MEHB 513 – INTRODUCTION TO NUCLEAR TECHNOLOGY GROUP ASSIGNMENT TITLE: Impact Evaluation of Fukushima Nuclear Accident on Technology Development of New Nuclear Power Plants BY, Cristine Huring Anak Patrick KennedyME Koguleshun SubramaniamME Mohamed Washim Bin NasirME Fahmi Zulfadli Bin Aminuddin ME Daniel Choon Chin AunnME LECTURER: Nasri A. Hamid, Assoc Prof, Dr.

Outline Introduction Problem Statement Site Location Development Plant & Reactor Design Safety Issues & Mitigation of NPPs End

1. Introduction

Introduction Fukushima Dai-ichi Nuclear Power Plant Accident 11 th March magnitude earthquake Power supply knocked out Tidal waves/tsunami Backup generators for cooling systems to active reactors disabled Hydrogen explosions High levels of radiation released into the atmosphere

Introduction

As a result of this accident, many nuclear power plants were forced to improve upon their current design for safety as well as having better counter measures in case of an emergency. New research contribute to the latest designs of nuclear power plants stemming from the data gathered from the Fukushima accident. This disaster will always serve as a constant reminder to the importance of safety as well as accident management for a nuclear power plant.

2. Problem Statement (Fukushima Incident)

Reactor cooling during station blackout scenario Severe accident management Spent fuel pools located in reactor site Long or intermediate storage issue of spent fuel The role of multiple units in one location and increase of radioactive source term Hydrogen generation and fires Radiation leakage to environment and decontamination Emergency relocation Adequacy of regulation in place related to safety culture Problem Statement

3. Site Location Development

The design was developed to meet 43 design requirement. The key features are: Net Electric power (MWe): 1400 (40% increase). Design Life (years): 60 (50% increase). Seismic Design (g): 0.3 (50% increase). Core Damage Frequency (/year): (10x decrease). Number of 16x16 fuel assemblies: 241 (36% increase). Site Location Development ADVANCE NUCLEAR PLANT NameGori Nuclear Power Complex LocationGori, Jangan-eup, Gijang- gun, Busan, South Korea Subordinate to Korea Hydro & Nuclear Power Co., Ltd. Size8 Power Reactors Reactor Status5 operational, 3 under construction The main developments are evolution in capacity, increased lifetime and enhanced safety. The design improvement also focus meet economic objectives and licensing requirements.

4. Plant & Reactor Design (Technology Development)

TAP is an advanced molten salt reactor that generates clean, passively safe, proliferation-resistant, and low-cost nuclear power. This reactor can consume the spent nuclear fuel (SNF) generated by commercial light water reactors or use freshly mined uranium at enrichment levels as low as 1.8% U-235. It achieves actinide burnups as high as 96%, and can generate up to 75 times more electricity per ton of mined uranium than a light- water reactor. Plant & Reactor Design Trans Atomic Power’s Reactor

Reactor Description and Design Considerations The Salt Solution: In Transatomic Power’s reactor, molten salt containing radioactive material would circulate inside a reactor vessel [1]. The heat generated by the self- sustaining nuclear fission reaction would be transferred to circulating water [2], which would boil into steam [3] to power a turbine. Valves made of frozen salt [4] beneath the reactor vessel would be kept solid and closed by an electrical system. In the event of a power outage, the valves would melt, allowing the molten salt to drain into a wide tank [5], where the fission reaction would naturally come to a halt.

Better Inherent Safety

Comparison to Other Waste- Burning Reactors Advanced fast reactor’s Molten salt It face proliferation concerns because it produce excess plutonium during operation. This issue is handled by sealing the reactor so that there is no external access to the core eventually leading to a fire risk because of their sodium metal coolant. Molten fluoride salts have been used at the industrial scale for decades in aluminium refineries, and there are well-established safety protocols for handling these materials. Molten salt reactors can also be built at considerably lower cost than gas fast reactors

Pressurized Core Flooding Tanks (Accumulators) 75% cold borated water 25% nitrogen / inert gas (pressurizer) Normal condition: Check valves closed due to greater reactor pressure Accident Incident: Check valves open due to reactor pressure drop One-time, preliminary cooling system Plant & Reactor Design Passive Reactor Core Cooling System

Elevated Tank Circulation Loops (Core Make-up Tanks) Contains cold borated water Tank inflow (top) is connected to reactor coolant system Accident Incident: Cold borated water flows into hot reactor core & back into the tank Short-term cooling system (no heat exchanger) Plant & Reactor Design Passive Reactor Core Cooling System

Elevated Gravity Drain Tanks Similar to accumulator, except this is driven by gravity rather than pressurized gas Accident Incident: Check valves open when weight of borated water is greater than reactor pressure Borated water volume sufficient to flood entire reactor cavity One-time, preliminary cooling system Plant & Reactor Design Passive Reactor Core Cooling System

Passively Cooled Steam Generator Natural Circulation Incorporated in PWRs to remove heat from steam generators Leaves steam generator undamaged from overheating during accident Continuous cooling system Plant & Reactor Design Passive Reactor Core Cooling System

Passive Residual Heat Removal (PRHR) Heat Exchangers Similar to passively cooled steam generator natural circulation (previous) Incorporated in PWRs to remove heat directly from reactor core rather than steam generator Continuous cooling system during accident Plant & Reactor Design Passive Reactor Core Cooling System

Containment Passive Heat Removal / Pressure Suppression Systems Steam vented into the containment condenses on incline tubes (red) Reduces temperature & pressure in containment Cooling water flows due to natural circulation (heated water rises) Plant & Reactor Design Passive Systems for Containment & Pressure Suspension

Passive Containment Spray Systems Hear transferred from containment wall to air outside the wall Heat outside the containment wall is cooled by cooler air blown from the bottom Pool on top of containment accelerates cooling process via gravity driven cold water spray Plant & Reactor Design Passive Systems for Containment & Pressure Suspension

Plant & Reactor Design Containment Designs The containment is the last barrier to prevent large radioactive releases from a severe accident Some designs also include core catchers to collect molten core material that melts through the reactor vessel and prevent it from escaping while also spreading it out to make it easier to cool. IMPROVEMENT Pre-stressed or reinforced single concrete containments with steel liners Cylindrical and spherical steel containments Pre-stressed double containments with and without steel liners

5. Safety Issues & Mitigation of NPPs

Safety Issues Emergency Power Long-term Cooling Containment performances plant siting emergency response design-basis events Safety Issues of Plant

Mitigation of Nuclear Accidents Mitigations Risk Information Regulation reduce design vulnerabilities that would lead to beyond-design-basis events Hazards from Extreme Natural Phenomena All risks to NPPs from severe natural events should be periodically (e.g., every decade) reassessed using the same methodologies and data Multiple-Unit-Site Considerations NPP Hardware Design Modifications Accident Diagnostics Tool Provide the operators with information regarding the accident progression

Cont.. Mitigations Command and Control During a Reactor Accident Emergency Planning Health Physics too early to make any firm conclusions regarding these data and the definitive health impacts NPP Hardware Design Modifications Severe Accident Management Guidelines the SAMGs need to be revised at NPPs according to the new criteria

6. Conclusion

Conclusion The Fukushima Dai-ichi accident will always serve as a constant reminder of the risks that come with operating nuclear power plants and the impact of a catastrophe of that scale. However, as we can see from this project that there have already been many changes in designs and procedures to make nuclear power plants much safer and reliable. The new power plants will be more resilient in the face of huge natural disasters. Safety procedures and accident management plans have also been reviewed in light of the accident. It is safe to conclude that with the constant development of technology, nuclear power plants can become safer and we can rely more on this very efficient technology.

7. References

INTERNATIONAL ATOMIC ENERGY AGENCY, Mission Report The Great East Japan Earthquake Expert Mission, IAEA International Fact Finding Expert Mission of the Fukushima Dai-ichi NPP Accident following the Great East Japan Earthquake and Tsunami, IAEA, Vienna (2011). IAEA Report on Reactor and Spent Fuel Safety in the Light of the Accident at the Fukushima Daiichi Nuclear Power Plant: INVESTIGATION COMMITTEE ON THE ACCIDENT AT THE FUKUSHIMA NUCLEAR POWER STATIONS (GOVERNMENT COMMITTEE OF JAPAN), Report on the Accident at Fukushima Nuclear Power Stations at Tokyo Electric Power Company, Interim Report, December 2011: INVESTIGATION COMMITTEE ON THE ACCIDENT AT THE FUKUSHIMA NUCLEAR POWER STATIONS (GOVERNMENT COMMITTEE OF JAPAN), Report on the Accident at Fukushima Nuclear Power Stations of Tokyo Electric Power Company, Final Report, July 2012: NATIONAL DIET OF JAPAN FUKUSHIMA NUCLEAR ACCIDENT INDEPENDENT INVESTIGATION COMMISSION (DIET COMMITTEE OF JAPAN), July 2012: References

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