Processes and events that could lead to ‘‘gross breaching’’ are of greatest
significance to long term performance because, as noted by the NAS,
‘‘canisters are likely to fail initially at small local openings through which
water might enter, but out of which the diffusion of dissolved wastes will be
slow until the canister is grossly breached.’’ (NAS Report p. 86) It is the
time of ‘‘gross breaching’’ that determines the time of more rapid
release of dissolved wastes from the repository and hence may have a
significant effect on the time and magnitude of the peak dose within 1
million years.