Debate centres on dose

The main focus of Waste Management has traditionally been the treatment and disposal of high and intermediate level wastes. This year, however, the symposium led off with fireworks in the area of low dose radiation and its effects. Later in the conference, the inconsistencies in the proposed radiological regulations in this area were also highlighted.

The opening plenary session addressed the science and statistical interpretations of studies in this area. The speaker was one with heavy credentials, Dr Theodore Rockwell, who had been technical director of Admiral Rickover’s programme to build the US nuclear navy and the world’s first commercial nuclear power plant at Shippingport, Pennsylvania. Rockwell is a founding director of Radiation, Science and Health, established to address questions of radiation science and policy.

LNT v Hormesis

Rockwell´s main target for attack was the linear no threshold (LNT) model, on which all radiation protection policy is based today. He said that the LNT model is invalidated by the phenomena of hormesis, which indicates that small doses of radiation can be beneficial to human health by its stimulating and protective effects.

Rockwell quoted from a paper by Professor Zbigniew Jaworowski in the September 1999 issue of Physics Today, which identified the first reports on hermetic effects in algae more than 100 years ago. More than 2000 scientific papers have been published on radiation hormesis but have been ignored, distorted or suppressed. Instead, in 1959, the International Commission of Radiation Protection (ICRP) chose the LNT model as an assumption to form the basis of regulating radiation protection. According to Jaworowski, the application of the LNT theory was, at that time, “regarded as an administrative decision, based on practical (not to mention political) considerations”. The assumed linear relationship between dose and effect (with no threshold) was intended to simplify the administration of radiation protection. The fear that even the smallest, near-zero dose of ionising radiation could cause harm was politically useful at that time and played a positive role in bringing about first, the moratorium, and then, the ban on atmospheric nuclear tests. “Over the years, however,” says Jaworowski, “what started as just a working assumption for the leadership of the ICRP came to be regarded – in public opinion and by the mass media, regulatory bodies, and many scientists, and even by some members of the ICRP – as a scientifically documented fact”.

Rockwell showed slides to illustrate how the hermetic effects of low radiation doses had been concealed at various scientific presentations.

One example was a curve showing the relative (excess) risk of breast cancer from exposure to radiation, in an article in the Journal of the American Medical Association (C E Land, JAMA, 274:5, 402-402, 2 August 1995). The figure presents the results of a number of studies, with relative risks plotted against exposures up to 6Sv. The red line at the risk level of 1 represents the normal cancer rate corrected for age, sex, etc. The dotted line depicts the LNT model. As shown, the mean data points (with the error spread of the respective number of cases studied at each exposure level) seem to agree with the LNT line. However, when the agglomeration of the 440 cases at the lowest exposure is plotted in detail to a magnified scale, it is clear that, at low doses of 0.05-0.1Sv, the relative risk curve dips below the normal cancer rate. An even more revealing example of such a hermetic effect is shown in the results of a Canadian TB Fluoroscopic Study, published in the New England Journal of Medicine in 1989. The deviation downward of breast cancer deaths at low doses, from the LNT line, is clearly indicated.

Earlier in 1999, in an article in Technology (Vol.6, pp43-61), Professor Bernard Cohen of the University of Pittsburgh published a wide ranging study on cancer risk from low level radiation. The analysis included studies on solid tumours among the Japanese A-bomb survivors and on occupational doses taken by radiation workers. It also updated the 1995 University of Pittsburgh study, which has been the most elaborate project hitherto testing the validity of the LNT theory. Hundreds of thousands of radon measurements from several sources were compiled to give the average level of radon in homes in well over half the counties of the US, comprising about 90% of the US population. Age-adjusted lung cancer mortality rates were plotted against grouped intervals of radon level.

The University of Pittsburgh study showed that the original theoretical basis for the LNT model had disintegrated, mainly because the vitally important role of biological defence mechanisms had been ignored. Essentially, all the evidence gathered and presented suggested that low level radiation may be protective against cancer. The data from the various analyses suggest a threshold of 50-200mSv.

After many years of ignoring the accumulating evidence on hormesis, in 1994 the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) finally acknowledged and endorsed the hormesis phenomenon. As Jaworowski puts it, “it caused a revolutionary upheaval of radiology’s ethical and technical foundations”. In April 1999 UNSCEAR “decided to study a possible revision of the basic dosimetric and biological concepts and quantities generally being applied in radiation protection”.

CLEARANCE LEVELS

Now that increasing numbers of nuclear power stations are reaching the end of their commercially useful lives, the management of the huge quantities of very low level radioactive material that arises during their decommissioning has become a major subject of discussion, with very significant economic implications.

The OECD Nuclear Energy Agency’s Co-operative Programme on Decommissioning has been very active in these discussions, representing as it does over 35 decommissioning projects from 13 countries. A paper presented on behalf on the programme focused on activities in the field of the regulation of clearance levels for various types of radioactively contaminated material. During 1999, many of these activities took place in the US:

• The US Nuclear Regulatory Commission (NRC) has followed up on its rule on site release (10 CFR Part 20, Subpart E) from 1997 with a draft NUREG 1640 on the release of equipment and material from nuclear sites. While the site release rule was based on a 250mSv/year individual dose criterion, material release was to be governed by a much stricter 10mSv/year rule.

• The American National Standards Institute’s (ANSI’s) Surface and Volume Radioactivity Standards for Unconditional Releases (N13.12) from 1997 was endorsed by the US Health Physics Society. It is interesting to note that the 1997 draft was based on a 100mSv/year criterion, with corresponding derived nuclide specific clearance levels. In the final version issued last year, the dose criterion has been changed to 10mSv/ year, but the tables of clearance levels remain unchanged. Which says something of the precision of the calculation methods and scenarios.

*The ANSI issued its second draft of “Guide for Control and Release of Technologically – Enhanced Naturally Occurring Radioactive Material” (TENORM). TENORM arisings in the US are radiologically similar to the candidate material for clearance from nuclear decommissioning. Tens of millions of tons of TENORM arises each year (in industries like coal, fertiliser, oil & gas, mining, etc) compared to the nuclear counterpart which can be measured in thousands of tons. The ANSI proposes, however, an individual dose criterion of 100mSv/year for TENORM, compared with the 10mSv/year for the nuclear industry. This is difficult to understand, especially against the background of the position taken by the US Academy of Sciences, that there is no difference in risks from radiation from artificial and natural sources.

• The US NRC published an “issues” paper to form the basis for discussions with the public at a series of open meetings, in order to encourage public input into the decision process regarding the release of solid materials from nuclear sites. An interesting feature of the paper was a reference to the 100mSv/year individual dose to the public used by the US Environmental Protection Agency for exempting 6 million tons of slightly radioactive coal ash for use in construction concrete. The NRC suggested that the same criterion “could be viewed as a precedent or benchmark for possible NRC release levels”.

On the international scene:

• The European Commission’s Basic Safety Standards (BSS) Directive of 1996 is due to be ratified by member states in May 2000. According to the BSS, radioactivity is divided into practices, which utilise radioactivity (ie the nuclear industry), for which clearance/exemption are based on the individual dose criterion of 10mSv/year; and work activities, where radioactivity is “incidental” and which covers all TENORM industries. No dose criterion is specified by the BSS, but values of 1000mSv/year are being used in Germany (to exempt slag resulting from the melting of oil and gas industry scrap) and Holland (e.g. in the Ionisation Radiation Safety Guide, issued by Shell International)

• The IAEA proposes the trivial dose (of 10mSv/year) approach for releasing material from the nuclear industry and “optimisation” for similar material from the TENORM industries. Lately, in a newly issued “Draft Safety Guide on Application of the Concepts of Exclusion, Exemption and Clearance”, the IAEA introduces the term “essential commodities” for TENORM, to be regulated at a 1000mSv/year level. As these materials are “essentially irreplaceable”, the regulatory action is termed intervention and therefore unsuitable for a trivial dose criterion.

COST ASPECTS

The economic effects of the assumption of the LNT model and of the double-standard regulation of very low level waste (with different regulation of waste depending on the industry in which it arises) are difficult to exaggerate.

According to Professor Cohen, the LNT-based cleanup of the Hanford site, Washington State, is estimated to cost US$85 billion, with comparable costs for other USDOE sites at Savannah River, Rocky Flats, Fernald, etc. Jaworowski points out that “every human life hypothetically saved in a western industrial society by implementation of the present radiation protection regulation is estimated to cost US$2.5 billion. He said that taking into account the costs of US$50-99 for saving a life in developing countries by immunisation against measles, diphtheria, etc, this state of affairs was absurd, immoral and scandalous.

The nuclear industry is living in a world where electricity is being deregulated and competition between various sources of power production is fierce. As noted above, double standards are being proposed by the IAEA and tolerated by the European Commission, with up to a 100 times more stringent release levels for slightly radioactive material from the nuclear industry, than for the enormously larger amounts of similar material from TENORM industries. This double standard takes on a special significance when we see that two of the largest sources of TENORM are the coal and oil & gas industries.

The double standard will thus give the fossil fuel power producers an unfair edge in competition with the nuclear power industry.

Post ScripT

The spring of 2000 has been an interesting and active period in the area of the regulation of very low level radioactive material.

At the IAEA meeting in Cordoba, March 2000 it was pointed out that a hamburger with a caesium content under the WHO/FAO Codex Alimentarius limit could cross a border, but a piece of wood with the same level of contamination could not. Consumption of food at the Codex Alimentarius limit level can lead to an individual dose of a few mSv/ year.

The same meeting failed to reach consensus on harmonising levels for clearance of material from regulatory control. The problems of TENORM were also discussed without any conclusions on whether or how to regulate it or the industries where it arises.

A protocol was signed late last year in Spain, between the Spanish Nuclear Safety Council (CSN), the national radwaste management agency (ENRESA) and representatives of the scrap and recycling industries. The protocol called for radiation detection systems to be installed at all scrap yards and steel facilities. The CSN has adopted the European BSS list of exemption levels below which scrap dealers and steel recycling plants will not require to report material as radioactive. Spanish utilities are asking for the same levels to be used for steel released from decommissioning projects. The European BSS exemption levels for nuclides like Co-60 and Cs-137 are 10 Bq/g, which are ten times higher than the EC´s recommended clearance levels.

A joint meeting of IAEA’s Radiation and Waste Safety standards Advisory Committees (RASSAC and WASSAC) rejected The Draft Safety Guide on Exclusion, Exemption and Clearance referred to earlier, and asked for it to be re-written.

The joint committees noted that practices involving exposures arising from TENORM may need to be considered in the same light as artificial radioactivity.

In short, it can well be said that revolutionary upheavals are taking place in the field of low dose radiation and its regulation. The preliminary plans for next year´s Waste Management 2001 symposium at Tucson envisage a follow-up on both the ‘science’ and the regulation aspects of low dose radiation.