1. Pressure vessel contains small
core & high-pressure water.
2. High-pressure driven primary
heat exchanger circuit.
3. Lower-pressure secondary
coolant circuit for steam and
4. Containment structure; with
std power plant outside.
Safety Features of Pressurized Water Reactor.
- Closed loop prevents radiativity loss.
- Fuel: ceramic pellets sealed in metal tubes.
- Ten-inch thick steel reactor vessel
corrosion 2001-4(Repair$600M/Fines28M)Text starts with bottom
entry on Aging Reactors
- Containment bldg prevents "incident" escaping.
- Closed loop prevents radiativity loss.
- Water thermalizes neutron for effective fission.
- Control rods (e.g., B or Cd) absorb neutrons to
fine-tune reactor operation.
- Emergency coolant water.
Details complicate design
- Enrichment. Natural uranium is 0.7% U-235; need
~4% for steady-state U-235 fission process.
- Light water. Pressurized to 150 atmospheres so 325 C water
doesn't boil; secondary steam produced in heat exchanger. Serves two
- Coolant. Transfers heat from the fissioning fuel rods to
- Moderator. Need "Cold" neutrons for effective U-235
fission. Negative feedback: higher reactivity increases
temperature that in turn decreases moderation and hence reactivity.
Reverse: decreases in temperature causes increases in reactor power.
- Control rods adjust delayed neutrons.
- 2.4/fission neutrons are prompt. Control rods
reduce to 0.993: subcritical reactor.
- 0.07% neutrons delayed by ms-min.
Control rods fine-tune steady state running.
- Emergency coolant water is positioned above reactor so that
in the event of loss of coolant water gravity flow would quickly
Too Many Designs for Nuclear Safety
Lack of international and business good sense proliferated
designs of nuclear reactors.
- Light Water used as moderator
- Pressurized water (PWR, US:69). Nuclear
submarine doesn't unreplenish fuel.
- Boiling water (BWR, US:36). Steam connects reactor core
to turbine; no PWR isolation.
- Graphite-moderated, often CO2 coolant.
- RBMK, no container vessel: Chernobyl!
- Advanced gas-cooled, UK, better thermal eff. than PWR.
- Magnox, UK, with natural uranium fuel.
- Candu, Canadian PWR. Natural uranium & other
advantages undermined by heavy water cost.
- Breeder produces more fuel than it consumed;
unmoderated natural uranium, fast neutrons sustain chain
reaction. Few running: Russian: since 1981; Japan:140 MW.
Others: Japan, India, China, UK, France, Germany, USA.
Nuclear electric capacity (GW): 372 World (65 under construction); Country: 102 USA, 65 Fr,
44 Japan, 24 Russia (10),
21 Korea (4), 14 Canada, 12 Ukraine, 13 China (29), 12 Germany, 10 UK, 9 Sweden,
8 Spain, 6 Belgium, 5 Taiwan (3), India (5); 4 Czech; 3 Switzerland, Finland; 2
Bulgaria, Hungary, Brazil, S Africa, Slovakia, Mexico; 1 Romania,
Argentina, Iran, Pakistan; Slovenia, Netherland, Armenia.
A Single Design
In 2000 the US Nuclear Regulatory Commission settled on a standard
design AP600 that incorporates the best foreign/US practices and
But none have been ordered, quickly. see below.
Steps in Changing the Approve Design
New design AP1000 was proposed to replace AP600: timeline
- 2002 March, NRC agreed to review Westinghouse AP1000 design.
- 2005 December, NRC voted ``final" approval.
- 2007 May Westinghouse ammended AP1000 design, sent to NRC. More
revisions were submitted Dec 2010 and Jun 2011.
- 2011 August, NRC issued final safety report.
- NRC description of AP1000:
"The AP1000 is a 1,100 megawatt electric pressurized-water reactor
that includes passive safety features that would cool down the reactor
after an accident without the need for electricity or human
What is being built?
NYTimes 22 Dec 2011 reports NRC unanimously approving a radical
new design (AP1000), thus clearing path for pair of plants being built
near Augusta GA by Southern Co. and another pair being added to Summer
plant of Carolina E & G in Fairfield county, SC in Augusta, GA. First
authorization since 1978! Other news outlet follow the story with Fox
news at tail end: 09 February 2012. Fox stresses the now replaced NRC
chair (Gregory Jaczko) was the only no vote.
Congress authorized $17.5 billion for loan guarantee, but banks
haven't stepped forward. Whoops! two days later NYT corrected story
to NRC approving design but not their actual construction.
Couldn't find that any new site being constructed.
The textbook goes thru the argument that the reaction
31H + proton
could produce the world's energy resources for 30 million years.
So why aren't we?
- Temperature. Fusion in the stars: ~108 K.
- Lawson's criterion. For sustained fusion (given the
temperature) we must confine matter sufficiently long: > 6
What are our chances? Ordinary matter has roughly 6 1027
atoms/m3. So we only need to confine it for 100 ps. Will
matter wait that long at 108 K?
======= ignore below; wait for time to tell
- Magnetic confinement.
Currently ITER is being worked on. Stay tuned.
- Inertial Laser confinement. At LLNL's NIF 32 multi-TW laser
will both confine and heat a pellet of fuel. Stay tuned.
For the future.
If we want more nuclear energy now, the only possibility is building nuclear
reactors. March 2013, World Nuclear Association:
2013: completionn expected (GWe) Iran 1, India 2, China ~9, Korea KHNP
2.4, Argentia 0.7, Russian 1.
2014: Russia 2, Slovakia 0.9, Taiwan 1.3, China 10.5, Korea KhNP 1.3,
Japan 1.4?, India 0.5.
2015: USA 1, Taiwan 1.3, China 7.5, India 0.6, Japan 1.4
2016: Finland 1.6, France 1.6, Russia 2.3, India 1.2, Pakistan,
2017 (updated Sept 2017): 50 reactors under contruction; most in
Asian region; capacity being created by plant upgrading; also lifetime
extension program, esp, in USA). Currently 440 nuclear power reactors
operating in 30 counties with 390 GWe. Under construction are 50
in 13 countries: Brazil 1 (CNNC); Chine 20 including world's first
Westinghou AP1000; Finland fifth very large reactor; France 1600 MWe,
India 6 to supplement current 22; Japan 2 (nothing on closed reactors);
Russia "several"; Slovakia 2 440 MWe; South Korea 3 1400 MWe adv PWRs;
USA 4 under construction altho 2 cancelled in August 2017. [These add to 38.].
[Wednesday, 21-Mar-2018 12:41:06 EDT]
Edited by: email@example.com on
Monday, 25-Sep-2017 14:22:29 EDT