Ontario Power Generation's Response to the Joint Review

Attachment 1 to OPG letter, Albert Sweetnam to Dr. Stella Swanson, “Deep Geologic Repository Project for Low and Intermediate Level Waste – Submission of
Responses to the Final Sub-set of Package #4 Information Requests”, CD#: 00216-CORR-00531-00143.
IR# EIS Guidelines
Section
EIS-04-135 � Section 11.4.7,
Atmosphere
Information Request and Response
Information Request:
Discuss the potential implementation of a part-time or emergency exhaust ventilation filtration system that could be
used to capture dust and aerosol releases in the event of accident scenarios such as underground fires or explosions.
Context:
In the description of the ventilation system design, it is stated that no exhaust air filtration will exist due to the rationale
that radioactive gases existing in this airflow will not be captured by a filtration system. It is stated, however, that
condensate water from the exhaust airflow stream will be recovered in order to sequester and treat tritium
contaminants. Under exceptional circumstances, however, as would exist in the event of underground fires, explosions
or other events, aerosols and fugitive dusts may be liberated and transported by the airflow that could potentially
contaminate the surface environment if they were not filtered.
OPG Response:
The ventilation system design does not include exhaust air filtration primarily because filtration is not required in order
to meet criteria under normal operations and credible accidents. Also, the primary radionuclides in the air exhaust -
tritium and carbon-14 - will be present mostly in gaseous form and therefore are not captured by industrial highefficiency
particulate filters.
1) Preliminary Design Basis
Under normal operating conditions, radioactive particulate releases are not expected at the DGR because: (1) there
will be no waste conditioning processes at the DGR; (2) all the waste packages arriving at the DGR will be closed with
lids, and (3) external loose contamination will be checked prior to acceptance at the DGR (Section 7.4.2.1 of the
Preliminary Safety Report (PSR), OPG 2011). The underground exhaust air is expected to contain diesel combustion
products (gases and particulate), dust/particulate (non-radioactive), tritium (primarily as HTO vapor) and C-14 (primarily
as CO2). The levels of airborne tritium and C-14 will be within respective criteria, and no filtration will be required (OPG
2011, Sections 7.4.2.3 and 7.4.3). The preclosure safety assessment has evaluated the consequences of a range of
accidents involving radioactive waste packages (OPG 2011, Section 7.5.1). These accidents include underground fires
and breach of packages. In all cases, the dose consequences from air released from the ventilation exhaust would be
within criteria at the relevant receptor points (i.e., within public dose criteria at the nearest Bruce nuclear site fence line)
(OPG 2011, Section 7.5.4). Consequently, exhaust filtration is not required to meet dose criteria in the event of
accidents. This is in part because of the following factors:
� the wastes are solid materials and not easily dispersed as particulate in air,
� the higher activity wastes are in more robust packages (e.g., intermediate level resin wastes are in steel
containers within concrete overpack),
� the containers are not moved quickly, nor in large numbers in any shipments.
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