NPD Closure Project: Calculating the Total Waste Inventory NS DF/ - - PowerPoint PPT Presentation

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NPD Closure Project: Calculating the Total Waste Inventory

NS DF/ NPD Breakfast Briefing

2019 December 04 | Andy McVeigh | NPD Health Physicist

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Agenda

• General Approach
• Establishing bounding source term
• Waste verification activities
• Waste database
• Hazardous Substances Inventory
• Radiological Inventory
• NPD Characterization Summary

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General Approach

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General Approach

• CSA 292.0-19 General principles for the management of radioactive

waste and irradiated fuel (e.g., waste classification and characterization)

• CSA 292.5 Guidance for the exemption or clearance from regulatory

control of materials that contain, or potentially contain, nuclear substances

• US NUREG-1575, Multi-Agency Radiation Survey and Site

Investigation Manual (MARSSIM).

• US NUREG-1575, Supp 1, Multi-Agency Radiation Survey and

Assessment of Materials and Equipment Manual (MARSAME).

• IAEA Safety Report Series (95) – Methodologies for Assessing the

Induced Activation Source Term for use in Decommissioning Applications

Relevant S tandards or Guidance

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General Approach

1. Ensure source term used in the safety case is the bounding waste inventory. 2. Characterize the Structure, System and Components (which are essentially the waste inventory of the final disposal facility).

NPD Characterization Plan Obj ectives

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General Approach

• Radionuclides embedded within

metals and other materials, present due to the interaction of neutrons from the reactor

• peration within the structure

and components.

• Contamination on surfaces,

mainly resulting from the handling of fuel elements which had suffered failure of their protective cladding, enabling the release of some radionuclides.

Establishing Bounding S

• urce Term

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General Approach

• Activated reactor components account for ~ 99% of the radiological

inventory:

• Concrete (containing characteristic activation products such as Cl‐36 and Ca‐41, become

soluble on contact with groundwater due to the porous nature of the material);

• Stainless steel (containing characteristic activation products such as Co‐60, Ni‐59 and Ni‐

63, released slowly as corrosion occurs);

• Carbon steel (with a similar activation products from stainless steel but greatly reduced in

some key isotopes such as Ni‐59 and Ni‐63, also released slowly by corrosion);

• Aluminium (with specific activation products, likely to corrode rapidly depending on water

chemistry);

• Zircaloy (with specific activation products such as Zr‐93, released very slowly by corrosion);
• Approximately 1% of the inventory is fission products and actinides present

as surface contamination in nuclear systems which are modeled to be released instantaneously on contact with water.

Establishing Bounding S

• urce Term – Reactor Vault Materials

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General Approach

Characterization of the reactor (i.e. sample collection and analysis) was performed for verification to the calculated estimates associated with the activated reactor core components. Internal sampling of the primary heat transport and moderator systems, as well as the other minor subsidiary systems, confirmed the radiological profile and verify the source term related to surface contamination. Systematic survey and volumetric sampling of the facility structure confirmed the hazardous substances inventory as well as verify the residual radiological contamination is negligible in comparison to the developed source term.

Waste Verification Activities

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General Approach

Post-Closure Safety Case Inputs: radionuclide inventory, non-radionuclide inventory, material types, mass/ density of waste, location within model compartments. Waste Database Inputs: radionuclide inventory, hazardous substance inventory, material type, mass of waste, disposal location within facility.

Waste Database

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General Approach

• Compliant with all CNL Waste Management Program

requirements.

• Waste database will be a format that is retrievable and entries

are verified.

• The individual radionuclide inventories, as well as total

inventory, are summed for the entire facility.

• Total inventories are then compared against the bounding

source term.

• Wastes that exceed the bounding case limits would be

removed for alternate disposition via other approved routes.

Waste Database

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General Approach

• NPD Historical Site Assessment and Characterization Plan were

developed by Oakridge Association of Universities (ORAU).

• Contracted ORAU to also provide on-the-job training to CNL

characterization technicians on the specific instruments and data collection requirements of the radiological Characterization Plan.

• Radiological data assessed, interpreted and reported by CNL

staff.

Training and Certification

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General Approach

• Original ORIGEN calculations undertaken in 1988 but the pressure/ calandria

tubes were verified in 2012 using updated models (WIMS-AECL 3.1) and modern libraries (ENDF/ B-VII) as well as spot checks of ANISN calculations.

• The Reactor components were re-calculated in 2018/ 19 using a later version
• f the ORIGEN-S code and Monte Carlo code MCNP5 to improve the reactor

estimate.

• Survey instruments used in the field have annual calibrations as well as daily

response and background checks.

• Sample management includes unique identifiers, mitigation measures for

cross contamination, and precautions to maintain sample integrity as well as Chain of Custody requirements.

• Laboratory performing the analysis is ISO 17025 qualified.
• Total inventory estimates or calculations are verified by technical reviewers.

QA/ QC

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Hazardous Substances

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NPD Source Term

• There is lead paint throughout facility as well as a significant quantity
• f lead associated with shielding.
• Residual amounts of mercury are possible in the facility, associated

with thermometers and switches.

• PCBs are present in light ballasts and potentially paint and caulking.

The remaining transformers present on site have been found to be PCB free.

• Asbestos is present in the form of pipe insulation, floor tiles and

building cladding.

• All systems were drained of oil during the first phase of

decommissioning and previous remediation work was completed

• utside of the facility.

Hazardous S ubstances Inventory

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NPD Source Term

Hazardous S ubstances Inventory – Lead

Location at start of Decommissioning Location‐Compartment at time of closure Lead based paint above grade (3.1 m3) – 351 kg Turbine Room – 351 kg Lead based paint below grade (3.5 m3) – 397 kg Fuelling Room – 161,000 kg Exposed lead bricks in Rm 408 – 2 m3(22,680 kg) Reactor Vault – 25,000 kg Rm 405 – Fueling gates (2) Lead encased in steel and masonite – 2.5 m3 (66,000 kg) Spent Fuel Storage Bay – 6,300 kg Rm 405 – Shielding walls and roof for Operator Rooms (lead encased in steel) – 35 m3 (90,000 kg) Boiler Room – 18,797 kg Rm 405 – Shield plugs lead encased in steel and concrete (5,000 kg) Rm 201 ‐ Boiler Room Roof – lead encased in steel (5400 kg) Reactor Vault – Lead encased in steel (25,000 kg) Spent Fuel Storage Room – steel encased lead for booster rods (4500 kg) Rm 307 – Exposed lead shielding wall (0.25 m3) (2,800 kg) Rm 201 – Lead encased in steel in Labyrinth between Boiler Room and Reactor Vault (13,000 kg) TOTAL: exposed lead – 26,228 kg encased lead – 208,900 kg

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NPD Source Term

Hazardous S ubstances Inventory –Asbestos, PCBs and Mercury

PCB LIGHT BALLASTS Location at start of Decommissioning Location‐Compartment at time of closure Boiler Room – 72 ballasts (1.699 kg) All PCB ballasts will be removed prior to grouting Condenser Pit – 54 ballasts (1.274 kg) ASBESTOS Location at start of Decommissioning Location‐Compartment at time of closure Sealand container outside facility (5) – 165 m3 Basement of Control Wing – 175 m3 Inside walls in above grade structure – 20 m3 Turbine Room (Condenser Pit) – 20 m3 Inside reactor vault – 5 m3 Inside reactor vault – 5 m3 Inside Boiler Room – 30 m3 Inside Boiler Room‐ 30 m3 Exterior Transite panels – 10 m3 MERCURY Location at start of Decommissioning Location‐Compartment at time of closure Boiler Room – residual contamination (<0.01 kg) Boiler Room – residual contamination (<0.01 kg)

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Radiological Inventory

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Radiological Inventory

• Sample collection and analysis was

required for correlation to the calculated estimates.

• Collect 3 representative samples of

each type of activated material that comprises reactor core components (calandria and pressure tubes) and the biological shield (reactor vault).

• Complete laboratory analysis, including

radionuclide inventory concentrations and total radioactivity activation products and fission products.

• Establish the relative correlation of

characterization data to activation product inventory estimates.

Reactor Components - Method

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Radiological Inventory

Calculation of the Reactor Inventory was repeated in 2018/ 19 from first principles using updated codes and libraries. Changes to the modelling of the original calculation were:

• A revised power history for the reactor operating

period.

• Updated and revised material compositions and

impurity levels.

• Use of updated codes and modern libraries for

neutron cross sections, nuclear decay and fission yields, etc.

• Introduce the use of the Monte Carlo code

MCNPv5 as supplementary to the ORIGEN calculation resulting in a 3D solution.

Reactor Components – Modeling results

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Radiological Inventory

Reactor Components – Results

Source Term: Final figure used as input to the PostSA was a composite figure which used the most conservative figures of either the sample results or the ORIGEN calculation with the exception of tritium which the model over

• estimated. Based on

this the final calculated inventory for the reactor vault is 7.51E+13 Bq.

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Radiological Inventory

Approach was adopted to limit the burden of taken multiple samples in potentially hazardous surroundings.

• Phased approach to implement a Ranked Set Sampling plan in order

to establish a mean radioactivity concentration using an 80% upper confidence level.

• Phase 1: Intrusive samples collected at judgemental locations and analyzed to establish

relationship between Cs‐137/Co‐60 and hard to detect radionuclides and to model the

• bserved results to obtain a gamma dose rate correlation.
• Phase 2: Externally measure gamma radiation dose rates at 14 systematic locations along

each system. Infer radionuclide inventories based on correlation determined in Phase 1.

• The mean radioactivity concentration for each the primary heat

transport and moderator systems was applied over their respective exposed surface area.

Primary Heat Transport and Moderator S ystems - Method

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Radiological Inventory

Previous estimated activity of the Primary Heat Transport system was 8.5E+ 11 Bq. This was estimated using gamma analysis of two scraped samples in 1988 at the time of shutdown and the newly derived figure shows only a slight increase.

Primary Heat Transport and Moderator S ystems - Results

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Radiological Inventory

• The “Other Systems” comprised all the subsidiary systems associated

with the Primary Nuclear systems such as Heat Transport System Demineraliser and the Moderator Helium systems but also included items such as the activity monitoring sample lines and building drain

• lines. Other nuclear systems include: fuel handling, emergency

systems, auxiliary systems, control systems.

• Were characterized in a similar manner as the primary heat transport

and moderator systems.

• The residual contamination in the majority of the other nuclear

systems was expected to be of minor significance in relation to the Primary Heat Transport and Moderator systems. In actual fact the total inventory of the twelve (12) “Other Systems”, was 6.54E10 Bq, so approx. 7% of the Primary systems.

Other Nuclear S ystems – Method and Results

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Radiological Inventory

Initial scoping survey work was completed within the facility in 2014/ 2015, including concrete sampling and analysis. This formed the basis for the Characterization Plan.

Facility S tructure – Initial S coping Work

Radionuclide Non‐Nuclear Area Nuclear Area Total Activity (Bq) H‐3 Concentration (Bq/g) 2.12E+02 3.26E+03 6.63E+12 Total Activity (Bq) 2.56E+11 6.38E+12 Cs‐137 Concentration (Bq/g) 4.35E‐03 4.42E‐01 5.65E+08 Total Activity (Bq) 2.82E+06 5.62E+08 Am‐241 Concentration (Bq/g) 1.97E‐04 9.51E‐03 1.43E+07 Total Activity (Bq) 7.40E+05 1.35E+07 Co‐60 Concentration (Bq/g) 2.10E‐04 4.28E‐02 1.16E+08 Total Activity (Bq) 2.88E+05 1.16E+08 Sr‐90 Concentration (Bq/g) 9.83E‐03 9.90E‐01 1.41E+09 Total Activity (Bq) 2.13E+06 1.41E+09

TOTAL 6.63 E+12

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Radiological Inventory

• Radiological surface scans – medium density (up to 50% coverage) gamma radiation

scans were conducted over most accessible floor and lower wall surfaces.

• Ranked Set Sampling-based characterization was implemented to develop the upper

confidence level of mean concentration of radionuclides in the facility structure.

• Volumetric samples were randomly distributed in each characterization unit.

Facility S tructure – Waste Verification Method

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Green = Class 3 Blue = Class 2 Red = Class 1

Facility S tructure – Classification Areas

Radiological Inventory

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Example of random- start/ systematic plan (Reactor Hall) that illustrates where samples are to be taken

Facility S tructure – Characterization Unit

Radiological Inventory

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Facility S tructure – Non-nuclear Area Results

Radiological Inventory

Class 1 SUs Class 2 SUs Class 3 SUs Radionuclide of Concern Mean Result (Bqg‐

1)

UCL1 (Bqg‐1) Mean Result (Bqg‐

1)

UCLa (Bqg‐

1)

Mean Result (Bqg‐

1)

UCLa (Bqg‐1) Am‐241 0.002 0.1 0.002 0.1 0.002 0.1 C‐14 1.00 1 0.09 1 0.81 1 Cs‐137 0.04 0.1 0.00 0.1 0.00 0.1 Cl‐36 0.02 1 0.06 1 0.06 1 Co‐60 0.00 0.1 0.00 0.1 0.00 0.1 Ni‐63 0.03 100 0.02 100 0.02 100 Pu‐238 0.00 0.1 0.00 0.1 0.00 0.1 Pu‐239/240 0.00 0.1 0.00 0.1 0.01 0.1 Sr‐90 0.01 1 0.01 1 0.01 1 Tc‐99 0.00 1 0.00 1 0.01 1 H‐3 241.05 100 4.89 100 5.86 100 U‐235 0.00 1 0.00 1 0.00 1 U‐238 0.02 1 0.03 1 0.03 1 Total Activity (Bq) By Area Class 7.4E+10 6.35E+09 2.41E+09 Total Activity (Bq), Non‐Nuclear Area 8.3E+10

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Facility S tructure – Nuclear Area Results

Radiological Inventory

Class 1 SUs Radionuclide of Concern Mean Result (Bqg‐1) UCLa (Bqg‐1) Am‐241 0.002 0.1 C‐14

2.00

1 Cs‐137

0.10

0.1 Cl‐36

0.09

1 Co‐60

0.01

0.1 Ni‐63

0.07

100 Pu‐238 0.03 0.1 Pu‐239/240

0.01

0.1 Sr‐90

0.05

1 Tc‐99

0.02

1 H‐3

2270

100 U‐235

0.007

1 U‐238

0.07

1 Total Activity (Bq), Nuclear Area 1.83E+12

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NPD Characterization

• The NPD bounding source term for the Post Closure Safety Assessment has

been established from acceptable sources and conservative assumptions.

• The radiological inventory at NPD is well characterized with beta-emitting

activation products being the primary long-lived radionuclides.

• The NPD Characterization Plan provides a defensible process for verifying

waste while the waste database will accumulate the inventories for comparison to the bounding source term.

• Characterization reports have been prepared for the individual characterization

campaigns including:

• NPD Reactor
• Primary Heat Transport and Moderator System
• Facility Structure (radiological and conventional)
• Other Systems

S ummary

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Questions?