SAFRAN Upgraded to support the implementation of the Borehole Disposal Concept Rodolfo Avila, Facilia AB

Outline Description of SAFRAN Adaptation to support the implementation of the BDC. Generic Operational Safety Assessment (GOSA)

What is SAFRAN SAFRAN is a software package for safety assessment in pre-disposal waste management. It implements the methodology developed within the IAEA project SADRWMS ( )

SADRWMS methodology Provides detailed guidelines for safety assessment. Based on the IAEA safety guide DS284: The Safety Case and Safety Assessment for Predisposal Management of Radioactive Waste

The SADRWMS methodology Provides detailed advice for each step of the Safety Assessment Describes the different types of assessments that might be required Provides methods for Hazard identification and screening Provides methods for performing qualitative and quantitative assessments for different scenarios

Disposal Borehole Design & Construction Borehole Diameter – 260mm Length – variable Casing Diameter – 160mm Length - variable Disposal Container Diameter – 115mm Length – 250mm Capsule Diameter - 21/48mm Length – 110/121mm

Disposal container (with concrete insert) and container lid. Bottom row: sealed capsules in two sizes.

Emplacement and Borehole Closure

Pre-disposal Activities

Construction of a borehole using percussion drilling

SAFRAN components System description Site features, waste producers, waste streams Regulatory Framework Safety Assessment Normal Operation, Accidents SAFREQ SAFCALCDATABASE Report

System Description For each configuration Site Facilities – Rooms » Areas (Storage or Processing) Safety elements Waste Management Activities – Processes – Check for clearance Waste Producers – Primary Waste Components » Waste Streams

Safety elements Site selection Safety functions Limits and conditions Mantainance requirements Operational procedures Emergency procedures Management systems Can be linked to physical elements and assessments

Waste management activities Description Output(s) from activities Reduction factors One and only one WMA can be assigned to an area A process is a sequence of WMAs which can be used in defition of Waste Streams (WS)

Waste Streams Waste streams represent the fate of waste components through different steps of processing, storing and clearing of wastes Accounting for changes in waste properties by waste management activities at each step.

Additions for BDC The user can define that one or more boreholes will be considered at a Site A library of safety elements of relevance for BOSS will be added A library of pre-disposal waste management activities relevant for BOSS A library of processes

Additions for BDC A library of sources SIMBOD – tool for management of the Borehole Disposal process Typical waste streams – resulting from application of Typical Processes to different Types of Sources Sources – Conditioned - Packaged

SAFRAN components System description Site features, waste producers, waste streams Regulatory Framework Safety Assessment Normal operation, accidents SAFREQ SAFCALCDATABASE Report

Assessment types For normal operation and accidents. Doses to workers and members of the public. Radiological impacts indoors and outdoors.

Graded approach to the assessments Impacts Screening or Hazards Dose Assessment Calculations of Hazard Quotients (HQ) for standardized conservative exposure situations calculations for specified endpoints and expecific exposure conditions

Assessments for accidents Impact 1 PIE Type PIE 1 PIE n Scenario 1Scenario n Impact n Endpoint 1Endpoint n Ass Case 1 Ass Case n Scenario m Impact m Screening of hazards

Example of Probability-Consequence plots HQ/ProbVery Low LowMediumHighVery High <0.1SC SC4 1-10SC >100SC1

Additions for BDC Update of the PIE database Library of typical scenarios Library of generic safety assessments

SAFRAN components System description Site features, waste producers, waste streams Regulatory Framework Safety Assessment Normal operation, accidents SAFREQ SAFCALCDATABASE Report

Models available in SAFCALC IAEA SR-19 models: screening models for routine releases to the atmosphere, lakes, rivers, estuarines and coastal areas. Model for accidental releases to the atmosphere. Model for accidental releases inside a room. Simple dosimetry models: point source, disc, cylinder, cube (with and without shielding)

SAFRAN components System description Site features, waste producers, waste streams Regulatory Framework Safety Assessment Normal operation, accidents SAFREQ SAFCALCDATABASE Report

Database Radionuclide half lives. Clearance levels. Gamma constants – dose rates at 1 m from a point source. Screening dose rates for Normal and accidental situations. Screening release rates for Normal operation. Screening releases for accidental situations. Release Fractions. Dispersion factors. Dose Conversion Factors for Normal and accidental situations.

Additions for BOSS Models and calculation methods used in Generic Operational Safety Assessment (GOSA). Parameter values required for GOSA.

SAFRAN components System description Site features, waste producers, waste streams Regulatory Framework Safety Assessment Normal operation, accidents SAFREQ SAFCALCDATABASE Report SPECIALIZED LIBRARIES FOR BOSS

SAFREQ Tool for assistance in developing the safety case by assessing compliance with Safety Requirements and Safety Guidelines.

Additions for BOSS Going from a prototype to a Released version Specific guidelines for safety case of BDC

GENERIC OPERATIONAL SAFETY ASSESSMENT (GOSA)

Assessment Context The assessment context of the GOSA should be consistent with the generic safety assessment (GSA) for borehole disposal (IAEA Safety Series Report: Generic Post- Closure Safety Assessment for Borehole Disposal of Disused Sealed Sources)

Purpose The purpose of the GOSA is to demonstrate that the proposed pre-disposal waste management activities are done in a safe manner, as required by the regulatory framework. The safety of operators (workers) and members of the public will be assessed, both for normal operations and for potential accidental situations.

Scope The starting point for the GOSA is that the Disused Sealed Sources (DSSs) have arrived at the site and a decision has been taken to “dispose” the DSS by borehole disposal Activities of the original producer [e.g. hospital] and transport to site are beyond the scope of the current project). Other disposal options (e.g. disposal in a near-surface or deep facility) and management options (long-term storage) are beyond the scope of this GOSA.

Inventory to be considered The inventory (Bq) and number of sources to be assessed in the GOSA need to be representative of what is found in practice in different countries. An initial proposal is to consider two cases: a country (Ghana being an example) with a low to medium inventory of relatively low level activity sources that do not require the use of hot cells, and a country (South Africa being an example) with a medium to large inventory which includes high activity sources that will require the use of hot cells. Different initial states of the sources should be considered, including sources in the original devices, in a transport package, in the working container, and conditioned in cement.

Regulatory Framework IAEA Safety Standards will be used as the basis for the regulatory framework. This will include normal operation and accidental situations, taking into account dose constraints as well as dose limits. One issue currently under evaluation is whether to include assessment of doses to the eye, extremities, etc., in addition to whole body doses.

Operational activities Duration (Minutes) 1) Prepare for Introduction into hot cell15 2) Lift Original Source Shield into the hot cell5 3) Close the hot cell20 4) Remove the source60 5) Characterise the source20 6) Encapsulation and test of the capsule20 7) Place capsule in disposal container and NDT20 8) Transfer disposal container to the transfer cask10 9) Disengage and prepare the transport cask for transport 15 10) Emplacement of the disposal container in borehole15 11) Backfilling of the borehole15 Typical activities and their duration

Examples of accidental scenarios (hot cell) The situation where the operation team is unaware that the source has an activity greater than the value for what the facility was designed for and the team proceeds with standard operations. Error during the determination of the density of the shielding material (sand) in the hot cell and the operation proceeds with a sand density below design requirements. Situation with the ZnBr 2 window density below design requirements being used by the operation team. Source is dropped after being removed from the original source shield. The source is found to be leaking when removed from the original source shield inside the hot cell. (Could have been damaged during removal). The manipulators malfunction whilst the source is inside the hot cell. The biological shield is damaged while bringing in the original source shield. Power outage in the hot cell. Lights are not operational in the hot cell.