Evidence for nuclear emissions during acoustic cavitation,”

Abstract: This paper extends the experimental and numerical results presented previously and addresses the major criticisms raised. In addition, the most recent results are discussed. In acoustic cavitation experiments with chilled (0 8C) deuterated acetone (C 3 D 6 O), the production of tritium and 2.45 MeV neutrons [which are characteristic of deuterium-deuterium (D -D) fusion] was observed during vapour bubble implosions in an acoustic pressure field. Similar experiments with deuterated acetone at room temperature (20 8C) and control experiments with normal acetone (C 3 H 6 O), at both 0 and 20 8C, showed no statistically significant increases in either tritium level or neutron emissions. Numerical simulations of the processes that account for the shock waves generated in the liquid and within the collapsing bubbles supported these experimental observations and showed that high densities and temperatures (510 8 K) may be achieved during bubble cloud implosions, yielding the conditions required for D -D nuclear fusion reactions. The present paper treats the bubble fusion experiments and theoretical results in greater detail than was possible in the previous publications, contains some refinements, addresses some important questions raised by reviewers and critics and discusses possible applications of this interesting phenomenon

Fundamental experimentation and theoretical modeling for prevention of molten aluminum-water steam explosions in casting pits

Explosive interactions between molten aluminum and water are being studied with a focus on fundamentals to determine what causes robust-enough triggers for explosion onset, to determine the extent of protection provided from various coatings and to develop a novel methodology for prevention. The workscope includes experimentation and mathematical modeling of the interactions between molten metals and water at various different coated and uncoated surfaces. Phenomenological issues related to surface wettability, gas generation from coatings, charring of coatings, inertial constraint, melt temperature, water temperature, external shocks are being investigated systematically to gage their relative impact on triggerability of surface-assisted steam explosion. The steam explosion triggering studies (SETS) facility was designed and constructed as a rapid-turnaround, cost-effective, and safe means to address these phenomenological issues and to derive quantitative, practically-fundamental data for situations covering melt masses relocating over submerged surfaces ranging from a few grams to {approximately} 1,000 kg. Initial testing has provided insightful results which are very consistent with empirical field observations taken over the past 40 years. This paper provides the scientific basis of the technical approach for design and operation of the SETS facility, along with key results and insights from tests conducted so far

Computational fluid dynamics tracking of UF{sub 6} reaction products release into a gaseous diffusion plant cell housing

A three-dimensional (3-D) computational fluid dynamics (CFD) model has been developed using CFDS-FLOW3D Version 3.3 to model the transport of aerosol products formed during a release of uranium hexafluoride (UF{sub 6}) into a gaseous diffusion plant (GDP) process building. As part of a facility-wide safety evaluation, a one-dimensional (1-D) analysis of aerosol/vapor transport following such an hypothesized severe accident is being performed. The objective of this study is to supplement the 1-D analysis with more detailed 3-D results. Specifically, the goal is to quantify the distribution of aerosol passing out of the process building during the hypothetical accident. This work demonstrates a useful role for CFD in large 3-D problems, where some experimental data are available for calibrating key parameters and the desired results are global (total time-integrated aerosol flow rates across a few boundary surfaces) as opposed to local velocities, temperatures, or heat transfer coefficients

Characterization of core debris/concrete interactions for the Advanced Neutron Source. ANS Severe Accident Analysis Program

This report provides the results of a recent study conducted to explore the molten core/concrete interaction (MCCI) issue for the Advanced Neutron Source (ANS). The need for such a study arises from the potential threats to reactor system integrity posed by MCCI. These threats include direct attack of the concrete basemat of the containment; generation and release of large quantities of gas that can pressurize the containment; the combustion threat of these gases; and the potential generation, release, and transport of radioactive aerosols to the environment

Analysis of containment performance and radiological consequences under severe accident conditions for the Advanced Neutron Source Reactor at the Oak Ridge National Laboratory

A severe accident study was conducted to evaluate conservatively scoped source terms and radiological consequences to support the Advanced Neutron Source (ANS) Conceptual Safety Analysis Report (CSAR). Three different types of severe accident scenarios were postulated with a view of evaluating conservatively scoped source terms. The first scenario evaluates maximum possible steaming loads and associated radionuclide transport, whereas the next scenario is geared towards evaluating conservative containment loads from releases of radionuclide vapors and aerosols with associated generation of combustible gases. The third scenario follows the prescriptions given by the 10 CFR 100 guidelines. It was included in the CSAR for demonstrating site-suitability characteristics of the ANS. Various containment configurations are considered for the study of thermal-hydraulic and radiological behaviors of the ANS containment. Severe accident mitigative design features such as the use of rupture disks were accounted for. This report describes the postulated severe accident scenarios, methodology for analysis, modeling assumptions, modeling of several severe accident phenomena, and evaluation of the resulting source term and radiological consequences

Source term evaluation for UF{sub 6} release event in feed facility at gaseous diffusion plants

An assessment of UF{sub 6} release accidents was conducted for the feed facility of a gaseous diffusion plant (GDP). Release rates from pig-tail connections were estimated from CYLIND code predictions, whereas, MELCOR was utilized for simulating reactions of UF{sub 6} with moisture and consequent transport of UO{sub 2}F{sub 2} aerosols and HF vapor through the building and to the environment. Two wind speeds were utilized. At the high end (Case 1) a wind speed of {approximately} 1 m/s (200 fpm) was assumed to flow parallel to the building length. At the low end (Case 2) to represent stagnant conditions a corresponding wind speed of 1 cm/s (2 fpm) was utilized. A further conservative assumption was made to specify no closure of crane and train doors at either end of the building. Relaxation of this assumption should provide for additional margins. Results indicated that, for the high (200 fpm) wind speed, close to 66% of the UO{sub 2}F{sub 2} aerosols and 100% of the HF gas get released to the environment over a 10-minute period. However, for the low (2 fpm) wind speed, negligible amount ({approximately} 1% UO{sub 2}F{sub 2}) of aerosols get released even over a 2 hour period

Overcoming Thermal Shock Problems in Liquid Targets

Short pulse accelerator-driven neutron sources such as the Spallation Neutron Source (SNS) employ high-energy proton beam energy deposition in heavy metal (such as mercury) over microsecond time frames. The interaction of the energetic proton beam with the mercury target leads to very high heating rates in the target. Although the resulting temperature rise is relatively small (a few {degree}C ), the rate of temperature rise is enormous ({approximately}10{sup 7} C/s) during the very brief beam pulse ({approximately}0.58 {micro}s). The resulting thermal-shock induced compression of the mercury leads to the production of large amplitude pressure waves in the mercury that interact with the walls of the mercury target and the bulk flow field. Safety-related operational concerns exist in two main areas, viz., (1) possible target enclosure failure from impact of thermal shocks on the wall due to its direct heating from the proton beam and the loads transferred from the mercury compression waves, and (2) impact of the compression-cum-rarefaction wave-induced effects such as cavitation bubble emanation and fluid surging. Preliminary stress evaluations indicate stress levels approaching yielding conditions and beyond in select regions of the target. Also, the induction of cavitation (which could assist in attenuation) can also release gases that may accumulate at undesirable locations and impair heat transfer

An analysis of molten-corium-induced failure of drain pipes in BWR Mark 2 containments

This study has focused on mechanistic simulation and analysis of potential failure modes for inpedestal drywell drain pipes in the Limerick boiling water reactor (BWR) Mark 2 containment. Physical phenomena related to surface tension breakdown, heatup, melting, ablation, crust formation and failure, and core material relocation into drain pipes with simultaneous melting of pipe walls were modeled and analyzed. The results of analysis have been used to assess the possibility of drain pipe failure and the resultant loss of pressure-suppression capability. Estimates have been made for the timing and amount of molten corium released to the wetwell. The study has revealed that significantly different melt progression sequences can result depending upon the failure characteristics of the frozen metallic crust which forms over the drain cover during the initial stages of debris pour. Another important result is that it can take several days for the molten fuel to ablate the frozen metallic debris layer -- if the frozen layer has cooled below 1100 K before fuel attack. 10 refs., 3 figs., 4 tabs