Arnold Gundersen

Arnold "Arnie" Gundersen is an American consultant and chief engineer of an anti-nuclear propaganda group called Fairewinds Energy Education, formerly Fairewinds Associates, which is led by his wife, Margaret "Maggie" Gundersen. The group offers expert testimony at various legal hearings related to nuclear power and produces anti-nuclear videos. Arnie's primary activity includes conjecturing safety flaws in the AP1000 reactor design, supporting the Vermont legislature in trying to shut down the Vermont Yankee nuclear power plant, and most recently spreading misinformation about the Fukushima accident.

For greater effect, the Fukushima-related materials on the Fairewinds website have been translated to Japanese by volunteers.

Expertise
Unlike a great majority of anti-nuclear activists, Gundersen has a master's degree in nuclear engineering, which he obtained in 1972 at the Rensselaer Polytechnic Institute, as well as a reactor operator's license from the U.S. Atomic Energy Commission (the predecessor of the Nuclear Regulatory Commission). He claims 40 years of experience in the nuclear industry.

The reality is that Gundersen operated only a simple, very low power (100 W), open-tank research reactor. He did not actually work in the nuclear industry since 1990 and through most of his career was employed in managerial positions. During his work at Northeast Utilities (1972-1976), when he calls himself the Responsible Nuclear Engineer for two power stations, he was actually responsible primarily for filing paperwork.

Claims
Below is a partial list of Gundersen's claims related to nuclear power.

AP1000
The Westinghouse AP1000 is a generation III+ reactor with passive safety features, adopted by China as a standard design. It has a water tank on top of the reactor building; during an emergency, it drains through gravity onto the internal steel containment vessel to provide evaporative cooling when no power sources are available. The reactor is designed to survive a complete loss of power for 72 hours without any operator action. Despite being a big improvement over existing designs (the Fukushima I accident would not happen if the reactors were AP1000 instead of BWR Mark I), which were already pretty resistant to accidents to begin with, Gundersen thinks it is very dangerous.
 * The design certification was fast-tracked under the influence of the Congress. A rather funny accusation given that a similar predecessor design, AP600, received the NRC certification in 1999, the original AP1000 design was certified in 2006, and it took the Commission another 5 years to certify an amended design with better protection against aircraft impact. Gundersen provided no evidence to substantiate this claim, and it's nothing but poisoning the well.
 * The water tank at the top of the reactor building is a novel and untested feature. Water tanks are routinely located on top of high-rise buildings. This special pleading is intended to increase costs by insisting that general engineering experience cannot be used in nuclear engineering.
 * The water tank is not designed for aircraft impact. In fact, the effects of aircraft impact on the water tank are explicitly addressed in the probabilistic risk assessment.
 * No full scale model of the reactor was built. This is true, but such a model would be prohibitively expensive to construct (possibly as expensive as a working reactor) and at the same time absolutely unnecessary. Skyscrapers, bridges, dams, tunnels, gas pipelines and other large structures that can cause many deaths if they fail are routinely built without full-scale models.

Fukushima

 * The spent fuel pool of unit 4 "blew up". The actual source of the explosion was hydrogen from unit 3 that leaked into the unit 4 building through shared piping. The spent fuel was never uncovered, even though the water in the pool did increase its temperature for some time.
 * Nuclear fission continues to occur in Fukushima reactors. This claim is based on reports of radioactive xenon gas, a fission product, being detected at the reactors. It was established long ago that the source of the xenon is spontaneous fission, which is a mode of radioactive decay of some heavy nuclides produced in the reactor, because xenon readings did not change after the injection of boric acid, and there was no increase in temperature or pressure. There were increased readings of temperature at one unit, but these were apparently caused by a faulty thermometer.