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Interstitial-impurity reactions during stage I of platinum alloys after thermal and fast-neutron irradiation
Volume 88A, number 5
PHYSICS LETTERS
15 March 1982
INTERSTITIAL-IMPURITY REACTIONS DURING STAGE I OF PLATINUM ALLOYS AFTER THERMAL AND FAST-NEUTRON IRRADIATION C.S.B. PIANI and J. ASPELING Atomic Energy Board, Private Bag X256, Pretoria 0001, Republic of South Africa Received 2 September 1981
Recovery spectra of pure platinum and selected dilute platinum alloys are compared to equivalent induced resistivities following either fast- or thermal-neutron irradiation at 4.4 K. Annealing during stage 1(7—30 K) was significantly retarded due to the fast-neutron irradiation. Although a reduction in recovery due to alloying impurities was observed, it appears that due to the highly-localised defect concentration, interstitial—interstitial reactions were predominant during annealing of the fast-neutron defects, whilst in the case of the thermal neutrons, due to the generalised low defect concentration, interstitial—impurity reactions were more important.
The dependance of the irradiation-recovery spectrum on the initial energy transferred to the lattice atoms by bombarding particles in various metals is a field of interest which has been receiving considerable attention
with more energetic particles (e.g. fast neutrons). Reference-grade Pt wire ‘~0.1mm (Sigmund Cohn) was chemically cleaned and resistance-annealed at 1700°Cand had a final RRR 3600 (p0 = 2.9 n&2cm).
recently [1—9],and which has been necessitated by the need to understand the radiation damage effect of high-energy neutrons in proposed fusion reactors, Isebeck et al. [2] presented a comparative study on the stage I recovery of several pure metals (including platinum) irradiated with thermal or fast neutrons at 4 K. More recent results regarding the recovery spectra in pure platinum (Pt) following thermal- and fissionneutron irradiation in comparison to high-energy d—Be neutron irradiation at 4.2 K have been reported for lowinduced defect concentrations [3—4].With the exception of the electron-irradiation work by Dibbert et al. [101 and our results [11] involving thermal-neutron studies on dilutewith Pt—Au alloys, very littleAs research been completed regard to Pt alloys. yet, nohas results on dilute Pt alloys after fast-neutron irradiation have been reported. Since a reasonable understanding of basic point-defect principles has been achieved with respect to simple induced defect configurations [12—14] (e.g. due to electrons, thermal neutrons), it became desirable to compare these with the more complicated defect agglomerates and configurations arising from irradiation of various dilute alloys
The alloys were prepared from 5N Pt (Heraeus) and 6N Cu (Asarco) or 5N Au (Sigmund Cohn), taking great care to prevent impurity contamination. Any deformation due to handling was removed by annealing the samples at 750°Cat I X iO~Torr for one hour. A set of four samples was mounted on the cryogenic irradiation facility (CIF) [15] and subsequently irradiated at 4.4 K with a thermal-neutron flux using a modified graphite moderator, which provided a purer thermal neutron spectrum than that used in earlier work [11]. Irradiation was terminated after a preselected value of induced resistivity was obtained. This was achieved using an estimated thermal-neutron 2. These samples were then fluence of ~5annealed X 1017 from n/cm 7 K to 30 K in steps of 0.5 isochronally K and from 30 K to 750 K in steps of ~T/T = 0.05 using five minute holding times. On completion of the isochronal annealing program, the samples were finally annealed in the CIF furnace at 500°Cat l0~ Torr for one hour, to restore the initial values of residual resistivity. These samples were then submitted to fast-neutron irradiation at 4.4 K until an induced resistivity, equivalent to that of the thermal-neutron irradiation,
0 031-9163/82/0000—0000/$02.75 © 1982 North-Holland
‘~
257
Volume 88A, number S
PHYSICS LETTERS
15 March 1982
10O’~
—
Pt 006 ~t ‘I.
Pt
01 cr,~ .‘L
z
9
1 0~01 c
1,40 (FAST) ‘~,
137
•
755
.
z 0
(THERMAL)
~5O
(FAST)
762 (THERMAL)
•
~50
O
10
100
,~,,T
~-._-__‘
~__1__,
~
100 TEMPERATURE
‘‘‘‘‘‘•‘
U
C
LII]
700
u 10
I__U_I,
I
I
100
III
~I
I
100 TEMPERATURE
K
700 4
‘‘‘‘‘‘II
I
I
ri~ -
‘S..-,
Pt 0,1101
P10,20
-
Ct
‘/,
I Tflcm Cr,,
•
lO
‘ ,
12,18 (FAST) 12,52 (THERMAL)
9
‘
“._,
•
6,53 (FAST) 6,44 (THERMAL)
Cr
~50
‘
6
‘
~50
-,
‘. Cr
0
I
10
1,,,,,,,
0
LIII’
100
‘S’,
700
TEMPERATURE K
IIII,fl,,I
10
100
700
TEMPERATURE K
Fig. 1. Isochronal recovery curves of Pt and dilute Pt alloys irradiated at 4.4 K with fast or thermal neutrons to the ~po values indicated. was obtained. In this case an estimated fast-neutron fluence of~~o5 X 1015 n/cm2 was used. A similar iso-
chronal annealing program was then followed. This method has the advantage that, since the same sample is used for both types of irradiation, influencing parameters such as specimen purity, fabrication history and 258
are eliminated [1]. The fast-neutron spectrum used was, for all practical purposes, devoid of thermal neutrons, whilst the spectrum used for the thermal-neutron irradiation consisted of fluxes of 2 X 1 ~7 n/cm2s (fast: > 0.1 MeV) and geometry, circuit interference, etc.
5 X 1010 n/cm2s (thermal) respectively. Using a mean
’
Volume 88A, number 5
PHYSICS LETTERS
‘11111
‘‘‘II’’’’r’’’I’’’’U
,,IIrI.,flI]~I]IIfli’Ifl’’II
2_SF.. 2,0
15 March 1982
2,5
2,0
lO9flcm 1,40 (FAST) • (37 (THERMAL)
1,5
t,5
i.e
1,0
C
__________________________
109fl cm 7,55 (FAST) • 7,62 (THERMAL)
-~
TEMPERATURE K
TEMPERATURE K
2.5
2,5r
Pt 0,11at~I~Cu
Pt 0,20
~
2,0
-
lO9flcm o
12,18 (FAST
‘‘‘‘II’III1’I’I’’’’III]’V’nr
Ct ~/,Au
2.0 1O99 cm
)
1 2,52 (THERMAL)
I0 20 TEMPERATURE K
0
6,53 (FAST
•
6,44 (THERMAL)
~ TEMPERATURE K
Fig. 2. Stage I differential recovery curves of the Pt and dilute Pt alloys corresponding to fig. 1.
259
Volume 88A, number 5
PHYSICS LETTERS
neutron energy of ~2 MeV for fast neutrons, this would imply that less than 7% of the damage observed in Pt during the thermal neutron irradiation could be attributed to fast neutrons [16]. A more detailed description of the experimental layout and procedure can be obtained elsewhere [11,17]. The completed isochronal recovery curves for the two types of neturon irradiation are shown in fig. I, for pure Pt and three selected dilute Pt alloys. The irradiation-induced resistivity is indicated as L~POand for a specific resistivity of 10 X 10—6 ~2cm/at% Frenkel defects in Pt, the defect concentration can readily be calculated [18,19]. It is obvious that for all the samples, the defect recovery is significantly retarded from as early as 10 K due to the fast-neutron irradiation. At the end of stage I (~~o30 K) approximately 30% more of the irradiation-induced defects are retamed in the lattice due to fast-neutron irradiation, Annealing above 30 K is more rapid in all the fastneutron irradiated samples, whilst the substages at S~120K and ~360 K, reported earlier [11,20] are
15 March 1982
much higher energy transfers of fast-neutron irradiation, might be interpreted as f~ollows: Although both types of irradiations (thermal and fast) produced practically identical total concentra-
tions of defects, the defect pattern for the thermalneutron irradiated specimens is that of evently distri-
buted simple defects (1—2 Frenkel pairs per capture event), whilst the generally accepted damage pattern due to fast-neutron irradiation consists of depleted zones with an inner peripheral of vacancies and a rich interstitial outer layer [12]. This highly-localised defect concentration could result in additional defect interaction, e.g. by the large elastic strains existing in such a depleted zone thus reducing close-pair recombination. At the same time, the higl1er knock-on energy transfer should result in the production of fewer close pairs. This would result in the sharp decrease observed in recovery during ‘A and ‘B(~6% less) whilst IC is a!most totally suppressed due to the fast-neutron irradiation. During free-interstitial migration (ID+E)~interstititial—interstitial reactions could compete with an—
still present. Total annihilation of all irradiation-induced defects had occurred at 1o730 K in all samples. The stage I recovery spectra, obtained by differentia-
nihilation at vacancies due to the highly-localised defect concentration and would explain the observed reduction in recovery. Similarily, substage ‘E’ although still
tion of the respective isochrones between 5 K and ~30 K, are indicated in fig. 2. (Results pertaining to recovery above stage I will be dealt with separately [21].)
observable, is significantly reduced by this strong interstititial—interstitial interaction after such a fast-neutron irradiation. The influence of impurities due to the dilute alloys
In the thermal-neutron irradiated pure Pt, recovery substages ‘A (10110 K), IB(1~~~0lS K), IC(rCrl9 K), ID(’~22K) and IE(~o~27 K)are visible and correspond well with those reported elsewhere for thermal-neutron
is minimal for the close-pair recovery substages (with-
of stage I recovery, in pure Pt irradiated at 4 K, on various electron bombardment energies, has shown that recovery during ‘A and ‘C decreases, while that in
in experimental error) for the above defect concentrations in both irradiations as shown in table 1. Effects Ofl ‘A and ‘B are just becoming apparent due to the 2000 ppm Au alloy. Although graphic representation indicates a higher and narrower recovery in ‘C and 1D in the thermal-neutron irradiated Pt—Cu alloys, actual
‘B and ‘DE increases with increasing electron energies [10]. The present results, which indicate suppression of all these substages in all the samples due to the
recovery is less than that of the pure metal — see table 1. (Care must, however, be taken when comparing individual samples, since they contain different concen-
[3,11] and electron irradiations [10]. The dependence
Table 1 Stage I recovery values (%) after fast- and thermal-neutron irradiation.
-
Substage
Neutron flux
Pt
Pt—0.06 Cu
P1—0.11 Cu
‘A + lB
Thermal fast
10.2 4.8
10.0 4.6
10.1 4.8
9.7 4.2
Thermal fast
56.6 31.8
55.0 30.7
55.2 30.6
50.1 28.5
+
260
ID + ‘E
Pt—0.20 Au
Volume 88A, number 5
PHYSICS LETTERS
trations of Frenkel defects, an important factor when comparing interstitial—impurity reactions in stage I [11,21].) The suppression of ‘E during thermal-neutron irradiation due to the addition of alloying impurities is also graphically significant, although calculations involving actual recovery during this substage are impeded due to the proximity and overlap of ‘D’ It appears from fig. 2 and table 1 that the addition of Cu has not significantly influenced the difference in recovery between fast- and thermal-neutron irradiations for these substages (IC, ‘D and IE). (The higher Au concen-
tration does, however, influence these substages although the effect is still small.) This can be attributed to the overwhelming number of interstitial—interstitial reactions present, due to the abovementioned localised defect concentrations as compared to the relatively low homogeneous distribution of the impurities.
In conclusion it can be stated that although substage
15 March 1982
References [11 J.A. Horak and T.H. Blewitt, Nucl. Tech. 27(1975)416. 121 K. Isebeck and K.F. Poole, Radiat. Eff. 22 (1974) 15. [3] J.B. Roberto, C.E. Klabunde, J.M. Williams and R.R. Coltman Jr., J. Nucl. Mater. 73 (1978) 97. [4] R.R. Coitman Jr., CE. Klabunde and J.K. Redman, J. NucI. Mater. 69,70(1978)720.
[5J R.S. Averback, R. Benedek and K.L. Merkie, J. Nuci. Mater. 75 (1978) 162. [6] P. Lucasson and A. Lucasson, Radiat. Eff. 39 (1978) 195. [7] MA. Kirk and T.H. Blewitt, Metall. Trans. 9A (1978)
1729. [8] C.A. English, J. NucI. Mater. 96 (1981) 341. [9] J. Morilo, C.H. de Novion and J. Dural, Radiat. Eff. 55
67. K. Sonnenberg, W. Schilling and U. Dedek, [10] (1981) H.J. Dibbert, Radiat. Eff. 15 (1972) 115. [11] C.S.B. Piani and J. Aspeling, Radial Eff. 45 (1980) 127.
recovery during stage I was shown to be strongly depen-
[12] W. Schilling, G. Burger, K. Isebeck and H. Wenzl,
dent on the relation between impurity and defect concentrations for thermal-neutron irradiated dilute Pt alloys [11], the same explanations do not necessarily apply to equivalent defect concentrations following fast-neutron irradiations. This may be attributed to the highly-localised defect concentrations after fastneutron irradiation and will apply in particular to the above cases of low-induced defect concentrations where
Vacancies and interstitials in metals, (North-Holland, p. of 255. [13] Amsterdam, Fundamental1970) aspects radiation damage in metals (Gatlinburg, CONF-751006 USERDA, 1975). [14] Properties ofatomic defects in metals, J. Nuci. Mater. 69, 70 (1978). [15] K. Isebeck, Radiat. Eff. 14 (1971) 143. [16] R.R. Coitman, C.E. Klabunde and J.K. Redman, Phys. Rev. 156 (1967) 715. [17] C.S.B. Piani, Atomic energy board report, Per 39
the cascades are still well separated.
(pretoria, 1978). [18] P. Lucasson, in: Fundamental aspects of radiation damage in metals (Gatlinberg, CONF-75 1006 USERDA,
We wish to express our thanks to A. Sliep, J. Louw and D. du Plessis for their technical assistance.
1975). [19] R.C. Birtcher and T.H. Blewitt, J. Nucl. Mater. 98 (1981) 63.
[20] W. Schilling, K. Sonnenberg and H.J. Dibbert, Radial. Eff. 16 (1972) 57. [21] C.S.B. Piani and J. Aspeling, to be published.
261
PHYSICS LETTERS
15 March 1982
INTERSTITIAL-IMPURITY REACTIONS DURING STAGE I OF PLATINUM ALLOYS AFTER THERMAL AND FAST-NEUTRON IRRADIATION C.S.B. PIANI and J. ASPELING Atomic Energy Board, Private Bag X256, Pretoria 0001, Republic of South Africa Received 2 September 1981
Recovery spectra of pure platinum and selected dilute platinum alloys are compared to equivalent induced resistivities following either fast- or thermal-neutron irradiation at 4.4 K. Annealing during stage 1(7—30 K) was significantly retarded due to the fast-neutron irradiation. Although a reduction in recovery due to alloying impurities was observed, it appears that due to the highly-localised defect concentration, interstitial—interstitial reactions were predominant during annealing of the fast-neutron defects, whilst in the case of the thermal neutrons, due to the generalised low defect concentration, interstitial—impurity reactions were more important.
The dependance of the irradiation-recovery spectrum on the initial energy transferred to the lattice atoms by bombarding particles in various metals is a field of interest which has been receiving considerable attention
with more energetic particles (e.g. fast neutrons). Reference-grade Pt wire ‘~0.1mm (Sigmund Cohn) was chemically cleaned and resistance-annealed at 1700°Cand had a final RRR 3600 (p0 = 2.9 n&2cm).
recently [1—9],and which has been necessitated by the need to understand the radiation damage effect of high-energy neutrons in proposed fusion reactors, Isebeck et al. [2] presented a comparative study on the stage I recovery of several pure metals (including platinum) irradiated with thermal or fast neutrons at 4 K. More recent results regarding the recovery spectra in pure platinum (Pt) following thermal- and fissionneutron irradiation in comparison to high-energy d—Be neutron irradiation at 4.2 K have been reported for lowinduced defect concentrations [3—4].With the exception of the electron-irradiation work by Dibbert et al. [101 and our results [11] involving thermal-neutron studies on dilutewith Pt—Au alloys, very littleAs research been completed regard to Pt alloys. yet, nohas results on dilute Pt alloys after fast-neutron irradiation have been reported. Since a reasonable understanding of basic point-defect principles has been achieved with respect to simple induced defect configurations [12—14] (e.g. due to electrons, thermal neutrons), it became desirable to compare these with the more complicated defect agglomerates and configurations arising from irradiation of various dilute alloys
The alloys were prepared from 5N Pt (Heraeus) and 6N Cu (Asarco) or 5N Au (Sigmund Cohn), taking great care to prevent impurity contamination. Any deformation due to handling was removed by annealing the samples at 750°Cat I X iO~Torr for one hour. A set of four samples was mounted on the cryogenic irradiation facility (CIF) [15] and subsequently irradiated at 4.4 K with a thermal-neutron flux using a modified graphite moderator, which provided a purer thermal neutron spectrum than that used in earlier work [11]. Irradiation was terminated after a preselected value of induced resistivity was obtained. This was achieved using an estimated thermal-neutron 2. These samples were then fluence of ~5annealed X 1017 from n/cm 7 K to 30 K in steps of 0.5 isochronally K and from 30 K to 750 K in steps of ~T/T = 0.05 using five minute holding times. On completion of the isochronal annealing program, the samples were finally annealed in the CIF furnace at 500°Cat l0~ Torr for one hour, to restore the initial values of residual resistivity. These samples were then submitted to fast-neutron irradiation at 4.4 K until an induced resistivity, equivalent to that of the thermal-neutron irradiation,
0 031-9163/82/0000—0000/$02.75 © 1982 North-Holland
‘~
257
Volume 88A, number S
PHYSICS LETTERS
15 March 1982
10O’~
—
Pt 006 ~t ‘I.
Pt
01 cr,~ .‘L
z
9
1 0~01 c
1,40 (FAST) ‘~,
137
•
755
.
z 0
(THERMAL)
~5O
(FAST)
762 (THERMAL)
•
~50
O
10
100
,~,,T
~-._-__‘
~__1__,
~
100 TEMPERATURE
‘‘‘‘‘‘•‘
U
C
LII]
700
u 10
I__U_I,
I
I
100
III
~I
I
100 TEMPERATURE
K
700 4
‘‘‘‘‘‘II
I
I
ri~ -
‘S..-,
Pt 0,1101
P10,20
-
Ct
‘/,
I Tflcm Cr,,
•
lO
‘ ,
12,18 (FAST) 12,52 (THERMAL)
9
‘
“._,
•
6,53 (FAST) 6,44 (THERMAL)
Cr
~50
‘
6
‘
~50
-,
‘. Cr
0
I
10
1,,,,,,,
0
LIII’
100
‘S’,
700
TEMPERATURE K
IIII,fl,,I
10
100
700
TEMPERATURE K
Fig. 1. Isochronal recovery curves of Pt and dilute Pt alloys irradiated at 4.4 K with fast or thermal neutrons to the ~po values indicated. was obtained. In this case an estimated fast-neutron fluence of~~o5 X 1015 n/cm2 was used. A similar iso-
chronal annealing program was then followed. This method has the advantage that, since the same sample is used for both types of irradiation, influencing parameters such as specimen purity, fabrication history and 258
are eliminated [1]. The fast-neutron spectrum used was, for all practical purposes, devoid of thermal neutrons, whilst the spectrum used for the thermal-neutron irradiation consisted of fluxes of 2 X 1 ~7 n/cm2s (fast: > 0.1 MeV) and geometry, circuit interference, etc.
5 X 1010 n/cm2s (thermal) respectively. Using a mean
’
Volume 88A, number 5
PHYSICS LETTERS
‘11111
‘‘‘II’’’’r’’’I’’’’U
,,IIrI.,flI]~I]IIfli’Ifl’’II
2_SF.. 2,0
15 March 1982
2,5
2,0
lO9flcm 1,40 (FAST) • (37 (THERMAL)
1,5
t,5
i.e
1,0
C
__________________________
109fl cm 7,55 (FAST) • 7,62 (THERMAL)
-~
TEMPERATURE K
TEMPERATURE K
2.5
2,5r
Pt 0,11at~I~Cu
Pt 0,20
~
2,0
-
lO9flcm o
12,18 (FAST
‘‘‘‘II’III1’I’I’’’’III]’V’nr
Ct ~/,Au
2.0 1O99 cm
)
1 2,52 (THERMAL)
I0 20 TEMPERATURE K
0
6,53 (FAST
•
6,44 (THERMAL)
~ TEMPERATURE K
Fig. 2. Stage I differential recovery curves of the Pt and dilute Pt alloys corresponding to fig. 1.
259
Volume 88A, number 5
PHYSICS LETTERS
neutron energy of ~2 MeV for fast neutrons, this would imply that less than 7% of the damage observed in Pt during the thermal neutron irradiation could be attributed to fast neutrons [16]. A more detailed description of the experimental layout and procedure can be obtained elsewhere [11,17]. The completed isochronal recovery curves for the two types of neturon irradiation are shown in fig. I, for pure Pt and three selected dilute Pt alloys. The irradiation-induced resistivity is indicated as L~POand for a specific resistivity of 10 X 10—6 ~2cm/at% Frenkel defects in Pt, the defect concentration can readily be calculated [18,19]. It is obvious that for all the samples, the defect recovery is significantly retarded from as early as 10 K due to the fast-neutron irradiation. At the end of stage I (~~o30 K) approximately 30% more of the irradiation-induced defects are retamed in the lattice due to fast-neutron irradiation, Annealing above 30 K is more rapid in all the fastneutron irradiated samples, whilst the substages at S~120K and ~360 K, reported earlier [11,20] are
15 March 1982
much higher energy transfers of fast-neutron irradiation, might be interpreted as f~ollows: Although both types of irradiations (thermal and fast) produced practically identical total concentra-
tions of defects, the defect pattern for the thermalneutron irradiated specimens is that of evently distri-
buted simple defects (1—2 Frenkel pairs per capture event), whilst the generally accepted damage pattern due to fast-neutron irradiation consists of depleted zones with an inner peripheral of vacancies and a rich interstitial outer layer [12]. This highly-localised defect concentration could result in additional defect interaction, e.g. by the large elastic strains existing in such a depleted zone thus reducing close-pair recombination. At the same time, the higl1er knock-on energy transfer should result in the production of fewer close pairs. This would result in the sharp decrease observed in recovery during ‘A and ‘B(~6% less) whilst IC is a!most totally suppressed due to the fast-neutron irradiation. During free-interstitial migration (ID+E)~interstititial—interstitial reactions could compete with an—
still present. Total annihilation of all irradiation-induced defects had occurred at 1o730 K in all samples. The stage I recovery spectra, obtained by differentia-
nihilation at vacancies due to the highly-localised defect concentration and would explain the observed reduction in recovery. Similarily, substage ‘E’ although still
tion of the respective isochrones between 5 K and ~30 K, are indicated in fig. 2. (Results pertaining to recovery above stage I will be dealt with separately [21].)
observable, is significantly reduced by this strong interstititial—interstitial interaction after such a fast-neutron irradiation. The influence of impurities due to the dilute alloys
In the thermal-neutron irradiated pure Pt, recovery substages ‘A (10110 K), IB(1~~~0lS K), IC(rCrl9 K), ID(’~22K) and IE(~o~27 K)are visible and correspond well with those reported elsewhere for thermal-neutron
is minimal for the close-pair recovery substages (with-
of stage I recovery, in pure Pt irradiated at 4 K, on various electron bombardment energies, has shown that recovery during ‘A and ‘C decreases, while that in
in experimental error) for the above defect concentrations in both irradiations as shown in table 1. Effects Ofl ‘A and ‘B are just becoming apparent due to the 2000 ppm Au alloy. Although graphic representation indicates a higher and narrower recovery in ‘C and 1D in the thermal-neutron irradiated Pt—Cu alloys, actual
‘B and ‘DE increases with increasing electron energies [10]. The present results, which indicate suppression of all these substages in all the samples due to the
recovery is less than that of the pure metal — see table 1. (Care must, however, be taken when comparing individual samples, since they contain different concen-
[3,11] and electron irradiations [10]. The dependence
Table 1 Stage I recovery values (%) after fast- and thermal-neutron irradiation.
-
Substage
Neutron flux
Pt
Pt—0.06 Cu
P1—0.11 Cu
‘A + lB
Thermal fast
10.2 4.8
10.0 4.6
10.1 4.8
9.7 4.2
Thermal fast
56.6 31.8
55.0 30.7
55.2 30.6
50.1 28.5
+
260
ID + ‘E
Pt—0.20 Au
Volume 88A, number 5
PHYSICS LETTERS
trations of Frenkel defects, an important factor when comparing interstitial—impurity reactions in stage I [11,21].) The suppression of ‘E during thermal-neutron irradiation due to the addition of alloying impurities is also graphically significant, although calculations involving actual recovery during this substage are impeded due to the proximity and overlap of ‘D’ It appears from fig. 2 and table 1 that the addition of Cu has not significantly influenced the difference in recovery between fast- and thermal-neutron irradiations for these substages (IC, ‘D and IE). (The higher Au concen-
tration does, however, influence these substages although the effect is still small.) This can be attributed to the overwhelming number of interstitial—interstitial reactions present, due to the abovementioned localised defect concentrations as compared to the relatively low homogeneous distribution of the impurities.
In conclusion it can be stated that although substage
15 March 1982
References [11 J.A. Horak and T.H. Blewitt, Nucl. Tech. 27(1975)416. 121 K. Isebeck and K.F. Poole, Radiat. Eff. 22 (1974) 15. [3] J.B. Roberto, C.E. Klabunde, J.M. Williams and R.R. Coltman Jr., J. Nucl. Mater. 73 (1978) 97. [4] R.R. Coitman Jr., CE. Klabunde and J.K. Redman, J. NucI. Mater. 69,70(1978)720.
[5J R.S. Averback, R. Benedek and K.L. Merkie, J. Nuci. Mater. 75 (1978) 162. [6] P. Lucasson and A. Lucasson, Radiat. Eff. 39 (1978) 195. [7] MA. Kirk and T.H. Blewitt, Metall. Trans. 9A (1978)
1729. [8] C.A. English, J. NucI. Mater. 96 (1981) 341. [9] J. Morilo, C.H. de Novion and J. Dural, Radiat. Eff. 55
67. K. Sonnenberg, W. Schilling and U. Dedek, [10] (1981) H.J. Dibbert, Radiat. Eff. 15 (1972) 115. [11] C.S.B. Piani and J. Aspeling, Radial Eff. 45 (1980) 127.
recovery during stage I was shown to be strongly depen-
[12] W. Schilling, G. Burger, K. Isebeck and H. Wenzl,
dent on the relation between impurity and defect concentrations for thermal-neutron irradiated dilute Pt alloys [11], the same explanations do not necessarily apply to equivalent defect concentrations following fast-neutron irradiations. This may be attributed to the highly-localised defect concentrations after fastneutron irradiation and will apply in particular to the above cases of low-induced defect concentrations where
Vacancies and interstitials in metals, (North-Holland, p. of 255. [13] Amsterdam, Fundamental1970) aspects radiation damage in metals (Gatlinburg, CONF-751006 USERDA, 1975). [14] Properties ofatomic defects in metals, J. Nuci. Mater. 69, 70 (1978). [15] K. Isebeck, Radiat. Eff. 14 (1971) 143. [16] R.R. Coitman, C.E. Klabunde and J.K. Redman, Phys. Rev. 156 (1967) 715. [17] C.S.B. Piani, Atomic energy board report, Per 39
the cascades are still well separated.
(pretoria, 1978). [18] P. Lucasson, in: Fundamental aspects of radiation damage in metals (Gatlinberg, CONF-75 1006 USERDA,
We wish to express our thanks to A. Sliep, J. Louw and D. du Plessis for their technical assistance.
1975). [19] R.C. Birtcher and T.H. Blewitt, J. Nucl. Mater. 98 (1981) 63.
[20] W. Schilling, K. Sonnenberg and H.J. Dibbert, Radial. Eff. 16 (1972) 57. [21] C.S.B. Piani and J. Aspeling, to be published.
261