AKTIEBOLAGET ATOMENERGI

STUDSVIK, NYKÖPING, SWEDEN 1970

AE-397

AKTIEBOLAGET ATOMENERGI

Section for Nuclear Chemistry

PROGRESS REPORT 1969

The results and data presented are generally preliminary and

must not be published elsewhere. Final results will usually be

submitted for publication in regular technical journals or pub-

lished in AE reports. Cited internal reports can often be pro-

vided upon request.

Printed and distributed _n May 1970.

Göran Carleson

LIST OF CONTENTS

Page

1 . SUMMARY 3

2. ISOTOPE EFFECTS IN SALT-WATER SYSTEMS 5

3. RADIATION CHEMISTRY OF AQUEOUS SOLUTIONS 7

4. TRANSIENT ELECTRONS IN PULSE-IRRADIATED

CRYSTALLINE H2O AND D2O ICE 1 3

5. AN ESR AND X-RAY DIFFRACTION STUDY ON SOME

VINYL MONOMER SINGLE CRYSTALS 1 8

6. DCSIMETRY AT HIGH IRRADIATION LEVELS 24

7. WOOD POLYMER COMBINATIONS 3 0

8. CHARGED PARTICLE AND NEUTRON ACTIVATION

ANALYSIS 34

- 3 -

1. SUMMARY

Phase diagrams of some lithium and calcium halides in light

and heavy water have been constructed in the temperature range -85

to +60 C. New hydrates were observed and their range of existence

determined.

Radicals formed after irradiations of highly purified water

and water solutions of simple aromatics with fast electrons and gam-

mas as well as their subsequent decay and kinetics have been studied

by pulse radiolytic technique and analysis of final products- Indications

of a repair mechanism were obtained in the aniline system. The point

of attack on toluene by primary radicals is probably changed after addi-

tion of Fe1 0 ions.

Pulse radiolytic irradiations of heavy ice between -5 and -l90°C

have shown that the absorption spectrum of the solvated electron is

shifted to higher energies with decreasing temperature. Compared to

H9O ice the maximum is displaced to an energy which is 0. 04 eV higher.

After an initial decrease the yield increases below -100 C. Several

kinetic models have been tested to fit the complex experimental decay

carves.

Single crystals of vinyl monomers have been prepared by a

special low temperature technique. After irradiations with gamma-rays

at 77 K radical pairs and other paramagnetic species were identified

by ESR spectroscopy. The crystal structures of methylacrylate and

metylmethacrylate were determined by X-ray diffraction. A mechanism

for the radical pair formation involving intermediate ion-pair species

is suggested.

Inorganic ion exchangers of zirconium phosphate and silica gel

type were shown to be completely stable to degradation up to a dose of

3* 10 Mrads. Sturdy solid dosimeters based on the measurement of

luminiscence or colour difference in higher benzene homologues were

developed and shown to have a precision better than ±15% in the dose

range 1 - 5* 10 Mrads.

Earlier observed anomalies for radiation-cured pine and birch

wood polymer combinations, such as inhomogeneous polymer distri-

bution in lengthy wood Samples and large variations in polymer conver-

sions for almost identical test materials, have been further studied and

- 4 -

the experimental results statistically treated. Some explanations are

proposed.

Methods for the determination of low contents of oxygen and

carbon in naetals such as aluminium and steel by means of charged

particle activation analysis are being developed. The sensitivities of

applicable nuclear reactions have been evaluated at various proton

energies. Low temperature technique has been adapted to neutron ac-

tivation analysis in aqueous and biological materials in order to in-

crease the sensitivity of the determinations.

- 5 -

2. ISOTOPE EFFECTS IN SALT-WATER SYSTEMS

Karl-Erik Holmberg

The determination of phase diagrams of salts in heavy and

light water [1, 2] has continued during part of the period. New salts inves

tigated are Lil, CaCl2 , CaBr2 and Cal -

For LiL 3 aq the solubility (expressed as amount of salt per mole

H-,O or D2O) is nearly the same in H_O and D2O over the whole range

from -70 to +60 C. A higher hydrate, existing at low temperature, has

a lower solubility in D?O-

For the calcium halides the relative solubility in D_O (defined as

the ratio of the amount of salt soluble in one mole of D_O to the amount

soluble in one mole H_O) tends to be >1 at high temperatures and

- 6 -

g Ca Br2per 5.55 mol aq

300

200

100

H2O

D2O

- 6 0

CaBr2 • 6aq

I—I—I 1 1 * 1 — I — I — I — f60 °C

temperature

Fig. 2.1 Phase diagrams for CaBr» with H2O and D2O.

- 7 -

3. RADIATION CHEMISTRY OF AQUEOUS SOLUTIONS

Hilbert Christensen

3. 1. Gamma radiolysis of aqueous solutions of aromatics

3. 1. 1. Toluene

The study of the radiolysis of aqueous toluene solutions in N~O,

Ar or air saturated solutions has been continued and a final report of

the system is now under preparation. The preliminary results are

shown in Table 1. It is seen that the yield of hydrogen even in acid argon

saturated solutions, where G(H) = 0- 55 + 2. 6 = 3. 15, is of the same or-

der as the molecular G value of hydrogen, indicating that hydrogen ab-

straction from the CH_ group does not take place.

The system has been irradiated in the presence of Fe(ni) ions

resulting in a remarkable change in product composition, in argon satu-

rated solutions the main products were bibenzyl with a G value of 1. 0

and benzylalcohol with a G value of 0. 61, indicating a considerably in-

creased attack on the methyl group.

3. 1. 2. Aniline

This study was carried out in co-operation with an IAEA stipen-

diary, L Karaivanov, Sofia, Bulgaria.

Acid or unbuffered aqueous solutions of aniline saturated with

N-O or Ar have been irradiated. Of the potential radiolysis products

examined we have found hydrogen with a G value of 0. 36, azobenzene

and 2-aminophenoxazine-3-on. Small yields of o-semidine, diphenylamine,

2-aminobiphenyl, phenol (G~0 . 01), o-aminophenol and ammonia have

also been detected. G(-aniline) was found to be 3. 3 and 0. 4 in unbuffered

N-O and Ar saturated solutions, respectively. In acid Ar saturated solu-

tions G(-aniline) was 1. 2. These yields indicate an effective recombina-

tion reaction between oxidized and reduced radical forms of aniline in

unbuffered argon saturated solutions. The low yield of hydrogen indicates

that hydrogen abstraction from the NH~ group does not take place.

3. 2. Pulse radiolysis of aqueous solutions

This study was carried out at the Danish Atomic Energy Research

Establishment at Risö in co-operation with S. O. Nielsen and P. Pagsberg.

Table 1. G values from radiolysis of aqueous toluene solutions

Aerated, unbuff.

Aerated acid m

Argon unbuff.

Argon acid

N_0 unbuff.

N20 acid

Argon acid

H

2

3

0

0

0

0

2°2

•2/neg

.1/0.16

.548

.76

.33

Acid

1.1

1.8

0

0

0

0

-

H

0

0

2

.48

.38

o

0.35

0.22

0.22

0.08

0.48

0.08

0.09

Cresol

P

0.34

0.17

0.14

0.03

0.26

0.04

0.05

m

0.25

0.13

0.09

0.03

0.13

0.02

0,01

Total

0.94

0.52

0.45

0.14

0.87

0.14

0.15

Benzylalcohol

0

0

0.02

0.05

0.06

0.05

0.61

Benz-aldehyde

0.17

0

0

0

0

0.24

Bibenzyl

• 9 -

E. J. Hart, on leave from ANL, participated in the study of the sol-

vated electron. Recently some experiments on the aniline system were

carried out at the Royal Institute of Technology in Stockholm using the

pulse radiolysis system of T. Reitberger.

The absorption spectrum of the hydrated electron was deter-1 2

mined between 200 and 250 nm . Similarly to the spectra of H and OH

the absorption of the hydrated electron increased with decreasing wave-

length near 200 nm, the extinction coefficient at 200 nm being 1080 ± 40.

This absorption is attributed to a red shift of the liquid water absorp-

tion band due to a partial electron transfer from the first excited singlet

state of water toe . A similar interpretation was given for the H and2 "

OH spectra .

The pulse radiolysis apparatus at Risö has been described .

The study of aqueous aniline solutions has been continued. From-4

the experiments in acid argon saturated solutions containing 2* 10 Maniline and 2* 10 M methanol, the extinction coefficient at the maxi-

4 - 1 - 1mum of the absorption spectrum was found to be 3. 300 M cm . Thetransient was identified as C/He(H)N Ho and the rate constant for the

9 - 1 - 1second order decay of this transient was found to be 1. 9' 10 M s . Of the

previously reported spectra the spectrum of the transients formed in N-O

saturated solutions has been extended down to 255 nm (Fig. 3. l). In

order to elucidate the aniline system the transients in pulse radiolyzed

aqueous dim ethyl aniline solutions were studied. The spectrum in N^O

saturated solutions is shown in Fig. 3. 2. The kinetics of the formation

and decay of the transients in aniline solutions has been studied. The

different peaks of Fig 3. 1 are formed with different rate constants as

shown in Table 2, demonstrating the initial formation of several transients.

Table 2. Rate constants of formation of transients in DMA solutions

Wavelength Rate constantnm of formation

.,-1 -1 /,n-10,M s . (10 )

500 1.5

410 0.6

355 3

295 1.0

- 10 -

The rate of decay at the different wavelengths also varies. At

320 and 350 nm the decay is fast and follows first order kinetics with

a rate constant of 1. 5* 10 s~ . At 420 nm the decay is slower andk 5

follows second order kinetics with——r- — 2. 5' 10 .

The decay at 350 nm may be caused by a protolytic transforma-

tion of the OH addition radical from the basic form into the acid form,

which absorbs at 410 nm.

In Figs. 3. 3 and 3. 4 the spectra in N?O saturated solutions are

shown at different times after the pulse.

The initial decay and subsequent kinetics are thus quite

complicated. One of the reactions has been studied in more detail,

viz. a slow formation reaction, which is seen below 370 nm and

above 550 nm. The reaction follows first order kinetics. The rate of

formation is independent of the aniline concentration but the rate con-

stant varies with the dose. The apparent ;'irst order rate constant is of

the order of 2000 s" at a dose of 1000 rad. The reaction can therefore

not be a water elimination reaction as might be expected from analogy

with pulse radiolyzed aqueous phenol solutions, but could be a reaction

between two radicals produced with G values differing by more than a

factor of 4. A reaction between . C6H5(H)NH2 (G = 0. 55) and . C6H5(OH)NH2

(G = 5. 3) would follow the described kinetics.

A similar slow formation reaction was found in aqueous dimethyl-

aniline solutions, where a water elimination reaction could hardly be

conceivable. The idea of a reaction between a reduced and an oxidized

radical form of aniline is corroborated by the results described earlier

in connection with the y-radiolysis of aqueous aniline solutions. Such a

repair mechanism suggests the application of aniline and derivatives of

2iilines as radiation protectors.

Recently Wigger et. al. published an examination of the primary

oxidation reactions in aqueous aniline solutions . Their spectra corre-4

spond quite well with our present and earlier reported spectra .

REFERENCES

1. NIELSEN S O, PAGSBERG P, HART E J, CHRISTENSEN H andNILSSON G,Absorption spectrum of the hydrated electron from 200 to 250 nm.J. Phys. Chem. 73 (1969) p. 3171.

2. PAGSBERG P, CHRISTENSEN H, RABANI J, NILSSON G,FENGER J and NIELSEN S O,Far-ultraviolet spectra of hydrogen and hydroxyl radicals frompulse radiolysi8 of aqueous solutions. Direct measurements of

- 11 -

3. CHRISTENSEN H C, NILSSON G , PAGSBERG P and NIELSEN S O,Pulse radiolysis apparatus for monitoring at 2000 Å.Rev. Sci. Instrum. 40 (1969) p. 786.

4. CHRISTENSEN H and NILSSON G,Radiolysis of aqueous solutions and ice. 1969.(AE-360) p. 9.

5. WIGGER A, GRUNBEIN W, HENGLEIN A and LAND E J,Pulsradiolytische Untersuchung pr imärer Schritte der Oxidationvon Aminen in wässr iger Lösung.Z. Naturf. 24 b (1969) p. 1262.

- 12 -

on •

on -

oot •

o » -

C Si -

0 02 -

n

•

+

//

1/ IJ+

A-\

\ HOMO

htltftfth Inm)

Fig. 3. 1 Absorption spectrum of tran-sients produced by a singlepulse of electrons in N?O sa-turated, 2- 1 0"^ Ivl aqueous an-iline solutions immediatelyafter the pulse. Uncorrectedfor aniline decomposition.

Fig. 3. 2 Absorption spectrum of tran-sients produced by a singlepulse of electrons in N-,O sa-turated, 2- 10"^ M aqueous di-methylaniline solutions imme-diately after the pulse.

\

Fig 3. 3 Absorption spectrum of tran-sients produced by a singlepulse of electrons in N2O sa-turated, 2- 10~4 M aniline so-turated, 2- 10~4 M aniline solutions at various times afterthe pulse.+ = I (is, 0=5O^s, 7 = 0.8 ms,0 = 16 ms.

Fig. 3.4 Absorption spectrum of tran-sients produced by a singlepulse of electrons in Ar satu-rated, 4- 10"4 M aqueous ani-line solutions and 4 10"3 M HCICLat various times after the pulse.+ = 1 (j.8, 0 = 40 (is, ? = 1 . 5 ms,Q= 40 ms.

- 13 -

4. TRANSIENT ELECTRONS IN PULSE-IRRADIATED CRYSTALLINE

H2O AND D2O ICE

Gösta Nilsson

The study of the transient solvated electron in crystalline H^O1

and D_O ice carried out in co-operation with the Danish Atomic Energy

Research Establishment (S. O. Nielsen and P. Pagsberg) has continued

and a final report is now under preparation. Some new results for the

D2O ice matrix and the kinetics of the decay of the electron in ice are

reported.

The optical absorption spectrum of the transient solvated elec-

tron in D_O ice has been recorded at several temperatures in the range

-6 to -190 C. The spectra are shown in Fig. 4. 1 and Fig. 4. 2 where

the optical density and the product of the extinction coefficient (e ) and

G are plotted as a function of wavelength. In the same way as in HJD

ice, Fig. 4. 3, the band maximum is shifted to higher energy with de-

creasing temperature and at the same time the yield decreases.

The shift of the band maximum with temperature has been thor-

oughly investigated, and the final result is shown in Fig. 4. 4. In all

cases the sanne graphical method has been used to find the peak posi-

tion, and the errors are estimated ones. The figure shows that the shift

is not a linear function of the temperature as it is in water and reported

by Taub and Eiben to be also in ice. Instead the energy reaches a con-

stant value at about -130°C. The positions of the band maximum at the

plateau are 1. 90 eV for H-O ice and 1. 94 for D2O ice. The energy dif-

ference between D~O ai.d H9O ice is 0. 04 eV throughout the whole tern-

perature range, which can be compared with a difference of 0. 06 eV

between the maximum for e~ ».. liquid HOO and D~O at +23 C. At 0 Ciuq ^ c c

the curves for the liquid phase fit smoothly to the curves for the solid

phase. The absence of a discontinuity at this point is an indication that

the trapping mechanism is essentially the same in the two phases. Neither

the temperature variation in the static dielectric constant nor a varia-

tion in the cavity radius due to the temperature variation of the density

can explain the magnitude of the temperature shift of the peak.

The yield decreases with temperature, at first very fast, between

-50°C and -100°C considerably slower, and finally it increases in D2O

ice at temperatures below -100°C, Fig. 4. 5. In this figure the product

- 14 -

of the extinction coefficient € and G is plotted because the value of e

is unknown for ice. The temperature variation of e is, however, small.

The yield versus temperature curve must therefore have a form very

close to that given in Fig. 4. 5. The large variation in G with tempera-

ture in ice is remarkable since the yield in liquid water is independent

of temperature between +4 and +90 C . The product sG is larger in

D~O ice than in H_O ice. The same is observed for the liquid phases.

The increase in eG below -100 C is due to a population of short-lived

electrons not observed at higher temperatures.

The half life of the transient increases about ten times when the

temperature is decreased from -5 to -50 C, and it is about twice as

long in D_O ice as in H-O ice. The decay is complex and we have tried

to fit the experimental decay curves with the aid of a computer ro dif-

ferent kinetic models. The standard deviation in each point has been

calculated and the points have been weighted according to the relative

error in each point. The goodness of the fit has been calculated from/ 2

KI , where £is the sum of the square of the errors in each point, nV n-s

the number of points and s the number of parameters. The best fit found

hitherto is for a model consisting of two populations of electrons, one

population decaying by first order kinetics (rate constant K.) and the

other by second order kinetics (rate constant K?).

= RG1 - K ^

de./dt =

where e is the concentration of electrons, R the dose rate and G the yield

The following results have been obtained:

Temp K.

°C s 1 1 5(xlO5)

- 5 2. 3

-10 3.5

-19 1.9

-31 1.3

-50 0. 5

- 6 1.2

-32 0. 8

?1 -1(xlO 1 1 )

3. 4

2. 8

4. 4

2.6

3. 1

1. 2

0. 8

Fractionfirst order

%

20̂

27

40

94

91

A

'* = !.

6=2.

ice

7- lO^^cm"1

ice

2- lO^^cnT1

- 15 -

REFERENCES

1. NILSSON G, CHRISTENSEN H C, FEUGER J, PAGSBERG P andNIELSEN SO,Pulse radiolysis of ice and frozen HF solutions.Radiation chemistry. Int. conf. Argonne, lii. Aug. 12 - 15, 1968.Washington i968. Vol. 1, p. 7i. (Advan. chem. ser. 81).

2. GOTTSCHALL W C and HART E J,The effect of temperature on the absorption spectrum of thehydrated electron and on its bimolecular recombination reaction.J. Phys. Chem. 71 (1967) p. 2102.

3. TAUB I A and EIBEN K,Transient solvated electron, hydroxyl, and hydroperoxy radicalsin pulse-irradiated crystalline ice.J. Chem. Phys. 49 (1968) p. 2499.

- 16 - D,O-ic«

200 300 400 500 600 700 800 900

WAVELENGTH(nm)

Fig. 4. 1 Absorption spectrum of thetransient electron in D?O icein the temperature range -6to -190°C.

10-

-i 5-o

200 300 400 500 600 700 800 900WAVELENGTH (nm)

Fig. 4. 2 Absorption spectrum of thetransient electron in D^C icein the temperature range -6to -190°C.

300 A 00 500 600 700 800 900

WAVELENGTH (nm)

Fig. 4. 3 Absorption spectrum of the transient electron inH2O ice in the temperature range -5 to -135°C.

- 17 -

20

19

1.8

r1.5

-200

-T

O Gottscnall and Hart

«4> Brown et oi

»wolf and Otmger

+ Eibtr and Taub

J present study H2O - ice

I „ D2O - 'C*

-150 -WO -50

TEMPERATURE (°C)

•50 • 100

Fig. 4.4 Temperature shift of the maximum of the absorptionband for transient electrons in r^O and D^O ice.

H2O-ice

D2O-ice

-WOTEMPERATURE (°C)

-150 -200

Fig. 4. 5 Temperature variation of eG (extinction coefficient xG)for transient electrons in rUO and D2O ice.

- 18 -

5. AN ESR AND X-RAY DIFFRACTION STUDY ON SOME VINYL

MONOMER SINGLE CRYSTALS

Tomas Gillbro

Numerous stable radicals formed in irradiated solid samples

of vinyl monomers by hydrogen addition to the double bond have been

investigated by the ESR method. When polycrystalline and glassy sam-

ples are used valuable information about the radicals can be gained, but

their exact conformation and position in the crystal matrix cannot be

evaluated. The use of single crystals, however, can provide the desired

information.

For this purpose a method has been devised to prepare single

crystals of vinyl monomers of the important type which are liquid at

room temperature. The crystalline structures are required for the d i s -

cussion of ESR results. Also for the understanding of solid state poly-

merization these data are of importance.

In this work the monomers chosen were methylmethacrylate (MMA)

and methylacrylate (MA), because of their stability to polymerization when

irradiated in the solid crystalline state. The radicals could consequently

be expected to be stable in the crystal matrix.

X-ray diffraction

For the preparation of crystals for X-ray diffraction studies a

method given by Olovs son was slightly modified. The main experimen-

tal difficulties were to avoid ice growth on the sample capillary and to

maintain a low temperature (about -100 C) for a long period of time

( 1 - 2 weeks). These problems can be avoided if a laminar flow of the

cooling gas is achieved by means of a proper location of the heating coil

and the thermocouple element in the gas stream. The study of the crystal

structure of MA gave briefly the following results. At -120°C MA forms

an orthorhombic unit cell, space group P with the dimensions a =° — nma —

= 12. 53 Å, b_= 6. 25 Å and jc = 5. 90 Å. The cell contains four molecules.

The molecules are planar and arranged in two planes with y = 1/4 and

3/4 perpendicular to the b-axis (Fig. 5. l). Intensity data for MMA at

about -100 C have been collected and a full evaluation of the structure

is under way. The calculations made so far show that MMA has a C-centred

- 19 -

monoclinic unit cell, space group C o r £ _ , with the dimensions£ = 14. 46 Å. b_ = 6. 30 Å and £ = 13.7l Å and~9 = 68°. The unit cellcontains eight molecules.

Electroil ^P^JLF^sonanc e

The single crystals used for ESR studies were prepared using3 4a low temperature technique developed at this laboratory * and were

then irradiated in a Co y-cell at 77°K. The results will be describedin more detail elsewhere , for which reason only a short summary isgiven here.

Besides the slightly anisotropic seven- and five-line spectrawith a coupling a = 22 G from the radicals (CH_),CCOOCH, and

(n) s L s

CH3CHCOOCH3V ' formed in MMA and MA, respectively, additional

outer groups of spectral lines were discovered, which is shown forMMA in Fig. 5. 2 and for MA in Fig. 5. 3. This behaviour is explainedby assuming that pairs of the radicals (I) as (II) are created in the crys-tal matrix. According to the theory for radical pairs , a pair of (I) wouldgive rise to a spectrum consisting of two groups of 13 lines with thesplitting a/2 = 11 G. The splitting (D) between the groups is caused bythe dipolar coupling of the two unpaired electron spins and determinedby the distance (R) between the radicals and the orientation of the pairin the magnetic field. The relation, _R £ 38. 2 D , holds for the pointdipole approximation.

In MMA the maximum separation measured between the groupsB and B (see Fig. 5. 2) was 343 G. The distance between the radicalsforming the pair is then less than 5. 45 Å. The groups A and A_ corre-spond to R s 6. 3 ± 1 Å between the radicals. The error is due io thedifficulty in locating the centres of A and A.. The intensity distribution

1 £»

in group B^ was in good accordance with a 13-line spectrum with acoupling a = 11. 2 G, Another proof of radical pairs in MMA is the ob-served weak A Mc = 2 transition at half field, see Fig. 5. 4. This spec-

otrum cculd be accounted for by assuming 12 coupling protons with a == 11.2 (dashed curve in Fig. 5. 4). When warming a MMA crystal to-140°C the B. and B, spectra disappeared, while the feature of the

l tt

ÅMO = 2 transition still remained unchanged, though about 40% weaker.From this we conclude that the radical pair causing Aj and A2 contains

- 20 -

the same monomer units (I) as the pair causing B and B^. Only the

distance between the radicals and/or the orientation of the radical

pairs are different.

Also in the case of MA single crystal spectra two different

pairs of radicals (II) were discovered. The AM^ = 2 transition was found

likewise in a polycrystalline sample. The spectra show an odd number

of lines with a splitting a = 11. 5 G.

In acrolein evidence was also found of radical pairs both in the

AMg = 1 and the A M_ = 2 spectra.

The ratio of radical pairs to the total number of radicals in MMA

was estimated by measuring the amplitudes of the M~ = 2 and M^ = 1

transitions. It was found that this ratio changed very little with the radi-

ation dose (Fig. 5. 5). From this it is concluded that the production of

radical pairs is not due to coincidence but to a fundamental process

occurring in the tracks and spurs of the interacting radiation. In order

to account for the non-occurrence of radicals formed when the monomer

loses a hydrogen atom, we have proposed the following mechanism for

radical pair formation involving four closely situated monomer mole-

cules:

RH RH

RH RH

RHV

RH

-21 -

4. DAHLGREN T, GILLBRO T, NILSSON G and LUND A,A simple method for preparation of single crystals ofcompounds with a low melting point.J. Scient. Instr.(To be published)

5. GILLBRO T , KINELL P-O and LUND A,An ESR single crystal study of radical pair formation inY -irradiated vinyl monomers,( lo be published)

6. KURITA Y,Electron spin resonance study of radical pairs trapped inirradiated single crystals of dimethylglyoxine at liquidnitrogen temperature.Nippon Kagaku Zasshi 85 (1964) p. 833. (In Japanese).

- 22 -

b.

Fig. 5. 1 The crystal structure of methyl-acrylate. The molecules are situated in two planes perpendicu-lar to the b-axes. The mole-cules with atoms joined withheavy strokes are in plane y == 0. 75, those joined with thinstrokes are in plane y = 0. 25.0 stands for oxygen atoms andC for carbon atoms.

Fig. 5. 2 a) ESR spectrum from an irradiatsingle crystal of methylmethacry-late.b) with the same orientation and athigher gain.

1Q0G

, WQ ,

Fig. 5. 3 ESR spectrum from an irradiated single crystalof methylacrylate. Temperature 77°K at irradiation and re>

M*. T\f\ a a

- 23 -

_50G_

I

atey-

at

Fig. 5.4 ESR spectrum of theAta

- 24 -

6. DOSIMETRY AT HIGH IRRADIATION LEVELS

Erik-Åke Tranberg, Sten Ahrland and Göran Carleson

*)Department of Inorganic Chemistry, University of Lund

The high stability of inorganic ion exchangers to radiations of

all types makes them particularly suitable for reactor chemistry and

burnt fuel applications. Methods for the preparation of resins of zirco-

nium phosphate, zirconium oxide and silica gel types have for some1 2years been developed by us and their properties studied ' . An earlier

investigation of their stability to Co gamma radiation has now been

extended to the upper dose limit, 3' 10 Mrad, which was possible to

reach in view of available dose rates and reasonable irradiation times.

The resin degradation was judged by the same methods as used before,

i. e. by comparing structural, physical and chemical properties before

and after irradiations to selected and calibrated doses. In the investi-

gated dose range, 0. 1 - 3* 10 Mrad, no significant change was detected

in any of the observed parameters.. This is also valid for a few experi-

ments where 7 MeV electrons were used as irradiation medium.

Radiation doses in the lower range were determined by Fricke

and polyethylene dosimeters. These are not very accurate above 100 Mrad,

and other types which are easy to handle and reliable do not seem to exist.

The decrease in efficiency of organic phosphors with regard to scintilla-

tion and ultraviolet photoluminescence on exposure to ionizing radiation

is well known. Luminescence degradation has also been observed in many

solid higher benzene homologues. A preliminary investigation showed

that anthracene, fluorene and p-quaterphenyl responded well to gamma

irradiation with their fluorescence intensities slowly decreasing with in-

creasing dose in the range of current interest.

To cover a wide range of doses with adequate sensitivity, all

three aromatics were chosen for further studies. The following technique

was developed. Powders of the materials are pressed without leaking in-

to wafers 2 mm thick and 13 mm in diameter, weighing 0. 4 g. The pro-

cedure is simple and the resulting wafers are compact and easy to handle.

If required they can also be manufactured in thinner forms. With the aid

of a fluorimeter of fixed geometry the fluorescence excited by 365 mm

photon is measured with a photomultiplier at a chosen wavelength. Be-

- 25 -

cause of the strong absorption of ultraviolet light in the wafers, lumi-

nescence is only observed from a thin surface layer. Some 90% of the

signal is estimated to originate from the first 4 p,m. After irradiations

by hard gammas the wafers yield two measurements of luminescence,

one for each side. These should agree and are averaged to give improved

accuracy.

The exposure to gamma radiation was done at varying dose rates

in the range 0. 2 - 8 Mrads/h. The Co sources were calibrated with

Fricke ferrous sulphate dosimetry. Contrary to previously reported re-

sults the luminescence in both anthracene and p-quaterphenyl slowly and

significantly recovers with time after exposure. A post-irradiation treat-

ment of 1 hour at 100°C is adequate to make the reading stable to within

2% over a month* s time and has only a negligible effect on unirradiated

wafers. The cause of the post-dose recovery is uncertain.

An auxiliary experiment with ultrapure anthracene in argon at-

mosphere has shown that the effect can hardly be attributed to oxygen or

initial impurities. Volatile degradation products have also been elimi-

nated. However, primary degradation can probably be ascribed to the4

formation of quenching molecules or electron traps which readily capture

incoming energy and dissipate it as heat before it can be reemitted as

light. We believe that a small part of the quenchers are thermally un-

stable and therefore easily eliminated by an elevation of the temperature.

To avoid contamination from adjacent wafers and other luminescent

material during irradiation and handling, the wafers should be completely

enclosed in a thin capsule of a low-atomic-number material. Graphite,

polystyrene, polyethylene and aluminium were found to have a negligible

dose rate effect. The degradation is also almost independent of dose

rate within the investigated range, 0. 2 - 8 Mrads/h.

After preliminary recordings of fluorescencespectra of anthra-

cene, fluorene and p-quaterphenyl in the wavelength range 365 - 650 nm

at five irradiation doses those peaks were chosen that gave relatively

high and slowly decreasing intensities. Final calibration curves together

with standard deviations (95%) found are shown in FigB. 6. 1 a-c. Appar-

ently the accuracy in measured doses is low on the first flat part of the/ 9

curve but in the dose ange 5* 10 - 3" 10 rads acceptable (standard9

deviations £ 15%). The low rest intensities above 3* 10 rads make meas-

urements uncertain except for p-quaterphenyl, for which a new and fairly

- 26 -

rapidly rising peak with a maximum at about 490 nm appears at a9

radiation dose above 10 rads. Due to the low strength of our cobalt

sources we have not been able to study this phenomenon in detail and

we cannot yet explain its reason. Because of its simplicity gamma

irradiation of the dosimeters in an air atmosphere is to be preferred.

Other media like argon, oxygen and nitrogen have been tried (see Fig. 6. l)

and gave somewhat divergent results, but no advantage is apparently

to be gained thro igh their use. The cause of the deviations is not fully

understood. Masspectrometric analysis showed that phenyl-6 and phenyl-8

polymers are among the degradation products formed.

Recommendations for luminescence dosimeters in air:

5 9anthracene: wavelength 498 nm; dose 5' 10 - 3- 10 rads; 3a ± 15%

fluor ene:

p-quaterphenyl:

i i

II

it

409

410

490

«

11 .»

II .«

M

It

II

1 0 6 -

4- 105

1 0 9 -

3-

-

?

i

3

o9

109

II

II

II

; 3a

; 3a

; 3a

±

±

±

10%

15%

10%

In the course of the study it was observed that the colour of the

wafers was slowly changing with increas ing degradat ion, which might

make them adaptable to the measu remen t of r e l a t ive ref lec tances to fi

filtered red, green and blue lights of specified spectral composition

with a tristimulus colorimeter (Colormaster). By a special mathematical

treatment reflectance readings can be transformed into three colour di-

mensions which are easily correlated with visual judgments of colour

differences, e. g. lightness, saturation and hue. These dimensions can

be used as the co-ordinate framework of a colour-space (Munsell system),

and the total colour difference E can, hence, be measured by computing

the straight-line distance between two points (unirradiated and irradiated)

in the visually uniform colour-space.

Results of colour difference determinations on anthracene,

fluorene and p-quaterphenyl, irradiated in the same way as before, are

collected in Figs. 6. 2 a-c. The calibration curves show that, by a suit-

able combination of wafer materials, gamma doses in the range5 9

10 - 3' 10 rads can be measured with about the same accuracy as with

- 27 -

the luminescence method. Air atmosphere is to be preferred. The

following limits are recommended:

anthracene:

fluorene:

p-quaterphenyl:

colour yellow-brown; 5- 10 - 10 rads; 3a < 10%

ft 711 white-yellow; 10 - 5- 10 " ; 3a < 15%

7 Qwhite-green; 10 - 10 " ; 3a < 20%

I

REFERENCES

1. AHRLAND S,Purification of reactor cooling water by inorganic ionexchangers. 1968.(AE-322) p. 20.

2. AHRLAND S, CARLESON G and TRANBERG E-Å,Inorganic ion exchangers. 1969.(AE-360) p. 27.

3. SCHULMAN J H, ETZEL H W and ALLARD J G,Application of luminescence changes in organic solidsto dosimetry.J. Appl. Phys. 28 (1957) p. 792.

4. KOBAYASHI S and HAYAKAWA S,Quenching effects of several compounds in naphtalonescintillators.Japan, j . appl. phys. 4 (1965) p. 181.

5. MUNSELL COLOR CO,"Munsell Book of Color",Baltimore 1943.

- 28 -

Fig. 6.1 Luminescence dosimeter calibrationx air; o argon; ? nitrogen; Q oxygen

lOOp - i

10-

o) ortthroctnt

ai-

H? 10 Dos* rads

a) anthracene, 498 nm

Inttflsity'/. b)

- 29 -

Fig. 6.2 Colour difference dosimeter calibrationx air; o argon; 7 nitrogen

**l«ti«* c*l«ur • ) snthrmn*difttfmc*

IS

10

°^? & sr

a) anthracene

R*'ativr cdour b) tlmrtntdiftorenrt

E

«

.X1

/

~ir • t r "̂r Oowrod»

b) fluorene

Rttalhrt cotour c) p-fluflrt«(lh»nyl

E

t 1—s—g—r

c) p-quaterphenyl

- 30 -

7. WOOD POLYMER COMBINATIONS

Per Aagaard

Earlier investigations of fully impregnated wood polymer speci-

mens in common Swedish woods were continued during the first half of

the year. Due to economical considerations and a lack of interest from

the industrial side for the rather expensive new products, our interest

was then mainly directed to the study of sur face-impregnated wood poly-

mer combinations and methods for their manufacture. Various pretreat-

ments of the wood surface were tried, among them chemical delignifi-

cation. These latter investigations, which are performed on a commer-

cial basis, will not be discussed further.

A reloading of the gamma-source to increase its dose rate from

c. 60 rads/s to c. 200 rads/s permitted some further studies of the dose

rate dependence for the polymerization of methylmethacrylate (MMA)

in wood. Earlier trouble with incomplete polymerization in pine per-

sisted and caused some ambiguity in the results, nevertheless fairly

consistent extrapolation to full conversion could be made. For poly-

merization in pire sapwood with ambient moisture (8-12%) 1. 8 Mrad

was needed at the higher dose rate (200 rads/s), while 0. 7 and 1. 2 Mrads

are the corresponding doses for full conversion at dose rates of 7 and

70 rads/s, respectively.

In pine, and especially in birch, uneven distributions of polymer

in lengthy test specimens were experienced after irradiation in the Gamma-

cell 220. This can be explained as a result of different effects: uneven

dose rate, temperature differences and dil atom eter effects in the poly-

merizing monomer in the sample. An experiment was designed to ascertain

whether crosslinking agents would affect this inhomogeneity. A small

addition (2%) of a di-vinyl monomer is sufficient to obtain on the average

at least one crosslink per polymer chain. Such an addition affects the

sanding characteristics of the PMMA-wood samples in a fortunate way .

•

- 31 -

Table Density distribution in long samples of pine sapwood with PMMA and

with crosslinked PMMA (2% allylmethacrylate). Samples cut into 12

pieces. The statistical width given is the % standard deviation of mean

density.

PMMAa

b

Crosslinked

c

d

Mean densityg/cm3

1. 138

1. 204

PMMA1. 127

1. 140

Width

6. 8

8. 2

9.6

10.3

Mean densityg/cm 3

1. 176

1. 149

1. 186

1. 203

Wi<

0.

2.

1.

1.

It

4

t

3

6

20 cm long test samples were polymerized and afterwards cut

into 12 sections. The density of each section was determined. A sta-

tistical record of the result is given in the table above, together with

corresponding values for samples treated with MMA alone. The sta-

tistical treatment of the data indicates a slightly more uneven distri-

bution in the crosslinked samples. This is seen as a larger increase in

density for the middle part of the crosslinked samples. This result might,

of course, be fortuitous, as there are many parameters determining the

final distribution, e. g. wood specimen and monomer system in relation

to the specific dose distribution in the irradiation facility.3

It was suggested by a wood chemist that one possible reason forthe incomplete polymerization experienced in wood from the same con-

signment of pine sapwood night be the presence of unsaturated acids in

the extractives of green or fresh wood. These would slowly change during

aging to give saturated resins. If this was the effect, aging of the wood

might give conversion results consistent with earlier determinations. As

the troublesome wood, by that time, had been in our laboratory for two

years, a new experiment on polymerization of MMA was performed. The

results are given in Fig. 7. 1 as a fully drawn curve. The older results

have been added for comparison as a dotted curve. The results are ob-

- 32 -

tained at different dose rates which is the reason for initially higher

conversion data in the 1967 data at the lower dose rate.

REFERENCES

1. AAGAARD P,Wood polymer combinations. 1969.(AE-360) p. 21.

2. MEYER J A,Crosslinking affects sanding properties of wood-plastic.Forest prod. j . 18 (1968) : 5y p. 89 (Tech. note).

3. JOHANSSON I,Private communication, 1969.

- 33 -

1,0

0,6

0,2

Conv.-

-

-

1

1

*

kJo Fall. Fall

11

19671969

•

1 : 1 c*5 Dose

Mrad

Fig. 7. 1 Conversion of MMA in pine sapwood as a function ofdose. Fully drawn curve: autumn 1969, do3e rate c.200rad / s ; dotted curve: autumn 1967 dose r^te 60 r ad / s .Wood from the same tree is used in both experiments andat the same humidity.

- 34 -

8. CHARGED PARTICLE AND NEUTRON ACTIVATION ANALYSIS

Dag Brune

The carbon content and depth distribution in steel at the 0. 1 - 1

per cent level has been studied. The analysis was carried out through

proton activation in the energy interval 1 - 4. 5 MeV with a Van de Graaff12 13

accelerator applying the reaction C (p, Y) N, which possesses two

resonances at the energies of 0. 46 and 1. 70 MeV. Carbon contents at the

surface of the steel samples as well as in layers of about 1 |JL thickness

were measured. At an appropriate proton energy the carbon content at

the surface of the material as well as in a layer below the surface was

measured simultaneously in a single operation utilizing both resonances.

Steel samples, especially heat-treated in order to obtain a good carbon

homogeneity, were used as reference in the depth distribution investiga-

tion. The proof of the carbon homogeneity at various depths was conse-

quently aimed at. Fig. 8. 1 shows the irradiation and measurement

arrangement and Fig. 8. 2 the differential cross-section curve for the re-12 13

action C (p, y ) N in a thick target of carbon. Fig. 8. 3 shows the

proportionality of the activities observed for the steel samples containing

0. 07, 0. 46 and 1. 06% carbon, respectively, both in the surface (3. 51 MeV y)

and in a layer below the surface (2. 36 MeV y) •

Carbon and oxygen contents in pure aluminium were also analyzed

with 185 MeV protons from the Gustaf Werner Institute synchrocyclotron

in Uppsala. The accelerator offers two possibilities for irradiation of

the samples:1. Irradiation at chosen proton energies inside the accelerator.

2. Irradiation at the fixed energy of 185 MeV in the extracted beam.

The extracted beam was preferred, as a homogeneous irradiation

of samples inside the accelerator is difficult to achieve.

185 MeV proton irradiation of carbon and oxygen produces the

positron emitters C and O by the following reactions:

12C(p,pn)UC

l6O(p,pn)15O

l6O(p,3P3n)MC

- 35 -

Even in pure aluminium C and O are formed to some extent

due to spallation reactions. In order to estimate the sensitivity of the

method for carbon and oxygen determination in aluminium, the "back-

ground" levels induced in the pure metal as well as the amounts of

C and O activities formed in a standard of Na,CO, were measured.

The decay curves were resolved by least square fits with the "Expamp"

programme using an IBM 360/30 F computer. It was assumed that the

aluminium decay curve in the time interval considered chiefly comprises

the nuclide activities O (2. 05 min), 13N (10. 0 min),UC (20. 5 min)18

and F (110 min). This seems to be verified by experiment» since the

measured half-lives amount to 1. 78 min, 8. 15 min, 20. 2 min and 109 min

respectively.

Further the detection limit is defined as the amount of an element

which yields an activity equal to five times the standard error (5 a ) of

the O or C activities produced from aluminium. On the basis of

these figures the detection limit for carbon and oxygen amounts to 0. 65 mg/g

and 1. 65 mg/g, respectively .

A liquid helium cryostat, inserted in a central position of the

swimming pool, reactor at the Technical University of Munich, has been

employed to facilitate the neutron activation analysis of small liquid samples.

The concentration of copper was determined in single water droplets

(0. 01 ml) of a solution containing 0. 1 M.g/ml copper from the enzyme

Stellacyanin.

Phase transitions occurring in single crystals of ice as well as

heat transfer processes due to the slowing down of recoil protons and to

gamma radiation in the solid aqueous samples have been considered with

reference to a possible activity transfer which would interfere with the

reliability of the analysis .

A special cooling device was constructed and applied for neutron

activation analysis in a heavy water moderated reactor in Stockholm.

Samples are irradiated in aluminium cans which are cooled with low-

temperature nitrogen gas. Temperatures down to about -30 C can be ob-

tained in frozen aqueous samples. The arrangement can, for instance, be

used for analysis of trace elements in aqueous, biological or pharmaceutical

material .

Low temperature technique has also been used in a study of the

formation of CrO4 in liquid or frozen neutron bombarded chromate

- 36 -

solutions . The investigation was carried out at the Technical University

of Munich . The retention was determined as a function of pH, Cr cone,

and gamma dose. The results are given in Figs. 8. 4 - 8. 7.

REFERENCES

1. BRUNE D and HELLBORG R,Studies of the carbon content of steel and its depth distributionby means of proton activation analysis.(To be published).

2. BRUNE D,Determination of carbon and oxygen in aluminium by meansof proton activation analysis with a 185 MeV synchrocyclotron.(To be published).

3. BRUNE D and WENZL H,The application of a liquid helium-cryostat in neutron activationanalysis of fluids.Anal. Chem.(To be published).

4. BERGLUND N, BRUNE D and SCHUBERG B,A nitrogen gas cooling device for operation in neutronactivation analysis.Nucl. Instr. Meth. 75 (1969) p. 103.

5. BRUNE D and ZAHN U,Recoil behaviour of ^^Cr, atoms in neutron-bombarded liquidand frozen chromate solutions.Int. Symp. Chemical Effects of Nuclear Transformations,Cambridge, 1-3 July, 1969.

- 37 -

Targe» Solder

Sample in irradiation

70-l5Omm

3«3U nitrogen dctectc

Fig. 8. 1 Irradiation and measurement arrangement.

3.o

* * *

i f

. I • I . I . I

1500 1606 1700 180̂ keV

Fig. 8. 2 Differential cross-section curve for the reaction12 13

C(p, Y ) N in a thick target of carbon.

- 38 -

if

> microcoulomb

ZOOO i—

looo

5OO

OS 10RercenV darbo*\ ii^ Steel

Fig. 8. 3 Proportionality of activities observed for steel samplescontaining 0. 07, 0. 46 and 1. 06 % carbon.

80

60 •

40

V< • I I 1 1—_J L51Fig. 8. 4 Dependence of C r O 4 " " -formation on pH in 0. 1 M

V

I - 39 -

0.001 0.005 0.01Cone, of Cr l * 4

51

0.05

Fig. 8. 5 Dependence of CrQ ~~ -formation on Cr+ + + -concentrationat pH 4. 5 in 0. 1 M K2CrO4 solutions.

so

60

40

20

51Cr04"-(0.1MJI'm fig. 1)

0.01 M yj

0.001 M

(at various cone.)

1M0.01 M

0.1 M £,

0.1 M

i i i i10

Fig. 8. 6 Dependence of CrO4~~ -formation on Cr -concen-

tration in liquid and frozen solutions of K-CrO. at various pH.

80 r

60

20

pH4,5

pH2.0

irradiation Time (i)- 1.106 - 2 . 1 0 6 ^ 3.106

Gamma dow (Rad)

Fig. 8. 7 51

•I

-I J__J J ' L ' ' ' . ' ' . ' ' 1 ' '20 40 60 80 100 120 140 »160

- 410*

Dependence of CrO4 " -formation on gamma-dose in 0. ii i - . _ - - . . . - i i i

LIST OF PUBLISHED AE-REPORTS

1-320 (See back cover earlier reports.)

121- Stability el • »te»m cooled fast power reactor, ils transient* due to mode-rat* perturbation* and accidents. By H. Voilmer. 1988- 36 p. Sw. cr. 10:-.

322 Progress report 1967. Nudeai chemistry. 196». 30 p. Sw. cr. 10.-.323 Noise in tho measurement of light with photomultipliers. By F. Robben.

19H. 74 f». Sw. cr. 10:-.324. Theoretical investigation of an electrogasdynamic generator. By S. Palm-

gren. 1968. 36 p. Sw. cr. 10:-.

325 Some comparisons of measured and predicted primary radiation levels inthe Agesta power plant. By E. Aalte, R Sandlin and A. Krell. 1968. 44 p.Sw cr. 10:-.

326. An investigation of an irradiated fuel pin by measurement of the productionof fast neutrons in a thermal column and by pile oscillation technique.By Vei ie Gustavsson. 1968 24 p. Sw. cr. 10:-.

327. Phytoplankton from Tviren. a bay of the Baltic. 1961-1963. By TorbiörnWiden. 1968. 76 p Sw. 10:-.

328. Electronic contributions to the phonon damping in metnU, B* Run* l»n*o»1S68. 38 p. Sw cr. 10:-.

329. Calculation of tesonance interaction effects using a rational approximationto the symmetric resonance line shape function. By H. Haggblom. 1968.48 p. Sw. cr 10:-.

330. Studies of the effect of heavy water in the fast reactor FRO. By L. I Tirén.R. Håkansson and B. Karmhag. 1968. 26 p. Sw. cr. 10:-.

331. A comparison of theoretical and experimental values of the activation Dop-pler efFect in some fas! reactor spectra By H. Haggblom and L. I. Tirén.1968. 28 p. Sw. cr. 10:-.

332. Aspects of low temperature irradiation in neutron activation analysis. ByD Brune 1963. 12 p. Sw. cr. 10. - .

333. Application of a betatron in photonuclear activation analysis. By D. Brune.S. Mattsson and K Liden. 1968. 13 p. Sw. cr. 10:-.

334. Computation of resonance-screened cross section by the Dorlx-Spengsystem. By H Haggblom. 1968. 34 p. Sw. cr 10:-.

335. Solution of large systems or linear equations in the presence of errorsA constructive criticism of the least squares method. By K. Nygaard. 1958.28 p. Sw cr 10:-.

336 Calculation of voia volume fraction in the subcooled and quality boilingregions. By S. Z. Rouhani and E. Axelsson. 1968. 26 p. Sw. cr. 10:-.

337. Neutron elastic scattering cross sections of iron and zinc in the energyregion 2.5 to 8.1 MeV. By B. Holmqvist, S. G. Johansson. A. Kiss. G. Lo-din and T. Wiedling. 1968. 30 p. Sw. cr. 10:-

333. Calibration experiments with a DISA hot-wire anemometer. By B. Kiell-ström and S. Hedberg. 1968. 112 p. Sw. cr. 10:-.

339 Silicon diode dosimeter for fast neutrons. By L. Svansson. P. Swedberg.C-O. Widell and M. Wik. 1968. 42 p. Sw. cr. 10:-.

340 Phase diagrams of some sodium and potassium salts in light and heavywater. By K. E. Holmberg. 1968 48 p. Sw. cr. 10:-.

341. Nonlinear dynamic model of power plants with single-phase coolant reac-tors. By H. Vollmer. 1968. 26 p. Sw. cr. 1 0 -

342. Report on the personnel dosimetry at AB Atomenergi during 1967. By JCarlsson and T. Wahlberg. 1968. 10 p. Sw. cr. 10:-.

343. Friction factors in rough rod bundles estimated from experiments in parti-ally rough annufi - effects of dissimilarities in »he shear stress and tur-bulence distributions. By B. Kjellström. 1968. 22 p. Sw cr. 10:-.

344. A study of the resonance interaction effect between '»U and »