Howard Dickson President Emeritus Health Physics Society

Transcription

1 Howard Dickson President Emeritus Health Physics Society

2 Summary of accident experience Differentiation between nuclear & radiation accidents Categories of accidents Examples of accidents & their severity What have we learned?

3 REAC/TS maintains a radiation accident registry that contains data on 469 radiation accidents (as of June 2013) worldwide. The criteria for including an accident in the registry consists of a dose exceeding 5x the current U.S. dose limits for a radiation worker. The accidents in the registry have resulted in 102 fatalities due to the acute radiation syndrome plus 8 trauma fatalities. Of the 26 deaths in the USA, 21 have occurred from medical misadministrations (mostly from therapeutic treatments) 3

4 A nuclear or radiation accident is defined by the International Atomic Energy Agency (IAEA) as "an event that has led to significant consequences to people, the environment or the facility. "Nuclear refers to something dealing with or at the level of the nucleus of an atom. (Nuclear bombs are so called because they involve the fission of the nucleus of an atom.) Radiation" refers to the energy being emitted from any source, including emissions from radioisotopes or from a machine such as an accelerator.

5 Nuclear meltdown, e.g. Fukushima Decay heat, e.g. Mayak Transport, e.g. Nuclear weapons Equipment failure, e.g. Three Mile Island Human error, e.g. medical misadministration Loss of control of source, e.g. large radiation sources left insecure

6 The nuclear industry is subject to accidents just like any other industry: Human folly Poor judgment Mechanical failures (design features) Acts on nature (acts of God)

7 Categories of radiation accidents are broader than just nuclear reactor accidents and include: 1) Industrial radiography 2) Industrial irradiation facilities 3) Medical procedures (primarily associated with therapy) 4) Loss of control of radiation sources 5) Nuclear energy (nuclear fuel cycle) 6) Natural phenomenon 7) Nuclear testing and nuclear weapons related activities, including criticality accidents 7

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9 Industrial Irradiation Facility Accidents Facilities use intense radiation sources for sterilization of foods, surgical instruments, and other items. Unintended exposures result from radiation sources not properly returning into shields or failures of staff to know sources are deployed. 9

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11 Radiation in Medicine accidents Accidents and incidents are generally over-exposures due to equipment malfunctions, lack of proper training, poor judgment or combinations. Serious overexposures leading to acute radiation effects occur more often in therapeutic procedures while modest overexposures leading to increases in cancer risk probably occur more often in diagnostic procedures. Overexposures range from a few times larger than appropriate to levels causing severe acute effects (such as seen to the right). 11

12 Orphan radiotherapy source accident: Goiania, Brazil September 1987 Abandoned cancer clinic discarded source canisters from radiotherapy machine. Junkyard worker opened canisters revealing iridescent blue powder. Public contaminated with radioactive Cesium ,350 Ci (5 x Bq!) CsCl source. About 10 g or a spoonful 12

13 Total Population Persons Monitored Persons w/measurable Doses Persons Admitted to Hospital Persons Needing Intensive Care Deaths Forearm Amputated Number 1,000, , % Pop n photo credits: IAEA

14 A nuclear criticality accident is the occurrence of a self-sustaining neutron chain reaction that is either unplanned or behaves unexpectedly. Total of 60 accidents in 9 countries 38 were at a reactor or in laboratory environment 22 were in a manufacturing or processing facility Total of 9 fatalities (all within 1 meter of source) and 36 significant exposures (within 5 meters) *Ref. ANS NCSD Education Committee Criticality Accident White Paper, April 2009.

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16 Tokaimura criticality accident occurred on 30 September Worst civilian nuclear accident in Japan prior to the Fukushima. Occurred in a uranium reprocessing facility. Three technicians were preparing a batch of fuel for an experimental fast breeder reactor using 18.8 % enriched U. The criticality continued intermittently for about 20 hours. Boric acid solution (neutron absorber) was use to the halt reaction. Local evacuation included 161 people from 39 households within a 350-meter radius. 39 plant workers and at least 667 others (emergency responders and nearby residents also exposed. Using blood Na activation, doses to techs involved determined to be 17 Sv, 10 Sv, and 3 Sv. The two with the largest doses died two more than Fukushima!

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18 Windscale, UK Three Mile Island, PA Chernobyl, Ukraine Fukushima, Japan 18

19 The Windscale fire of 10 October 1957 was the worst nuclear accident in Great Britain's history. The fire burned for 3 days causing a release of radioactive contamination that spread across the UK and Europe. Major concern was iodine-131, which can lead to cancer of the thyroid (estimated that the incident caused 240 additional cancers). No one was evacuated from the surrounding area, but milk from about 500 km 2 was collected and destroyed for about a month. A 2010 study of workers directly involved in the cleanup found no significant long-term health effects from their involvement.

20 Three Mile Island Cause of accident: Combination of equipment failure and operator error. Consequences: TMI 2 accident caused no injuries or deaths. At least a dozen epidemiological studies conducted since 1981 have found no discernible health effects. Over 2000 lawsuits seeking damages denied for lack of evidence of harm. 20

21 The 1986 accident at the Chernobyl nuclear plant in Ukraine is the only accident in the history of commercial nuclear power to cause fatalities from radiation. This reactor was the product of a severely flawed Soviet-era reactor design combined with human error. Twenty-eight highly exposed reactor staff and emergency workers died from radiation within 4 months of the accident. Likely that nearly 7,000 youngsters developed thyroid cancers and 15 had died by Most emergency workers and people living in contaminated areas received relatively low whole-body radiation doses, according to a United Nations study published in The study found no evidence of increases in solid cancers, decreased fertility or congenital malformations. However, there was slight indication of increased leukemia and cataract risk among most highly exposed workers.

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23 Thyroid cancer rates lower in Fukushima children than other regions. Fukushima seafood safe to eat. Fukushima evacuation zone is mostly habitable. Cancer rates in USS Reagan crewmembers lower than control group. Fukushima radiation death toll is too small to measure. * pub.iaea.org/books/iaeabooks/10962/the- Fukushima-Daiichi-Accident

24 NUCLEAR TESTING-RELATED ACCIDENTS KEY: number of atmospheric tests, MT of explosive yield Simon et al. Am Sci, 94:48-57,

25 Nevada Test Site and Exposure of the American Public: Testing of about 100 nuclear devices from 1951 to 1962 in the atmosphere at the NTS exposed military and public. Testing resulted in unintended exposure of ~160 million persons to an average of 20 mgy to the thyroid gland. more than Geographic pattern of average internal dose (mgy) to the thyroid of a child born 1 January 1951 from 131 I from all NTS tests Source: NCI 25

26 Russian nuclear sub accidents There have been 32 nuclear weapon accidents, known as "Broken Arrows." A Broken Arrow is defined as an unexpected event involving nuclear weapons that result in the accidental launching, firing, detonating, theft or loss of the weapon. Six nuclear weapons have been lost and never recovered. Broken Arrow examples: Palomares, Spain Thuele, Greenland Goldsboro, NC Generally resulting in few fatalities, mostly contamination A few MT in the early morning hours over NTS

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29 What we have learned about radiation accidents Many hundreds of nuclear or radiation accidents have occurred. Only a few have resulted in directly-related deaths or can be associated with confirmed cancer cases. Most accidents are associated with radiation exposures and acute effects to only a small number of people. Several accidents, however, are associated with a large numbers of projected cancers, using LNT theory. Numerous accidents are associated with large cost impacts (>$100 M). Accidents which result in environmental releases can affect, by far, the most people. 29

30 Health physics is the science dedicated to protecting man and his environment from the harmful effects of radiation. Radioactive material and radiation producing machines require appropriate health physics controls to ensure safe use.

31 How the material on Radiation Accidents might relate to CPALMS Body of Knowledge SC.912.E: Earth and Space Science SC.912.E.5.8 Connect the concepts of radiation and the electromagnetic spectrum to the use of historical and newly-developed observational tools. Body of Knowledge SC.912.P: Physical Science SC.912.P.10.1 Differentiate among the various forms of energy and recognize that they can be transformed from one form to others. SC.912.P Compare the magnitude and range of the four fundamental forces (gravitational, electromagnetic, weak nuclear, strong nuclear). SC.912.P Explain and compare nuclear reactions (radioactive decay, fission and fusion), the energy changes associated with them and their associated safety issues. SC.912.P Differentiate between chemical and nuclear reactions. SC.912.P Explain that all objects emit and absorb electromagnetic radiation and distinguish between objects that are blackbody radiators and those that are not. 31

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