Opportunity to Use Science to Establish Radiation Standards
- Jul 13, 2014 4:00 am GMT
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The Environmental Protection Agency (EPA) has issued an Advanced Notice of Proposed Rulemaking (ANPR) to solicit comments from the general public and affected stakeholders about 40 CFR 190, Environmental Radiation Protection Standards for Nuclear Power Operations.
The comment period closes on August 3, 2014. The ANPR page includes links to summary webinars provided to the public during the spring of 2014, including both presentation slides and recorded audio, including questions and answers. This is an important opportunity for members of the public, nuclear energy professionals, nuclear technical societies, and companies involved in various aspects of the nuclear fuel cycle to provide comments about the current regulations and recommendations for improvements.
The existing version of 40 CFR 190 — issued on January 13, 1977 during the last week of the Ford Administration — established a limit of 0.25 mSv/year whole body dose and 0.75 mSv/year to the thyroid for any member of the general public from radiation coming from any part of the nuclear fuel cycle with the exception of uranium mining and long term waste disposal. Those two activities are covered under different regulations. Naturally occurring radioactive material is not covered by 40 CFR 190, nor are exposures from medical procedures.
40 CFR 190 also specifies annual emissions limits for the entire fuel cycle for three specific radionuclides for each gigawatt-year of nuclear generated electricity – krypton-85 (50,000 curies), iodine-129 (5 millicuries), Pu-239 and other alpha emitters > 1 year half-life (0.5 millicuries)
It is important to clarify of the way that the US federal government assigns responsibilities for radiation protection standards. The Nuclear Regulatory Commission (NRC) has the responsibility for regulating individual facilities and for establishing radiation protection standards for workers, but the EPA has a role and an office of radiation protection as well.
The Atomic Energy Act of 1954 initially assigned all regulation relating to nuclear energy and radiation to the Atomic Energy Commission. However, as part of the President’s Reorganization Plan No. 3 of October 1970, President Nixon transferred responsibility for establishing generally applicable environmental radiation protection standards from the Atomic Energy Commission (AEC) to the newly formed Environmental Protection Agency (EPA).
…to the extent that such functions of the Commission consist of establishing generally applicable environmental standards for the protection of the general environment from radioactive material. As used herein, standards mean limits on radiation exposures or levels or concentrations or quantities of radioactive material, in the general environment outside the boundaries of locations under the control of persons possessing or using radioactive material.
Before the transfer of environmental radiation responsibilities from the AEC to the EPA and until the EPA issued the new rule in 1977, the annual radiation dose limit for a member of the general public from nuclear fuel cycle operations was 5 mSv – 20 times higher than the EPA’s limit.
The AEC had conservatively assigned a limit of 1/10th of the 50 mSv/year applied to occupational radiation workers, which it had, in turn, conservatively chosen to provide a high level of worker protection from the potential negative health effects of atomic radiation.
The AEC’s occupational limit of 50 mSv was less than 1/10th of the previously applied “tolerance dose” of 2mSv/day, which worked out to an annual limit of approximately 700 mSv/year.
Aside: After more than 100 years of human experience with working with radiation and radioactive materials, there is still data that prove negative health effects for people whose exposures have been maintained within the above tolerance dose, which was initially established for radiology workers in 1934. End Aside.
From the 1934 tolerance dose to the EPA limit specified in 1977 and still in effect, requirements were tightened by a factor of 2800. The claimed basis for that large conservatism was the lack of data at low doses, leading to uncertainty about radiation health effects on humans.
The only measured human health effects were determined from the acute doses greater than 100 mSv received by the lowest exposed portion of the population of atomic bomb survivors. Based on data from the Life Span Study of atomic bomb victims, which supported a linear relationship between dose and effect, the National Academy of Sciences committee on the Biological Effects of Ionizing Radiation (BEIR) recommended a conservative assumption that the linear relationship continued to exist all the way down to a zero dose, zero effect origin.
For the radionuclide emissions limits, the EPA chose numbers that stretch the linear no-threshold dose assumption by applying it to extremely small doses spread to a very large population.
The Kr-85 standard is illustrative of this stretching. It took several hours of digging through the 240 page final environmental impact statement and the nearly 400 page long collection of comments and responses to determine exactly what dose the EPA was seeking to limit and how much it thought the industry should spend to achieve that protection.
The EPA determined that allowing the industry to continue its established practice of venting Kr-85 and allowing that inert gas to disperse posed an unacceptable risk to the world’s population.
It calculated that if no effort was made to contain Kr-85, and the US industry grew to its projected 1000 GW of electricity production by 2000, an industry with full recycling would release enough radioactive Kr-85 gas to cause about 100 cases of cancer/year.
The EPA’s calculation was based on a world population of 5 billion people exposed to an average of 0.0004 mSv/year per individual.
At the time that the analysis was performed, the Barnwell nuclear fuel reprocessing facility was under construction and nearly complete. It had not been designed to contain Kr-85. The facility owners provided an estimate to the EPA that retrofitting a cryogenic capture and storage capability for krypton-84 would cost $44.6 million.
The EPA finessed the exceedingly large cost for tiny benefit by saying that the estimated cost for the Barnwell facility was not representative of what it would cost other facilities that were designed to optimize the cost of Kr-85 capture. It based that assertion on the fact that Exxon Nuclear Fuels was in a conceptual design phase for a reprocessing facility and had determined that it might be able to include Kr-85 capture for less than half of the Barnwell estimate.
GE, the company that built the Midwest Fuel Recovery Plant in Morris, Illinois provided several comments to the EPA, including one about the low cost benefit of attempting to impose controls on Kr-85.
Comment: The model used to determine the total population dose should have a cutoff point (generally considered to be less than 0.01 mSv/year) below which the radiation dose to individuals is small enough to be ignored.
In particular, holdup of krypton-85 is not justified since the average total body dose rate by the year 2000 is expected to be only 0.0004 mSv/year.
Response: Radiation doses caused by man’s activities are additive to the natural radiation background of about 0.8-1.0 mSv/year [note: the actual level at that time, as indicated by other parts of the documents was 0.6 – 3.0 mSv/yr] whole-body dose to which everyone is exposed. It is extremely unlikely that there is an abrupt discontinuity in the dose-effect relationship, whatever its shape or slope. at the dose level represented by the natural background that would be required to justify a conclusion that some small additional radiation dose caused by man’s activities can be considered harmless and may be reasonably ignored.
For this reason, it is appropriate to sum small doses delivered to large population groups to determine the integrated population dose. The integrated population dose ay then be used to calculate potential health effects to assist in making judgements on the risk resulting from radioactive effluent releases from uranium fuel cycle facilities, and the reasonableness of costs that would be incurred to mitigate this risk.
Existing Kr-85 rules are thus based on collective doses and a calculation of risks that is now specifically discouraged by both national (NCRP) and international (ICRP) radiation protection bodies. It is also based on the assumption of a full recycle fuel system and ten times as much nuclear power generating capacity as exists in the US today.
There are many more facets of the existing rule that are worthy of comment, but one more worth mentioning today is concluding paragraph from the underlying policy for radiation protection, which is found on the last page of the final environmental impact statement.
The linear hypothesis by itself precludes the development of acceptable levels of risk based solely on health considerations. Therefore, in establishing radiation protection positions, the Agency will weigh not only the health impact, but also social, economic, and other considerations associated with the activities addressed.
In 1977, there was no consideration given to the fact that any power that was not generated using a uranium or thorium fuel cycle had a good chance of being generated by a power source producing a much higher level of carbon dioxide. In fact, the EPA in 1977 had not even begun to consider that CO2 was a problem. That “other consideration” must play a role in any future decision making about radiation limits or emission limits for radioactive noble gases.
Note: Dose rates from the original documents have been converted into SI units.
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