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Description / Abstract:
Part I - Review of Current Operating Conditions
Allowable Stresses in ASME Section III Subsection NH and Overview
of the Availability of the Original and Augmented Databases Needed
to Establish So, St, and Sr
The current operating condition allowable stresses provided in
ASME Section III, Subsection NH were reviewed for consistency with
the criteria used to establish the stress allowables and with the
allowable stresses provided in ASME Section II, Part D. It was
found that the So values in ASME IIINH were consistent with the S
values in ASME II-D for the five materials of interest. However, it
was found that 0.80Sr was less than So for some
temperatures for four of the materials. Only values for alloy 800H
appeared to be consistent with the criteria on which So values are
established. With the intent of undertaking a more detailed
evaluation of issues related to the allowable stresses in ASME
III-NH, the availabilities of databases for the five materials were
reviewed and augmented databases were assembled.
Part II and Part III - Assessment of the Databases
Leading to the Establishment of Allowable Stresses in ASME Section
III Subsection NH and Recommended Action for the Correction of
Currently Listed Values for So, St and
Sr
Based on a review of the current operating condition allowable
stresses provided in ASME BPV Section III, Subsection NH and the
finding of inconsistencies between the S values in ASME BPV Section
II, Part D and the So values in ASME BPV III-NH for the five
materials included in ASME BPV III-NH, expanded databases for
stress-rupture, tertiary creep and time to 1% strain were assembled
for use estimating and possibly revising the stress allowables in
ASME BPV III-NH. A preliminary evaluation showed that, in spite of
the substantially larger databases, the stress allowables St and Sr
for some materials were within 5% of the existing values. It was
judged that the existing values in ASME BPV III-NH for alloy 800H
and 9Cr-1Mo-V steel were conservative and adequate for use in the
temperature range of interest to the Generation IV reactor design.
A number of issues were identified in using the databases to
estimate the stresses based on tertiary creep and time to 1% strain
criteria. Some actions were suggested to resolve the issues. The
greatly expanded times for the databases were expected to help in
extending allowable stresses to at least 500,000 hours.