Leakpath Factor (LPF)

DOE-HDBK-3010-94

1.0 Introduction

molecules, and the ratio of Cunningham factors can be ignored. The aerodynamic shape

factor is not typically known and is assumed to be 1. Therefore, DAED may be estimated

from Dg by simply multiplying Dg by the square root of the particle density. More

discussion of this subject can be found in available references (e.g., Fry, T.M., 1980).

Although the principal emphasis in this document is directed toward the potential downwind

hazard to the populations at some distance from the point of source term generation, airborne

particles larger than 10-m AED released from the facility may constitute an onsite hazard

(direct radiation) and may (if the larger particles are agglomerates that deagglomerate with

time or can be subdivided by local conditions) be subject to re-dispersal. If direct shine can

be a significant contributor to doses (e.g., fission product release from a criticality

excursion), the respirable factor should not be accounted for in evaluating that pathway

contributor.

This handbook specifically addresses RFs. RFs for particles made airborne under accident-

induced stresses are dependent upon a variety of factors, such as the bulk density (i.e., how

well the powder at rest compacts), the presence of moisture, how effectively the type and

level of stress deagglomerates the powder or subdivides the solid/liquid, the efficiency with

which the stress suspends the powder/fragments of solid over varying size ranges, and the

degree of immediate proximity of surfaces on which airborne particles may impact/settle.

Data to evaluate these factors individually for all cases are not found in the literature.

Measured RF data from the experimental studies are applied where available.

Measured experimental data for RFs are much more limited but are from the same general

sources used for the ARFs. To keep RFs at a reasonable bounding rather than an

ultraconservative level, the RF associated with the measured bounding ARF is generally

selected rather than the highest RF value measured. The highest RF values are often

associated with the smallest ARFs, and when used in conjunction with the bounding ARF,

result in ultraconservative estimates of the respirable fraction released. When no measured

RF is associated with the maximum measured ARF, but other measured RFs are available for

the experimental set, the greatest RFs are generally used. In some cases where significant

uncertainty may exist, RFs are arbitrarily set to a value of 1.0 for conservatism.

Leakpath Factor (LPF)

The LPF is the fraction of the radionuclides in the aerosol transported through some

confinement deposition of filtration mechanism. There can be many LPFs for some accident

conditions (e.g., the fraction transported from the package, such as a shipping container, to

the cell or enclosure; the fraction leaked from the enclosure, cell, or glovebox to the

operating area around the enclosure or room; the fraction leaked from the room to the

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