Electrical failure during NPP cable fires

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1 Electrical failure during NPP cable fires RIGOLLET Laurence ZAVALETA Pascal PILLER Marc AUDOUIN Laurent International Experts Meeting on Strengthening Research and Development Effectiveness in the Light of the Accident at the Fukushima Daiichi Nuclear Power Plant

2 Contents Safety needs Damage criteria of electrical equipment IRSN approach Real fire tests Analytical tests Conclusion TP1-2 Electrical failure during NPP cable fires 2/13

3 Safety needs: Fire PSA Main objectives of IRSN Fire PSA Analyze the main factor contributing to the core damage frequency Assess the design and the operating measures implemented by the utility Perform an independent assessment of utility Fire PSA and evaluate the employed methodology General Method Critical rooms selection Quantification of fire scenario frequencies Modelling and quantification of core damage Results and analysis TP1-2 Electrical failure during NPP cable fires 3/13

4 Safety needs: Fire PSA Critical rooms selection Quantification of fire scenario frequencies Modelling and quantification of core damage Results and analysis Critical rooms selection: Based on the most critical safety equipment during fire scenarios in terms of firerelated risks Modelling and quantification of core damage Fire simulations that use Fire source data The fire source characteristics (HRR, fire growth, combustion products ) based on open and confined fire tests representative of fire scenarios in NPPs Failure criteria of electrical safety equipment The malfunction criteria of electrical safety equipment due to smoke and heat stresses generated by the compartment fire TP1-2 Electrical failure during NPP cable fires 4/13

Safety needs: Fire PSA Fire scenario What are the

electrical/electronic Adjacent room Target: electronic

5 Safety needs: Fire PSA Fire scenario What are the consequences of a cable trays fire on an electronic equipment? What are the malfunction criteria of an electrical/electronic equipment? Adjacent room Target: electronic or electrical equipment Fire room Fire source: horizontal cable trays TP1-2 Electrical failure during NPP cable fires 5/13

Damage criteria of electrical equipment Literature review: NUREG-CR/6850: a thermal damage target of 65 C is recommended NUREG/CR-4596: thermal stress of relay in an environmental chamber by step

6 Damage criteria of electrical equipment Literature review: NUREG-CR/6850: a thermal damage target of 65 C is recommended NUREG/CR-4596: thermal stress of relay in an environmental chamber by step increases of temperature. Thermal failures were observed from 150 C up to 350 C. Objectives of IRSN experimental studies: Getting further information about malfunction of electrical equipment of interest due to a fire Investigating the malfunction of electrical equipment due the effect of hot smoke from real fire source TP1-2 Electrical failure during NPP cable fires 6/13

Damage criteria of electrical equipment Experimental studies Thermal stress

electronic card Real fire tests Stress inducing malfunction: combined effect

an experimental device able to investigate the combined effect of ambient

7 Damage criteria of electrical equipment Experimental studies Thermal stress tests Stress inducing malfunction: temperature For example, 170 C for an electronic card Real fire tests Stress inducing malfunction: combined effect of both soot concentration and ambient temperature New device Need to build an experimental device able to investigate the combined effect of ambient temperature and soot concentration TP1-2 Electrical failure during NPP cable fires 7/13

temperature Real fire tests Behavior of electronic equipment submitted to fire conditions Comparison of malfunction criteria Analytical tests

8 IRSN approach Need: To determine experimentally the malfunction criteria of electronic or electrical safety equipment in fire conditions Objectives of IRSN DELTA Program To develop an experimental protocol to study the combined effect of soot concentration and ambient temperature Real fire tests Behavior of electronic equipment submitted to fire conditions Comparison of malfunction criteria Analytical tests Determine malfunction criteria 2 Experimental protocol to determine malfunction criteria of safety equipment TP1-2 Electrical failure during NPP cable fires 8/13

Real Fire tests Fire Scenarios providing fire conditions (temperature and smoke) close to analogic converter Fire source: cable trays or electrical cabinets and cable trays Equipment of

9 Real Fire tests Fire Scenarios providing fire conditions (temperature and smoke) close to analogic converter Fire source: cable trays or electrical cabinets and cable trays Equipment of interest: Analogic converter Location: Adjacent room, lower and upper zones (red line) Adjacent room Fire room 2 2 Analogic converter TP1-2 Electrical failure during NPP cable fires 9/13

10 Soot concentration [g/m 3 ] Real Fire tests Some results Electrical malfunction of analogic converters during fire scenarios in DIVA facility Temporary failures Operating zone Thermal zone: permanent failure Temperature [ C] TP1-2 Electrical failure during NPP cable fires 10/13

11 Analytical tests New Experimental Apparatus Objectives: Design and built a new experimental apparatus able to investigate the combined effect of ambient temperature and soot concentration Experimental device: Furnace (DANAIDES) able to monitor both thermal stress (up to 250 C) and soot concentration (up to 5 g/m 3 ) Soot branch Chamber of exposure Heater TP1-2 Electrical failure during NPP cable fires 11/13

Operating range Analytical tests Experimental Program (DELTA) in progress Objectives: Develop an experimental protocol to characterize the

Two challenges: Use of a soot surrogate: carbon powder Limited number of tests for determining the operating range of equipment in case of

12 Operating range Analytical tests Experimental Program (DELTA) in progress Objectives: Develop an experimental protocol to characterize the malfunction of electrical components due to both thermal stress (T) and soot concentration (Cs). Two challenges: Use of a soot surrogate: carbon powder Limited number of tests for determining the operating range of equipment in case of fire Expected results: Malfunction curve (T, Cs) for an electrical component First encouraging results Cs (g/m 3 ) Malfunction TP1-2 Electrical failure during NPP cable fires 0 T ( C) 12/13

13 Conclusion Support studies of Fire-PSA: Need to assess the malfunction of electrical equipment important for safety (i.e. fire-related risks to reach the core melting): damage criteria of electrical equipment considered Main outcomes of real fire tests Electrical malfunction of analogic converters in real fire conditions depends on both soot concentration and ambient temperature: Malfunction = f(t,cs) DELTA Program (in progress at IRSN) This program proposes to define an experimental procedure to characterize properly malfunction of electrical components by means of a dedicated furnace (named DANAIDES) After this step, the expected outcomes will be to determine the malfunction of electrical equipment in case of fire by means of a quasi-standards experimental method TP1-2 Electrical failure during NPP cable fires 13/13

14 Thank you for your attention Enhancing nuclear safety

Data collection in Fire PSA. Institut de Radioprotection et de sûreté Nucléaire (IRSN), BP 68, 91192, Gif-sur-Yvette, France,

Data collection in Fire PSA. Institut de Radioprotection et de sûreté Nucléaire (IRSN), BP 68, 91192, Gif-sur-Yvette, France, Data collection in Fire PSA F. Nicoleau 1, J. Richard 2, G. Georgescu 3 1 Institut de Radioprotection et de sûreté Nucléaire (IRSN), BP 17, 92262, Fontenay-aux-Roses, France, fabienne.nicoleau@irsn.fr