Abstract
Two baffle bolts, one from a Finnish VVER and one from a
French PWR, were examined by using analytical
transmission electron microscopy (TEM). The examined
VVER bolt was removed from the plant due to indications
found in non-destructive examinations (NDE). During the
removal of the bolt, it was found that the bolt washer
had been inappropriately spot welded to the shielding
plate during assembly. Destructive investigations showed
that the VVER bolt had two large intergranular cracks,
and the TEM samples were prepared from the material
adjacent to those cracks. The PWR bolt had not failed,
although cracks in similar bolts had been found
previously. The VVER bolt was made of solution annealed
titanium stabilized 0X18H10T (corresponding to Type AISI
321) and had accumulated a maximum fluence of about 2.9
dpa. The fluence for the cold-worked AISI 316 PWR bolt
was estimated to be about 15 dpa. Both the examined
bolts showed a clear radiation induced segregation of
alloying elements at the grain boundaries (GB-RIS),
presence of dislocation loops, formation of precipitates,
and linear deformation microstructures. Additionally,
voids were found from the PWR bolt and a high density of
dislocations in the VVER bolt. Finite element modeling
(FEM) was performed for the VVER bolt to examine the
stress state of this particular bolt. Most importantly,
the results indicate that it is not possible to set a
limit for IASCC based solely on the fluence as the stress
state of the bolt and gradients in local chemistry also
play a critical role.
| Original language | English |
|---|---|
| Title of host publication | Proceeding of the 16th International Conference on Environmental Degradation of Materials in Nuclear power Systems |
| Subtitle of host publication | Water Reactors 2013 |
| Publisher | National Association of Corrosion Engineers (NACE) |
| Pages | 994-1007 |
| Volume | 1 |
| ISBN (Print) | 978-1-5108-1923-8 |
| Publication status | Published - 2013 |
| MoE publication type | A4 Article in a conference publication |
| Event | 16th International Conference on Environmental Degradation of Materials in Nuclear power Systems - Water Reactors - Asheville, North Caroline, United States Duration: 11 Aug 2013 → 15 Aug 2013 |
Conference
| Conference | 16th International Conference on Environmental Degradation of Materials in Nuclear power Systems - Water Reactors |
|---|---|
| Country/Territory | United States |
| City | Asheville, North Caroline |
| Period | 11/08/13 → 15/08/13 |
Keywords
- baffle bolts
- IASCC
- transmission electron microscopy
- finite element modeling