Ultrasonic Immersion System for Space Shuttle Components

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  New equipment

raphite brick tests

Under a contract from Nuclear

Electric plc, supported by Scottish

Nuclear, graphite moderator

bricks and slices of bricks, typical

of those which are interlocked in

layers to construct the cores of

Advanced Gas-cooled Reactor

(AGR ) power stations, are being

subjected to an extensive series of

tests to provide more

comprehensive information on the

strength of the bricks. The results

of these tests will be used in

conjunction with sophisticated

finite element analysis

calculations to increase accuracy

in formulating the safety case for

core integrity.

The tests are being carried out at

the Risley Laboratory of AEA

Reactor Services and will examine

the effects of stresses within

bricks caused by external loads

and a sequence of stresses arising

from the complex shrinkage

behaviour of the graphite over the

operating lifetime of the reactor.

Radiation dose rates across the

cores are not uniform, and this

causes differential shrinkage and

distortion of the graphite

components. As a consequence

the bricks start by shrinking more

on the inside adjacent to the fuel

than on the outside. Later this is

reversed as the graphite on the

inside characteristically stops

shrinking and begins to expand.

Towards the end of the reactor

lifetime this process leads to a

build-up of internal stress at the

roots of the keyways by which

the bricks are interlocked. These

keyway roots are the most

stressed parts of the graphite core

bricks.

The core design mainly

compensates for the graphite

dimensional changes and the

necessary movements due to

temperature changes during

operation by having the individual

bricks loosely keyed together in

an arrangement which permits

expansion and contraction of the

whole core without affecting its

stability or integrity.

110

Graphite moderator bricks being measured as part of an assessment of the effects of stresses

Large-scale tests using full-scale

core bricks and brick slices of

thicknesses up to 250 mm will

push and pull the specimens in

order to determine the ability of

bricks to withstand external loads.

In other tests graphite slices are

being subjected to bending forces

designed to mimic the stresses

imposed on the keyways during

the lifetime of the reactor, to test

the resilience of the bricks to this

type of stressing.

As it is not practicable to replace

damaged graphite, AGR station

operation depends on maintaining

satisfactory integrity of the bricks

and their keyways. An extension

to the graphite core lifetime

would have enormous

implications for the economics of

nuclear power generation since

the stations have high capital

costs but low marginal fuel costs.

AEA Technology Ride y

Warrington Cheshire WA3 6A T

UK

Ultrasonic rail

inspection system

RMK’s Zenica rail fabrication

plant in Yugoslavia is the first

purchaser of the Micro Plus

ultrasonic inspection system from

Sonomatic. The plant

manufactures rail for Yugoslav

railways, and is gearing up to

export to other European

countries. To do this, the plant

will have to demonstrate its

quality control procedures and the

consequent quality of its product.

The Micro Plus system will

provide continuous,

full-volumetric inspection for

internal flaws, and will eventually

be able to handle five different rail

profiles, using the non-contact

immersion technique which has

proved successful for the

inspection of round and square

steel billet and bar.

The system was developed from

Sonomatic’s Midas ultrasonic

inspection and data acquisition

system, and is based around a

386 computer.

The Micro Plus is a multi-channel

inspection system with an array of

ultrasonic transducers which

examine the rail as it passes

through a water-injected stuffing

box at line speeds up to

1.5

m s-‘. The water acts as an

ultrasonic couplant, and

consequently the inspection

heads do not touch the surface of

the rail. This means that there is

no wear and the system is very

reliable.

The 32-channel system which

will be installed at Zenica will

N DT E International April 1991

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 N e w e q u i p m e n t

incorpora te an au tomat ic pa in t

sprayer to mark the loca t ion o f

defects, use r-f r iend ly d isp lays and

audib le a larms. For each batch of

ra il inspected , a co lour -g raph ic

hard-copy inspect ion repor t w i l l

be generated as eviden ce of test ing.

Menu screens have been wr i t ten

in Serbo-Croa t fo r th is

appl icat ion, and heaters and

ant i f reeze for the immersion tank

wil l be able to keep the system

opera t iona l in Yugos lav w in te r

tempera tu res dow n to m inus 15 °C.

Sono rna t ic L td 20 R iv ing ton

Cour t H ardw ick Grange

Woo ls ton Wa rr ing ton WA 1 4RT

U K

U l t r a s o n i c i m m e r s i o n

s y s t e m f o r S p a c e

S h u t t l e c o m p o n e n t s

A computer ized u l t rason ic

immers ion system, inc lud ing a

2.1 x 1.2 x 1.2m tank, has been

de l ive red by Phys ica l Acoust ics

Corpora t ion to Marsha l l Space

Center in Hunts vi l le , Alabama. For

te s t in g co mp o s i t e co mp o n e n ts o f

the space shut t le , the Marshal l

System w i l l be ab le to loca te and

size structura l f laws, such as

de lamina t ions, c racks and vo ids.

The U l t raPAC I I w i l l be used to

inspect parts of the space shut t le

in te r tank door and o ther

associated f l ight hardware.

Po s i t io n e d b e tw e e n t h e o xyg e n

and hyd rogen tanks o f the Shu t t le ,

the in te r tank door p rov ides access

to e lect ron ics , a t tach ing shu t t le

struts and fuel l ines, and is where

the tanks feed the three main

eng ines on the Shut t le .

As w e l l as the tank, the un i t

includes mo tor ized X, Y, Z axes

and tu rn tab le , a long w i th

th rough- t ransmiss ion adapte r and

squ i r te r -bubb le r t ransducer

assembly. Pump, f i l ters and

cont ro ls tha t can accommodate

either the squir ter assembly or fu l l

immers ion tank, comple te the

system hardware. Ma ter ia ls w hic h

cannot be immersed in water,

UltraPAC I I u l t rasonic imme rsion test ing system, for test ing Space Shutt le comp one nts

such as g raph i te w i th a foam

back ing , a re tes ted w i th the

squ i r te r assembly ; f la t, m id -s ized

panels can be tested in the

customized tank.

The U l t raPAC I I system so f tware

incorpora tes a 386 SX computer

w i th VGA graph ics . For smoother

scann ing and improved inspect ion

accuracy, a new four -axes motor

contro l ler card has been designed.

System features include A, B,

C-scan , f law de tect ion and

t ransducer characte r iza t ion

so f tware .

Phys ica l Aco ust ics Corpora t ion

P.O. Box 3135 Pr ince ton NJ

08543 - 3135 USA

N o n c o n t a c t

m e a s u r i n g s y s t e m s

Elect ro -op t ica l inspect ion system

specia l ists, C. E. Joha nsso n, have

in t roduced the i r Q-SEE

non- con ta ct m easur ing systems to

rep lace the ex is t ing Vid icom

range. Q-SEE machines use

s imi la r op t ica l systems and

Non-c on tac t o p t ica l gaug ing sys tem w i th comp ute r con t ro l , f rom C. E. Johansson

N DT E In te rna t iona l Apr i l 1 991 111