A Fundamental Cause for the Fukushima Accident and A Proposed Effective Remedy

Transcription

1 A Fundamental Cause for the Fukushima Accident and A Proposed Effective Remedy Jason Chao, Ph.D. MIT VP System Analysis, United Nuclear David Johnson, Sc.D. MIT VP Quantitative Risk, ABS Consulting Presented at PSAM Tokyo April 15 18, 2013

2 The Cause and The Solution Today I have only two points to make 1.A real cause for the Accident (and it is not the tsunami.) 2.A Remedy

3 No SBO for DBA No Protection -The design basis accidents should have included SBO when we design the plant 50 years ago. -This is the real cause for the accident.

4 NRC Asked Utilities to Respond on how to address Beyond Design basis accident and SBO Refreshing the concept of design basis accidents All products, devices, machines, equipments have a design basis for featured functionality as well as safety measures

5 Using this chart to illustrate the concept of Design Basis Accidents

6 Tsunami was not the cause Missing SBO in Chart was We had many near SBO incidents that could have led to Fukushima-like consequences (A Tsunami was an initiating event for SBO. Lack of SBO in DBA was the cause.)

7 Fort Calhoun Nuclear Plant Missouri River Flooding of 2011

8 US Operating Experience Missouri River Flooding of 2011

9 2 DECEMBER 1999 BLAYAIS FLOOD High water level in the river Gironde : high tide + storm surge (+2m) and waves (2m) generated by the wind on the estuary (200 km/) Waves came over the dyke and caused flooding on site and in units 1 and 2 On-site Emergency plan (36 hours)

10 SBO at Maanshan (Taiwan) Most older nuclear plants these days are vulnerable to station blackout because they were never designed to protect against it. On March 17, 2001, Maashaan a Westinghouse 3 loop PWR had a station blackout (SBO).

11 SBO at Maanshan As most nuclear plants these days may not be designed for surviving a station blackout event, yet the Maanshan plant survived SBO. This was because the plant has an extra safety measure against a station blackout. It had an extra emergency diesel generator that at the last minute worked and saved the plant.

12 Without Considering SBO, Plants are Vulnerable All these incidences indicates that without the SBO as a design basis accident a plant was designed against, The plant would be vulnerable to nature disasters. Either we were lucky we could get by or we would have something like the Fukushima accident.

13 We should Address the Problem in Fundamental Manner Not simply by enhancing communication, by strengthening operating training, by reviewing procedures, by re-evaluating guidelines, by examining licensee s rule compliance. We need to address the more fundamental technical issue first.

14 Now How to Fix the Problem Introducing Co-Authors 1st Jason Chao David Johnson Taken at Argonne National Lab summer 1976

15 Introducing Co-Authors (outside Beznau) Dr. David Johnson Dr. Jason Chao (2007)

16 Now How to Fix the Problem Many nuclear plants in Switzerland and Germany had done it. They had spent the necessary extra costs to build the Bunker Decay Heat Removal System (BDHRS) so that the Fukushima Accidents would never happen to them.

17 What Bunker Safety System Does Facts about the Bunker Safety System: It can make commercial operating nuclear plants genuinely safe so that the Fukushima related accidents would never have happen. These include flood, tsunami, earthquake, fire, LOOP initiated SBOs. It includes 9 pieces of major design changes. It costs roughly 0.5 billion US dollars per unit. It increases the safety by a factor of 30 quantifiably

18 What features would be included? Varied somewhat from plant to plant They should be selected based on specific risk profile of a plant For one plant, the features included: An independent feedwater system to deliver water to a steam generator An independent system to keep pump seals intact An independent well water system to act as an ultimate heat sink An independent high pressure injection pump And so forth Where the safety factor of 30 quantifiably come from?

19 Bunker Safety System Safer by 30

20 Bunker-like Safety System is the solution It addresses the SBO issue. It makes commercial nuclear power plants safer quantifiably (by a factor of 30) It eliminates Fukushima related accidents It helps policy makers to avoid premature shutdowns It addresses the public s unsettling minds It offers safe nuclear power for public acceptance of nuclear power, for current generation and future generation

21 Nuclear News 8/2012 Issue Page 162 French regulator ASN (Autorité de Sûreté Nucléaire) announced: Requirements include power supply systems that are protected by a bunker,..by 2018.

22 Cost a lot money? Not Really! The cost for building a nuclear plant is roughly 6 to 10 Billion US dollars. The annual revenue from a nuclear plant is roughly 1.3 to 2.0 US Billion dollars. The extra cost to add design features against Station Blackout is roughly 0.5 US Billion dollars (per unit).

23 Conclusions Not having SBO as a DBA was the fundamental cause for the Fukushima accident Adding a Bunker Safety System or the similar would be a resolution to the current problem we are facing in light of the Fukushima Accident.

24 Ask me 5 instead of 1 1. Is Nuclear Power Safe?