A STUDY OF A DOSE CONSTRAINT FOR OCCUPATIONALLY EXPOSED WORKERS IN THE US NUCLEAR POWER PLANTS.

One of the most important issues in the nuclear power industry is the implementation of the 2007 Recommendations of the International Commission on Radiological Protection (ICRP) published in ICRP Publication 103. These recommendations include the implementation of the concept of dose constraints for occupationally exposed workers at nuclear power plants (NPPs). When considering these changes from a cost-benefit standpoint, the implementation of dose constraints is still highly controversial. This study analysed annual occupational dose distributions to determine whether a dose constraint is needed for occupationally exposed workers at the US NPPs. Results of the analysis showed that the use of dose constraints had no positive impact on radiation safety of workers at NPPs in the USA. In fact, it appears that the implementation of dose constraints will impose an unnecessary regulatory burden on licensees. Based on these results, implementation of dose constraints is not recommended.

Fortieth Lauriston S. Taylor Lecture: Radiation Protection and Regulatory Science.

It took about 30 y after Wilhelm Konrad Roentgen's discovery of x rays and Henri Becquerel's discovery of natural radioactivity for scientists in the civilized world to formulate recommendations on exposure to ionizing radiation. We know of these efforts today because the organizations that resulted from the concerns raised in 1928 at the Second International Congress of Radiology still play a role in radiation protection. The organizations are known today as the International Commission on Radiological Protection and, in the United States, the National Council on Radiation Protection and Measurements (NCRP). Today, as we have many times in the past, we honor Dr. Lauriston Sale Taylor, the U.S. representative to the 1928 Congress, for his dedication and leadership in the early growth of NCRP. NCRP's mission is "to support radiation protection by providing independent scientific analysis, information, and recommendations that represent the consensus of leading scientists." The developments in science and technology, including radiation protection, are occurring so rapidly that NCRP is challenged to provide its advice and guidance at a faster pace than ever before. NCRP's role has also expanded as the Council considers newer uses and applications of ionizing radiation in research and medicine as well as the response to nuclear or radiological terrorism. In such a technical world, new areas have been established to deal with the nexus of science and regulation, especially in the United States. Lord Ernest Rutherford supposedly said, "That which is not measurable is not science. That which is not physics is stamp collecting." I wonder what he would say if he were alive today as now many embrace a new field called "regulatory science." This term was suggested by Professor Mitsuru Uchiyama in Japan in 1987 and was reviewed in literature published in English in 1996. Some have attributed a similar idea to Dr. Alvin Weinberg, for many years Director of the Oak Ridge National Laboratory. He actually introduced the term "trans-science," which he defined as the policy-relevant fields for which scientists have no answers for many of the questions being asked. He was influenced by the heavy involvement of the Laboratory in developing methods to assess environmental impacts as mandated by the 1969 National Environmental Policy Act. Professor Uchiyama defined regulatory science as "the science of optimizing scientific and technological developments according to objectives geared toward human health." In essence, regulatory science is that science generated to answer political questions. This paper will introduce regulatory science and discuss the differences between what some call "academic science" and "regulatory science." In addition, a short discussion is included of how regulatory science has and will impact the practice of radiation protection and all areas involving the use of radiation and radioactivity.

Warren K. Sinclair Keynote Address: Current challenges in countering radiological terrorism.

Terrorism, although perhaps known by other names, is not a new phenomenon. It dates back to Roman times and perhaps even further in world history. Caleb Carr says terrorism "is simply the contemporary name given to, and the modern permutation of, warfare deliberately waged against civilians with the purpose of destroying their will to support either their leaders or policies... " In modern times, in the United States, there have been isolated violent acts of citizens against each other, although these acts often were directed toward symbols of the federal government. In the Middle East and other parts of the world, acts of violence against U.S. citizens and military personnel date back into the early 1960's. Some of these acts seem to be almost random in nature. But these events occurred in distant lands of sometimes uncertain locations to the American public, who soon forgot them and their important message. Even though there had been at least one other attempt on the World Trade Center, it was not until 11 September 2001 that successful, large-scale acts of terrorism came to our shores. In 1998, the National Council on Radiation Protection and Measurements (NCRP) formed a Scientific Committee and charged the committee with the task of providing a report on the state of preparation and the potential use by terrorists of radiation and radioactivity. The draft report of the Committee was produced a year in advance of the events of 11 September 2001 and was published in its final form about a month after these terrible events. The report brought together, in one place, information that existed in a number of areas, not all of which were easily accessible. However, there were a number of gaps in the information and in the planning and preparation for such events. These were reflected in a series of recommendations for organization, planning, and training, as well as for research and development in a number of areas. This brief presentation will address a few selected areas that remain a challenge for those preparing for terrorist events involving radioactive materials. More detailed discussions will be provided by the presentations at this NCRP Annual Meeting.

External dosimetry and personnel monitoring.

The early history of our profession, as well as the discoveries that form its foundations, provide an interesting background on which to assess our progress in measuring exposure to ionizing radiation (i.e., dosimetry). One of the first challenges faced by scientists working with radiation and radioactivity was appropriate measurement techniques. has provided an excellent review of the history and development of radiation detection techniques and devices. In the early 20th century, some of these techniques were extended to measurements of the doses received by the individual scientists although it is not known exactly when organized personnel monitoring actually began. This manuscript will discuss some of the history of external dosimetry (specifically personnel monitoring), consider the developments that led to improved monitoring, attempt to assess the current status of the field and, also, to try to predict the future. The focus of this review will be primarily on personnel monitoring or personnel dosimetry. Obviously, it will not be possible to discuss every development in the field in detail and some choices have been made as to what to include and what to ignore. The author takes full responsibility for these choices. However, the goal is to provide sufficient coverage that the current situation and the future of personnel monitoring can be understood in the context of past developments. The discussion of the current status of external dosimetry will include some recent developments that hold great promise. In addition, a concern will be raised regarding the interpretation of the current U.S. federal regulations and the impact of the regulations on personnel dosimetry. Finally, there will be a discussion of what the future may hold in terms of the types of dosimeters and the approaches to personnel monitoring, in particular.

External dosimetry and personnel monitoring.

The early history of our profession, as well as the discoveries that form its foundations, provide an interesting background on which to assess our progress in measuring exposure to ionizing radiation (i.e., dosimetry). One of the first challenges faced by scientists working with radiation and radioactivity was appropriate measurement techniques. has provided an excellent review of the history and development of radiation detection techniques and devices. In the early 20th century, some of these techniques were extended to measurements of the doses received by the individual scientists although it is not known exactly when organized personnel monitoring actually began. This manuscript will discuss some of the history of external dosimetry (specifically personnel monitoring), consider the developments that led to improved monitoring, attempt to assess the current status of the field and, also, to try to predict the future. The focus of this review will be primarily on personnel monitoring or personnel dosimetry. Obviously, it will not be possible to discuss every development in the field in detail and some choices have been made as to what to include and what to ignore. The author takes full responsibility for these choices. However, the goal is to provide sufficient coverage that the current situation and the future of personnel monitoring can be understood in the context of past developments. The discussion of the current status of external dosimetry will include some recent developments that hold great promise. In addition, a concern will be raised regarding the interpretation of the current U.S. federal regulations and the impact of the regulations on personnel dosimetry. Finally, there will be a discussion of what the future may hold in terms of the types of dosimeters and the approaches to personnel monitoring, in particular.

A novel algorithm for solving the true coincident counting issues in Monte Carlo simulations for radiation spectroscopy.

Coincident counts can be observed in experimental radiation spectroscopy. Accurate quantification of the radiation source requires the detection efficiency of the spectrometer, which is often experimentally determined. However, Monte Carlo analysis can be used to supplement experimental approaches to determine the detection efficiency a priori. The traditional Monte Carlo method overestimates the detection efficiency as a result of omitting coincident counts caused mainly by multiple cascade source particles. In this study, a novel "multi-primary coincident counting" algorithm was developed using the Geant4 Monte Carlo simulation toolkit. A high-purity Germanium detector for 6°Co gamma-ray spectroscopy problems was accurately modeled to validate the developed algorithm. The simulated pulse height spectrum agreed well qualitatively with the measured spectrum obtained using the high-purity Germanium detector. The developed algorithm can be extended to other applications, with a particular emphasis on challenging radiation fields, such as counting multiple types of coincident radiations released from nuclear fission or used nuclear fuel.

Development of new two-dosimeter algorithm for effective dose in ICRP Publication 103.

The two-dosimeter method, which employs one dosimeter on the chest and the other on the back, determines the effective dose with sufficient accuracy for complex or unknown irradiation geometries. The two-dosimeter method, with a suitable algorithm, neither significantly overestimates (in most cases) nor seriously underestimates the effective dose, not even for extreme exposure geometries. Recently, however, the definition of the effective dose itself was changed in ICRP Publication 103; that is, the organ and tissue configuration employed in calculations of effective dose, along with the related tissue weighting factors, was significantly modified. In the present study, therefore, a two-dosimeter algorithm was developed for the new ICRP 103 definition of effective dose. To that end, first, effective doses and personal dosimeter responses were calculated using the ICRP reference phantoms and the MCNPX code for many incident beam directions. Next, a systematic analysis of the calculated values was performed to determine an optimal algorithm. Finally, the developed algorithm was tested by applying it to beam irradiation geometries specifically selected as extreme exposure geometries, and the results were compared with those for the previous algorithm that had been developed for the effective dose given in ICRP Publication 60.

How do we combine science and regulations for decision making following a terrorist incident involving radioactive materials?

Approaches to safety regulations-particularly radiation safety regulations-must be founded on the very best science possible. However, radiation safety regulations always lag behind the science for a number of reasons. First, the normal scientific process of peer-review, debate, and confirmation must ensure that the conclusions are indeed correct, the implications of the research are fully understood, and a consensus has been established. Second, in the U.S., there is a well-established, all-inclusive political process that leads to changes in radiation safety regulations. This process can take a very long time, as was demonstrated when the process was initiated to change the Code of Federal Regulations more than 20 y ago in response to International Commission on Radiation Protection Publication 26 and other recommendations. Currently, we find ourselves in a situation where the possibility of a terrorist radiological attack may occur and where the existing body of regulations provides very little guidance. Many international and national bodies, including several federal agencies, have provided recommendations on the appropriate levels of exposure for first-responders and first-receivers, as well as for the general public. However, some agencies provide guidelines based on very conservative dose limits which are not appropriate in situations where there is a substantial chance for the loss of lives and critical infrastructure. It is important that an emergency response is not hampered by overly cautious guidelines or regulations. In a number of exercises the impact of disparate guidelines and training in radiological situations has highlighted the need for clear reasonable limits that maximize the benefit from an emergency response and for any cleanup after the incident. This presentation will focus first on the federal infrastructure established to respond to radiological accidents and incidents. It will review briefly the major recommendations, both international and national, for responders and will attempt, where possible, to establish the scientific foundation for these guidelines. We will also stress the need to clearly and openly communicate the recommendations to the first-responders and the public so that no unnecessary anxiety or associated actions on their part impedes the ability to respond to a disaster. Finally, the use of these guidelines and recommendations by decision-makers at all levels will be discussed.