Experimental studies on role of scattering centers on wave energy attenuation
In accelerator-driven neutron sources such as the Spallation Neutron Source (SNS) powers in the 2-MW range (time-averaged), the interaction of the energetic proton beam with the mercury target can lead to very high heating rates in the target. Although the resulting temperature rise is relatively small (a few degrees centigrade), 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. Understanding and predicting propagation of pressure pulses in the target are considered critical for establishing the feasibility of constructing and safely operating such devices. Safety-related operational concerns exist in two main areas: (a) 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 (b) impact of the compression-cumrarefaction wave-induced effects such as cavitation bubble emanation and fluid surging. Preliminary stress evaluations indicate stress levels approaching yielding conditions and beyond in selected regions of the target. Also, the induction of cavitation (that could assist in attenuation) can also release gases that may accumulate at undesirable locations and impair heat transfer. A companion paper introduces the concept of scattering centers (SCs) in the fluid to mitigate thermal shock issues. The general approach is based on wave energy attenuation via use of appropriately configured SCs (such as gas-filled low-impedance cylinders/spheres, or gas injection) in the bulk or at liquid-structure interface regions. Benefits of using such approaches are briefly described in the companion paper. The same companion paper also describes a numerical simulation demonstrating attenuation in thermal shock-induced pressure waves that one may expect with introduction of SCs into mercury fluid. This paper documents results of scoping experiments conducted to assess the relative role and extent of SCs on wave energy attenuation. This scoping study had the goal to assess and confirm the relative roles of (a) low-impedance SCs distributed in mercury and water and (b) large-impedance SCs distributed in a relatively low impedance liquid.
- Research Organization:
- Oak Ridge National Lab., TN (US)
- OSTI ID:
- 20086962
- Journal Information:
- Transactions of the American Nuclear Society, Journal Name: Transactions of the American Nuclear Society Vol. 82; ISSN 0003-018X; ISSN TANSAO
- Country of Publication:
- United States
- Language:
- English
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Experimental Studies on Role of Scattering Centers on Wave Energy Attenuation
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