1. Fire Safety in Nuclear Power Plants and Modeling Fire in a Generic EDG Room by COMPBRN III M. B. Öztemiz, Ş. Ergün Hacettepe University Nuclear Engineering Department BgNS Conference 2013

2. Outline Introduction Introduction COMPBRN Modeling COMPBRN Modeling Simulations Simulations Results Results Conclusions Conclusions

3. Introduction Operational experiences and fire safety assessments showed that fires and explosions have substantial effects on NPP safety Operational experiences and fire safety assessments showed that fires and explosions have substantial effects on NPP safety –Diesel generators and batteries (which are primarily critical to maintain electricity to pumps) have to be well protected from the effects of fires and explosions.

4. Introduction Fukushima Daiichi accident showed us that no matter how well an NPP is protected against internal and external events, failure of diesel generators ends up with a severe nuclear accident. Fukushima Daiichi accident showed us that no matter how well an NPP is protected against internal and external events, failure of diesel generators ends up with a severe nuclear accident. –These systems can be mentioned as shoulder to shoulder systems, which cannot perform their primary tasks when they operate alone.

5. Introduction History of the nuclear power plant fires shows that most of the fires are cable related. History of the nuclear power plant fires shows that most of the fires are cable related. –San Onofre, Brown’s Ferry, Greifswald, Beloyarsk, Zaporoshye, Kalinin, Ignalina, Waterford fires.

6. COMPBRN Modeling COMPBRN uses Hot Gas Layer Model COMPBRN uses Hot Gas Layer Model

7. COMPBRN Modeling For the analysis, the validity of using COMPBRN III for cable fires was investigated (an experiment performed as part of International Collaborative Fire Modeling Project was modeled and simulated) Hot Gas Layer Temperature Prediction by COMPBRN III

8. COMPBRN Modeling Once the validation calculations showed that conservative calculations can be performed with the code a typical diesel generator building was modeled and to simulate the fire three scenarios were carried out in a diesel generator. Fire was assumed to break out in the burned air cleaning room, A3 Once the validation calculations showed that conservative calculations can be performed with the code a typical diesel generator building was modeled and to simulate the fire three scenarios were carried out in a diesel generator. Fire was assumed to break out in the burned air cleaning room, A3

9. COMPBRN Modeling Set up for Scenario 1.Set up for Scenario 2. Set up for Scenario 3.

10. Results After 157 minutes of fire start Scenario 1Scenario 2Scenario 3 Target cable set surface temperature (K) 329 354 Wall surface temperature (K) 311335 Heat Flux measured on the target cable set surface (W/m 2 ) 3363401790

11. Conclusions Cables should be routed on different paths and separated physically in order to maintain diversity. Cables should be routed on different paths and separated physically in order to maintain diversity. Cables having same tasks should be used in different places of different systems in order to maintain redundancy. Cables having same tasks should be used in different places of different systems in order to maintain redundancy.

12. Conclusions Beyond the all analyses conducted or will be conducted, serious importance should be given into human factor. Even if all analyses are made clearly perfect, in the past or in the future, often ignored human factor can be trouble and reason for fires to breakout. Beyond the all analyses conducted or will be conducted, serious importance should be given into human factor. Even if all analyses are made clearly perfect, in the past or in the future, often ignored human factor can be trouble and reason for fires to breakout. Each fire broke out and lessons learned from fires should be assessed in a cause and effect relationship, documentation should be maintained and utilities, designers and regulators should analyze these parameters well. Each fire broke out and lessons learned from fires should be assessed in a cause and effect relationship, documentation should be maintained and utilities, designers and regulators should analyze these parameters well.