Thermal response of the multiplier of an accelerator driven system to beam interruptions. Page: 2 of 10
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channel is 164 K, and the average coolant
temperature rise is 139 K.Tube Sh et
Cover Gas
Outl~t Plenum =4L
9 j
- - H
-- -- - Pump
Inlet PlenumSteam
GeneratorFig. 1, Schematic of Multiplier Coolant Flow
The third multiplier concept is the
Subcritical Multiplier (SCM-100) used with the
Accelerator Driven Test Facility (ADTF). This
concept is based on the EBR-II reactor, scaled up
to 100 MWt from 62.5 MWt. Thus, this concept
is significantly smaller than the first two. The
third multiplier concept also uses metal fuel and
sodium coolant. In addition, in the third concept
there is a cover on the outlet plenum and a pipe
from the outlet plenum to the IHX. In this
concept the average coolant temperature rise
across the core is 100 K.
III. ANALYSIS METHODS
In order to analyze the consequences of a
beam loss and return to power transient, the
SASSYS-1 LMR systems analysis code3 was
used to obtain the time dependent temperatures
of the coolant in contact with various structural
components. Multi-node structural temperature
calculations were then used to obtain minimum,
maximum and average structure temperatures.
The difference between the minimum or
maximum temperature and the average structure
temperature was multiplied by the thermal
expansion coefficient to obtain the strainm
magnitude. The peak strain magnitude was used
with the American Society of Engineers (ASME)
Boiler and Pressure Vessel Code4 to determine
the allowable number of cycles the structural
component can be subjected to. Beam reliability
data5 for the LANSCE accelerator were used to
obtain the number of beam interruptions per year
of a particular duration. The integral over
interruption duration of the ratio of the
interruptions per year for a particular interruption
duration to the allowable number of cycles of
that duration gave a damage function which
determined the allowable lifetime for the
structural component.
The SASSYS-1 LMR systems analysis
code contains neutron kinetics coupled with a
detailed thermal hydraulics treatment of the core,
the primary and intermediate heat removal loops,
and the steam generators. Both steady-state and
transient calculations are done by the code. The
neutron kinetics treatment contains point
kinetics, with or without an external source.
Also in the code is an optional 3-D time
dependent neutron kinetics capability.
The method used for evaluation of low
cycle fatigue at elevated temperatures is based on
article T-1432 of Appendix T of Subsection NH
of the ASME Boiler and Pressure Vessel Code.
This type of analysis is required when the
temperatures exceed 700 or 800 F. The
difference between the average structure
temperature and the minimum or maximum
temperature is multiplied by the thermal
expansion coefficient to obtain the strain. The
peak strain for a cycle is used to obtain the
allowable number of cycles that the structure can
be subjected to. Figure 2 shows results for 304
stainless steel. Note that an increase of only a
few degrees in peak temperature difference can
lead to a decrease of a factor of two in the
allowable number of cycles.
Evaluation of low cycle fatigue in the
HT-9 steel alloy used for cladding, subassembly
duct walls, and shielding in the subassemblies is
a special problem. Appendix T only includes
data for four materials: 304 stainless steel, 316
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Dunn, F. E. Thermal response of the multiplier of an accelerator driven system to beam interruptions., article, May 15, 2002; Illinois. (https://digital.library.unt.edu/ark:/67531/metadc742851/m1/2/: accessed April 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.