Neptune and Company, Inc.

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Background

The operators of the Nevada Test Site (NTS) faced a problem: it was discovered that two important power transmission lines in Area 8 of the NTS (see NTS map) ran through the site of several aboveground nuclear tests, where the ground surface is contaminated with a variety of radionuclides. One test was a thermonuclear detonation, which distributed fission products around the area, and other tests were hydrodynamic tests (where the fissionable material does not actually fission), which littered the area with bomb parts and actinides (see map of alpha and ²⁴¹Am contamination). The area was fenced to prevent casual access, but the powerlines (two are indentifed on the map as red lines) still need to be maintained. Furthermore, the area, like much of the NTS, is subject to erosion and sediment transport in washes that periodically experience flash floods. This means that any localized cleanup of a given wash is likely to be recontaminated by the migration of upstream sediments that may be contaminated.

The Problem

The problem faced by the NTS operators is how to maintain access to the powerlines for maintenance or emergencies. Several options were considered:

• Force powerline workers to suit up in protective gear while working on the powerlines.
• Clean up the ground surface under the powerlines.
• Clean up the ground surface in the entire fenced area.
• Clean up the ground surface in the washes.
• Contain the contamination to prevent migration.
• Move the power transmission lines and abandon the existing ones.
• Construct a causeway of clean fill dirt under the powerlines.
• Do a combination of the above alternatives.
• Do nothing.

Each of these alternatives has costs and benefits associated with it, and the job of Neptune and Company is to determine what those costs and benefits are and to rank the options available to the site operators. The decision of which option to choose lies with the operator.

The Options Analysis

Neptune and Company constructed a GoldSim model to evaluate the alternatives in a cost/benefit framework. This analysis involved an assessment of the contamination, based on spatial data obtained from flyovers and surface surveys, as well as the construction of a dose model for the population and for individuals who would be involved in surveys, remediation work, powerline maintenance, and site monitoring. The dose to the inadvertent intruder is also considered. Risk assessments are driven by U.S. Department of Energy Order 5400.5 for human health risks and 10 Code of Federal Regulations 835 for occupational exposure.

The costs of these various options was considered as was the benefit gained from each. Cost categories include

• As Low As Reasonably Achievable (ALARA) dose-based costs,
• Price-Anderson Amendments Act (PAAA) fines,
• cleanup costs,
• transportation costs incurred in migration control,
• access control costs (fencing, signs), and
• cost of moving the powerlines.

Since the contamination at the site is long-lived, the risk associated with that contamination and the activities required to monitor the site are carried into the distant future. Likewise, the benefits gained from complete site cleanup and its lack of future costs are considered, as is the potential for the imposition of fines for doing nothing with the site. A decision framework was developed and implemented in GoldSim.

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Go to Neptune's GoldSim page

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Last modified: 27 July 2004