Core-concrete interactions with overlying water pools. The WETCOR-1 test

Abstract

The WETCOR-1 test of simultaneous interactions of a high-temperature melt with water and a limestone/common-sand concrete is described. The test used a 34.1-kg melt of 76.8 w/o A1203, 16.9 w/o CaO, and 4.0 w/o SiO2 heated by induction using tungsten susceptors. Once quasi-steady attack on concrete by the melt was established, an attempt was made to quench the melt at 1850 K with 295 K water flowing at 57 liters per minute. Net power into the melt at the time of water addition was 0.61 + 0.19 W/cm 3. The test configuration used in the WETCOR-1 test was designed to delay melt freezing to the walls of the test fixture. This was done to test hypotheses concerning the inherent stability of crust formation when hightemperature melts are exposed to water. No instability in crust formation was observed. The flux of heat through the crust to the water pool maintained over the melt in the test was found to be 0.52 + 0.13 MW/n_. Solidified crusts were found to attenuate aerosol emissions during the melt concrete interactions by factors of 1.3 to 3.5. The combination of a solidified crust and a 30-cm deep subcooled water pool was found to attenuate aerosol emissions by factors of 3 to 15.

OECD MCCI Project: Category 4 Integral Test to Validate Severe Accident Codes (Rev. 1, Final Report)

“…In particular, given the measured melt temperature drop adjacent to the wall as well as the known mass of eroded concrete, then a simple energy balance reveals that the energy required to erode the concrete would have been extracted from a melt mass of ~ 340 kg, which amounts to ~ 38 % of the initial melt mass used in the experiment. Another possible explanation 5 for the transient is based on a cement paste liquefaction concept where the siliceous aggregate was only partially melted when the crust disappeared. This relatively cold material was then introduced into the melt pool once the crust failed, causing the temperature decrease.…”

“…This database includes experiments conducted with both low and high temperature simulants, and with prototypic reactor materials. Low temperature simulant experiments have been conducted by Theofanous et al [3] to identify phenomena associated with melt coolability, while high temperature simulant experiments have been conducted at Sandia National Laboratories by Blose et al [4,5] to investigate coolability with concurrent concrete erosion. In terms of reactor material testing, the COTELS [6,7] and MACE [8,9] experiment programs have been carried out to investigate coolability mechanisms under prototypic MCCI conditions.…”

“…Three melt coolability experiments were conducted at Sandia National Laboratories using high temperature simulants with sustained heating and concurrent concrete erosion. These experiments include the SWISS tests [4], conducted with stainless steel melts interacting with limestone/common sand concrete, and the WETCOR test [5] that was conducted with an oxide simulant interacting with Basaltic concrete. These tests also provided valuable data on debris coolability, but complete quench was not obtained in any of these experiments due in part to the formation of crusts that anchored to the test section sidewalls, eventually leading to decoupling of the melt pool from the crust as the core-concrete interaction proceeded downwards.…”

“…Thus, the concept that the ablation transient was localized and involved only a fraction of the overall melt pool seems plausible. Another possible explanation 5 for the transient is based on a cement paste liquefaction concept where the siliceous aggregate was only partially melted when the crust disappeared. This relatively cold material was then introduced into the melt pool once the crust failed, causing the temperature decrease.…”

Source term attenuation by water in the Mark I boiling water reactor drywell

“…Extrapolation of these results to reactor accident conditions is, of course, uncertain. Furthermore, recent tests [51,52] suggest that there can be episodic eruptions of melt into a well-established water pool that might, in extreme cases, result in, at least, localized disruptioJl of the water pool. For these reasons the incremental decontamination of the dryweli by sprays is of interest.…”