The Contractor at the Boundary Fence
A contractor is excavating near the boundary fence of a facility that stores sealed sources. The license sets a public dose limit of 1 mSv/yr and a boundary dose-rate criterion of 0.5 µSv/h at the fence. The contractor's survey meter reads 0.7 µSv/h at the fence line during work, and the contractor's workers spend about 6 hours/day at that location for 10 days. The contractor has no dosimeters and is not a radiation worker. The facility's RSO is on site and must decide whether work can continue, whether the contractor needs to be monitored, and whether the regulator must be notified.
1. Estimate the contractor's likely dose and decide whether work can continue as planned.
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Estimate: 0.7 µSv/h × 6 h/day × 10 days = 42 µSv = 0.042 mSv, well below the 1 mSv public limit. But the boundary criterion of 0.5 µSv/h is exceeded, so the situation is outside the license's stated condition even if the annual dose is small. The judgement: the dose estimate is low, but the criterion breach must be addressed. Options: (1) pause work and investigate the source of the elevated reading (is it the facility's sources, or the contractor's own equipment/soil?), (2) if facility-related, apply controls (shielding, distance, time) to bring the fence reading below 0.5 µSv/h, (3) resume with monitoring and a revised work plan. Do not simply continue because the annual dose is small - the license condition is a prospective control, and breaching it is a compliance issue even when the dose is trivial.
2. Does the contractor need to be classified as a radiation worker and issued dosimeters?
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Not necessarily. Classification as a radiation worker is triggered by the potential for significant exposure and by the license/regulatory framework, not by a single low reading. At 0.042 mSv projected, the contractor is well within public-dose territory. However, because the boundary criterion is exceeded and the work is near stored sources, a precautionary approach is defensible: issue a dosimeter (or at least a survey meter and a work-time log), brief the workers, and set an action level (e.g., 0.1 mSv) that triggers reassessment. The judgement is proportional: don't over-classify a low-dose contractor, but don't leave them unmonitored when the fence criterion is breached. Document the decision and the basis.
3. What notification and record-keeping obligations arise, and how do they differ from an emergency?
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This is a compliance/administrative event, not an emergency: no acute hazard, dose far below limits. Obligations likely include: (1) recording the survey results and the investigation; (2) notifying the licensee's management and, depending on the license, the regulator within a stated period for a boundary-criterion exceedance; (3) correcting the condition and documenting the corrective action; (4) retaining records per the license's retention schedule. An emergency notification (immediate, e.g., within hours) is reserved for actual or suspected significant releases, lost sources, or doses near limits. The judgement is to classify the event correctly - over-notifying as an emergency wastes resources and misrepresents risk, while under-notifying breaches the license. The RSO should consult the license's notification matrix and document the classification rationale.