TY - BOOK
T1 - DL-EPR measurements on a sensitised Type 304 stainless steel pipe section
AU - Autio, Juha-Matti
AU - Ehrnsten, Ulla
N1 - Project code: 85618
PY - 2014
Y1 - 2014
N2 - lntergranular stress corrosion cracking has been the most
frequent failure mode in BWR primary piping. Modern, low
carbon stainless steels, improved welding and water
chemistry has reduced the amount of IGSCC drastically.
Simultaneously the need for investigations on
sensitisation has decreased. This could cause a lack of
knowledge transfer which could be harmful should the
problem arise again. The SAFIR 2014 ENVIS project got
permission to use a pipe section from a BWR steam line,
suffering from IGSCC, for measurements on the degree of
sensitisation. The intentions were twofold: to transfer
the knowledge on IGSCC sensitisation measurements from
the main investigator (who performed these measurements
in the ao·s for BWR primary piping) to the younger
generation, and to actually measure the degree of
sensitisation as a function of distance from the weld
fusion line. Both objectives were achieved, and this
report summarises the results. The performed DL-EPR
measurements showed that the SS2333 material (Type 304)
is slightly sensitised. The highest values were measured
at a distance of 6.25 mm from the fusion line. The crack
in the pipe was located still further away from the
fusion line, between 7 and 12 mm. That the highest DL-EPR
value was measured closer to the fusion line than the
location of the crack is understandable, since the crack
was located in a region where the most severe repair had
been performed (based on the appearance of the weld.) The
DL-EPR measurements, again, where measured from a region
without a crack, and with less severe repair welding. The
results show also that intergranular stress corrosion
cracking is the result of the three parameters, stress,
material and environment. In this case, sensitisation has
played a role, but the probably high residual stresses
from the repairs during the assembly welding, was likely
also been decisive. The third factor, the environment, is
involved since the steam environment is oxidising.
AB - lntergranular stress corrosion cracking has been the most
frequent failure mode in BWR primary piping. Modern, low
carbon stainless steels, improved welding and water
chemistry has reduced the amount of IGSCC drastically.
Simultaneously the need for investigations on
sensitisation has decreased. This could cause a lack of
knowledge transfer which could be harmful should the
problem arise again. The SAFIR 2014 ENVIS project got
permission to use a pipe section from a BWR steam line,
suffering from IGSCC, for measurements on the degree of
sensitisation. The intentions were twofold: to transfer
the knowledge on IGSCC sensitisation measurements from
the main investigator (who performed these measurements
in the ao·s for BWR primary piping) to the younger
generation, and to actually measure the degree of
sensitisation as a function of distance from the weld
fusion line. Both objectives were achieved, and this
report summarises the results. The performed DL-EPR
measurements showed that the SS2333 material (Type 304)
is slightly sensitised. The highest values were measured
at a distance of 6.25 mm from the fusion line. The crack
in the pipe was located still further away from the
fusion line, between 7 and 12 mm. That the highest DL-EPR
value was measured closer to the fusion line than the
location of the crack is understandable, since the crack
was located in a region where the most severe repair had
been performed (based on the appearance of the weld.) The
DL-EPR measurements, again, where measured from a region
without a crack, and with less severe repair welding. The
results show also that intergranular stress corrosion
cracking is the result of the three parameters, stress,
material and environment. In this case, sensitisation has
played a role, but the probably high residual stresses
from the repairs during the assembly welding, was likely
also been decisive. The third factor, the environment, is
involved since the steam environment is oxidising.
KW - stainless steel
KW - sensitisation
KW - DL-EPR
M3 - Report
T3 - Helsinki University of Technology: Systems Analysis Laboratory. A: Research Reports
BT - DL-EPR measurements on a sensitised Type 304 stainless steel pipe section
PB - VTT Technical Research Centre of Finland
ER -