Issue Number:FDR-204
Phase: Design
Decommissioning Process Fuel Debris Retrieval
Investigation Subject Improving working environment
Issue Site Boundary Dose Assessment

Needs

① Evaluating site boundary doses
Time Axis: Fuel Debris Retrieval [Short-Term]

Desired state and reasons for it

Since the exposure dose at the site boundary are expected to increase due to fuel debris retrieval, it is desirable to evaluate the dose appropriately and minimize it.

Current state against ideal

TEPCO conducted a comprehensive risk review in 2015, covering a wide range of risks that could potentially impact outside the site boundary.
As a result, TEPCO clarified risk sources and spill routes and operations for mainly liquids and dust, and then identified 190 items to be addressed.
The items, including those that had been identified previously, are being reevaluated from a new perspective, and the need for taking additional countermeasures is being organized, and the content and timing of such measures are being investigated in terms of priority, aiming to further reduce risks that could affect areas outside the site boundaries.

Issues to be resolved

It is necessary to evaluate the exposure dose at the site boundary (for direct radiation, skyshine, and dust effects) at each stage of the decommissioning process, including fuel debris retrieval, by precisely estimating the condition at each stage.
If the increase of the exposure dose at the site boundary exceeds the permissible range, the debris retrieval method should be reviewed, and additional measures should be taken. Otherwise, countermeasures for other factors such as radiation shielding for storing waste should be considered.

Relevant Issues

References

Please note that this English text is a provisional translation of the Japanese original.