Press Release

Table of Contents

Acknowledgements

Main findings

Recommendations

I. Introduction

II. National Primary Drinking Water Regulations – Radionuclides
A. Bone dose estimation in ICRP 2
B. Bone dose estimation, present-day dose conversion factors
1. Bone doses according to FGR 11
2. Bone doses according to FGR 13

III. Conclusions

IV. Costs

V. Estimating the impact of residual radioactivity

VI. Other risks and radionuclides

References

V. Estimating the impact of residual radioactivity

Vast areas of land and huge amounts of water remain contaminated with dangerous long-lived radionuclides from operations of nuclear weapons facilities.³⁴ The DOE has been given the task to clean up these sites. It is therefore of great importance that the levels of residual radioactivity meet strict standards that will protect the health of individuals of this and future generations that will be exposed to the residual contamination.

In the early 1990s, the DOE embarked on a cooperative process with the EPA to develop national cleanup standards, but the DOE pulled out of the process abruptly in 1996 without any plans for its resumption.³⁵ Since then, the DOE has proceeded on a site-by-site basis that has led to a welter of proposals for cleanup using various scenarios.

At the Savannah River Site in South Carolina, the DOE is grouting high-level waste in tanks as if it were low-level waste. This waste contains significant amounts of transuranic radionuclides. For instance, the residual waste in Tank 19, which has been grouted, had a concentration of plutonium 14 times above the EPA 100 nanocurie-per-gram limit for transuranic waste. DOE is grouting large amounts of plutonium in the tanks even though it has not yet obtained convincing evidence of the durability of grout. The tanks are buried underground in the watershed of the Savannah River, one of the most important rivers in the South Carolina-Georgia region. Experimental and field data leave room for considerable skepticism as to its performance. IEER's evaluation of the state of the research on grout indicates that the performance of grout remains highly uncertain. There is at present no sound basis, whether in experiment or in field data, to assume that leaving large amounts of grouted alpha-emitting, long-lived transuranic radionuclides in the tanks would be protective of the Savannah River.³⁶

A large part of the urgency that our recommendations be incorporated into EPA's forthcoming review of MCLs for radionuclides in drinking water derives from the fact that, in 2004, Congress passed a law allowing DOE to reclassify residual high-level waste as incidental waste at its South Carolina and Idaho sites. The law did not set any limits as to the residual radioactivity in waste so reclassified.³⁷ Several long-lived radionuclides, including plutonium isotopes, strontium-90, and cesium-137, may be grouted in the tanks or disposed of in shallow saltstone vaults. A realistic framework to guide DOE's decision-making, so that it does not endanger crucial water resources, is therefore of urgent and immense importance.

The consequences of the DOE cleanup policy on the concentrations of residual transuranic contamination in the soil and their potential effect on the health of individuals are discussed in a study by IEER entitled Setting Cleanup Standards to Protect Future Generations: The Scientific Basis of the Subsistence Farmer Scenario and Its Application to the Estimation of Radionuclide Soil Action Levels (RSALs) for Rocky Flats, December 2001.³⁸ In this study, IEER showed that the specific assumptions about future use have a major impact on what are considered acceptable residual radioactivity levels. A large part of this result is because different future site use scenarios have different assumptions about the use of water and food from the contaminated area in question. Since some radionuclides, including the alpha-emitting, long-lived transuranic radionuclides discussed in this report, are very long-lived, a basic assumption that there will be loss of institutional control over the long-term is essential to sound planning and cleanup.

However, even the adoption of a subsistence farmer scenario as the basis for cleanup cannot assure that levels for residual radioactivity on contaminated sites will be set in a manner that is protective of health and the environment. This is because the translation of residual levels into radiation dose and risk estimates requires the use of complex models and assumptions about the behavior of radionuclides in the environment. For instance, the amount of rainfall, the mobility of radionuclides in specific soil conditions, the porosity of the soil, the solubility of the radionuclides under various circumstances, and the rate of soil erosion are among the critical parameters that need to be known and characterized.

At present, remediation levels are typically assessed by the use of a model developed by Argonne National Laboratory called RESRAD (for residual radioactivity).³⁹ This computer code is complex and has, over the years, been developed to consider pathways for movement of radioactivity in a sophisticated way. Yet, it does not contain libraries of dose conversion factors for, and thus does not account for, infants or for young people at sensitive times in their hormonal development or for the fetus at various stages of fetal development. The estimation of doses to various segments of the population at sensitive periods in their lives may also require consideration of how the environmental pathways and the systems in the human body are represented in the model's source code.

The RESRAD source code is closely held by the U.S. government; it is not public. Ostensibly, the official rationale is that since RESRAD is used for regulatory decisions, such as those that are made in the context of cleanup at nuclear weapons sites, it should not be made public. However, we do not accept this rationale. The code can be made public and can be an open source code, available for modification in the same manner as the Linux operating system source code. That has resulted in its improvement and efficiency, without problems actually creeping into mass use of the code as an operating system. The U.S. government can surely retain its version of the code for regulatory purposes while making the source code publicly available for examination and improvement. If at a certain stage, the code is improved in a manner that regulatory bodies such as the EPA consider it useful for regulatory purposes, they will freely be able to adopt the changes but will be under no obligation to so.

Footnotes

³⁶ Smith 2004 and Makhijani and Boyd, 2004.

³⁷ PL 108-375, 2004, Sec. 3116.

³⁸ Makhijani and Gopal 2001.

³⁹ RESRAD.