r e

cooled reactors and

being developed on a

virtually limited to a m o r e

a d v a n c e d gas cooled reactor, using h e l i u m cooling.

and successful collaboration w a s

the D r a g o n

ad-

reactor such as the aqueous h o m o g e n e o u s

In any event,the h e l i u m cooled high t e m p e r a t u r e

projects in the U S A

phase.

later established with the national

and G e r m a n y .

Project w a s

reactor w a s chosen,

It is w o r t h recalling that, w h e n

started, the reactor s y s t e m w a s

envisaged

as one with fission product emitting fuel, a very active h e l i u m circuit, and with a clean up plant w h i c h would hopefully r e m o v e neutron absorbing fission products. Reactor E x p e r i m e n t

of the

The initial design of the D r a g o n

( D R E ) w a s b a s e d on these assumptions. ORGA

The

some

NIZ A TION

technical objectives of the Project w e r e

specified in the re-

307

Achievements of the Dragon Project vised a g r e e m e n t

and are given in .Appendix I to this paper as it is

against these objectives that the w o r k However,

before discussing the technical side, it is worth looking at

the organization of the Project. Project,

of the Project m u s t be judged.

which w a s

the Signatories, management It w a s

In fact, the first achievement

not due to its o w n

was

of the

efforts but to the w i s d o m

to have been set up within a workable

of

and efficient

and administrative f r a m e w o r k . laid d o w n

that all legal acts,

including the placing of con-

tracts,

should be carried out by the Signatory of the host country,

namely

the UK.AE.4,

acting on behalf of the Project,

clearly stated that the Project w a s UK.AE.A

Purposes

Committee,

the responsibility of the

of M a n a g e m e n t

on which each Signatory w a s

.A key provision of the a g r e e m e n t w a s seconded

to the Project f r o m

and its General represented.

that staff should be

their current e m p l o y e r

bursed for their services f r o m

Project funds.

who was

career prospects.

that the budget of the Project w a s period of years,

Another key provision w a s

set, not annually,

agreed by the B o a r d

the Signatories then paid the agreed a m o u n t s

These

from

of pension

but over a

initially eight years and latterly over three years.

The annual expediture w a s

all p a y m e n t s

reim-

This provision m e a n t

that the Project did not have to get involved in p r o b l e m s funds and long t e r m

also

completely independent of the

or any other individual signatory,

Chief Executive being to the B o a r d

but it w a s

of M a n a g e m e n t

and

into a separate account,

this account being authorized b y the Project.

provisions enabled the Signatories to k n o w

exactly w h e r e

they stood at all times as regards

Project funding and assured t h e m

that no over-spend w a s

O n the other hand, the s a m e

possible.

visions enabled the Project to plan a p r o g r a m knowing that funds would be m a d e

staff, and hence

than expected,

Of course,

savings had to be m a d e

could quickly be m a d e

or increase the n u m b e r

staff costs w a s

within the $greed total budget.

of years

available within a agreed total amount.

The facility of being able to decrease seconded

over a n u m b e r

pro-

a major

factor in keeping

if one p r o g r a m

elsewhere,

of

cost m o r e

but such changes

by the Project through the B o a r d

of M a n a g e m e n t .

308

C. A. Rennie REACTOR The DRE

was

based

DESIGN

initially on the use of fission product emitting

fuel with a highly radioactive helium coolant circuit and this accounts for such features of the design as P u r g e d fuel elements Provision of a very c o m p r e h e n s i v e fission product r e m o v a l Gas

helium purification and

system

bearing circulators with no rotating seals

Only one small (about l-ft diameter) entry to the pressure An

machine

flange

vessel

elaborate fuel handling procedure

discharge

removable

with a charge and

inside the pressure

vessel and a fuel

handling cell outside A

leak-tight double containment

While the reactor w a s under ing fuel w a s

structure.

construction,

fission product

retain-

developed and later used for the reactor but it was

too late to change the basic design of the reactor.

However,

then

the

original design concept proved to be extremely useful as it m a d e possible,

among

of m e a s u r e m e n t s major

other things,

it

to carry out a very detailed p r o g r a m

on fission product release and deposition.

fault in the original design concept w a s

T h e only

in the heat r e m o v a l

s y s t e m which gave considerable trouble later on due to excessive corrosion on the water The

side of the p r i m a r y

heat exchangers.

reactor operated very satisfactorily over its ten-year life

and the m a i n

problems

that w e r e

encountered and successfully dealt

with were: Oscillation and bowing power

of the control rods,

swings and s o m e

causing

sticking of the rods which w a s

cured by fitting suitable d a m p i n g

restraints on articulated

rods. Replacement

of the inner reflector graphite blocks which

had b o w e d

due to irradiation effects.

Corrosion

of the p r i m a r y

heat exchangers

which was

cured by correcting the water treatment procedures, modifying the gas inlet p l e n u m

to avoid hot spots caused

309

Achievements of the Dragon Project by channeling of the hot inlet gas,

and reducing flow

instabilities in the boiler tubes. Removal

of identification tape containing polyvinyl

chloride, which w a s

causing stress corrosion on small

stainless steel pipes. Correcting the first two p r o b l e m s charge m a c h i n e

as a general purpose

these functions perfectly. charge m a c h i n e contractors.

was

manipulator

one of the achievements was

operated for the next 13 years It would,

Another

was

inside the pressure

however,

have needed 1976,

some

vessel without any maintenance

if

as the positional accuracy

not as good as it had been.

achievement

of the Project and its contractors w a s

gas bearing

circulators which gave

problems.

It w a s

tube bundles w e r e

the

14 years use without any m a j o r

possible to r e m o v e

intervals and in fact it w a s changer

of the Project and its

installed in the reactor in 1963 and

the Project had been extended beyond of the m a c h i n e

and it p e r f o r m e d

In fact, the behavior of the charge dis-

The m a c h i n e

maintenance.

involved using the charge dis-

and inspect the circulators at

necessary

to do this w h e n

changed.

The

the heat ex-

successful carrying out of

these operations without having to resort to expensive and timeconsuming

decontamination

procedures

virtues of the high temperature

reactor.

REACTOR The was

OPERATION

original timetable proposed

to c o m m e n c e

can be counted as one of the

in 1958 before the Project started

detailed design and construction of the D R E

1959 with construction essentially complete m i d - 1962,

and operation at p o w e r

construction w o r k achieved

in August

in m i d -

and criticality achieved by

beginning in mid- 1963.

In practice

did not start until early 1960 and criticality w a s 1963.

Operation at p o w e r

1965 with full operation in April 1966. about two years late on the p r o g r a m

began in the middle of

The D R E

was,

therefore,

envisaged at the start of the

Project. A b o u t one year of this delay w a s starting the w o r k

due to initial difficulties in

such as obtaining the right staff, placing the m a j o r

C. A. Rennie

310

contracts and setting up the proper organization, while the other year was

due to over o p t i m i s m about the time needed.

H o w e v e r , on balance

it can be counted a real a c h i e v e m e n t of the Project to have got thus far in the first 7 years of its life, bearing in m i n d that the p r o g r a m of r e s e a r c h and d e v e l o p m e n t w o r k ment

studies w a s

fact, in t e r m s

on fuel and materials and on assess-

progressing very favorably at the s a m e

of timescale the progress

of the D r a g o n

time.

In

Project c o m p a r e s

favorably with that for other national projects on high temperature

re-

actors. One

of the objectives of the Project w a s

to demonstrate the

feasibility of operating a reactor using a high pressure h e l i u m circuit.

cooling

It v,as s h o w n that welds p r o d u c e d by standard m e t h o d s w h i c h

passed the conventional radiographic and ultrasonic tests w e r e tight and r e m a i n e d leak tight.

Similarly O-ring

valves and high quality gasket joints w e r e the required p e r f o r m a n c e . testing procedures,

leak

seals, bellows sealed

all s h o w n to be capable of

With economically sensible design and

leakage f r o m

in trivial h e l i u m losses f r o m

a large reactor plant should result

the point of view of cost and of contami-

nation levels. Another

important p r o b l e m

high purity h e l i u m and it w a s with m o l y b d e n u m

is that of m o v i n g parts operating in s h o w n that selected materials lubricated

disulphide p e r f o r m e d well.

or frequently used m e c h a n i s m s

However,

all c o m p l e x

are best sited in cooler zones w h e r e

oil and grease contamination is negligible so that conventional lubricants can be used.

It w a s

found during m a i n t e n a n c e w o r k

actor e x p e r i m e n t that no difficulties w e r e mating

on the re-

encountered in dismantling

surfaces even in hot zones of the reactor such as the piston

ring seals on the nimonic hot ducts.

Helium

seems

to be an ideal

coolant gas for reactors on the basis of experience with the D R E . T h e effective heat transfer properties and f r e e d o m f r o m

corrosion

effects have been k n o w n for a long time and experience s h o w s that good design can o v e r c o m e One

problems

of lubrication and of leakage.

of the uses of a reactor e x p e r i m e n t that has good instrumen-

tation is to investigate the transient behavior of the reactor system. Many

tests of this type w e r e

carried out and the following e x a m p l e s

Achievements of the Dragon Project

311

illustrate the effects of reducing and increasing coolant flow with no movement

of the control rods.

speed and hence m a s s

With a slow reduction of circulator

flow the p o w e r

while the gas outlet temperature perature falls slightly.

output reduces

rises slightly and the gas inlet tem-

Increasing the circulator speed to its f o r m e r

value returns the reactor to its n o r m a l The test.

rate at w h i c h p o w e r

It w a s

operating conditions.

can be increased w a s

found that an increase

in p o w e r

obtained in about 5 seconds with changes temperature. mass

correspondingly

T h e nuclear p o w e r

studied in another

of about 15%

could be

of less than 5 ° C

response

in fuel

lags behind the coolant

flow increase but this is covered by the release of stored heat

f r o m the graphite in the core.

These

and m a n y

other tests d e m o n -

strated the practicability of control by coolant flow for both steady state and p o w e r

following conditions. FUEL

Numerous

studies were

which consists discuss

entirely

made

mentioning

provided for tests in l o o p t e s t s system

reactor.

available

of t h e p r i m a r y

reactor

over

fission product particles graphite retains

matrix fission

transparent

to f i s s i o n

of p a r t i c l e s

in p r o p e r t i e s

provides

is a d i f f u s i o n b a r r i e r

:lamaged by o p e r a t i o n number

of y e a r s ,

matrix

products

products.

the r e v e r s i b l e

purge out

dependence

a real double

containment.

at n o r m a l

of f i s s i o n

of

conditions, inherent

products

The

temperatures,

is m o r e

Although coated particles

adverse

by t e s t s

T h e f u e l c o n c e p t of c o a t e d

which,

i n v o l v ed and t h e i r

the r e l e a s e

out

significant

w a s to c o n f i r m ,

but at high t e m p e r a t u r e s

under

to c a r r y

to f a i l w i t h o u t p r o d u c i n g

on t e m p e r a t u r e .

in a g r a p h i t e

experiment

d i f f i c u l t to c a r r y

was possible

to

However,

of the f u e l e l e m e n t

of the P r o j e c t

a number

release

Because

core,

circuit.

O n e of t h e a c h i e v e m e n t s in t h e

w h i c h the r e a c t o r

if r e q u i r e d , i t

expected

is n o t s p a c e

in d e t a i l in t h i s p a p e r .

which would have been very

on f u e l w h i c h w a s

contamination

work

of t h e r e a c t o r

but t h e r e

th e o p p o r t u n i t i e s

in a n o t h e r

which was

of th e b e h a v i o r

of f u e l e l e m e n t s ,

the fuel d e v e l o p m e n t

it is w o r t h

tests

AND M A T E R I A L S

or less m a y be

because

of t h e l a r g e

statistical

variability

into the

c o o l a n t is s l o w

C. A. R e n n i e

312

but

progressive.

checks

and

However,

on

shut-down

reducing

of the

the

reactor

fuel

and

graphite

temperature

stops

the

release

of fission

feature

was

products. A good demonstration by a high 1250°C sively the

was

reactor

only

experimental

the

release

removed

slightly

the

irradiation

period

On another

cause

set was

a maximum

and

the

element

problems

correctly.

The

fuel

the

reactor

for

the

reactor

experiment

the

deposition

of fission

be.

when

Even

fission was

found

deposited formly

that

or was

of t h e support

pass

any

structure

would

confirmed

circuit clamps

was

observed

were

life

cells

with

no

set in

that

of the

expected

helium

to

where circuit

products

exchanger

shut

operation

conditions

fission

the

normally

the

3

serious

then

it was

into the

for

was

demonstrated

under

which

until

were

problem

the heat

gags

reactor

In fact,

run

design

during

examination

evidence

and

it

were not uni-

The

reactor

in the its

reactor

ten-year

compo-

life and which

on the helium

effects use

experiment,

of components

of d a m a g e

the possible

not detectable.

of t h e

deterioration

occurred

and

for

circuit.

appreciable

significant

was

operated

The

gags

life.

conservative

have

flow

and behaved

condensible

by the detailed

No

flow

emitted

gas

of

fuel

reactor

2000oc,

located.

not the

through the

the

in the

and

of a b o u t

were

of the

around

that

removed.

of fuel

all

reactor

ten-year

was

on shut-down

equipment

coolant

to the hot

design

its

progres-

increases.

reloaded

deliberately

of the fairly

unlikely

nents

were

first

distributed

it was

this

nearly

on the

In view

over products

were

the

was

was

set

with

coolant

of its

samples

products

the

element rest

large

into

removed

and

failed

at

b e l o w 10 - 4 . In this -Z 10 over the 80-day

to

element

activity

to operate

and when

limit

temperature

coolant

fuel

contamination

fuel

Yet

provided

133 w a s

sudden

loaded

expected

the handling

steadily

a fuel

as

stopped

normal

xenon

no

designed

of 80 d a y s .

reactor

increased

occasion

of t h e h i g h

down

for

but with

incorrectly with

the

fuel

and

coolant

The

ratio

ratio

1800°C

into the

contaminated.

experiment

days

at

mentioned

in which

period

from

release-to-birth

were

run

the

was

above

experiment

deliberately

over

element

the

temperature

of t h e

of the

of fretting reactor

side

on various experiment

313

Achievements of the Dragon Project for fuel testing m e a n t from

some

individual channels.

helium streams there w e r e

h e l i u m outlet gas t e m p e r a t u r e s of up to 9 5 0 ° C There was

affecting the nimonic liners of the outlet ducts, but

no obvious signs of d a m a g e

tion w h i c h w a s

the possibility of these hot

made

when

from

the reactor w a s

the superifical e x a m i n a -

shut down.

GENERAL CONSIDERATIONS The

easy m a i n t e n a n c e

of any reactor is of p r i m a r y

importance

to the operator because of the high ratio of capital to operating costs. In this respect the h e l i u m cooled reactor is almost unique as the inert nature of the coolant m a k e s the circuit m u c h

more

the prediction of activity levels in

reliable c o m p a r e d

to reactors with chemically

active coolants such as water or carbon dioxide. DRE

in c o m m o n

Pebble B e d

with that for the P e a c h

B o t t o m reactor and the A V R

reactor has confirmed that n e w

in the p r i m a r y

Experience with the

standards of low activity

circuit can be achieved.

In practice the w o r s t difficulties in p r i m a r y usually c o m e

circuit m a i n t e n a n c e

f r o m deposited activity arising either f r o m fission pro-

ducts or activated materials transported round the circuit and the behavior of such deposits is often unpredictable.

In a h e l i u m cooled

reactor the generation of any corrosion products is reduced e n o r m o u s l y by the inert nature of the coolant and the fairly high t e m p e r a t u r e around the circuit m e a n s

that m o s t fission products plate out in the

coolest part of the circuit such as the heat exchanger tubes and circulator impellers.

One

of the m o s t

encouraging features w a s

highly adherent nature of any activity because

the

it w a s deposited on clean

metal surfaces rather than on easily detached corrosion products. general only very simple m e a s u r e s of activity f r o m

components

were

needed to prevent any spread

or e q u i p m e n t r e m o v e d

f r o m the reactor,

such as the use of plastic bags or sheeting, but in m o s t activity could be r e m o v e d It is n o w

some

sign,

cases such

by wiping with a cloth.

fifteen years

particle fuel, w h i c h w a s

In

since tests w e r e

an entirely n e w

b e g u n on coated

concept of fuel element de-

only really possible with h e l i u m cooling.

Progress

in this n e w

field has b e e n very encouraging indeed and fuel of this type is n o w

314

C. A. Rennie very m u c h

a practical possibility as is evidenced by the Fort St.Vrain

and the A V R

power

not so m u c h

The

In fact, the p r o b l e m s

those arising f r o m

might arise f r o m the p r i m a r y

reactors.

normal

operation,

which r e m a i n are

but those which

the accidental ingress of air or water vapor

helium circuit.

safety a r g u m e n t s

will, of course,

for future high temperature

power

Such factors are the use of a fuel element

withstanding very high temperatures strophic failure,

reactors

depend on the detailed design of the reactor but they

can be based on factors which have been demonstrated elsewhere.

into

and

capable of

for long periods without cata-

the slow temperature

the low level of p r i m a r y

in D R E

response

to p o w e r

transients,

circuit activity and contamination,

and the

ease of detecting helium leakage. The

main

safety hazard

dation and water

is the possibility of excessive

gas production,

of the helium p r i m a r y

resulting f r o m

core oxi-

simultaneous failures

circuit and the boiler tubes.

However,

there

is every reason to expect that proper design of the prestressed

con-

crete pressure vessel and of the boiler circuits will enable acceptable safety a r g u m e n t s

to be put forward

of single failures are very m u c h REA CTOR

in this unlikely case.

Other cases

easier to deal with. ASSESSMENT

In the course of the life of the Project several reactor assessment

studies w e r e

carried out both on the u r a n i u m

the low e n r i c h m e n t u r a n i u m

fuel cycle.

The

235 thorium,

and

engineering features of

the reactor are largely independent of the fuel cycle and resulted in designs within a prestressed

concrete pressure

flow through the reactor core and u p w a r d pods around the core.

The

vessel with d o w n w a r d

flow through the boilers in

concept of podded boilers inside the pre-

stressed concrete pressure vessel w a s

first proposed by the Project

and has been a feature of later designs of gas cooled reactors elsewhere. The main

difference between the various designs of high t e m p e r a -

ture reactor has been in the kind of fuel element proposed.

While

all the proposals are based on the use of coated particles in a graphite

Achievements of the Dragon Project matrix,

both the geometrical a r r a n g e m e n t

specified have been different. posed as one w a y

315

and the type of coating

T h e pebble bed type of reactor w a s pro-

of simplifying the fuel handling p r o b l e m s

type of reactor is being actively studied in the G e r m a n

and this

national pro-

gram. The

earlier studies in the Project w e r e

based on using a prismatic

type of fuel with the actual fuel carried in graphite tubes in a graphite block,

the core of the reactor consisting of a n u m b e r

these graphite blocks.

At the s a m e

element being considered w a s and fuel holes in it.

time in the U S A

of stacks of the basic fuel

a graphite block with both coolant holes

In practice,

the D R E

was

sufficiently versatile

to be able to test to a certain degree all three basic types of fuel and latterly it w a s

generally agreed that for the prismatic

reactor fuel

the preferred type should be the graphite block with fuel and coolant holes in it. With regard to coated particles the simplest type is the B I S O particle with two distinct layers of pyrolytic carbon coating but the TRISO

particle with an additional silicon carbide layer between the two

carbon layers w a s now

also studied extensively in the Project.

a very considerable a m o u n t

and p e r f o r m a n c e

There

is

of data available about the fabrication

of these coated particles to assist the reactor de-

signers in specifying the fuel element for a p o w e r

reactor.

Different

fuel cycles require different heavy metal densities in the fuel bodies and it is mainly in this area that w o r k

is continuing,

so that full ad-

vantage can be taken of the potential of coated particle fuels. Besides the use of the high temperature steam

cycle generating plant,

Project,

studies w e r e

reactor with a conventional also carried out by the

both on direct cycle gas turbine p o w e r

heat applications.

A

program

of w o r k

plants and on process

to investigate materials,

would be suitable for the higher gas temperatures 1000oc

or m o r e ,

the Project w a s

was

started but w a s

by no m e a n s

envisaged,

which

of

complete w h e n

terminated. CONCLUSION

In this short account of the achievements

AXE 5 : 8

10

o

of the D r a g o n

Project

316

C. A. Rennie it has not been possible to cover everything and even the points that have been dealt with, have only been treated rather superficially. This is not so surprising w h e n izing seventeen years w o r k during its life.

The

of a Project which achieved a great deal

seventeen A n n u a l Reports of the Project have

been published by the O E C D the w o r k

of the Project.

in Paris, In addition,

of the Project over the whole shortly as D r a g o n detail all the w o r k

one is in effect reviewing or s u m m a r -

and cover in considerable detail a technical review of the w o r k

seventeen-year

Project Report

i000,

period will be published

and this report will cover in

referred to in this paper and very m u c h

more

besides. However,

it is possible to list s o m e

of the achievements

of the

Project during its life of seventeen years. I. from,

The

international nature of the Project in no w a y

and in m a n y

out the w o r k Z.

ways

it w a s

enhanced,

detracted

the ability of the Project to carry

asked to do.

The experience

the right m a n a g e m e n t

of the Project s h o w e d

and administrative

that it is possible with

structure to have a viable

and successful Project which can be easily controlled financially and can,

if necessary, 3.

be terminated in an orderly m a n n e r .

T h e need to invite tenders

to ensure that contracts w e r e difficulties.

The

widely distributed did not cause undue

O n balance the Project gained both f r o m

view of cost and delays f r o m 4.

in all the Signatory countries and

the point of

this international competition.

objectives of the Project w e r e

stage and the Project m a n a g e m e n t

was

clearly defined at every

given adequate authority to

carry out its tasks with simple procedures

for obtaining rapid authori-

zation for planning and executing its p r o g r a m . 5.

N o particular difficulty w a s

the international t e a m

at the A t o m i c

experienced

in the integration of

E n e r g y Establishment at Win-frith,

and a considerable esprit de corps quickly sprang up and has been maintained. 6.

Although the actual operation of the D R E

two years later than originally planned,

at p o w e r

was

this delay is c o m p a r a b l e

some to

that often occurring in national projects and probably arose for the

317

Achievements of the Dragon Project same

reason,

namely

over o p t i m i s m

in the very early stages of the

Project. 7.

The actual operation of the D R E

very successful,

apart f r o m

the serious loss of operating time caused

by failures in the heat exchangers, operation.

T h e s e failures w e r e

gained w a s

not relevant to p o w e r

fit w a s

the experience

and r e p l a c e m e n t 8.

The

during the first four years of

just a nuisance as the experience reactors and the only positive bene-

and confidence gained in reactor maintenance

of components.

results of the fuel and materials p r o g r a m

pressive but difficult to s u m m a r i z e , confirmed

that there s e e m

area for p o w e r 9.

The

temperature

very im-

except £o say that the results in either

reactors. work

10 years ago which reactors.

that these ideas are Finally,

were

to be no insuperable p r o b l e m s

reactor a s s e s s m e n t

studies s o m e

ment

over the 10-year period w a s

set out the m a i n features of high

Subsequent w o r k

by industry has confirmed

still relevant today.

and in s o m e

of the D r a g o n

by the Project produced design

ways

Project,

perhaps

was

the m o s t

important achieve-

to s h o w that it w a s

possible to have

international collaboration and sharing of costs in an area of technology which

some

of the Signatories could not afford to do on their own.

The fact that the Project w a s ture p o w e r

terminated without a n e w high t e m p e r a -

reactor project being started in any of the Signatory

countries w a s

disappointing but due m o r e

to other factors than to any

failure of the Project in carrying out its p r o g r a m It s e e m s

fair to say that the a n s w e r

at the beginning of this paper Project w a s

a success f r o m

tories to the a g r e e m e n t

of work.

to the two questions posed

can be given as 'yes'.

The D r a g o n

the technical point of view and the Signa-

did get value for their m o n e y . APPENDIX

I

A n n e x to Revised Project A g r e e m e n t (The Signatories to this A g r e e m e n t France,

Germany,

w e r e Austria, Belgium, D e n m a r k ,

Italy, L u x e m b o u r g ,

Switzerland and the United K i n g d o m )

Netherlands,

Norway,

Sweden,

C. A. Rennie

318

Technical outline of Joint P r o g r a m m e I.

The original objectives of the joint prograrnrne w e r e twofold:

the

carrying out of a progranu-ne of research and development w o r k in the field of high temperature gas cooled reactors, and the design, construction and operation of a reactor experiment to translate the results of this research and development w o r k into practical experience of this type of reactor.

These objectives have governed the w o r k which w a s carriedout

in the period Ist April 1959 to 31st M a r c h 1962. 2.

A n additional objective of the prograrnzne f r o m ist April 196Z,

is to provide the Signatories with information leading to the design of an economic,

land-based, gas cooled, carbon moderated,

high temperature

power reactor. The a i m will be to acquire sufficient knowledge and experience over the period ending 31st M a r c h 1967, to f o r m the basis for the design and construction of a large power station. Preliminary reference designs will be prepared as early as possible. The potentialities of power reactor systems using either fission product emitting fuels or fission product retaining fuels will be considered. 3.

The prograrnrne f r o m ist April 1962, comprises the following

broad area:a. Completion of design and construction work, followed by commissioning and operation of the reactor experiment. b. R e s e a r c h and development w o r k concerned both with the additional objective, and including m o r e basic w o r k needed to guide longer-term developments. c. W o r k on the development,

fabrication and irradiation of

fuel elements and the materials used in them, including post- irradiation examination. d. A s s e s s m e n t work, reference designs, and design studies for large power reactor systems. 4. The reactor experiment will be brought into operation as soon as possible, information on day-to-day running will be compiled and the behavior of components will be analyzed.

The experimental p r o g r a m m e

operations will be planned so as to obtain the m a x i m u m

for

amount of informa-

tion which will be applicable to large power reactor systems.

Types of

319

Achievements of the Dragon Project fuel elements which e m e r g e f r o m the early assessment studies and f r o m fuel development w o r k will be tested in the reactor, the m o s t promising types being tested in conditions as close as possible to those which will obtain in a large power reactor. 5. The research and development p r o g r a m m e

will include:-

a. Reactor physics and theoretical studies, including experiments utilizing the reactor experiment,

and the interpretation of

these results. b. Completion of the present w o r k in the field of heat transfer, including the seven-element experiment. c. Continuation of w o r k on development of components,

and

studies in the bearing shaft seal and gas bearing fields. d. Continuing studies on m a s s transfer and coolant processing. e. Studies of compatibility problems affecting high temperature reactors, and investigations of techniques such as high temperature m e a s u r e m e n t

applicable to these reactors.

f. R e s e a r c h of a m o r e fundamental nature necessary for longer t e r m development will also be undertaken,

largely through

external contracts with national research centres and other institutes. This p r o g r a m m e

will include studies on the

behavior of fission products in carbon, graphite and carbon bodies, the characteristics of possible fuel element materials and fuel bodies, and the factors determining the reactivity of materials with impurities which m a y be found in the helium coolant. 6.

]Emphasis will be given in the research and development

programme

to the development of the graphite and the fuel compacts

needed for fuel elements.

Both fission product retaining fuels andfission

product emitting fuels will be investigated.

Irradiation experiments will

be carried out both in the reactor experiment and elsewhere together with the necessary post-irradiation examination.

Estimates will be m a d e of

the cost of fuel element fabrication, reprocessing and refabrication. 7.

The assessment work, which is an additional objective of the

Project, will include:-

C. A. Rennie

320

a. T h e o r e t i c a l s t u d i e s , i n c l u d i n g r e a c t o r p h y s i c s , h e a t t r a n s f e r f l u i d flow. b. E n g i n e e r i n g s u r v e y s a n d r e f e r e n c e d e s i g n s t u d i e s . c. T h e p l a n n i n g a n d i n t e r p r e t a t i o n of e x p e r i m e n t a l w o r k a n d t e s t s r e l a t i n g to (a) a n d (b) u s i n g the f a c i l i t i e s a v a i l a b l e to the P r o j e c t ,

i n c l u d i n g the r e a c t o r e x p e r i m e n t .

d. D e v e l o p m e n t of p r e l i m i n a r y

r e f e r e n c e d e s i g n s as e x p e r i e n c e

is a c c u m u l a t e d b o t h f r o m the r e s e a r c h programme

and development

a n d f r o m the o p e r a t i o n of the r e a c t o r

experiment.

e. E c o n o m i c s u r v e y s b a s e d u p o n the f o r e g o i n g s t u d i e s a n d u p o n t h e g e n e r a l e x p e r i e n c e g a i n e d b y the P r o j e c t in the h i g h temperature

field.

8. I n a d d i t i o n to the w o r k c a r r i e d out a t W i n f r i t h a n d u n d e r c o n t r a c t w i t h o t h e r o r g a n i z a t i o n s in the S i g n a t o r i e s ' c o u n t r i e s , tion arrangements

suitable coopera-

m a y be m a d e w i t h o t h e r o r g a n i z a t i o n s w o r k i n g in the

same high temperature

gas cooled reactor field.

In t h i s w a y , the b e n e f i t

of the e x p e r i e n c e of o t h e r s in t h i s f i e l d c a n be b r o u g h t to b e a r on the w o r k of the P r o j e c t .