Nuclear Autopsies

, former director, Nuclear Safety Project | July 14, 2015, 6:00 am EDT
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Nuclear Energy Activist Toolkit #59

Medical professionals diagnose the health of their patients using non-destructive techniques (keeping with the Hippocratic Oath to do no harm) like taking temperatures and pulses and, when necessary, peering inside bodies using X-rays and Cat-scans.

Medical coroners, on the other hand, can use destructive techniques on persons when determining the causes of their deaths. Chest cavities and skulls are cut open to enable organs to be assessed. Tissue samples may be cut from bodies for microscopic examinations.

Insights gained during autopsies supplement the information gathered from treatments and examinations of living patients to broaden the knowledge of human health, allowing medical professionals and researchers to make health care advances.

Nuclear autopsies have been undertaken, and more are planned, for similar purposes—to supplement information gathered during tests and inspections conducted during reactor operation and support technological advances.

For example, the NRC outlined “harvesting” (their use, my re-use) several components during the decommissioning of permanently shut down nuclear power reactors.

Samples from the Zorita nuclear plant

Samples from the baffle plate and core barrel were harvested from the José Cabrera Nuclear Power Station (also known as the Zorita nuclear plant) in Spain as part of the Zorita Internals Research Project.

Fig. 1.

Fig. 1. (click to enlarge)  (Source: Nuclear Regulatory Commission)

Zorita was a pressurized water reactor similar to about two-thirds of the reactors currently operating in the United States. The baffle plate and core barrel formed a metal enclosure around the nuclear fuel within the reactor pressure vessel. They function to direct cooling water flow through the reactor core. Metal specimens attached to the core barrel and other internal components are periodically removed during refueling outages over the reactor’s lifetime for laboratory analysis of radiation effects.

The Zorita samples supplement those insights. Among other things, the results from the examinations will factor into the NRC’s decision-making about subsequent license renewal (SLR)—operating reactors beyond 60 years.

Additionally, there are plans to for samples from concrete structures surrounding the reactor pressure vessel at Zorita to be harvested. Previous concrete samples have been harvested from the containment building at Crystal River 3, from the shield building at Davis-Besse, and from the auxiliary building at Seabrook. The  samples at Zorita will come from concrete structures within the containment building and closer to the high temperature and high radiation emitted from the reactor pressure vessel.

Fig.. 2. (click to enlarge)

Fig.. 2. (click to enlarge) (Source: Nuclear Regulatory Commission)

Samples from the Zion nuclear plant

There are plans to harvest neutron absorber materials from the spent fuel pool at the Zion nuclear plant in Illinois, which permanently shut down a decade ago.

Fig. 3. (click to enlarge)

Fig. 3. (click to enlarge) (Source: Nuclear Regulatory Commission)

Spent fuel pools originally relied on geometry to prevent a nuclear chain reaction—the fuel assemblies in the storage racks were far enough apart to preclude a critical mass from being formed. When reprocessing was eliminated and the repository delayed, spent fuel pools were re-racked to store more fuel assemblies. The fuel assemblies within storage racks are typically closer together than when they are in the reactor core.

To guard against nuclear chain reactions, the walls of the storage racks contain neutron absorbing material. The objective of this material is to “soak” up neutrons emitted by the decay of unstable radioactive byproducts in the nuclear fuel and thus prevent them from interacting with uranium and plutonium atoms to cause fissions. But experience with neutron absorbing materials has not been stellar. There were fabrication problems, degradation problems, leaching problems, analytical problems, and expansion problems to list some of the many problems.

The Zion harvests may complement the humongous trial and error database.

Electrical cables will be harvested from both the Zion nuclear plant in Illinois and Crystal River 3 in Florida. Cables consist of metal wires that carry electricity throughout the nuclear plant wrapped in insulating material that guards against the electricity touching things along the way. The focus is on the cable insulation because it tends to age (degrade) faster at higher temperatures.

Fig. 4. (click to enlarge)

Fig. 4. (click to enlarge)  (Source: Nuclear Regulatory Commission)

Bottom Line

Harvesting of materials to enable fuller insights from their destructive examinations (i.e., nuclear autopsies) has not waited until nuclear power reactors have permanently shut down. As parts have worn out and been replaced (e.g., steam generators, reactor vessel heads, eroded pipes, etc.), specimens have been harvested and analyzed.

The nuclear industry and the NRC seek to expand those insights by harvesting materials from previously un-examined plant areas. These collections permit real data to replace positions established by extrapolating from other real data and/or by computer analyses. Hopefully, the real data reinforces previous positions. Either way, the real data supports better decision-making in the future.

Nuclear autopsies yield insights that cannot be obtained by other means.


The UCS Nuclear Energy Activist Toolkit (NEAT) is a series of post intended to help citizens understand nuclear technology and the Nuclear Regulatory Commission’s processes for overseeing nuclear plant safety.

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  • dinkydave

    OK, I’ve been following your “fission tales” for a while, appreciate your effort as one of authors of “Fukushima, The Story of a Nuclear Disaster.” Now we are on the subject of reactor materials, am requesting your comments on my “Lonely Neutron” hypothesis.

    Two reactors in Belgium are shut down because engineers found too many cracks and too much hydrogen embrittlement. Last I read, there were questions about whether this was a specific problem with Rotterdam Drydock, or general to all reactors.

    We know that a neutron left alone, my “lonely neutron” will decay into a proton and an electron–a hydrogen atom, with a certain half life. We also know many neutrons spend time transiting through reactor pressure vessel, RPV material. Do any of these neutrons become becalmed in the steel material? To my point, how many hydrogen atoms are created in RPV steel during the service, life? We know neutron flux damages reactor materials over time. I believe this hypothesis is original. I am asking response from you and any of our readers. Thanking all for any attention to this.

  • n_coast

    The condition of critical welds in reactor plants is monitored by nondestructive testing when the plants are refueled.

    It would appear to be relatively easy to monitor conditions in the spent fuel pools.

  • OddPlaceToMeet

    There are a lot of reasons for the deterioration of all materials near ionizing radiation from particle physics to the chemistry of ion migration. These are some of the toughest FMEA studies to be done and the predictive models for where these materials should end up are weak to say the least, (full life cycle analysis please), are yet to be done.
    It is time to have a true debate on the extent of decades of tritium releases just to mention one of the thousands of elements and compounds we are creating.
    Slow down and quit acting dumb about it all, is it that simple?

    • dinkydave

      Thank you. At least, my question is getting out. To you and n_coast, do we know how many RPV’s are ultrasound tested as thoroughly as the two Belgian reactors mentioned?

      Btw, from where I took formal retirement, a lot of our steel bars went into auto parts like axle shafts and suspension parts. A lot of those bars went through magnetic and ultrasound testing to verify quality.

      • OddPlaceToMeet

        Fairwinds,org has good information about embrittlement problems around US reactors and it usually takes a court case for the industry to respond properly. He has been working for decades to “enlighten” the public but it is a tough subject and sell, more than a few reactors did not get operating license extensions for containment or heat exchanger “issues” so kudos to him and others involved.

        Scrap metal yards and foundries also have radiation detectors in various parts of the process, how good or effective they are is debatable. Worked with the lab instruments that measured the compositions and structures of the foundry products and there was very little focus on looking for nuclear contamination (expensive testing), hope that has changed.