Bernard L. Cohen

This is the easiest to write of the articles on this blog. The only important part is a link to Prof. Bernard L. Cohen's website, THE NUCLEAR ENERGY OPTION. Here you'll find the most authoritative treatment anywhere of all aspects of nuclear energy as it relates to the public, and it's written clearly enough that any reasonably well-educated person can understand it perfectly.

This article could end right here, but maybe it's worthwhile to offer one example of his explanations. Since safety is the one place where most people's knowledge of nuclear energy is dodgy, what follows makes a good sample.

RISKS OF NUCLEAR ENERGY IN PERSPECTIVE

With the benefit of this perspective, we now turn to the risks of nuclear energy, and evaluate them as if a large fraction of the electricity now used in the United States were generated from nuclear power. The calculations are explained in the Chapter 8 Appendix, but here we will only quote the results.

According to the Reactor Safety Study by the U.S. Nuclear Regulatory Commission (NRC) discussed in Chapter 6, the risk of reactor accidents would reduce our life expectancy by 0.012 days, or 18 minutes, whereas the antinuclear power organization Union of Concerned Scientists (UCS) estimate is 1.5 days. Since our LLE from being killed in accidents is now 400 days, this risk would be increased by 0.003% according to NRC, or by 0.3% according to UCS. This makes nuclear accidents tens of thousands of times less dangerous than moving from the Northeast to the West (where accident rates are much higher), an action taken in the last few decades by millions of Americans with no consideration given to the added risk. Yet nuclear accidents are what a great many people are worrying about.

The only other comparably large health hazard due to radiation from the nuclear industry is from radioactivity releases into the environment during routine operation (see Chapter 12). Typical estimates are that, with a full nuclear power program, this might eventually result in average annual exposures of 0.2 mrem (it is now less than one-tenth that large), which would reduce our life expectancy by another 37 minutes (see Chapter 8 Appendix). This brings the total from nuclear power to about 1 hour (with this 37 minutes added, the UCS estimate is still about 1.5 days).

If we compare these risks with some of those listed in Table 1, we see that having a full nuclear power program in this country would present the same added health risk (UCS estimates in brackets) as a regular smoker indulging in one extra cigarette every 15 years [every 3 months], or as an overweight person increasing her weight by 0.012 [0.8] ounces, or as in raising the U.S. highway speed limit from 55 miles per hour to 55.006 [55.4] miles per hour, and it is 2,000 [30] times less of a danger than switching from midsize to small cars. Note that these figures are not controversial, because I have given not only the estimates of Establishment scientists but also those of the leading nuclear power opposition group in this country, UCS.

I have been presenting these risk comparisons at every opportunity for several years, but I get the impression that they are interpreted as the opinion of a nuclear advocate. Media reports have said "Dr. Cohen claims . . ." But there is no personal opinion involved here. Deriving these comparisons is simple and straightforward mathematics which no one can question. I have published them in scientific journals, and no scientist has objected to them. I have quoted them in debates with three different UCS leaders and they have never denied them. If anyone has any reason to believe that these comparisons are not valid, they have been awfully quiet about it.

Nuclear Accidents

There have been two serious accidents involving nuclear power reactors and it's right that they have received very much attention. They are at the heart of the debate over whether or not to expand nuclear energy to minimize global warming.

The reactor at Chernobyl was different from all the other power reactors outside the Soviet Union: it was inherently unstable, meaning that the reactivity in the core went up when it got hotter so that once the operators lost control there was no way to get it back.

The accident happened this way[source]. The night crew was told to perform a test to see if the reactor could sustain a sudden disconnection from the power grid. It happened that the night crew was inexperienced (presumably because of seniority rules), though that probably wouldn't have made any difference. What was supposed to happen was that the flywheel inertia of the turbine blades in the electrical generators would give enough power to run the coolant pump until the diesel-powered generators could start and power up.

The crew didn't know that the reactor was operating at an abnormal condition, having run at full power all day and then being cut back to part load, but that probably wouldn't have made any difference, either.

It's not clear why, but the coolant pumps were run at their maximum flow. Possibly the crew thought they were increasing the safety margin. But the resulting cooler temperatures lowered the steam pressure and water filled more of the reactor's internals. Water absorbs neutrons more than steam does, so the control rods had to be withdrawn to maintain power.

The automatic controls would ordinarily have shut down the reactor under these conditions, so the crew disabled the emergency cooling system and the emergency shutdown rods (usually called SCRAM rods).

The crew disconnected the plant from the power grid. But the pump power from the turbine blades wasn't sufficient so the reactor started heating up. Because of the instability this reactor had, the higher temperature raised the reactivity rate, causing more heating, etc. At that point the reactor was out of control. Steam drove water out of the core, and reactivity increased more. Once the crew realized something was wrong, they inserted the control rods. But the control rods inserted slowly, not quickly as the shutdown rods would have. To make matters worse, the tips of the control rods were made of graphite instead of boron. Graphite raised the reactivity rate instead of lowering it as boron would have done. The rods jammed when they were partly inserted.

The reactor continued to heat up. A steam explosion drove some parts out through the sheet-metal roof that kept rain off the reactor. Finally, the reactor body, which was made of graphite, reached its ignition point. The hole in the roof allowed air to enter and the reactor caught fire.

After the accident, the World Health Organization did an extensive investigation and continual followup; its findings were that actual deaths have numbered about 50 and theoretically there could be as many as 4000 fatal cancers in the future.[source] As tragic as that is, it doesn't approach the death rate due to burning coal.  Even in the US, tens of thousands of people die every year just from the pollution from generating electricity with fossil fuels.[Abt Associates Report, Exhibit 6-4]

What's interesting is that a big part of the region around Chernobyl now is healthier than before the accident. The chemical refineries and coal-burning plants caused terrible health problems. Now that they're shut down, the air is clean. Some people have moved back into the parts which officially are quarantined but where radiation isn't especially high. They eat vegetables from their gardens and drink water from their wells, and take eggs from their bug-eating chickens, and they're doing just fine. Wildlife have flourished in the area, including the hot spots. Wildlife biologists are studying the animals and plants and even after all these years they're not finding any radiation-related health problems. There's a superb book on Chernobyl's aftermath: Wormwood forest : a natural history of chernobyl by Mary Mycio.

So what are the differences between Chernobyl-style Soviet reactors and all the power reactors in the rest of the world? There are too many differences to list here, but we'll tick off the major differences that led to the accident.

1. The reactor was unstable.
2. The reactor had no containment structure.
3. The reactor was made of graphite, protected only with a sheet-metal shed. Outside the Soviet Union, power reactors have multiple layers of steel and concrete protection.
4. The crew hadn't been trained for the test it was performing.
5. The crew was working without supervision and went against plant operating regulations.


To understand why the reactor was built and operated so unsafely, you'd have to understand how the Soviet system worked. I'm not qualified to explain it, but if you read some Solzhenitzyn you'll get the idea. The accident did, however, prove that anti-nukes had vastly overstated the harm such an accident could cause. It turned out that the consequences, serious as they were, were of the same scale as disasters that happen every year.

More important, the accident at Three Mile Island in Pennsylvania in 1979 totally destroyed the reactor but resulted in no adverse health effects, which validated the defense-in-depth designs used in all US power reactors.[source]