Nuclear weapons and their effects –Educating for a change. Alan Slavin, Department of Physics, Trent University, March 9, 2007. AGENDA Militarism in a broader context Nuclear weapons and their effects Existing treaties Changing US policy What we can do KEEP IN MIND:
Nuclear weapons and their effects –Educating for a change.
Alan Slavin, Department of Physics, Trent University, March 9, 2007
Broader Context: Three closely related problem areas in the world today.
About 80% of the world’s military expenditure goes conventional (non-nuclear) arms. Most exported arms are used against the inhabitants of the purchasing country.
Canada was the world's 8th largest arms exporter in 2002.
Poorer countries often destroy their environments, through deforestation, unregulated mining, etc, to pay for basic services such as health and education.
Global warming is aggravated by the rapid development of poorer countries as they burn coal to provide electrical power.
Emissions from military operations cause 6 to10% of global air pollution and contribute significantly to global warming. (World Watch Institute 2000).
CONSTRUCTION OF NUCLEAR WEAPONS
-heavy nucleus contains protons and neutrons
-surrounded by orbiting electrons
For example, Uranium-235 (or 235U) has 235 neutrons and protons in its nucleus. That is, mass number A = 235.
+ n +ENERGY as heat, X-rays and gamma rays.
radioactive fission fragments
E = mi c2 – mf c2
ENERGY CAN BE RELEASED FROM THE NUCLEUS IN TWO WAYS
1.Fission is the breaking up of a heavy nucleus to release energy ("fissure“)
2.Fusion is the melting together (fusing ) of 2 light nuclei to form a heavier one.
Example: 2H + 3H 4He + n + energy
FISSION CHAIN REACTION
If only small amount of 235U, most of the neutrons will escape without causing another fission process.
If more than a "critical mass" of 235U, a chain reaction will occur.
Simplest is “gun“ approach: 2 sub-critical 235U masses shot together to form a critical mass (Hiroshima bomb). Most countries could
make such a bomb if they had the U or Pu (32 do, in 2007).
Critical mass: ~50 kg for 235U, ~12 kg for plutonium-239 (about the size of a grapefruit). 239Pu was used in the Nagaski bomb.
Energy released from 12 kg of 239Pu
= 4000 tons of TNT (1000 tons = 1 kiloton = 1 kT).
= electrical output of Pickering A power plant for 6 days at 2000 MW (1 MW = 1 megawatt = 1 million watts)
The Hiroshima bomb was 12 to 15 kT.
Fusion bomb (or helium-bomb, or H-bomb)
X- rays &
2H & 3H
U or Pu
Fission bomb trigger ignites fusion bomb fuel
Chemical explosives compress U or Pu → fission bomb.
X- and gamma rays compress fusion fuel → fusion bomb.
Fusion bombs up to 20 MT = 1000 x Hiroshima bomb.
More typical: 0.2 to 1 MT (10 to 50 x Hiroshima).
1 MT = energy in coal train 300 km long.
First hydrogen-bomb test, Operation Ivy, at Enewetak atoll, 10.4 MT.
The mushroom cloud climbed to 17 km in only 90 seconds, entering the
stratosphere. One minute later it reached 33 km, eventually stabilizing
at a ceiling of 37 km. Half an hour after the test the mushroom stretched
100 km across, with the base of the mushroom head joining the stem at
14 km. http://www.radiochemistry.org/history/nuke_tests/ivy/index.html
EFFECTS OF A 1-MT BOMB EXPLODED AT 1.8 KM HEIGHT
SHORT-TERM EFFECTS1. Heat pulse 2. Blast 3. Radiation sickness
1. Heat pulse:
- second degree burns at 13 km
- 3rd degree burns at 10 km
- ignition of clothing at 8 km
If 2nd degree burns over 30% of the body or 3rd degree burns over 25% of the body, the burns are fatal if not treated promptly.
In all the USA, there are facilities for a few thousand burn cases. A single bomb could cause 10,000.
The intense heat of the explosion causes a pressure pulse that extends out in all directions from the blast.
2. Blast: 1-megaton Air Burst over Toronto at Yonge and Bloor
Explosion causes a pressure pulse = blast
Peak Overpressure Distance Effects
(14.7 lb/in2 = 1 atmos)
20 lb/in2 ~Pape2.9 km -reinforced concrete buildings destroyed; no survivors; 800 kmh wind
10 lb/in2 ~Dufferin 4.3 km -commercial buildings collapsed; no survivors; 480 kmh wind
5 lb/in2 ~Victoria Pk6.4 km -brick & wood houses destroyed; 50% fatalities, rest injured; 260 kmh
2 lb/in2 ~Kennedy11 km-significant damage to houses; 50% casualties: 5% dead, rest
injured; 115 kmh wind; high fire hazard, destroys 50% buildings
1 lb/in2 ~Markham Rd16 km-moderate damage to residences; 25% injured
(The Effects of Nuclear War, US Office of Technology Assessment, 1979)
3. Radiation sickness
Radiation = high-energy particles: gamma (γ) rays, X-rays, neutrons and electrons [beta (β) rays].
Damages cells: can cause sickness or death.
Sources: "prompt" radiation from the explosion + "decay" of radioactive fission fragments.
Air burst, neutrons and gammas are absorbed on passing through air: only people near the blast centre seriously exposed, and they would die anyway from blast and fire.
Ground burst: more serious; n & γ convert nuclei in ground into radioactive nuclei. Blown into air and settle back to earth as "fallout".
The radiation from fallout decreases with time
- 80% gone in 1 day
- 90% gone in the first week
- the rest lasts for months
Effects of radiation on humans
(from Hodges, Environmental Pollution 1977, and Miller) Radiation dose = sievert,Sv
Fig. 2 7-day Fallout from a 1-Megaton Bomb Ground Burst over Toronto
At 5 Sv, 50% of exposed people die
At 10 Sv, 100% of exposed people die.
Each dose shown represents the
minimum value within that contour, in the absence of any shielding. The exact distribution depends on the wind speed and the terrain. Several bombs totalling much more than 1 MT would be expected for a city the size of Toronto.
(The Effects of Nuclear War, US Office of Technology Assessment, 1979)
Fallout Distribution over the USA from an All-out Exchange of Strategic Weapons, US-USSR Shaded = > 10 Sv if no shelter: 100% fatalities.
Decrease in frost-free days from 100 15-kT bombs.
Toon et al., Science 315 1224 (2007)
Number of nuclear weapons in the world (+Wikipedia 2006)
MAD = Mutually Assured Destruction = 200
Fig. 4 . Global firepower of nuclear weapons in terms of World-War II firepower.
The one dot in centre = firepower of WWII = 3 MT.
Circle at lower left = 24 MT =firepower on 1 Trident sub.
Dots in two squares = destroy all large and medium cities in world.
Current global firepower, ~ 0.5 of 1990
MAJOR TREATIES TO DATE
1963 Limited Test Ban Treaty: no tests in the atmosphere, outer space, under
water: Eliminate the spreading of fallout in the atmosphere, which has been
responsible for about 11,000 cancer deaths in the USA alone as of 2002.
1967 Outer Space Treaty: No nuclear weapons in outer space.
1970 Non-Proliferation Treaty: The 5 nuclear-weapons states (NWS: USA,
Russia, England, France, China) agreed to reduce the number of their nuclear
weapons (NW) if the other signatories do not develop NW.
Affect: Only 4 other countries have developed NW, but the 5 NWS
have not seriously reduced their weapons.
1972 Seabeds Treaty: No nuclear weapons stationed on the seabed.
1972 Antiballistic missile (ABM) treaty (modified 1976), USA and USSR: The
number of missiles stationed to shoot down incoming missiles is limited to a
single site in each of USA and Russia (e.g. Moscow). This treaty recognized
that ABM's could easily be overcome by building more attacking missiles,
leading to a serious arms race.
1976 SALT II (Strategic Arms Limitation Treaty).
- Limits number of ICBM (Intercontinental Ballistic Missile) launchers and heavy
- Limits number of warheads on each to 10 for ICBM's and 14 for SLBM's
- Only 1 new ICBM can be developed and built.
- Prohibits interference with verification measures, such
1987 Intermediate-Range Nuclear Forces Treaty (INF)
- prohibits development and deployment of all land-based (in Europe and Russia)
short-, medium- and intermediate-range ballistic missiles (IRBMs) with
ranges of 300 to 3,400 miles, as well as all ground-launched cruise missiles.
1996 Comprehensive Test Ban Treaty (CTBT). Signed by most countries, but not ratified by USA.
Bans all NW tests, with the goal of stopping the development of new weapons, and eventually eliminating all weapons as they must be tested periodically. As of July 2002, 165 states signed and 93 ratified. No USA or Russian tests since 1992.
1998 ... Middle Powers Initiative: Brazil, Egypt, Ireland, Mexico, New Zealand, South Africa, and Sweden + 8 NGOs. Working to influence NWS to follow the NPT.
RECENT US POLICY CHANGES RE NUCLEAR WEAPONS
2002 ‑ US withdraws from ABM Treaty, to enable it to develop ballistic missile
defence (BMD) from "rogue states". (Maybe Alaska from N. Korea?)
Result: BMD does not yet work (may never work) but other countries, such as
China, now fear a pre‑emptive attack from US, so are building more nuclear
weapons. (China will increase its military budget 18%; March 2007).
2002 Nuclear Posture Review
‑ US includes integrates NW with conventional weapons in its war strategies;
assumes it will have NW for next 50 years.
‑ claims the right to use NW to attack any country suspected of developing
"weapons of mass destruction“ (nuclear, chemical, biological).
‑ names Iraq, China and N. Korea as possible nuclear targets if they attack
Potential Result: Signing the NPT is no guarantee that NW will not be used
against you, so why not develop NW? Terrorist danger from nuclear weapons
increases with the number of nuclear weapons states.
2002 Bush threatens to withdraw from the CTBT as the US is developing the NW
"robust earth penetrator" as a "bunker buster", which is nearing completion.
However, in 2005, Senate denied more funding for this project.
2007 (March) Russia threatens to withdraw from the INF (Intermediate Nuclear
Forces) Treaty as USA plans ABM system in Europe.
Overall result: world is now in much more danger from NW use and proliferationthan before 2002.