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-04-123 � Section 12,
Accidents,
Malfunctions, and
Malevolent Acts
Information Request and Response
Information Request:
Is the shielding to be in place for ILW and LLW waste expected to provide any incidental barrier function?
Will the additional shielding used during waste transport be retained during emplacement in the proposed DGR?
Context:
In the Reference Low and Intermediate Level Waste Inventory for the Deep Geologic Repository Report, Executive
Summary, on page 7, it is stated that no extra processing/packaging will be required with the exception of shielding of
most of the ILW and overpacking of a small portion of the LLW for waste retrieved from various storage structures at
the Western Waste Management Facility (WWMF) and transferred to the DGR for emplacement.
OPG Response:
In general, the design purpose of shielding is to reduce the gamma radiation field outside waste packages to minimize
radiation doses to workers during handling. Most Low Level Waste (LLW) packages do not require any additional
shielding to meet this objective. Some Intermediate Level Waste (ILW) packages (e.g., reactor refurbishment waste
containers) have substantial shielding built into their original designs. Other ILW packages will need to be provided
with an add-on shield to protect workers while these waste packages are transferred underground. This shielding will
sometimes be removed if safe to do so and re-used if practical, otherwise it will be retained on the waste after
emplacement. In the case of resin liners, the intent is to leave the shield on the waste package in the repository (see
Section 6.5.3.6 of the Preliminary Safety Report (PSR) (OPG 2011) for a discussion on handling of shielded resin
liners).
Any additional material provided around the waste could provide an additional barrier function, besides radiation
shielding. Add-on shields are usually robust concrete or steel structures, and therefore could provide additional
mechanical protection of the containers. In some circumstances they could also provide an additional layer of material
that could delay the release of radionuclides (e.g., resin liner shields).
In the preclosure safety assessment, the complete waste package is considered, including presence of shields, with
respect to the likelihood and consequences of accidents (see Section 7.5.3.1 of the PSR).
In the postclosure safety assessment, the waste containers, including shields, are conservatively not credited for any
barrier function (see Section 8.6.2.1 of PSR). The materials (e.g., concrete and steel) represented by these shields are
included in the reference inventory, specifically in Tables 2.9 and 2.10 of the Reference Inventory Report (OPG 2010)
respectively for LLW and ILW.
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