Radiological & Nuclear Incidents Carolyn Mac Kenzie December 4th, 2014

Transcription

1 Radiological & Nuclear Incidents Carolyn Mac Kenzie December 4th, 2014 Workshop for Journalists from the Middle East Vienna, Austria

2 Radiation is ENERGY Radiation is ENERGY travelling through space and matter at different frequencies, wavelengths and energetic levels. It is given off by unstable radioactive atoms Our normal senses (sight, smell, hearing) fail us in detecting radiation only detection equipment will confirm it s presence.

3 Radiation can be either non-ionizing or ionizing when it interacts with matter, depending on how much energy it has.

4 Units of Radioactivity -Curie and Becquerel The conventional unit of measure for radioactivity is the Curie (Ci), and the International System of Units (SI) unit is the Becquerel (Bq). A Curie of radioactivity is equal to 3.7 x (nuclear) disintegrations per second (dps) A Becquerel is equal to 1 disintegrations per second, or 1 dps This is the amount of radioactive material that is contained in the bottle or in a sealed source.

5 Units of Radioactivity- conversions -Curie and Becquerel Common unit conversions are: Conventional units SI Units 1 Curie = 1000 mci 1 mci = 1000 µci 1 TBq = 27 Ci 37 GBq = 1 Ci 37 MBq = 1 mci

6 Radiation Dose Units-rem and sievert The conventional unit for radiation dose to people or Dose Equivalence is the Roentgen Equivalent in Man (rem) and it s SI equivalent is the sievert (Sv) which takes into account the biological effects from different types of radiation Conventional units SI Units 1 rem = 1000 millirem 1 millirem = 1000 µrem 1 Sv = 100 rem 1 msv = 100 millirem 10 μsv = 1 millirem

7 Naturally Occurring Sources of Radiation Some sources of radiation occur naturally. The four major sources of naturally occurring radiation exposures are: cosmic radiation terrestrial radiation internal sources radon gas Background radiation results in a radiation dose of ~ Sv/year (0.3 rem/year)

8 Chronic dose versus Acute Dose Chronic Dose- A chronic dose is a small exposure to radiation over a long period of time e.g., working with radiation occupationally and routinely receiving a small amount of radiation exposure. Acute dose- An acute dose is a large exposure in a short time. It can result in a physical reaction due to massive cell damage.

9 Health Effects Possible from an Acute Radiation Dose Dose Received Resulting Effects Background radiation ~0.3 rem/year (~0.003 Sv/year) <10 rem (< 0.10 Sv) No detectable effects rem ( Sv) Minor blood changes 100 rem (1.0 Sv) Temporary sterilization in males rem ( Sv) Gastrointestinal effects - nausea, gut lining damage rem ( Sv) LD 50/30= Lethal Dose to 50% of the population within 30 days 1000 rem (10.0 Sv) Lethal Dose - 100% of the population will die within 30 days 5000 rem (50.0 Sv) Lethal Dose - central nervous system failure, brain damage, death within 3 days If a population receives acutely rem (3-5 Sv), 50% of the population would die within 30 days of the exposure. This is called the LD 50/30.

10 Radiation Exposure Risks- Heritable Effects The term Heritable effects refers to an effect on future generations through the mutation of the DNA. Heritable effects from radiation exposure have never been seen in humans, including the Hiroshima, Nagasaki and Chernobyl victims, but they have been demonstrated in other species. In the absence of human data, the estimation of hereditary effects is based on animal and insect studies. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) in their 2001 Report on Hereditary Effects of Radiation concluded: the risk of a heritable effect from radiation exposure is estimated to be < 0.5% per 100 rem (1 Sv) to the first generation following the radiation exposure.

11 Radiation Exposure Risks Excessive exposure to radiation can have potential health effects to you and to the unborn. Risk to the Unborn Risk of Cancer

12 Risk to the Unborn- Birth Defects Some of the children who were exposed while in the womb to radiation from the atomic bombs in Nagasaki and Hiroshima experienced smaller than average head size and an increased rate of mental retardation. Radiation-induced malformations in the embryo/fetus have a threshold of 10,000-20,000 mrem ( Sv) or higher and are typically associated with central nervous system problems.

13 Risk of Cancer ICRP 103: Recommendations of the International Commission on Radiological Protection, 2007 Cancer is a potential health effect from significant radiation exposure. The International Commission on Radiological Protection (ICRP) in Publication 103 issued in 2007 has made the following estimates of risk from radiation exposure: Assuming a conservative estimate of a linear response at low doses, the combined detriment due to excess cancer and heritable effects is ~5% per 1 Sv (100 rem) exposure.

14 What is a radiological or nuclear incident? An event that has led to significant consequences to people, the environment or the facility from radiation or radioactive materials. Nuclear incident- refers to incidents involving nuclear materials - such as nuclear fuel melting in a reactor. Nuclear materials are radioactive materials that are capable of a chain reaction. Radiological incident- refers to incidents involving radioactive materials other than nuclear materials such exposure from a lost radioactive source or an overexposure during radiation therapy.

15 Types of facilities with nuclear materials.. Nuclear fuel fabrication plant, enrichment plant, reprocessing facility, or spent fuel storage facility Nuclear reactor, research reactor, nuclear power plant, nuclear submarine Military sites with nuclear weapons.

16 Nuclear Incidents What can go significantly wrong with special fissionable material? Reactor meltdown/explosion and release to the environment from a research reactor, power reactor or nuclear submarine Criticality Accident Nuclear Weapons Test and release of radioactivity to the environment Use of a Nuclear Weapon Illicit trafficking

17 International Nuclear & Radiological Events Scale (INES)

18 What is an accident and what is an incident in INES? Examples Accident & Incidents = Impact on people and the environment Logarithmic ranking system takes into account onsite and offsite effects, as well as a loss of safety systems (defense in depth.) Can be set by a variety of people and is subjective Started in 1990 s to help communicate the seriousness of an accident.

19 INES Level Examples Level 7-major accident -Major release of radioactive material with widespread health and environmental effects-chernobyl (1986) and Fukushima (2011)-explosion Level 6-serious accident -Significant release of radioactive material likely to require implementation of planned countermeasures. Mayak Chemical Combine (1957) failed cooling system at a reprocessing plant-explosion Level 5: accident with wider consequences -Limited release of radioactive. Several deaths from radiation. Severe damage to reactor core. Examples: Windscale fire, United Kingdom (1957) and Three Mile Island Accident, USA partial meltdown(1979), Goiania accident, Brazil (1987)-An unsecured Cs-137 radiation source HUGE social and financial impacts

20 INES Level Examples Level 4- Accident with local consequences-minor release of radioactive material. At least one death from radiation. Fuel melt. Examples: Sellafield UK (5 incidents ), SL-1 Experimental Power Station, US (1961), criticality accident 3 deaths, Tokaimura nuclear accident, Japan (1999)- criticality accident 2 deaths. Level 3- Serious incident- Exposure in excess of ten times the statutory annual limit for workers. Threshold health effect (e.g., burns) from radiation. Exposure rates of more than 1 Sv/h in an operating area. Lost or stolen highly radioactive sealed source. Examples: THORP plant Sellafield, UK (2005) Level 2- Incident-Exposure of a member of the public in excess of 10 msv. Exposure of a worker in excess of the statutory annual limits. Found highly radioactive sealed orphan source, device or transport package with safety provisions intact. Examples: Blayais Nuclear Power Plant flood, France (1999) Level 1- Anomaly-Overexposure of a member of the public in excess of statutory annual limits Examples: Penly, France, (2012) - an abnormal leak on the primary circuit of the reactor Level 0- Deviation-No safety significance. Examples: Krsko, Slovenia (2008): Leakage from the primary cooling circuit.

21 Chernobyl On April 26 th, 1986 the Chernobyl nuclear power plant exploded. 134 cases of Acute Radiation Syndrome (~1 Sv) were recorded amongst the fire-fighters and recovery operation workers. A total of 28 people died in 1986 from a combination of high external doses of gamma radiation exposure and skin burns due to beta radiation exposure. Increased incidents of thyroid cancer occurred throughout Europe

22 Radioactive Releases at Fukushima March 11, Three of the 6 nuclear reactors experienced partial melt downs due to loss of cooling water from damage to the plants from the tsunami. Estimated to be 10-30% of the magnitude of Chernobyl accident. Effects limited to the region of the accident. No deaths from radiation exposure. Key radionuclides released to the food chains in the immediate area were: Iodine-131- radioactive half-life is ~8 days accumulates in thyroid Common pathway is from drinking milk short term issue Cesium-137-radioactive half-life is ~30 years distributed in soft tissues Bioaccumulation in fish and terrestrial food webs Other concerns (small releases) Sr-90 and Pu-239

23 Nuclear Incidents- Major Reactors Incident immediate needs Evacuate the immediate area to prevent external radiation exposure (close to the reactor) and internal exposure from breathing contaminated air ( msv dose range-is this too low?) Control human consumption of possibly contaminated food products

24 Criticality Event A criticality event involves an uncontrolled chain reaction that releases large quantities of heat, neutrons, and gamma radiation. It does not create an atomic explosion. ~60 criticality accidents are documented Small but potentially lethal impact typically to a few people

25 Nuclear Weapons Test Releases radioactivity to the environment. The closer to the surface of the earth, the larger the release to the environment. Over 2000 tests have been done to date by 8 countries. The National Resources Defense Council estimated the total yield of all nuclear tests conducted between 1945 and 1980 at 510 megatons (Mt). Atmospheric tests alone accounted for 428 Mt, equivalent to over 29,000 Hiroshima size bombs. The main man-made contribution to the exposure of the world's population [to radiation] has come from the testing of nuclear weapons in the atmosphere, from 1945 to 1980.

26 Radioactive Materials are both found naturally (e.g., uranium, Carbon 14) or are made in accelerators or nuclear reactors. They are widely used in medicine, industry and research.

27 Universities/Research institutes where sources are in use Medical facilities with Oncology / Radiotherapy departments Sterilization / irradiation facilities Industry-industrial radiography, well-logging sites, ports Factories, mining operations, Radioactive waste storage facilities 27

28 Radioactive Sources Involved in Accidents Irradiators Industrial gauges RTG s Cancer treatment Industrial radiography Well logging

29 The abundance of sealed radioactive sources, once no longer needed..become a significant waste problem

30 And when not secured and discarded, they can result in incidents

31 Radiological Accident in Brazil 1987 Abandoned 137 Cs teletherapy source stolen and opened. 4 people died, contaminated buildings demolished Costs to government exceeded US $20 million

32 Unsecured Sources Found In December 2001, two large, unsecured radiation sources were found in an isolated river valley near the town of Lja, Georgia.

33 Consequences of Unsecured Radiation Sources Two woodcutters in Georgia found 2 hot objects in the forest. They stay outdoors overnight and used the sources as personal heaters After 3 hours, symptoms of Acute Radiation Syndrome occurred The woodcutters required hospitalization and experienced severe burns.

34 Accident Involving Industrial Radiography Source: Gilan, Iran 1996 => 192 Ir source used for industrial radiography fell out of a shielded container..a worker picked up the source and put it in his chest pocket

35 Other Radiation Injuries from lost radioactive sources 2010 New Delhi, India <3 TBq (<100 Ci) of 60 Co in a research irradiator mistakenly sent to a scrap metal dealer- 1 death, 7 injuries 2000 Samut Prakarn, Thailand TBq (425 Ci) of 60 Co teletherapy source in scrap yard - 10 high exposures including 3 deaths Istanbul, Turkey - one teletherapy source of 3.3 TBq (88 Ci) of 60 Co and a potential second source treated as scrap metal - 10 people with acute radiation syndrome, one finger amputated 1999 Yanango, Peru TBq (37 Ci) 192 Ir radiography source unknowingly picked up by welder - welder s leg amputated and family overexposed 1997 Lilo, Georgia 60 Co, 137 Cs, 226 Ra high level sources- 11 overexposed individuals with severe radiation induced skin injuries 1994 Tammiku, Estonia large 137 Cs source stolen from radioactive waste repository - 1 death / several injuries

36 Radiological Dispersion Device (RDD) a radioactive source could be used with conventional explosives.

37 Disused Teletherapy Heads Inappropriately Stored

38 Irradiator in a Garden

39 Radioactive sources abandoned and easily removable by the public!

40 One problem: abandoned orphan sources

41 IAEA Categorization Table Category Practice 1 RTG s; Irradiators; Teletherapy; Gamma Knife 2 Gamma radiography Brachytherapy (high and medium dose) 3 Fixed industrial gauges; calibration sources (e.g.: level, dredger, conveyor gauges) Well logging 4 Brachytherapy (low dose except eye plaques & perm implants) Portable gauges; Static eliminators; Bone densitometers 5 Brachytherapy (eye pl. & perm implants); XRF; ECD

42 IAEA Category 1 Teletherapy Sources Used for treating tumors Found in medical clinics Typically contains 60 Co or 137 Cs Activity ranges from: 60 Co TBq ( ,000 Ci ) 137 Cs TBq (500 1,500 Ci)

43 IAEA Category 1 - Radioisotope Thermoelectric Generators (RTGs) Devices that used sources to generate heat that is converted to electricity to power lighthouses, space vessels 90 Sr Activity ranges from: 90 Sr PBq (90, ,000 Ci )

44 IAEA Category 1 Blood Irradiators Used to sterilize blood Found in medical or research applications Typically 60 Co or 137 Cs Activity ranges from: 60 Co TBq(1,500 3,000 Ci) 137 Cs TBq( Ci)

45 IAEA Category 1 Industrial Irradiators Typically 137 Cs or 60 Co TBq(10, ,000 Ci )

46 IAEA Category 2 Brachytherapy Sources placed inside or near a tumor to deliver a large dose to the tumor tissue Radionuclide and activity depends varies based on type of tumor i.e., 137 Cs 198 Au 60 Co 125 I 192 Ir 252 Cf

47 IAEA Category 2 Industrial Radiography Sources Used to take pictures of dense objects Portable 192 Ir, 60 Co, 75 Se, 169 Yb, 170 Tm Typical activities are TBq (5 200 Ci)

48 IAEA Category 2 Instrument Calibration Sources

49 IAEA Category 3 Industrial Level Gauges

50 IAEA Category 3 Well Logging 241 Am/Be 37 GBq (1 Ci) neutron and gamma dose rate Well logging

51 IAEA Category 4 Neutron Gauges 241 Am/Be 1.85 GBq (~50 mci) neutron and gamma dose rate

52 IAEA Category 4 Moisture Density Gauge Unit can have two sources: 137 Cs or 226 Ra 241 AmBe or 252 Cf Activities are typically MBq( mci)

53 IAEA Category 4 & 5 High and Low Level Lightning Rod Arrestors 154/152 Eu 2-15 GBq ( mci)

54 IAEA Category 5 Sealed Sources Smoke detector

55 October 2013 Experience of working with a journalist on a major news article: DOE Legacy- Waste Lands article in the Wall Street Journal nominated for Pulitzer Prize 3 page article by John Emshwiller