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CSNI2003 MCCI.
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CSNI2003 MCCI.

MCCI, Molten Core Concrete Interaction Project

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1. NAME

MCCI

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2. COMPUTERS

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Program name Package id Status Status date
MCCI CSNI2003/01 Arrived 24-JAN-2007

Machines used:

Package ID Orig. computer Test computer
CSNI2003/01 Many Computers
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3. DESCRIPTION OF THE PROJECT

In a core melt accident, if the molten core is not retained in-vessel despite severe accident mitigation actions, the core debris will relocate to the reactor cavity region and interact with the structural concrete – potentially resulting in basemat failure through erosion or overpressurisation. This would result in the release of fission products into the environment. Although this is a late release event, the radiological consequences could be substantial enough to warrant an effective mitigation strategy for preventing such a release. The severe accident management guidance (SAMG) for operating light water reactor plants includes, as one of several strategies, flooding the reactor cavity in the event of an ex-vessel core melt release.

The Melt Coolability and Concrete Interaction (MCCI) Project was dedicated to provide experimental data on this type of severe accident phenomena and to resolve two important accident management issues:

  • verify that molten debris that has spread on the base of the containment can be stabilised and cooled by water flooding from the top,

  • assess the two-dimensional, long-term interaction of the molten mass with the concrete structure of the containment, as the kinetics of such interaction is essential for assessing the consequences of a severe accident.

 

To achieve these basic objectives, supporting experiments and analyses were performed at Argonne National Laboratory (ANL), with a view to provide an understanding of the phenomena, and to produce a consistent interpretation of the results relevant to accident management.

 

Previously, an internationally-sponsored programme had already been carried out at ANL to address the corium coolability issue. The MCCI project aimed to complete this earlier research and achieve the following technical objectives:

  • resolve the ex-vessel debris coolability issue through a redirected programme which focuses on providing both confirmatory evidence and test data for the coolability mechanisms identified in previous ANL integral effect tests,

  • address remaining uncertainties related to the long-term, two-dimensional, melt-concrete interaction under dry cavity conditions.

 

MCCI phases

First phase (2002-2005)

 

The first MCCI experiments focused on water ingress mechanisms, as these are thought to be the most effective ones for cooling the melt. The experiments demonstrated how cooling of the melt with water was affected by the concrete-melt composition and that cooling the melt with water was reduced by increasing concrete content, i.e. cooling by water flooding is more effective in the early phase of the melt-concrete interaction. The effect of concrete type, such as siliceous and limestone types (used respectively in Europe and the United States), had also been addressed. Material properties such as porosity and permeability had been derived from these tests as well.

 

In 2003, a first melt-concrete interaction test with siliceous concrete produced unexpected results (a strong asymmetry in concrete ablation), although the associated analytical exercise proved very valuable in helping to understand code capabilities and shortcomings. A second test was carried out in 2004 at 30% lower power than the first on limestone concrete (instead of the siliceous concrete used in the first test). The strength of the solid upper crust, a parameter that is of great interest for modelling and understanding MCCI at plant scale, was also determined during these experiments. A third test with siliceous concrete was successfully carried out in 2005, yielding excellent data on axial and radial concrete ablation.

 

The first phase of the programme (MCCI-1) was completed in 2005. The experiments on water ingress mechanisms showed that cooling of the melt by water is reduced at increasing concrete content, implying that water flooding is more effective in the early phase of the melt-concrete interaction. The effect of concrete type, i.e. siliceous and limestone types (used respectively in Europe and the United States), was also addressed in the first phase of the programme. Material properties such as porosity and permeability were derived. Tests also showed appreciable differences in ablation rate for siliceous and limestone concrete, which is a relevant finding that requires confirmation. A workshop on the results of MCCI-1 took place on 10-11 October 2007 in Cadarache, France.

 

Phase 1 final report is available at OECD MCCI project final report.

 

Second phase (2006-2009)

 

After successful completion of the first phase at Argonne National Laboratory (ANL), a second phase (MCCI-2) using the same ANL facilities was set up. The MCCI‐2 Project was carried out from 2006 to early 2010 to help bridge data gaps not fully covered during MCCI‐1. Testing fell into four categories:

  • combined effect tests to investigate the interplay of different cooling mechanisms and to provide data for model development and code assessment,

  • tests to investigate the effectiveness of new design features that enhance debris coolability,

  • tests to generate additional 2‐D core‐concrete interaction data for model development and code validation,

  • an integral test at larger scale to confirm synergistic effect of different cooling mechanisms and to provide data for validation of severe accident codes.

 

Aside from these tests, a supporting task analysis was carried out to further develop and validate debris coolability models that formed the basis for extrapolating the experiment findings to plant conditions. In total, ten tests were conducted in this programme and they were all successful.

 

Four category one tests were performed using the Small Scale Water Ingression and Crust Strength (SSWICS) apparatus. Tests were conducted to provide additional crust strength data to confirm the concept of a floating crust boundary condition at plant scale and to investigate the effect of gas sparging on water ingression cooling of corium. Crust strength tests (2) showed that the strength of un‐sectioned crust samples was consistent with that of the sectioned specimens tested in MCCI‐1. Gas sparging tests (2) showed that the presence of sparging significantly increases the cooling rate of a solidifying corium pool over those observed when sparging is absent.

 

Category two tests to examine the effectiveness of design features for augmenting coolability, i.e. melt stabilisation concepts, were of two cooling types:

  • water‐cooled basemat test (WCB‐1) addressed cooling with external water‐cooled surfaces,

  • SSWICS‐12 and SSWICS‐13 tests addressed water ingress into the melt volume by fragmentation.

 

Category three tests provided additional 2‐D core-concrete interaction data. CCI tests in both the MCCI and French VULCANO facilities had shown a marked dependence of cavity erosion behaviour on the concrete type. Tests with limestone/common sand (LCS) concrete generally exhibited a radial/axial power split of ~1; conversely, siliceous tests exhibited splits that were significantly greater than one. The CCI‐4 test was conducted with LCS concrete, but with increased metal content (structural and cladding) to evaluate effect on cavity erosion behaviour. The CCI‐5 test was conduced with siliceous concrete, but the apparatus was modified to increase lateral scale to diminish the wall effects to the greatest extent possible. Test aspect ratio (cavity width/melt depth) increased from 1 to 3.7.

 

Category four was an integral test to validate severe accident codes. The large-scale CCI‐6 test was conducted with early flooding to focus on debris coolability. Key features were:

  • 70 cm x 70 cm cross section, 28 cm melt depth: 900 kg (63/25/6/6 wt % UO2/ZrO2/Cr/concrete),

  • siliceous concrete,

  • cavity flooding ~ 1 minute after melt contact with basemat.

 

The design incorporated an embedded array of water injection nozzles at a depth of 27.5 cm into the concrete. If debris did not quench, then a second test phase would have been initiated to provide additional category two data on bottom water injection cooling. Results demonstrated that: 1) early cavity flooding significantly enhances debris coolability, even for siliceous concrete; and 2) melt eruptions are a viable cooling mechanism for siliceous concrete. The test was terminated on the basis of debris quench well before water injection of the nozzles was reached.

 

Phase 2 final report is available at OECD MCCI-2 Project. Final Report

 

A concluding seminar of the MCCI-2 Project was held in Cadarache, France from 15 to 17 November 2010.

 

Project participants: Belgium, Czechia, Finland, France, Germany, Hungary, Japan, Norway, Korea, Spain, Sweden, Switzerland and United States.

 

Project period: January 2002-December 2005

 

For more detailed information visit Nuclear Energy Agency (NEA) - Melt Coolability and Concrete Interaction (MCCI) Project

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9. STATUS
Package ID Status date Status
CSNI2003/01 24-JAN-2007 Masterfiled restricted
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10. REFERENCES

Publications

  • M. T. Farmer, S. Lomperski, D. Kilsdonk, R. W. Aeschlimann, and S. Basu:
    A Summary of Findings from the Melt Coolability and Concrete Interaction (MCCI) Program, Paper 7544, 2007 International Congress on Advances in Nuclear Power Plants (ICAPP'07), Nice, France, 13-18 May 2007.

 

CSNI2003/01, included references:
Conference Proceedings:

1. M. T. Farmer, S. Lomperski, and S. Basu,'The Results of the CCI-3 Reactor
Material Experiment Investigating 2-D Core-Concrete Interaction and Debris
Coolability,' Proceedings ICAPP '06, Reno, Nevada, June 6-8, 2006.

2. S. Basu, M. T. Farmer, and S. Lomperski,'Significance of the OECD-MCCI
Program in Relation to Severe Accident Uncertainties Evaluation,' CSNI Workshop
on Evaluation of Uncertainties in Relation to Severe Accidents and Level 2
Probabilistic Safety Analysis, Aix-en-Provence, France, 7-9 November, 2005.

3. M. T. Farmer, S. Lomperski, and S. Basu,'The Results of the CCI-2 Reactor
Material Experiment Investigating 2-D Core-Concrete Interaction and Debris
Coolability,' 11th International Topical Meeting on Nuclear Reactor
Thermal-Hydraulics (NURETH-11), Avignon, France, October 2-6, 2005.

4. M. T. Farmer, S. Lomperski, and S. Basu,'Status of the Melt Coolability and
Concrete Interaction (MCCI) Program at Argonne National Laboratory,'
Proceedings ICAPP '05, Seoul, Korea, May 15-19, 2005.

5. M. T. Farmer, S. Lomperski, and S. Basu,'Results of Reactor Material
Experiments Investigating 2-D Core-Concrete Interaction and Debris
Coolability,' Paper 4102, Proceedings ICAPP '04, Pittsburgh, PA USA, June 13-17,
2004.

MCCI-Program Technical Reports:

1. M. T. Farmer, S. Lomperski, D. J. Kilsdonk, and R. W. Aeschlimann,'OECD
MCCI Project Final Report,' OECD/MCCI-2005-TR06, February 28, 2006.

2. M. T. Farmer, S. Lomperski, D. J. Kilsdonk, and R. W. Aeschlimann,'OECD
MCCI Project 2-D Core Concrete Interaction (CCI) Tests: Final Report,'
OECD/MCCI-2005-TR05, February 28, 2006.

3. M. T. Farmer, S. Lomperski, D. J. Kilsdonk, R. W. Aeschlimann,'2-D Core
Concrete Interaction (CCI) Tests: CCI-3 Test Data Report-Thermalhydraulic
Results,' Rev. 0, OECD/MCCI-2005-TR04, October 15, 2005.

4. S. Lomperski, M. T. Farmer, D.J. Kilsdonk, and R. W. Aeschlimann,
'Small-Scale Water Ingression and Crust Strength Tests (SSWICS) SSWICS Final
Report: Thermal Hydraulic Results,' OECD/MCCI-2005-TR03, June 2005.

5. S. Lomperski, M. T. Farmer, D. J. Kilsdonk, and R. W. Aeschlimann,'Project
Small-Scale Water Ingression and Crust Strength Tests (SSWICS) SSWICS Final
Report: Crust Strength Measurements,' OECD/MCCI-2005-TR02, June 2005.

6. S. Lomperski, M. T. Farmer, D. J. Kilsdonk, and R. W. Aeschlimann,
'Small-Scale Water Ingression and Crust Strength Tests (SSWICS); SSWICS-7 Test
Data Report:  Thermalhydraulic Results,' Rev. 0, OECD/MCCI-2005-TR01, January
11, 2005.

7. M. T. Farmer, S. Lomperski, D. J. Kilsdonk, R. W. Aeschlimann, and S. Basu,
'2-D Core Concrete Interaction (CCI) Tests: CCI-2 Test Data
Report-Thermalhydraulic Results,' Rev. 0, OECD/MCCI-2004-TR05, October 15, 2004.

8. S. Lomperski, M. T. Farmer, D. J. Kilsdonk, and R. W. Aeschlimann,
'Small-Scale Water Ingression and Crust Strength Tests (SSWICS); SSWICS-6 Test
Data Report:  Thermalhydraulic Results,' Rev. 0, OECD/MCCI-2004-TR03, March 22,
2004.

9. M. T. Farmer, S. Lomperski, D. J. Kilsdonk, R. W. Aeschlimann, and S. Basu,
'2-D Core Concrete Interaction (CCI) Tests: CCI-1 Test Data
Report-Thermalhydraulic Results,' Rev. 0, OECD/MCCI-2004-TR01, January 31,
2004.

10. M. T. Farmer, D. J. Kilsdonk, S. Lomperski, R. W. Aeschlimann, and S. Basu,
'2-D Core Concrete Interaction (CCI) Tests: CCI-2 Test Plan,' Rev. 0,
OECD/MCCI-2004-TR02, January 31, 2004.

11. S. Lomperski, M. T. Farmer, D. J. Kilsdonk, and R. W. Aeschlimann,
'SSWICS-5 Test Data Report - Thermalhydraulic Results,' Rev. 0,
OECD/MCCI-2003-TR06, October 22, 2003.

12. M. T. Farmer, D. J. Kilsdonk, P. Pfeiffer, and S. Lomperski,'Crust Failure
Test Design Report,' Rev. 0, OECD/MCCI-2003-TR05, March 31, 2003.

13. S. Lomperski, M. T. Farmer, D. J. Kilsdonk, and R. W. Aeschlimann,
'Small-Scale Water Ingression and Crust Strength Tests (SSWICS); SSWICS-4 Test
Data Report:  Thermalhydraulic Results,' Rev. 0, OECD/MCCI-2003-TR04, March 21,
2003.

14. S. Lomperski, M. T. Farmer, D. J. Kilsdonk, and R. W. Aeschlimann,
'Small-Scale Water Ingression and Crust Strength Tests (SSWICS); SSWICS-3 Test
Data Report:  Thermalhydraulic Results,' Rev. 0, OECD/MCCI-2003-TR03, February
19, 2003.

15. S. Lomperski, M. T. Farmer, D. J. Kilsdonk, and R. W. Aeschlimann,
'Small-Scale Water Ingression and Crust Strength Tests (SSWICS); SSWICS-2 Final
Data Report,' Rev. 0, OECD/MCCI-2003-TR02, February 12, 2003.

16. S. Lomperski, M. T. Farmer, D. J. Kilsdonk, and R. W. Aeschlimann,
'Small-Scale Water Ingression and Crust Strength Tests (SSWICS); SSWICS-1 Final
Data Report,' Rev. 1, OECD/MCCI-2003-TR01, February 10, 2003.

17. M. T. Farmer, S. Lomperski, D. J. Kilsdonk, and R. W. Aeschlimann,
'Long-Term 2-D Molten Core Concrete Interaction Test Design Report,' Rev. 0,
OECD/MCCI-2002-TR05, September 30, 2002.

18. S. Lomperski, M. T. Farmer, D. J. Kilsdonk, and R. W. Aeschlimann,
'SSWICS-1 Test Data Report - Thermalhydraulic Results,' Rev. 0,
OECD/MCCI-2002-TR04, September 20, 2002.

19. S. Lomperski, M. T. Farmer, D. J. Kilsdonk, and R. W. Aeschlimann,
'SSWICS-2 Test Data Report - Thermalhydraulic Results,' Rev. 0,
OECD/MCCI-2002-TR06, September 20, 2002.

20. M. T. Farmer, S. Lomperski, D. J. Kilsdonk, and R. W. Aeschlimann,'Melt
Eruption Test (MET) Design Report,' Rev. 2, OECD/MCCI-2002-TR03, April 15, 2003.

21. M. T. Farmer, S. Lomperski, D. J. Kilsdonk, R. W. Aeschlimann, and P.
Pfeiffer, 'Small-Scale Water Ingression and Crust Strength Tests (SSWICS)
Design Report,' Rev. 2, OECD/MCCI-2002-TR01, October 31, 2002.

22. S. Lomperski,'Enhancing Instrumentation for Reactor Material Experiments,'
OECD/MCCI-2002-TR02, September 3, 2002.

NRC-Sponsored Technical Reports and Conference Proceedings:

1. M. T. Farmer,'Phenomenological Modeling of the Melt Eruption Cooling
Mechanism During Molten Core-Concrete Interaction,' Proc. ICAPP '06, Reno,
Nevada, June 6-8, 2006.

2. M. T. Farmer, J. J. Sienicki, and A. Kovtonyuk,'OECD MCCI Analytical
Support (Stand Alone Task): Water Ingression Modeling of the OECD/MCCI SSWICS
Tests,' NRC/MCCI/2003-TR01, October 15, 2003.

3. H. Ley,'MELCOR Parameter Studies for 2-D Molten Core Concrete Interaction
Experiments,' September 30, 2002.
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12. PROGRAMMING LANGUAGE(S) USED
No specified programming language
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15. NAME AND ESTABLISHMENT OF AUTHORS

S. Basu
Project Manager
U.S. Nuclear Regulatory Commission
MS-T10K8
11545 Rockville Pike, Rockville, MD 20852 U.S.A.

 

Mitchell T. Farmer
Manager, Engineering and Development Laboratory
Argonne National Laboratory
Argonne, IL 60439 USA

 

Stephen W. LOMPERSKI
Reactor Engineering Division
Argonne National Laboratory
Argonne, IL 60439 USA

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16. MATERIAL AVAILABLE
CSNI2003/01
Data files
Design reports, Data reports, and final reports (PDF)
7 small-scale water ingression and crust strength (SSWICS) tests
3 large-scale core/concrete interaction (CCI) tests
1 melt eruption (MET) test
Videos recorded by the lid camera looking down onto the melts during
the large scale tests CC1-1,-2,-3 and MET-1
Readme file
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17. CATEGORIES
  • Y. Integral Experiments Data, Databases, Benchmarks

Keywords: core concrete interactions, experiment, nuclear reactor safety, reactor materials, severe accidents.