Page 419 - Fundamentals of Magnetic Thermonuclear Reactor Design

Structural and Functional Materials Chapter | 13 397

TABLE 13.3 Estimates of Copper Radiation Damageability in the MFR and
Fission Reactor Environments [3]

Radiation Transmutation intensity
−6
damageability (10 particles/dpa)
Object (dpa) H He Fe Co Ni Zn
MFR first ∼15 40 7 0.02 7 190 90
wall
Fast neutron ∼65 7 0.1 — 0.1 51 46
reactor

of fusion neutrons, as shown in Table 13.3. The data in the table are normalised
.
.
−2
to 1 MWyearm of neutron load. A displacement energy is taken to be 30 eV
for the radiation damageability calculation purposes. The main effect is the
impact of transmutants on the thermal conductivity of a copper alloy. This effect
is especially pronounced in copper alloys accumulating nickel and zinc, the
dominant transmutation products.
Transmutation processes are much more intensive in fusion reactors com-
pared with fast neutron fission reactors. Copper irradiation by neutrons with a
mixed energy spectrum of fission reactors gives a different picture: the rate of
−3
nickel and zinc generation due to thermal neutron resonance grows to ∼2·10
−3
at.% and 1·10 at % per 1 dpa, respectively, while the iron and cobalt transmu-
tations rates remain almost unchanged.
The distinct sensitivity of transmutation processes to the energy spectrum of
neutron fluxes is one more reason to be critical and cautious about the results of
mockup experiments on fission reactors.
The rates of transmutation product accumulation in pure copper and high-
strength copper alloys are very close. One exception is the Cu–Ni–Be alloy, in
−4
which helium accumulation rate is very high: by 7·10 at.% per 1 dpa in the
−4
MFR and by 5 × 10 at.% per 1 dpa in the fission reactor. It is the impact of
nuclear reaction on Be with threshold energy, E > 2 MeV.

13.5.3 Recovery of Properties of Irradiated Copper Alloys
The effectiveness and technological prospects of annealing of radiation-induced
defects in copper alloys were studied as part of the ITER project materials sci-
ence support. Annealing impact on the plasticity and electrical conductivity of
the Cu–Cr–Zr IG and GlidCopAl 25 IG alloys and their HIP joining using the
316L(N) grade stainless steel was analysed. Some experimental results are sum-
marised next.