TheSafety of Nuclear Power Plants

Dr. RichardDenning, Professor of Nuclear, Mechanical and Aerospace Engineering at The OhioState University explained the hazards of radiation, the recent nuclearemergency at the Japanese Fukushima Power Plant and safety principles for U.S.nuclear power plants.

Radiation Dose Measurement

Power-plantreactors do not have highly enriched fuel like a nuclear bomb and cannotproduce a large amount of high-energy gamma rays like a bomb. Power plantreactors do generate radioactive products of nuclear fission. If large amounts of these products areingested or inhaled, they can cause illnesses including cancer.

The rem is the radiation measurement used in the US.

425+ rem is a lethal dose.

100 rem will cause radiation sickness and anincreased cancer risk.

25 rem will cause anemia and an increased cancerrisk.

2 - 5rem/year is the maximumallowable dose for radiation workers under normal conditions.

               It is impossible to determine an increased medical risk for this low of a radiation dose.

Less than 1rem/year is the increaseof low-level radiation to those living near a nuclear power plant.

Each of us isexposed to radiation at a rate of approximately 0.6 rem/year. Radon gas fromthe earth below our feet is the biggest contributor to natural backgroundradiation. Other sources include cosmic rays, medical diagnostics procedures, stoneused in building materials and many other commonly used products. Dr. Denningheld a radiation detector over salt substitute used in food preparation to showthat it emits low levels of radiation. Weare also exposed to slightly higher radiation levels every time we take acommercial airline flight because there is less atmosphere to filter out cosmicrays at that altitude. Denver has higherbackground radiation than Columbus because of the difference in altitude.

What Went Right/Wrong at the FukushimaNuclear Power Plant?

After the earthquakehit Fukushima, the nuclear chain reactions shut down and emergency dieselgenerators started to cool the reactors. When the tsunami hit, water swamped thediesel generators causing a station blackout and failure of emergency coolingsystems. Emergency power came from backup batteries which provided only sixpercent of normal operating power; this dropped to less than one percent withinthe week. There was no cooling of the fuel rods for 78 hours. Steam oxidizedthe fuel rod coatings to produce hydrogen which exploded and rupturedcontainment vessels. Technicians began to use sea water for cooling and thearea became more stable.

DamageDone by the Earthquake and Tsunami

There were20,000 lives lost to the earthquake and tsunami. There have been no lives lostto power plant explosion and radiation contamination. The maximum rem dosagefor Fukushima emergency responders was increased to 25 rem, which increasedtheir cancer risk by 1.5%. No member ofthe public will get near that level of exposure because the risk was greatlyreduced by dispersion of the contaminants in the atmosphere. The livelihoods offisherman and farmers have been curtailed because of radiation contaminants inthe soil and water.

Reactor Safety in the U.S.

There are fourkey radiation safety principles that are needed for crisis management at the104 nuclear power plants in the US.

·        Shutdown reactor

·        Removeheat from fuel

·        Transferheat and hydrogen to the environment

·        Containradioactive isotopes

New nuclearplants undergoing certification are engineered to be passive safe,which means that emergency procedures are automatedby design and need no human intervention or electricity to start them. Safetysystems are redundant and diverse; there are more than one backup system andmore than one kind of power source. The Nuclear Regulatory Commission performsconfirmatory analysis and extensive experiments before licensing nuclearreactors.