Engineering topics

Basu, S

Publications and source records attributed to Basu, S.

30 records · Page 2

DOE OSTI2011

OECD MCCI project long-term 2-D molten core concrete interaction test design report, Rev. 0. September 30, 2002.

The Melt Attack and Coolability Experiments (MACE) program at Argonne National Laboratory addressed the issue of the ability of water to cool and thermally stabilize a molten core-concrete interaction when the reactants are flooded from above. These tests provided data regarding the nature of corium interactions with concrete, the heat transfer rates from the melt to the overlying water pool, and the role of noncondensable gases in the mixing processes that contribute to melt quenching. As a follow-on program to MACE, The Melt Coolability and Concrete Interaction Experiments (MCCI) project is conducting reactor material experiments and associated analysis to achieve the following two technical objectives: (1) resolve the ex-vessel debris coolability issue through a program that focuses on providing both confirmatory evidence and test data for the coolability mechanisms identified in MACE integral effects tests, and (2) address remaining uncertainties related to long-term two-dimensional molten core-concrete interactions under both wet and dry cavity conditions. Achievement of these two objectives will demonstrate the efficacy of severe accident management guidelines for existing plants, and provide the technical basis for better containment designs for future plants. In terms of the first program objective, the Small-Scale Water Ingression and Crust Strength (SSWICS) test series has been initiated to provide fundamental information on the ability of water to ingress into cracks and fissures that form in the debris during quench, thereby augmenting the otherwise conduction-limited heat transfer process. A test plan for Melt Eruption Separate Effects Tests (MESET) has also been developed to provide information on the extent of crust growth and melt eruptions as a function of gas sparging rate under well-controlled experiment conditions. In terms of the second program objective, the project Management Board (MB) has approved startup activities required to carry out experiments to address remaining uncertainties related to long-term two-dimensional molten core-concrete interaction. In particular, for both wet and dry cavity conditions, there is uncertainty insofar as evaluating the lateral vs. axial power split during a core-concrete interaction due to a lack of experiment data. As a result, there are differences in the 2-D cavity erosion predicted by codes such as MELCOR, WECHSL, and COSACO. The first step towards generating this data is to produce a test plan for review by the Project Review Group (PRG). The purpose of this document is to provide this plan.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2011

OECD MMCI 2-D Core Concrete Interaction (CCI) tests : CCCI-1 test data report-thermalhydraulic results. Rev 0 January 31, 2004.

The Melt Attack and Coolability Experiments (MACE) program addressed the issue of the ability of water to cool and thermally stabilize a molten core-concrete interaction when the reactants are flooded from above. These tests provided data regarding the nature of corium interactions with concrete, the heat transfer rates from the melt to the overlying water pool, and the role of noncondensable gases in the mixing processes that contribute to melt quenching. As a follow-on program to MACE, The Melt Coolability and Concrete Interaction Experiments (MCCI) project is conducting reactor material experiments and associated analysis to achieve the following objectives: (1) resolve the ex-vessel debris coolability issue through a program that focuses on providing both confirmatory evidence and test data for the coolability mechanisms identified in MACE integral effects tests, and (2) address remaining uncertainties related to long-term two-dimensional molten coreconcrete interactions under both wet and dry cavity conditions. Achievement of these two program objectives will demonstrate the efficacy of severe accident management guidelines for existing plants, and provide the technical basis for better containment designs for future plants. In terms of satisfying these objectives, the Management Board (MB) approved the conduct of two long-term 2-D Core-Concrete Interaction (CCI) experiments designed to provide information in several areas, including: (i) lateral vs. axial power split during dry core-concrete interaction, (ii) integral debris coolability data following late phase flooding, and (iii) data regarding the nature and extent of the cooling transient following breach of the crust formed at the melt-water interface. This data report provides thermal hydraulic test results from the CCI-1 experiment, which was conducted on December 19, 2003. Test specifications for CCI-1 are provided in Table 1-1. This experiment investigated the interaction of a fully oxidized 400 kg PWR core melt, initially containing 8 wt % calcined siliceous concrete, with a specially designed two-dimensional siliceous concrete test section with an initial cross-sectional area of 50 cm x 50 cm. The report begins by providing a summary description of the CCI-1 test apparatus and operating procedures, followed by presentation of the thermal-hydraulic results. The posttest debris examination results will be provided in a subsequent publication. Observations drawn within this report regarding the overall cavity erosion behavior may be subject to revision once the posttest examinations are completed, since these examinations will fully reveal the final cavity shape.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2011

OECD 2-D Core Concrete Interaction (CCI) tests : CCI-2 test plan, Rev. 0 January 31, 2004.

The Melt Attack and Coolability Experiments (MACE) program addressed the issue of the ability of water to cool and thermally stabilize a molten core-concrete interaction when the reactants are flooded from above. These tests provided data regarding the nature of corium interactions with concrete, the heat transfer rates from the melt to the overlying water pool, and the role of noncondensable gases in the mixing processes that contribute to melt quenching. As a follow-on program to MACE, The Melt Coolability and Concrete Interaction Experiments (MCCI) project is conducting reactor material experiments and associated analysis to achieve the following objectives: (1) resolve the ex-vessel debris coolability issue through a program that focuses on providing both confirmatory evidence and test data for the coolability mechanisms identified in MACE integral effects tests, and (2) address remaining uncertainties related to long-term two-dimensional molten core-concrete interactions under both wet and dry cavity conditions. Achievement of these two program objectives will demonstrate the efficacy of severe accident management guidelines for existing plants, and provide the technical basis for better containment designs for future plants. In terms of satisfying these objectives, the Management Board (MB) approved the conduct of two long-term 2-D Core-Concrete Interaction (CCI) experiments designed to provide information in several areas, including: (i) lateral vs. axial power split during dry core-concrete interaction, (ii) integral debris coolability data following late phase flooding, and (iii) data regarding the nature and extent of the cooling transient following breach of the crust formed at the melt-water interface. The first of these two tests, CCI-1, was conducted on December 19, 2003. This test investigated the interaction of a fully oxidized 400 kg PWR core melt, initially containing 8 wt % calcined siliceous concrete, with a specially designed two-dimensional siliceous concrete test section with an initial cross-sectional area of 50 cm x 50 cm. The second of these two planned tests, CCI-2, will be conducted with a nearly identical test facility and experiment boundary conditions, but with a Limestone/Common Sand (LCS) concrete test section to investigate the effect of concrete type on the two-dimensional core-concrete interaction and debris cooling behavior. The objective of this report is to provide the overall test plan for CCI-2 to enable pretest calculations to be carried out. The report begins by providing a summary description of the CCI-2 test apparatus, followed by a description of the planned test operating procedure. Overall specifications for CCI-2 are provided in Table 1-1.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2011

OECD MCCI 2-D Core Concrete Interaction (CCI) tests : CCI-2 test data report-thermalhydraulic results, Rev. 0 October 15, 2004.

The Melt Attack and Coolability Experiments (MACE) program addressed the issue of the ability of water to cool and thermally stabilize a molten core-concrete interaction when the reactants are flooded from above. These tests provided data regarding the nature of corium interactions with concrete, the heat transfer rates from the melt to the overlying water pool, and the role of noncondensable gases in the mixing processes that contribute to melt quenching. As a follow-on program to MACE, The Melt Coolability and Concrete Interaction Experiments (MCCI) project is conducting reactor material experiments and associated analysis to achieve the following objectives: (1) resolve the ex-vessel debris coolability issue through a program that focuses on providing both confirmatory evidence and test data for the coolability mechanisms identified in MACE integral effects tests, and (2) address remaining uncertainties related to long-term two-dimensional molten core-concrete interactions under both wet and dry cavity conditions. Achievement of these two program objectives will demonstrate the efficacy of severe accident management guidelines for existing plants, and provide the technical basis for better containment designs for future plants. In terms of satisfying these objectives, the Management Board (MB) approved the conduct of two long-term 2-D Core-Concrete Interaction (CCI) experiments designed to provide information in several areas, including: (i) lateral vs. axial power split during dry core-concrete interaction, (ii) integral debris coolability data following late phase flooding, and (iii) data regarding the nature and extent of the cooling transient following breach of the crust formed at the melt-water interface. This data report provides thermal hydraulic test results from the CCI-2 experiment, which was conducted on August 24, 2004. Test specifications for CCI-2 are provided in Table 1-1. This experiment investigated the interaction of a fully oxidized 400 kg PWR core melt, initially containing 8 wt % Limestone/Common Sand (LCS) concrete, with a specially designed two-dimensional LCS concrete test section with an initial cross-sectional area of 50 cm x 50 cm. The report begins by providing a summary description of the CCI-2 test apparatus and operating procedures, followed by presentation of the thermal-hydraulic results. Detailed posttest debris examination results will be provided in a subsequent publication. Observations drawn within this report regarding the overall cavity erosion behavior may be subject to revision once the posttest examinations are completed, since these examinations will fully reveal the final cavity shape.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2011

OECD/MCCI 2-D Core Concrete Interaction (CCI) tests : final report February 28, 2006.

Although extensive research has been conducted over the last several years in the areas of Core-Concrete Interaction (CCI) and debris coolability, two important issues warrant further investigation. The first issue concerns the effectiveness of water in terminating a CCI by flooding the interacting masses from above, thereby quenching the molten core debris and rendering it permanently coolable. This safety issue was investigated in the EPRI-sponsored Melt Attack and Coolability Experiments (MACE) program. The approach was to conduct large scale, integral-type reactor materials experiments with core melt masses ranging up to two metric tons. These experiments provided unique, and for the most part repeatable, indications of heat transfer mechanism(s) that could provide long term debris cooling. However, the results did not demonstrate definitively that a melt would always be completely quenched. This was due to the fact that the crust anchored to the test section sidewalls in every test, which led to melt/crust separation, even at the largest test section lateral span of 1.20 m. This decoupling is not expected for a typical reactor cavity, which has a span of 5-6 m. Even though the crust may mechanically bond to the reactor cavity walls, the weight of the coolant and the crust itself is expected to periodically fracture the crust and restore contact with the melt. Although crust fracturing does not ensure that coolability will be achieved, it nonetheless provides a pathway for water to recontact the underlying melt, thereby allowing other debris cooling mechanisms to proceed. A related task of the current program, which is not addressed in this particular report, is to measure crust strength to check the hypothesis that a corium crust would not be strong enough to sustain melt/crust separation in a plant accident. The second important issue concerns long-term, two-dimensional concrete ablation by a prototypic core oxide melt. As discussed by Foit the existing reactor material database for dry cavity conditions is solely one-dimensional. Although the MACE Scoping Test was carried out with a two-dimensional concrete cavity, the interaction was flooded soon after ablation was initiated to investigate debris coolability. Moreover, due to the scoping nature of this test, the apparatus was minimally instrumented and therefore the results are of limited value from the code validation viewpoint. Aside from the MACE program, the COTELS test series also investigated 2-D CCI under flooded cavity conditions. However, the input power density for these tests was quite high relative to the prototypic case. Finally, the BETA test series provided valuable data on 2-D core concrete interaction under dry cavity conditions, but these tests focused on investigating the interaction of the metallic (steel) phase with concrete. Due to these limitations, there is significant uncertainty in the partition of energy dissipated for the ablation of concrete in the lateral and axial directions under dry cavity conditions for the case of a core oxide melt. Accurate knowledge of this 'power split' is important in the evaluation of the consequences of an ex-vessel severe accident; e.g., lateral erosion can undermine containment structures, while axial erosion can penetrate the basemat, leading to ground contamination and/or possible containment bypass. As a result of this uncertainty, there are still substantial differences among computer codes in the prediction of 2-D cavity erosion behavior under both wet and dry cavity conditions. In light of the above issues, the OECD-sponsored Melt Coolability and Concrete Interaction (MCCI) program was initiated at Argonne National Laboratory. The project conducted reactor materials experiments and associated analysis to achieve the following technical objectives: (1) resolve the ex-vessel debris coolability issue through a program that focused on providing both confirmatory evidence and test data for the coolability mechanisms identified in MACE integral effects tests, and (2) address remaining uncertainties related to long-term 2-D core-concrete interactions under both wet and dry cavity conditions. Data from the various tests conducted as part of the program are being used to develop and validate models and codes that are used to extrapolate the experimental findings to plant conditions. Achievement of these technical objectives will demonstrate the efficacy of severe accident management guidelines for existing plants, and provide the technical basis for better containment designs of future plants. The project completed three large scale CCI experiments to address the second technical objective defined above.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2011

OECD MCCI project 2-D Core Concrete Interaction (CCI) tests : CCI-3 test data report-thermalhydraulic results. Rev. 0 October 15, 2005.

The Melt Attack and Coolability Experiments (MACE) program addressed the issue of the ability of water to cool and thermally stabilize a molten core-concrete interaction when the reactants are flooded from above. These tests provided data regarding the nature of corium interactions with concrete, the heat transfer rates from the melt to the overlying water pool, and the role of noncondensable gases in the mixing processes that contribute to melt quenching. As a follow-on program to MACE, The Melt Coolability and Concrete Interaction Experiments (MCCI) project is conducting reactor material experiments and associated analysis to achieve the following objectives: (1) resolve the ex-vessel debris coolability issue through a program that focuses on providing both confirmatory evidence and test data for the coolability mechanisms identified in MACE integral effects tests, and (2) address remaining uncertainties related to long-term two-dimensional molten core-concrete interactions under both wet and dry cavity conditions. Achievement of these two program objectives will demonstrate the efficacy of severe accident management guidelines for existing plants, and provide the technical basis for better containment designs for future plants. In terms of satisfying these objectives, the Management Board (MB) approved the conduct of a third long-term 2-D Core-Concrete Interaction (CCI) experiment designed to provide information in several areas, including: (i) lateral vs. axial power split during dry core-concrete interaction, (ii) integral debris coolability data following late phase flooding, and (iii) data regarding the nature and extent of the cooling transient following breach of the crust formed at the melt-water interface. This data report provides thermal hydraulic test results from the CCI-3 experiment, which was conducted on September 22, 2005. Test specifications for CCI-3 are provided in Table 1-1. This experiment investigated the interaction of a fully oxidized 375 kg PWR core melt, initially containing 15 wt% siliceous concrete, with a specially designed two-dimensional siliceous concrete test section with an initial cross-sectional area of 50 cm x 50 cm. The sand and aggregate constituents for this particular siliceous concrete were provided by CEA as an in-kind contribution to the program. The report begins by providing a summary description of the CCI-3 test apparatus and operating procedures, followed by presentation of the thermal-hydraulic results. Detailed posttest debris examination results will be provided in a subsequent publication. Observations drawn within this report regarding the overall cavity erosion behavior may be subject to revision once the posttest examinations are completed, since these examinations will fully reveal the final cavity shape.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2011

OECD MCCI project Melt Eruption Test (MET) design report, Rev. 2. April 15, 2003.

The Melt Attack and Coolability Experiments (MACE) program at Argonne National Laboratory addressed the issue of the ability of water to cool and thermally stabilize a molten core-concrete interaction when the reactants are flooded from above. These tests provided data regarding the nature of corium interactions with concrete, the heat transfer rates from the melt to the overlying water pool, and the role of noncondensable gases in the mixing processes that contribute to melt quenching. The Melt Coolability and Concrete Interaction (MCCI) program is pursuing separate effect tests to examine the viability of the melt coolability mechanisms identified as part of the MACE program. These mechanisms include bulk cooling, water ingression, volcanic eruptions, and crust breach. At the second PRG meeting held at ANL on 22-23 October 2002, a preliminary design1 for a separate effects test to investigate the melt eruption cooling mechanism was presented for PRG review. At this meeting, NUPEC made several recommendations on the experiment approach aimed at optimizing the chances of achieving a floating crust boundary condition in this test. The principal recommendation was to incorporate a mortar sidewall liner into the test design, since data from the COTELS experiment program indicates that corium does not form a strong mechanical bond with this material. Other recommendations included: (i) reduction of the electrode elevation to well below the melt upper surface elevation (since the crust may bond to these solid surfaces), and (ii) favorably taper the mortar liner to facilitate crust detachment and relocation during the experiment. Finally, as a precursor to implementing these modifications, the PRG recommended the development of a design for a small-scale scoping test intended to verify the ability of the mortar liner to preclude formation of an anchored bridge crust under core-concrete interaction conditions. This revised Melt Eruption Test (MET) plan is intended to satisfy these PRG recommendations. Specifically, the revised plan focuses on providing data on the extent of crust growth and melt eruptions as a function of gas sparging rate under well-controlled experiment conditions, including a floating crust boundary condition. The overall objective of MET is to determine to what extent core debris is rendered coolable by eruptive-type processes that breach the crust that rests upon the melt. The specific objectives of this test are as follows: (1) Evaluate the augmentation in surface heat flux during periods of melt eruption; (2) Evaluate the melt entrainment coefficient from the heat flux and gas flow rate data for input into models that calculate ex-vessel debris coolability; (3) Characterize the morphology and coolability of debris resulting from eruptive processes that transport melt into overlying water; and (4) Discriminate between periods when eruptions take the form of particle ejections into overlying water, leading to a porous particle bed, and single-phase extrusions, which lead to volcano-type structures.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2011

OECD MCCI project enhancing instrumentation for reactor materials experiments, Rev. 0 September 3, 2002.

Reactor safety experiments for studying the reactions of a molten core (corium) with water and/or concrete involve materials at extremely high temperature. Such high temperature severely restricts the types of sensors that can be employed to measure characteristics of the corium itself. Yet there is great interest in improving instrumentation so that the state of the melt can be established with more precision. In particular, it would be beneficial to increase both the upper range limit and accuracy of temperature measurements. The poor durability of thermocouples at high temperature is also an important issue. For experiments involving a water-quenched melt, direct measurements of the growth rate of the crust separating the melt and water would be of great interest. This is a key element in determining the nature of heat transfer between the melt and coolant. Despite its importance, no one has been able to directly measure the crust thickness during such tests. This paper considers three specialized sensors that could be introduced to enhance melt characterization: (1) A commercially fabricated, single point infrared temperature measurement with the footprint of a thermowell. A lens assembly and fiber optic cable linked to a receiver and amplifier measures the temperature at the base of a tungsten thermowell. The upper range limit is 3000 C and accuracy is {+-}0.25% of the reading. (2) In-house development of an ultrasonic temperature sensor that would provide multipoint measurements at temperatures up to {approx}3000 C. The sensors are constructed from tungsten rods and have a high temperature durability that is superior to that of thermocouples. (3) In-house development of an ultrasonic probe to measure the growth rate of the corium crust. This ultrasonic sensor would include a tungsten waveguide that transmits ultrasonic pulses up through the corium melt towards the crust and detects reflections from the melt/crust interface. A measurement of the echo time delay would provide the location of the interface. These three sensors would provide a considerable upgrade of the instrumentation used in our reactor materials tests. The infracouple is a commercial product that could provide an immediate improvement in temperature measurements. The sensor could also serve to corroborate thermocouple data by providing a measurement based upon a different physical principle. The ultrasonic temperature sensor would involve a greater investment and longer time frame than the infracouple, but offers all the advantages of the infracouple along with miniaturization and the ability to measure at multiple locations. In addition, the UTS is the platform from which we would begin development of the crust detector. Of the three sensors, the crust detector requires the most effort and entails the greatest uncertainty. However, a real-time crust thickness measurement has never before been made and such data would be unique and of great benefit to reactor materials experiments.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2011

OECD MCCI project final report, February 28, 2006.

Although extensive research has been conducted over the last several years in the areas of Core-Concrete Interaction (CCI) and debris coolability, two important issues warrant further investigation. The first issue concerns the effectiveness of water in terminating a CCI by flooding the interacting masses from above, thereby quenching the molten core debris and rendering it permanently coolable. This safety issue was investigated in the Melt Attack and Coolability Experiments (MACE) program. The approach was to conduct large scale, integral-type reactor materials experiments with core melt masses ranging up to two metric tons. These experiments provided unique, and for the most part repeatable, indications of heat transfer mechanism(s) that could provide long term debris cooling. However, the results did not demonstrate definitively that a melt would always be completely quenched. This was due to the fact that the crust anchored to the test section sidewalls in every test, which led to melt/crust separation, even at the largest test section lateral span of 1.20 m. This decoupling is not expected for a typical reactor cavity, which has a span of 5-6 m. Even though the crust may mechanically bond to the reactor cavity walls, the weight of the coolant and the crust itself is expected to periodically fracture the crust and restore contact with the melt. The fractured crust will provide a pathway for water to recontact the underlying melt, thereby allowing other debris cooling mechanisms to proceed and contribute to terminating the core-concrete interaction. Thus, one of the key aims of the current program was to measure crust strength to check the hypothesis that a corium crust would not be strong enough to sustain melt/crust separation in a plant accident. The second important issue concerns long-term, two-dimensional concrete ablation by a prototypic core oxide melt. As discussed by Foit, the existing reactor material database for dry cavity conditions is solely one-dimensional. Although the MACE Scoping Test was carried out with a two-dimensional concrete cavity, the interaction was flooded soon after ablation was initiated to investigate debris coolability. Moreover, due to the scoping nature of this test, the apparatus was minimally instrumented and therefore the results are of limited value from the code validation viewpoint. Aside from the MACE program, the COTELS test series also investigated 2-D CCI under flooded cavity conditions. However, the input power density for these tests was quite high relative to the prototypic case. Finally, the BETA test series provided valuable data on 2-D core concrete interaction under dry cavity conditions, but these tests focused on investigating the interaction of the metallic (steel) phase with concrete. Due to these limitations, there is significant uncertainty in the partitioning of energy dissipated for the ablation of concrete in the lateral and axial directions under dry cavity conditions for the case of a core oxide melt. Accurate knowledge of this 'power split' is important in the evaluation of the consequences of an ex-vessel severe accident; e.g., lateral erosion can undermine containment structures, while axial erosion can penetrate the basemat, leading to ground contamination and/or possible containment bypass. As a result of this uncertainty, there are still substantial differences among computer codes in the prediction of 2-D cavity erosion behavior under both wet and dry cavity conditions. Thus, a second key aim of the current program was to provide the necessary data to help resolve these modeling differences. In light of the above issues, the OECD-sponsored Melt Coolability and Concrete Interaction (MCCI) program was initiated at Argonne National Laboratory. The project conducted reactor materials experiments and associated analysis to achieve the following technical objectives: (1) resolve the ex-vessel debris coolability issue through a program that focused on providing both confirmatory evidence and test data for the coolability mechanisms identified in previous integral effects tests, and (2) address remaining uncertainties related to long-term 2-D core-concrete interaction under both wet and dry cavity conditions. Data from the various tests conducted as part of the program is used to develop and validate models and codes that eventually form the basis for extrapolating the experimental findings to plant conditions. Achievement of these technical objectives will demonstrate the efficacy of severe accident management guidelines for existing plants, and provide the technical basis for better containment designs of future plants. The project completed a total of eleven reactor material tests to investigate melt coolability and 2-D core-concrete interaction mechanisms under both wet and dry cavity conditions.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2011

OECD MCCI project Small-Scale Water Ingression and Crust Strength Tests (SSWICS) SSWICS-1 test data report : thermal hydraulic results. Rev. 0 September 20, 2002.

The Melt Attack and Coolability Experiments (MACE) program at Argonne National Laboratory addressed the issue of the ability of water to cool and thermally stabilize a molten core/concrete interaction (MCCI) when the reactants are flooded from above. These tests provided data regarding the nature of corium interactions with concrete, the heat transfer rates from the melt to the overlying water pool, and the role of noncondensable gases in the mixing processes that contribute to melt quenching. However, due to the integral nature of these tests, several questions regarding the crust freezing behavior could not be adequately resolved. These questions include: (1) To what extent does water ingression into the crust increase the melt quench rate above the conduction-limited rate and how is this affected by melt composition and system pressure and (2) What is the fracture strength of the corium crust when subjected to a thermal-mechanical load and how does it depend upon the melt composition? A series of separate-effects experiments are being conducted to address these issues. The first employs an apparatus designed to measure the quench rate of a pool of corium ({approx}{phi}30 cm; up to 20 cm deep). The main parameter to be varied in these quench tests is the melt composition since it is thought to have a critical influence on the crust cracking behavior which, in turn, alters quench rate. The issue of crust strength will be addressed with a second apparatus designed to mechanically load the crust produced by the quench tests. This apparatus will measure the fracture strength of the crust while under a thermal load created by a heating element beneath the crust. The two apparatuses used to measure the melt quench rate and crust strength are jointly referred to as SSWICS (Small-Scale Water Ingression and Crust Strength). This report describes results of the first water ingression test, designated SSWICS-1. The report includes a description of the test apparatus, the instrumentation used, plots of the recorded data, and some rudimentary data reduction to obtain an estimate of the heat flux from the corium to the overlying water pool.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2011

OECD MMCI Small-Scale Water Ingression and Crust Strength Tests (SSWICS) SSWICS-2 test data report : thermal hydraulic results, Rev. 0 September 20, 2002.

The Melt Attack and Coolability Experiments (MACE) program at Argonne National Laboratory addressed the issue of the ability of water to cool and thermally stabilize a molten core/concrete interaction (MCCI) when the reactants are flooded from above. These tests provided data regarding the nature of corium interactions with concrete, the heat transfer rates from the melt to the overlying water pool, and the role of noncondensable gases in the mixing processes that contribute to melt quenching. However, due to the integral nature of these tests, several questions regarding the crust freezing behavior could not be adequately resolved. These questions include: (1) To what extent does water ingression into the crust increase the melt quench rate above the conduction-limited rate and how is this affected by melt composition and system pressure and (2) What is the fracture strength of the corium crust when subjected to a thermal-mechanical load and how does it depend upon the melt composition? A series of separate-effects experiments are being conducted to address these issues. The first employs an apparatus designed to measure the quench rate of a pool of corium ({approx}{phi}30 cm; up to 20 cm deep). The main parameter to be varied in these quench tests is the melt composition since it is thought to have a critical influence on the crust cracking behavior which, in turn, alters quench rate. The issue of crust strength will be addressed with a second apparatus designed to mechanically load the crust produced by the quench tests. This apparatus will measure the fracture strength of the crust while under a thermal load created by a heating element beneath the crust. The two apparatuses used to measure the melt quench rate and crust strength are jointly referred to as SSWICS (Small-Scale Water Ingression and Crust Strength). This report describes results of the second water ingression test, designated SSWICS-2. The report includes a description of the test apparatus, the instrumentation used, plots of the recorded data, and some rudimentary data reduction to obtain an estimate of the heat flux from the corium to the overlying water pool.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2011

EVIDENCE FOR THE IMPACT OF STELLAR ACTIVITY ON THE DETECTABILITY OF SOLAR-LIKE OSCILLATIONS OBSERVED BY KEPLER

We use photometric observations of solar-type stars, made by the NASA Kepler Mission, to conduct a statistical study of the impact of stellar surface activity on the detectability of solar-like oscillations. We find that the number of stars with detected oscillations falls significantly with increasing levels of activity. The results present strong evidence for the impact of magnetic activity on the properties of near-surface convection in the stars, which appears to inhibit the amplitudes of the stochastically excited, intrinsically damped solar-like oscillations.

79 ASTRONOMY AND ASTROPHYSICS↗