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Savannah River Site L reactor testing

Description: Flow tests were conducted in the Savannah River Site L reactor to evaluate the performance of the primary coolant system under simulated Loss of Coolant Accident (LOCA) conditions. Results were obtained with a prototypic cold fuel charge in the core. Core flows typical of normal and shutdown operation were studied. The tests consisted of measuring hydraulic parameters while lowering tank moderator levels to allow air entrainment from the reactor tank through operating coolant pumps. Data were collected continuously as the flows changed from single-phase to a two-component mixture of water and air. Minimum tank levels equivalent to those resulting from a hypothetical double-ended guillotine break of a coolant pipe were simulated. System pressures, water levels, densities, flows, and pump parameters were measured by over 200 instruments especially designed or adapted for in-reactor use. Special in-reactor video cameras provided visual observation of flow regimes and confirmed water levels in the reactor tank, plenum, and pump suction and plenum inlet pipes. The tests provided a unique opportunity to study full-scale pump degradation and two-component flow distributions in the reactor under ambient temperature conditions. Results showed the different pump operating regimes and points of transition and some of the other key features of the reactor response system during a severe loss of coolant event. 4 refs., 24 figs.
Date: January 1, 1990
Creator: Menna, J.D. & Whitehouse, J.C.
Partner: UNT Libraries Government Documents Department

Buoyancy-driven flow excursions in fuel assemblies

Description: A power limit criterion was developed for a postulated Loss of Pumping Accident (LOPA) in one of the recently shut down heavy water production reactors at the Savannah River Site. These reactors were cooled by recirculating moderator downward through channels in cylindrical fuel tubes. Powers were limited to prevent a flow excursion from occurring in one or more of these parallel channels. During full-power operation, limits prevented a boiling flow excursion from taking place. At low flow rates, during the addition of emergency cooling water, buoyant forces reverse the flow in one of the coolant channels before boiling occurs. As power increases beyond the point of flow reversal, the maximum wall temperature approaches the fluid saturation temperature, and a thermal excursion occurs. The power limit criterion for low flow rates was the onset of flow reversal. To determine conditions for flow reversal, tests were performed in a mock-up of a fuel assembly that contained two electrically heated concentric tubes surrounded by three flow channels. These tests were modeled using a finite difference thermal-hydraulic code. According to code calculations, flow reversed in the outer flow channel before the maximum wall temperature reached the local fluid saturation temperature. Thermal excursions occurred when the maximum wall temperature approximately equaled the saturation temperature. For a postulated LOPA, the flow reversal criterion for emergency cooling water addition was more limiting than the boiling excursion criterion for full power operation. This criterion limited powers to 37% of historical levels.
Date: December 31, 1995
Creator: Laurinat, J.E.; Paul, P.K. & Menna, J.D.
Partner: UNT Libraries Government Documents Department

Buoyancy-driven flow excursions in fuel assemblies. Revision 1

Description: A power limit criterion was developed for a postulated Loss of Pumping Accident (LOPA) in one of the recently shut down heavy water production reactors at the Savannah River Site. These reactors were cooled by recirculating heavy water moderator downward through channels in cylindrical fuel tubes. Powers were limited to safeguard against a flow excursion in one or more of these parallel channels. During full-power operation, limits safeguarded against a boiling flow excursion. At low flow rates, during the addition of emergency cooling water, buoyant forces reverse the flow in one of the coolant channels before boiling occurs. As power increases beyond the point of flow reversal, the maximum wall temperature approaches the fluid saturation temperature, and a thermal excursion occurs. The power limit criterion for low flow rates was the onset of flow reversal. To determine conditions for flow reversal, tests were performed in a mock-up of a fuel assembly that contained two electrically heated concentric tubes surrounded by three flow channels. These tests were modeled using a finite difference thermal-hydraulic code. According to code calculations, flow reversed in the outer flow channel before the maximum wall temperature reached the local fluid saturation temperature. Thermal excursions occurred when the maximum wall temperature approximately equaled the saturation temperature. For a postulated LOPA, the flow reversal criterion for emergency cooling water addition was more limiting than the boiling excursion criterion for full power operation. This criterion limited powers to 37% of the limiting power for previous long-term reactor operations.
Date: July 1, 1995
Creator: Laurinat, J.E.; Paul, P.K. & Menna, J.D.
Partner: UNT Libraries Government Documents Department