4.1. Overview of Corroboration Activities

The IAEA’s safety review of the handling of ALPS treated water at FDNPS includes the following three components: the assessment of protection and safety; the review of regulatory activities and processes; and independent sampling, data corroboration, and analysis activities. The third component is included in the overall safety review to provide confidence in the accuracy of data provided by TEPCO and the Japanese authorities. Additionally, these corroboration activities provide another layer of assurance that TEPCO and the Government of Japan are adhering to relevant international safety standards. The IAEA’s corroboration will not be exhaustive but rather is intended to allow interested parties to infer the accuracy of all the available data by validating the key data provided by the laboratories in Japan responsible for producing and publishing analytical results from the ALPS treated water discharge process. The IAEA’s corroboration activities will complement the broader monitoring and verification regime that is the responsibility of the Government of Japan who maintains the overall responsibility for the safety of its nuclear facilities and activities. The IAEA’s involvement is a critical element for demonstrating the accuracy and validity of data being reported by Japanese authorities related to the discharge of ALPS treated water, and therefore building confidence in the overall IAEA safety review.

Currently, the IAEA’s independent sampling, data corroboration, and analysis activities include three major components:

? Sampling, analysis and interlaboratory comparison for ALPS treated water from the FDNPS.?

? Sampling, analysis and interlaboratory comparison for environmental samples (e.g., seawater, fish) from the surrounding environment of FDNPS.?

? Assessment of the capabilities of dosimetry service providers involved in the monitoring of internal and external radiation exposure of workers at FDNPS.

Corroboration of Source and Environmental Monitoring

The IAEA corroboration of source and environmental monitoring related to discharges of ALPS treated water from FDNPS is comprised of three distinct elements (see also Figure 4.1):?

? Review of sampling and analytical methods for source and environmental monitoring related to ALPS treated water at FDNPS used by TEPCO and relevant Japanese authorities8 .?

?? Corroboration of source monitoring undertaken by TEPCO, including a comprehensive radiological characterization of ALPS treated water samples.?

? Corroboration of environmental monitoring undertaken by TEPCO and relevant Japanese authorities.

Figure 4.1: A schematic overview of the elements of the corroboration being undertaken by the IAEA laboratories and the links between these elements

The corroboration of source and environmental monitoring will be based on interlaboratory comparisons (ILCs). ILCs, along with proficiency tests (PTs), are standard methods for laboratories to assess the quality of their measurement results in comparison with those of other participating laboratories, and to identify any potential improvements. PTs involve the evaluation of performance against pre-established criteria whereas ILCs involve the organization, performance and evaluation of measurements on the same or similar items by two or more laboratories in accordance with predetermined conditions.

For the corroboration of source monitoring, samples of ALPS treated water that is considered by TEPCO to be ready for dilution and discharge – pending final confirmation by analyses – are being collected from tanks at FDNPS. For the corroboration of environmental monitoring, samples of seawater, sediment and marine biota are being collected from locations on the east coast of Japan around FDNPS.Sample collection and pre-treatment activities undertaken by TEPCO, and relevant Japanese authorities will be facilitated and observed by the IAEA. The homogeneity of all samples will be ensured. These samples will be split, and sub-samples will be provided to the laboratories participating in the ILCs for the analysis of the activity concentrations of a range of relevant radionuclides.