7 research outputs found
Perturbations of Noise: The origins of Isothermal Flows
We make a detailed analysis of both phenomenological and analytic background
for the "Brownian recoil principle" hypothesis (Phys. Rev. A 46, (1992), 4634).
A corresponding theory of the isothermal Brownian motion of particle ensembles
(Smoluchowski diffusion process approximation), gives account of the
environmental recoil effects due to locally induced tiny heat flows. By means
of local expectation values we elevate the individually negligible phenomena to
a non-negligible (accumulated) recoil effect on the ensemble average. The main
technical input is a consequent exploitation of the Hamilton-Jacobi equation as
a natural substitute for the local momentum conservation law. Together with the
continuity equation (alternatively, Fokker-Planck), it forms a closed system of
partial differential equations which uniquely determines an associated
Markovian diffusion process. The third Newton law in the mean is utilised to
generate diffusion-type processes which are either anomalous (enhanced), or
generically non-dispersive.Comment: Latex fil
Modular Pebble Bed Reactor
This project is developing a fundamental conceptual design for a gas-cooled, modular,
pebble bed reactor. Key technology areas associated with this design are being
investigated which intend to address issues concerning fuel performance, safety, core
neutronics and proliferation resistance, economics and waste disposal. Research has been
initiated in the following areas:
• Improved fuel particle performance
• Reactor physics
• Economics
• Proliferation resistance
• Power conversion system modeling
• Safety analysis
• Regulatory and licensing strategy
Recent accomplishments include:
• Developed four conceptual models for fuel particle failures that are currently being evaluated
by a series of ABAQUS analyses. Analytical fits to the results are being performed over a
range of important parameters using statistical/factorial tools. The fits will be used in a
Monte Carlo fuel performance code, which is under development.
• A fracture mechanics approach has been used to develop a failure probability model for the
fuel particle, which has resulted in significant improvement over earlier models.
• Investigation of fuel particle physio-chemical behavior has been initiated which includes the
development of a fission gas release model, particle temperature distributions, internal
particle pressure, migration of fission products, and chemical attack of fuel particle layers.
• A balance of plant, steady-state thermal hydraulics model has been developed to represent
all major components of a MPBR. Component models are being refined to accurately reflect
transient performance.
• A comparison between air and helium for use in the energy-conversion cycle of the MPBR
has been completed and formed the basis of a master’s degree thesis.
• Safety issues associated with air ingress are being evaluated.
• Post shutdown, reactor heat removal characteristics are being evaluated by the Heating-7
code.
• PEBBED, a fast deterministic neutronic code package suitable for numerous repetitive
calculations has been developed. Use of the code has focused on scoping studies for
MPBR design features and proliferation issues. Publication of an archival journal article
covering this work is being prepared.
• Detailed gas reactor physics calculations have also been performed with the MCNP and
VSOP codes. Furthermore, studies on the proliferation resistance of the MPBR fuel cycle
has been initiated using these code
• Issues identified during the MPBR research has resulted in a NERI proposal dealing with
turbo-machinery design being approved for funding beginning in FY01. Two other NERI
proposals, dealing with the development of a burnup “meter” and modularization techniques,
were also funded in which the MIT team will be a participant.
• A South African MPBR fuel testing proposal is pending ($7.0M over nine years)