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

WIPP RH PSAR DOE/WIPP-03-3174 CHAPTER 5
Material at Risk - Both the radiological and non-radiological hazardous material are at risk of being
released as the result of a fire in the Hot Cell that results in breach of a waste drum. A conservative
approach in determining the accident consequences is taken. As discussed in Section 5.2.1.1, ten waste
drums from a 10-160B cask can be stored in the Hot Cell after they are unloaded from the cask with the
entire 20 PE-Ci inventory located in a single waste drum (CI = 20 PE-Ci). The storage of up to six fully
loaded facility canisters in the Hot Cell is allowed for 90 days. The maximum number of drums stored in
the Hot Cell at any one time is 28. Because the cask holds 10 drums, at times one of the canisters may
contain one or two waste drums from another cask shipment and be unsealed in the inspection station.
However, the combustible loading of the Hot Cell is very low. All of the remote handling equipment in
the Hot Cell is electrically operated, there are no hydraulics and therefore no hydraulic oil. The only
significant combustible material in the Hot Cell is the electrical cable insulation. Since the release of
material in this scenario requires the fire outside of the drums to heat the drum contents to the point
where the combustible materials in a drum ignites, the limited combustible loading in the Hot Cell will
limit the number of drums that can be heated to a high enough temperature to ignite. Additionally, the
drums stored in the facility canisters are provided a second confinement barrier by the canister. These
drums are effectively shielded from the direct effects of a fire. Therefore, only the ten drums stored in
the Hot Cell awaiting placement in a facility canister are at risk from a fire. There is insufficient
combustible loading and direct access to the drums by the fire (some of the drums will be shielded from
the fire by other drums) to reasonably expect that multiple drums would be heated to ignition
temperature. Therefore, it will be assumed that only one waste drum is heated to a high enough
temperature for the contents to ignite, resulting in a release of the radiological material (CD = 1). The
radiological MAR for this event is 20 PE-Ci (CD x CI).
As discussed in Section 5.2.1.1, the non-radiological MAR of one waste drum is 243 pounds. The total
hazardous chemical compound inventories for the waste drums are shown in Table 5.1-3.
Damage Ratio - As discussed in Section 5.2.1.1, the analysis performed for the CH TRU Central
Characterization facility showed that only 16.3 percent of the combustible material in the waste drums is
actually burned (DR = 0.163).
Airborne Release Fraction - The ARF for combustible materials in a drum is 5.0E-04 and the ARF for
noncombustible materials in a drum is 6.0E-03. These values represent bounding ARFs for the burning
of contaminated packaged mixed waste and the heating of noncombustible contaminated surfaces
(DOE-HDBK-3010-94, subsection 5.2.1.1 and 5.3.1). 4
Respirable Fraction - The respirable fractions for the combustible solids (CRF) and noncombustible
solids (NCRF) are taken directly from DOE-HDBK-3010-94 4 . The CRF is 1.0 and the NCRF is 0.01.
Leak Path Factor - The scenario of a fire in the Hot Cell would result in the release of the material from
the waste drums stored in the Hot Cell to the Hot Cell atmosphere. The Hot Cell atmosphere is
exhausted through a HEPA filter bank in the Hot Cell filter gallery and then to the WHB exhaust header.
As discussed in Section 5.2.1, the LPF for this scenario is 1.0E-06 with mitigation and 1.0 for
no-mitigation.
The LPF due to the HEPA filters is only applicable to the material released as particulates. The liquid
hazardous material is vaporized due to the thermal stress of the fire. The HEPA filters are not effective in
removing vapor. However, credit is taken for plateout of mercury by assuming 50 percent of the mercury
is removed due to plateout (LPF = 0.5). The LPF for all other liquid hazardous materials is 1.0.
5.2-50 January 22, 2003