Tiêu chuẩn iso 11537 1998

A Reference number ISO 1 1 537 1 998(E) INTERNATIONAL STANDARD ISO 1 1 537 First edition 1 998 07 1 5 Non destructive testing — Thermal neutron radiographic testing — General principles and basic rule[.]

Fir st e itio

19 8-0 -15

Es ais non destru tifs — Es ai de neutr onogra hie ther miq e — Prin ip s

générau et règles de b se

© ISO 19 8

Al r i hts r es r ve Unle s oth r w is s e ifie ,n p r t of this p blc tio ma b r epr od c d or uti z d in a y for m or b a y me n ,ele tr onic

or me h nic l in lu in p oto o yin a d micr ofim,w ith ut p r mis io in wr itin fr om th p bls e

Inter natio al Org niz tio for Sta d r diz tio

Ca e p stale 5 • C -121 Ge è e 2 • Switz r l n

Intern t is @is c

1 Sc p 1

2 Backgr ou d mate al

1 3 Ne tr on r adio r ap y meth d 1

4 F ci tie 3

5 Ne tr on s ur ce 3

6 Ne tr on c l mator s 4

7 Imagin meth d an c n er sio s r ee s

6 8 Fim 7

9 Cas ete

7 10 Ap lcatio s for th r mal n utr on r adio r ap y 8

1 Impr ov d c ntr ast 9

12 Imag q alty in icator s

9 13 Ne tr on activatio 9

A (informativ ) Glos ary of terms related to neutro radio rap y 10

B

(infor mativ )

s ctio s for the naturaly oc ur in elements 12

C (infor mativ ) Biblo rap y 15

For ew or d

ISO (t he Int erna t io a l Orga niza t io f or St a nda rdiza t io ) is a w orl wid f ed ra t io of na t io a l st a nda rds b die (ISO memb r

b die ) T he w ork of prepa rin Int erna t io a l St a nda rds is n rma lly ca rrie o t t hrou h ISO T ec nica l Commit t ee Ea ch

memb r b d int erest ed in a s bje t f or whic a T ec nica l Commit t ee ha s b e e t a bls e ha s t he ri ht t o b repren e t ed

o t ha t c mmit t ee Int erna t io a l orga niza t io s, g v ernme t a l a nd n n-g v ernme t a l, in la is n w it h ISO, a ls t a ke pa rt in t he

w ork ISO c la bora t es clo ely w it h t he Int erna t io a l Ele t rot ec nica l Commis io (IEC) o a ll ma t t ers of ele t rot ec nica l

st a nda rdiza t io

Dra f t Int erna t io a l St a nda rds a do t ed b t he T ec nica l Commit t ee a re c ircula t ed t o t he memb r b die f or v ot in

Pu lca t io a s a n Int erna t io a l St a nda rd req ires a pprov a l b a t lea st 7 % of t he memb r b die ca st in a v ot e

Int erna t io a l St a nda rd ISO 1 5 7 w a s prepa red b T ec nica l Commit t ee ISO/T C 13 , No -d st ruct iv e t est in ,

Su c mmit t ee SC 5, Ra dia t io met ho s

A nn x s A , B a nd C of t his Int erna t io a l St a nda rd a re f or inf orma t io o ly

Intr oduction

T his Int erna t io a l St a nda rd is int en e t o prov id g id ln s f or t he prod ct io of n ut ron ra dio ra ph t ha t p s e s

c on ist ent q a lit y c ha ra c t eri t ic , a nd a s a n aid t o t he u er in d t erminin t he s it a bi t y of h rma l n ut ron radio ra phic

in p ct io f or a pa rt ic la r ap lca t io

Re omme d d pra ct ic s a re st a t ed wit ho t d t a ile dis u sio of t he t ec nica l ba ck rou d f or t he pref eren e

Non-destructive testing — T her mal neutron radiographic

Ra iation pr otection - Health w ar ning

Ex posur e of an par t of the h man b d to neutr ons, X - or gamma r ays c n be inju o s to he lth It is ther ef or e

e s ntial that whenev er neutr on r adio r ap ic eq ipment or r adioa tiv e so r ce ar e us d, adeq ate pr ec utio s

sh uld be taken to pr ote t the r adio r ap er an an other per so in the v icinity

Limits f or the s f e lev els of neutr on, X - or gamma r adiatio a wel a the r ecommen ed pr actic f or r adiatio

pr ote tio ar e th s v ald in dif f er ent co ntr ie If ther e ar e n of f icial r eg latio s or r ecommen atio s in a co ntr y,

the late t r ecommen atio s of the Inter natio al Commis io o Radiolo ic l Pr ote tio sh uld be ap led

T his Int erna t io a l St a nda rd s e if ie t he ba sic pra ct ic s a nd c n it io s t ha t a re t o b o s rv ed f or t herma l n ut ron

ra dio ra ph of ma t eria ls a nd c mp n nt s for f la w d t ect io It is c n erne w it h t ec niq e u in p ot os n it iv e f ilm a s a

rec rdin me ium How ev er, it rec g ize t ha t a lt erna t iv e met ho s of ima gin ma y b u e more w id ly in t he f ut ure T he

s o e in lu e n ut ron prod c tio a nd c ol ma tio meth d , c onv erter s re n s lec t io , radio ra phic f ilm, n utron

ra dio ra phic in p ct io t ec niq e a nd t he t yp of ma t eria l t o b in p ct ed T his pra ct ic is g n ra lly a pplca ble t o s e if ic

ma t erial c mbina tio s, proc s e a nd te h iq e

A glo sa ry of t erms rela t in t o n ut ron ra dio ra ph is pres nt ed in a nn x A A t t en a t io of n ut ron in ma t t er is pres nt ed in

a nn x B

Ne t ron ra dio ra ph a nd X -ra dio ra ph s a re s me simia rit ie b t prod c dif f erent res lt s w he a pple t o t he sa me

o je t Ne t ron repla ce X -ra ys a s t he p n t ra t in b a m of ra dia t io w ho e int en it y is mo ula t ed b a n o je t , res lt in in

a f ilm ima ge of t he f ea t ures of t he o jec t Sin e t he a bs rpt io c a ra ct eri t ic of ma t eria ls f or X -ra ys a nd n ut ron a re v ery

dif f eren t he t w o t ec niq e g n ra lly t en t o c ompleme t o e a not he Ne t ron a nd X -ra y a t t en a t io c ef f ic ie t s,

pres nt ed in f ig re 1 a s a f un t io of a t omic n mb r,a re a mea sure of t his dif f erenc e

Fig re 1 — A compariso of ma s aten atio coeficients for thermal neutro s an X-rays

4 Fa i tie

A n utron ra dio rap y fa c ilt y t ypic a lly in lu e a s urc e of t herma l n utro s, a n ut ron b a m c ol ma t or, a c onv ersio

s ree , f ilm an a n e p s re c a ss t t A s h ma tic diagra m of a repres nt at iv e n utro ra dio ra ph f a ci t y is s ow n in

— s a le t ub s a nd a cc lera t ors of pa rt icle ; a nd

— n clea r rea c t ors

Ea ch of t he e s urce prod c es hig -e ergy n ut ron t ha t req ire mo era t io (slow in d w n) t o t herma l e ergie T his ca n

b a c c ompls e b s rrou din t he n ut ron s urc e w it h b ry llum, gra phit e, w a t er, oi, pla st ic or s me ot her mo era t or

ma t erial

5.1 Isoto ic sour ce

Is t opic s urce ha v e t he a dv a nt a ge of b in sma ll a nd p rt a ble b t b ca us of t heir rela t iv ely low n ut ron yield req ire lo g

e p s re t ime t o a chiev e a giv en ra dio ra phic q a lit y Ma ny is t opic s urc es ha v e b e u e f or n ut ron ra dio ra ph a nd

t he mo t c mmo of t he e a re s ow n in t a ble 1 Ca lif ornium (

2 5 2

Cf ) is o e of t he mo t p p la r is t opic s urce u e f or

t herma l n ut ron ra dio ra ph b ca us of it s low n ut ron e ergy a nd sma ll p y ica l size w hic p rmit ef f icie t mo era t io a nd

hig t ot a l n ut ron yield

Table 1 — Radioa tive so rc s for neutro radio rap y

n ut ron yield, ea siy mo era t ed

2 5 2

ea sy mo era t io of n ut ron e ergie ma ke t his

a n a t t ra ct iv e p rt a ble s urce

5.2 Ac eler ator so r ce

Sea le t ub s a nd low -v olt ag a c celerat ors ut ilzin t he

3

H(d,n)He rea c t io , hig -e ergy X -ra y ma c hin s ut ilzin t he (x, n)

rea c t io , a nd Va n d Gra a ff a c c elera t ors a nd c y c lot ron u in c ha rge -pa rt ic le n ut ron rea c t io s ha v e b e u e a s

n ut ron s urce f or t herma l n ut ron ra dio ra ph T he t a rget s of t he e a cc lera t ors a re s rrou d d b ma t eria ls t ha t wil

mo era t e t he n ut ron t o t herma l e ergie T he t herma l n ut ron f lu nc e ra t e of a c c elerat or s urc es b f ore c ol ma t io c a n

Nu lea r rea ct ors a re a pref erred n ut ron s urce f or t herma l n ut ron ra dio ra ph b ca us of t heir hig n ut ron yield T he

hig n ut ron int en it y mak s it p s ible t o prov id a t ig t ly c ol ma te b am a nd hig -res lut io radio rap s c a n b

prod c d wit h a rela t iv ely s ort e p s re t ime Some of t he disa dv a nt a ge of u in n clea r rea ct ors f or n ut ron ra dio ra ph

a re t he hig c ost of in t a lla t io a nd o erat io , la c k of p rt a bi t y , a nd v uln rabi t y t o st ric t a nd c omple re ula t io

Ne t ron a re emit t ed in a ll direct io s f rom a s urce a nd a re f urt her s a t t ered ra nd mly b t he mo era t or A mea ns of

c ol ma t in t herma l n ut ron into a b a m is prov id d t o prod c e a hig q a lit y n ut ron ra dio ra ph A w el c ol ma t ed t herma l

n ut ron b a m c ou le w it h th a bi t y t o pla c e t he o jec t b in in p c t ed c lo e t o t he ima gin sy st em w il prov id t he b st

ra dio ra phic res lut io

Ne t ron c ol mat ors ut ilze ma t eria ls hav in a hig cros s c tio f or t he ab orptio of t herma l n ut ron s c h as b ron or

c a dmium T he e ma t eria ls s o ld b a pple to ma ximize t he n mb r of n ut ron reac hin t he ima gin sy st em direc t ly form

t he s urce a nd minimize t he n mb r of n ut ron s a t t ered ba ck int o t he b a m Of t en, a c mbina t io of ma t eria ls is u e t o

a c hiev e t he b st n ut ron c ol ma t io an t o ma sk o t u w a nt ed s c on a ry ra dia t io f rom t he b a m It is s met ime

n c es a ry t o u e ma t eria ls, s c h a s lt hium c a rbo a te, t ha t prod c e n ut ron c a pt ure d c a y prod c t s t ha t w il n t res lt in

f og in of t he ima gin f ilm Ma t eria ls t ha t ha v e a hig n ut ron s a t t eri g cros s ct io , s c a s h drog n o s ma t eria ls, or

ma t erials t ha t emit radia t io d ri g n ut ron c apt ure tha t ma y f og t he imagin f ilm s o ld n t b u e in is rimina t ely n a r

t he ima gin sy st em Exa mple of t his la t t er c las of ma t eria ls in lu e in ium, d s rosium an c a dmium Fim f og in ma y

a ls res lt f rom t he 4 0 k V ga mma ra y prod c d b n ut ron c a pt ure in b ron

T he s a t ia l res lut io of a n ut ron ra dio rap y sy st em is inf lu nc ed b t he le gt h (L) of t he c ol ma t or, t he dia met er, or

lo g st dime sio of t he inlet a pert ure (D) a nd a pert ure s a pe T he ra t io of L /D is u e g n ra lly t o d s rib t he ef f ect iv e

c ol ma t io of t he sy st em For e a mple, if h L /D rat io of a sy st em is s v era l h n red, o e c a n e p c t t he sy stem to b

c apa ble of prod c in ra dio ra ph of hig er res lut io t ha n a sy st em hav in a n L /D of 10 A lt ho g L /D is a n imp rt a nt

mea sure of sy st em ca pabi ty , oth r fa c t ors, s c h as o jec t size a nd sc a tt eri g c ha ra c t eri t ic , o v io sly af f ec t t he ult ima t e

ra dio ra phic q a lit y t ha t ca n b a chiev ed In a ddit io t o t he L /D v a lu , t he L v a lu it self is imp rt a nt Be a us t he L v a lu is

f init e, a s pa ra t io , l, b t w ee t he o je t a nd ima gin d v ic res lt s in a n u s a rpn s in t he imag d s ri e b

ma gnif ica t io f a ct or L /L-l)

A lt ho g t here ha v e b e ma ny dif f ere t c ol ma t or d sig s t ha t ha v e b e u e e p rime t a lly , f ew of t he e ha v e s rv iv ed

f or u e in c ommercia l n ut ron ra dio ra ph f a c ilt ie T he n e t o ra dio ra ph rela t iv ely la rge o jec t s ha s le t o t he

w id s rea d u e of t he div erge t c ol ma t or d sig s ow n in f ig re 2 T he div erge t c ol ma t or c on ist s of a t a pered c ha nn l

ma de of n ut ron-a bs rbin ma t eria l a nd o gina t in a t it s sma ll e d (inlet a pert ure) a t t he s urce of hig e t n ut ron f lu in th

mo era t or

A not her c ol ma t or t y pe w ort hy of n t e is t he pin ole c ol ma t or s ow n in f ig re 3 Hig res lut io n ut ron ra dio ra ph c a n b

pro uc ed w it h sy st ems ut ilzin pin ole c ol ma t ors T he pin ole is fa bric at ed from ma t eria l s c h as c a dmium, gad lnium or

b ron whic ha v e a v ery hig a t t en a t io f or t herma l n ut ron

K ey

F ig r e 3 — Ty pic l neutr on r adio r ap y f aci ty with pin ole col mator

6.3 Be m f ilter s

It is of t en d sirable t o minimize t he ga mma radia t io t ha t c nt a minat es t he n ut ron b a m T his ga mma ra dia t io c me f rom

t he n ut ron s urc e a nd ca n ca us f ilm f og in a nd red c d ima ge c nt ra st Fit ers ma de of lea d or bismut h ma y b in t a lle

n ar t he c ol mat or inlet t o red c e t his u w a nt ed ga mma ra diat io in t he b am W he u in a bismut h f ilt er it is adv isa ble t o

e ca se t he f ilt er in a s a le a luminium ca n t o prev ent t he s rea d of a lp a c ont a mina t io d e t o t he

Ba ck-s a t t ered ra dia t io f rom t he w a lls or e uipme t ca n b red c d b ma skin t he n ut ron b a m t o t he sma lle t pra ct ica l

e p s re a rea a nd b t he ca ref ul u e of n ut ron a bs rber a nd ga mma s ieldin ma t eria ls Ba ck-s a t t ered ra dia t io ca n b

d t ect ed b pla c in a ma rker ma de of n ut ron a bs rbin ma t eria l s c a s ga dolnium a nd a ma rker ma de of ga mma

s ieldin ma t eria l s c a s lea d, o t he ba ck of t he f ilm ca ss t t e d ri g n ut ron e p s re If ba c k-sc a t t ered ra dia t io is a

problem, o e or b t h of t he ma rkers w il a pp a r o t he f ilm If bac ksc a t t eri g is pres n o e s o ld minimize mat eria ls t ha t

s a t t er or emit ra dia t io in t he e p s re a rea (s e 7.1) Ga dolnium or s me ot her s it a ble n ut ron a bs rber ca n b pla ce

b hin t he d t ect or t o ef f ect iv ely minimize t he inf lu n e of ba ck-s a t t ered n ut ron o t he ima ge

Ne t ron , a s t heir na me imple , ca rry n elec t rica l c a rge a nd a re t heref ore n n-io izin a nd prod c lt t le ef f ect o

ra dio ra phic f ilm T o prod c a n ut ron ra dio ra phic ima ge o f ilm it is n c s a ry t o emplo a c nv ersio s ree t ha t , u o

n ut ron c a pture, w il emit io izin ra dia tio or lg t t ha t c an e p s t he f ilm a s s ow n in f ig re 2 It is imp rt a nt tha t t he

c nv ersio s ree b in int ima t e c nt a ct w it h t he f ilm in order t o prod c t he b st q a lit y ra dio ra ph Sin e c nv ersio

s ree s a re e p n iv e a nd repres nt a sizea ble inv est me t , ca re s o ld b t a ke t o st ore t hem in a n e v ironme t t ha t w il

prot ec t t hem f rom p y ic a l dama ge an c orrosio St ori g dy sprosium sc ree s in a v a c uum w he n t in u e w il minimize

a t mo p e c c rrosio a nd s b t a ntia lly le gt he t heir u ef ul lf e

In t he direct e p s re met ho , t he f ilm a nd t he c nv ersio s re n a re pla ce in a lg t -t ig t ca ss t t e a nd e p s d t o t he

n ut ron b a m T he f ilm is e p s d b t he emis io of ele t ron f rom t he c nv ersio s ree u o n ut ron ca pt ure

Ga dolnium s ree s a re pref erred f or mo t a pplca t io s a nd a re a v a ila ble eit her a s a f ree st a ndin f oi or a s a

sa pp ire-c a t ed, v a po r-d p sit ed ga dolnium c a t in o a n a luminium s b trat e Gad lnium emit s a 7 k V ele t ron a s

t he res lt of n ut ron int era ct io

A s c on t yp of c onv ersio sc ree is t he lg t -emit t in f lu resc ent sc ree s c h a s ga dolnium o y sulf id (Gd

2O

2S:Gd

6or

lt hium f lu ri e/zin s lf id (L iF/ZnS) It is rec me d d t ha t t he s e t ra l res o s of t he sc ree emis io a nd f ilm b

ma t ch d f or o t imum res lt s

T he direct f ilm met ho u in ga dolnium met a l s ree s prov id s hig res lut io a nd e c le t c nt ra st a nd ha s b c me t he

ref eren e a ga in t whic ot her n ut ron ra dio ra ph t ec niq e a re c mpa red T his met ho c a nn t b u e if t he n ut ron

b a m c nt a in s b t a nt ia l ga mma ra diat io or if t he o je t is hig ly ra dioa ct iv e

Ot her direct e p s re met ho s a re u e b t a re b y n t he s o e of t his Int erna t io a l St a nda rd

T he in irect e p s re met ho is u e a lmo t e clu iv ely f or t he ra dio ra phic in p ct io of ra dioa ct iv e o je t s T his met ho

is in e sit iv e t o ga mma ra dia t io a nd ut ilze c onv ersio sc ree s, w it ho t f ilm, tha t b c ome t emp ra rily radioac t iv e w he

e p s d t o t he n utron b a m T he f ilm ima ge is ma de b plac in t he a ct iv a te foi in a ca ss t t e or ot her lg t -t ig t d v ic

t og t her w it h f ilm a f t er t he n ut ron e p s re is t ermina t ed Bet a pa rt icle emit t ed b t he d ca y proc s of t he a ct iv a t ed f ois

s n it i e t he f ilm w hic ca n t he b proc es e Dy prosium, in ium, rho ium a nd g ld a re a ll ca ndida t es f or in irect

c nv ersio s ree s Dy prosium a nd in ium a re t he b st c oic e f or mo t a pplca t io s w it h d s rosium ha v in t he grea t er

s e d Some ma t eria ls s c a s g ld a re le s d sira ble f or prod ct io n ut ron ra dio ra ph b ca us of t heir rela t iv ely lo g

ha lf -lfe (2,7 da y s) w hic h res lt s in u a c c ept a bi t y lo g e p s re a nd d c ay t ime

In irect c nv ersio s ree s s o ld b e p s d f or a p ri d of t ime n t t o e c e t hree ha lf -lv es of t he ma t eria l b in u e

Furt her irra dia t io prov id s n b n f it sin e t he a ct iv a t io ra t e a nd d ca y ra t e a re n a rly t he sa me a t t ha t p in T hree or f our

ha lflv es is a ls s f ficie t t ime t o t ra nsf er t he ima ge f rom t he a ct iv a t ed f oi t o t he f ilm a lth u h t he a re s metime lef t in

c nt a ct ov ernig t a s a ma t t er of c nv enie c X -ra y ima ge int en if ica t io s ree s ma y b u e t o in rea se t he s e d of t he

t ra nsf er proc s if d sired T he in irect c nv ersio s ree s ca n sa f ely b reu e w it ho t f ea r of d u le e p s re a f t er

d ca yin f or f our ha lf -lv es

Ot her ima gin sy stems c ould b u eful f or s me a pplc a t io s How ev er t he e a re n t a ddres e in d t a il in t his Int erna t io a l

St a nda rd w hic is c n erne w it h f ilm ra dio ra ph

Table 2 — Some Repre entative T ermal Neutro Dete tor Materials

Ga dolnium

15 5

Gd(n,γ)15

Gd

15 7

Gd(n,γ)15

1) Cros -sec t io s are f or t he rea ct io a nd isot op sh wn f or th rma l n ut rons (so rc e BNL-3 5, 3rd e itio , v olume I 19 3)

2) T hese d t ec tors are oft en use for t r a c k-et c h n utron radio ra phy

Nea rly a ny p ot o-s n it iv e f ilm ma y b u e f or n ut ron ra dio ra ph b t it is rec mme d d t ha t in u t ria l ra dio ra phic f ilm

b u e f or mo t a pplca t io s, eit her direct or in irec f or b st res lt s Sin le-sid d f ilms prod c t he b st res lut io In

a pplc at io s req iri g t he a ddit io a l s e d of a f ilm ha v in emulsio o b t h sid s s me res lut io ma y b sa crif ic d T he

rec mme da t io s a nd pra ct ic s t ha t a pply t o t he ma nua l or a ut oma t ic proc es in of ra dio ra phic f ilms ca n a ls b a pple

g n ra lly t o t he proc s in of ra dio ra phic f ilms u e f or n ut ron ra dio ra ph

Ca ss t t es a re req ired f or e p s re of t he f ilm a nd c nv ersio s ree s in t he direct met ho , f or e p s re of t he c nv ersio

s ree s in t he in irect met ho , a nd f or t he d ca y t ra nsf er proc s in t he in irect met ho V a cu m ca ss t t es a re hig ly

rec mme d d f or al a pplca t io s inv olv in f ilm, a s t he e e s re t hat t he f ilm a nd c nv ersio s ree s a re in int ima t e c nt a ct

a nd t hu prev ent f ilm f la w s d e t o p or c nt a ct

9.2 Mater ial of constr uction

Ma t eria ls u e in t he f a bri a t io of ca ss t t es t o b u e in t he n ut ron b a m s o ld b s le t ed w it h ca re t o a v oid ima ge

d gra da t io ca us d b n ut ron s a t t eri g or s c n a ry ra dia t io f rom t he ca ss t t e T he ca ss t t es s o ld b f a bri a t ed f rom