March 26, 2002Andrej Stritar

1
The Concept of Nuclear Safety

• Dr. Andrej Stritar
• President, European Nuclear Society
• c/o J. Stefan Institute, Ljubljana, Slovenia

2
Nuclear Power Plants (NPPs) - excellent source of
energy

• Reliable
• Cost effective
• Environmentally friendly...

• However, there are safety concerns!
• Why?

3
Simple principle of NPP
electrical energy
mechanical energy
fission energy
heat
4
Different types of NPPs
5
Where is the danger?
reactor
fuel element
fuel rod
reactor core
uranium pellet
6
What is going on in Uranium?
radiation
n
n
n
heat
7
Fission products

• Typically highly radioactive
• We want them to stay inside fuel rods
• The First Safety Problem

8
Decay heat

• Unpleasant property of reactors
• Heat is released also after fission is stopped
• The Second Safety Problem

9
Two Basic Safety Goals

• Prevent spread of radioactivity into the
  environment
• Provide adequate cooling of the core

10
Cooling, cooling...

• Additional cooling systems are needed because of
  the decay heat
• Cooling must be always available failures,
  thunderstorms, earthquakes,

11
If reactor core is not cooled...

• the core could melt
• Radioactivity could be released into the
  environment

failed containment
radioactive cloud
melted core
melted reactor vessel
corium
12
Multiple barriers
1st barrier Fuel cladding.
2nd barrier Primary system boundary.
3rd barrier Containment.
13
Active safety systems

• G

14
Basic Hardware Design Principles

• Anything may break
• Single failure should not lead to core melt
• Redundancy
• Always several means to do something
• Fail safe
• Breaking into the safe position
• Negative feedback
• .

15
Human Factor

• Bad driver
• can be killed in the best Volvo

• Careful driver
• may reach destination with any vehicle.

16
Safety Culture

• Operating the plant is very responsible job!
• That must be never forgotten!
• Strictly follow the rules!
• Nuclear power plants are dangerous
• keep thinking about that!
• Never be complacent!
• You are never doing good enough!

17
Complacency

• As long as you are aware, that nuclear power
  plant is dangerous
• it is quite safe.
• As soon as you believe it is not dangerous
• it becomes unsafe!

18
Quality Assurance System
19
International Safety System

• IAEA Standards
• Framework for National Standards
• Each Country must have its own system
• International Safety Missions

20
A look into the future

• Advanced Nuclear Power Plant Designs
• Evolutionary
• New Designs
• Revolutionary
• Generation IV...

21
Advanced Designs

• Based on existing plants
• Passive Safety Systems
• Less need for operator action

22
Westinghouse AP600
23
Pebble Bed Modular Reactor
24
PBMR Specifications

• Max. sent out power 100-115 MW
• Continuous stable power range 0-100
• Ramp rate (0-100) 10/min
• Step change 10 of current power
• Load Rejection w/o trip 100
• Cost 1000/kWe
• Construction Schedule 24 months
• General Overhauls 30 days per 6 years
• Outage rate 2 planned 3 forced
• OM and Fuel costs 4-5/MWh
• Emergency Planning Zone lt 400 meters
• Plant Operating Life Time 40 years

25
PBMR Core Temperature
26
So, is it worth starting nuclear?

• Absolutely yes!
• Benefits are much higher than risks!

27
Some geographical facts
28
Electricity consumption per capita per year
Vietnam 252 kWhLaos 98 kWhCambodia 17
kWhThailand 1293 kWhMalaysia 2552
kWhFrance 6600 kWhNorway 25,000 kWh
29
Vietnam
252 kWh per capita
25,000 kWh per capita 100 times more!
30

• This World will be fair
• once everybody is given the same opportunity,
• which includes
• electrical power.
• 10, 20, fifty times more electricity than today!

31

• and we want to do it sustainable,
• without damaging the environment!

32

• It can be done safely with
• NUCLEAR POWER,
• but hardly without it.