Isotope Effects in Chemical Processes

neutron cross section of 4,000 barns, has found wide use in nuclear par- ... chemical tracer, while the less abundant isotope 1 7 0 is the only oxygen...
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Isotope Separation Practice

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JACOB

BIGELEISEN

Chemistry Department, Brookhaven National Laboratory, U p t o n , L o n g Island, N . Y . 11973

Downloaded by 60.199.249.3 on January 17, 2016 | http://pubs.acs.org Publication Date: June 1, 1969 | doi: 10.1021/ba-1969-0089.ch001

A

survey

is presented

distinction

is made

scale isotope of laboratory rator,

thermal

are discussed. operated cussed

of isotope

between

separation

diffusion, Large

distillation,

scale

by their

Thermal by

in distillation

dual

temperature

sepaexchange

must be designed These

implications

to the

processes.

reflux can be achieved the

Examples

principles.

and exchange

are

and dis-

produc-

The cost of reflux

processes

in chemical and

A

laboratory

and chemical

processes

tion of heavy water by various

tems

for

by the electromagnetic

with cascade

and illustrated

operations

processes.

suitable

and large scale processes.

scale separation

in accord

separation

processes

is

stressed.

exchange

exchange

sys-

distillation

processes.

T n t e r e s t i n the s e p a r a t i o n of isotopes started as a scientific c u r i o s i t y . T h e A

q u e s t i o n arose as to w h e t h e r it w a s i n d e e d at a l l feasible or possible to

separate isotopes. (24),

A f t e r this q u e s t i o n was a n s w e r e d i n t h e affirmative

i t b e c a m e of interest to separate isotopes o n a l a b o r a t o r y scale f o r

use i n scientific research. separated isotopes.

A f e w examples s h o w the range of u t i l i t y of

D e u t e r i u m has a t t a i n e d w i d e s p r e a d use as a b i o -

c h e m i c a l a n d c h e m i c a l tracer. I t is n o w a b u n d a n t l y a v a i l a b l e a n d is u s e d as freely as a n y c h e a p c h e m i c a l reagent.

3

H e has o p e n e d u p a n e n t i r e l y

n e w field of research i n l o w t e m p e r a t u r e p h y s i c s a n d has i m p o r t a n t a p p l i cations i n the p r o d u c t i o n of temperatures b e l o w 1°K.

l 0

B , with a thermal

n e u t r o n cross section of 4,000 b a r n s , has f o u n d w i d e use i n n u c l e a r p a r ticle detectors—neutron

p r o p o r t i o n a l counters.

1

3

C s t i l l finds use as a

tracer, b u t i n recent years its most f r e q u e n t use has b e e n i n electron s p i n a n d n u c l e a r m a g n e t i c resonance

spectroscopy.

p o s i t i o n as the o n l y usable tracer for n i t r o g e n . 1

l r ,

l

s

N occupies a u n i q u e

O finds a p p l i c a t i o n as a

Present address: Univ. of Rochester, Rochester, N . Y. 14627.

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In Isotope Effects in Chemical Processes; Spindel, William; Advances in Chemistry; American Chemical Society: Washington, DC, 1969.

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ISOTOPE E F F E C T S IN C H E M I C A L PROCESSES

c h e m i c a l tracer, w h i l e the less a b u n d a n t isotope istotope w i t h a n u c l e a r m a g n e t i c m o m e n t .

1 7

1 7

0 is the o n l y o x y g e n

0 is scarce a n d m u c h sought

after for n u c l e a r m a g n e t i c resonance studies of o x y g e n

compounds.

S e p a r a t e d isotopes h a v e p l a y e d a n i m p o r t a n t role i n the p r o d u c t i o n of n u c l e a r p o w e r a n d i n the d e v e l o p m e n t of n u c l e a r energy.

The impor-

tance of separated isotopes i n this field c a n be seen at once b y c o n s i d e r i n g the t h e r m a l n e u t r o n cross sections of those isotopes w h i c h h a v e b e c o m e i m p o r t a n t i n the n u c l e a r i n d u s t r y . A f e w of these are g i v e n i n T a b l e I. T h e v e r y s m a l l n e u t r o n a b s o r p t i o n cross section of d e u t e r i u m , c o m p a r e d

Downloaded by 60.199.249.3 on January 17, 2016 | http://pubs.acs.org Publication Date: June 1, 1969 | doi: 10.1021/ba-1969-0089.ch001

with p r o t i u m , together w i t h its excellent m o d e r a t i n g p o w e r , has h e a v y w a t e r a v e r y i m p o r t a n t reactor moderator. Table I.

1 ( )

made

B has f o u n d w i d e -

Thermal Neutron Cross Sections of Some Isotopes Useful for Nuclear Energy Production

Isotope m m

'Natural Abundance (%)

235TJ

99.99 0.015 19 81 99.6 .37 0.7

238TJ

99.3

IOB n

B

14

N

15

N

o- (barns) 0.33 0.0005 4000. 2 3

30 MASS SPECTROMETE BACKGROUND

Downloaded by 60.199.249.3 on January 17, 2016 | http://pubs.acs.org Publication Date: June 1, 1969 | doi: 10.1021/ba-1969-0089.ch001

29. -»28 20

30

40

510

1 6|0

1

7|0

30 TANK NITROGEN -» 2 9 1 • 1 = » 2 8 x shunt 5

If

1

|

1

1

1 1

Figure 7. Mass spectrometric comparison of N obtained from HN0 enriched by Taylor and Spindel with tank N . "Proceedings of the International Symposium on Isotope Separation" {Kef. 17) North Holland Publishing Co. 2

3

2

COLD

TOWER A

WASTE

SOLUTION

PRODUCT TO N E X T

TRANSFER STAGE

WITHDRAWAL

JHEAT EXCHANGER

2 HEAT