DOE 2000. - Waste Isolation Pilot Plant - U.S. Department of Energy

WIPP RH PSAR DOE/WIPP-03-3174 CHAPTER 5
analysis 6 . The 30 seconds is based on 10 seconds to stop the waste handling activity once the accident
has occurred and 20 seconds to examine the cask or drums and determine a breach has occurred and
begin to exit from the area. The 30 second time frame specifically excludes a disabled worker scenario (a
worker injured by the accident). Therefore, the worker will be exposed to the cloud from 15 seconds (T 1
in the equation 5-10) when the cloud reaches him to 30 seconds (T 2 in the equation 5-10) when he leaves
the area. Substituting these values into the above equation and reducing:
D = (Q * 3.33E-04 m 3 /s * 5.1E+08 rem/Ci) * [3/(4π(0.25 m/s) 3 )] * ((15 s) -2 - (30 s) -2 ) (5-11)
D = Q (Ci) * 8.65E+03 (rem/Ci) (5-12)
This is the form of the consequence equation that will be used in this analysis to determine the
radiological dose to the immediate worker due to the accidents occurring while processing a 10-160B
cask.
For the assessment of consequences to workers in the Underground, the source term is assumed to be
released instantaneously into a slug of air with a volume of 850 ft 3 (24 m 3 ). This volume is based on an
instantaneous release and the assumed ventilation flow rate of 2 ft [0.6 m] per second, and the
dimensions of the underground exhaust drift, or
V = (2 ft/s [0.6 m/s]) * (1 sec) * (33 ft [10 m] ) * (13 ft [4 m]) = 24 m 3 .
A volumetric flow of 25 m 3 was used for the assessment of consequences to the workers in the
Underground and for Waste Hoist accidents.
5.2.2 Off-site and On-site Risk Evaluation Guidelines
The evaluation guidelines that are established should not be regarded as a "bright line" criterion and
doses challenging the guidelines or in the rem range should indicate the need to consider classifying
preventative or mitigative SSCs as safety class.
Guidelines do not exist for the frequency range of beyond extremely unlikely (frequency # 1E-06/yr).
The consequences of accidents in that range are conservatively evaluated against the guidelines for the
extremely unlikely range for the sole purpose of evaluating the risk associated with facility operations.
5.2.2.1 Radiological Risk Evaluation Guidelines
Off-site radiological dose criteria for accident analyses have been well established by national standards
through the licensing process of nuclear facilities regulated by the NRC. These criteria are based on the
probabilities of occurrence of the accidents or events hypothesized for the accident analysis. For nuclear
power plants, the operational accidents or events are classified as Plant Conditions (PC) in accordance
with the estimated frequency of occurrence. 23, 24 This established scheme (ANSI/ANS-51.1) 23 has been
adopted by the WIPP to compare accidental releases from postulated events to dose limits based on
estimated frequency of occurrence. Table 5.2-1a summarizes the risk evaluation guidelines for the
assessment of off-site radiological exposures.
5.2-17 January 22, 2003