Simulation of the management
and disposal of Low Level
Radioactive Waste in the United
Kingdom
Emma Woodham (DAS Ltd)
Si6n Cave (DAS Ltd)
Tony Lawrence (DAS Ltd)
Martin Walkingshaw (LLW Repository Ltd)
Alison Gray (LLW Repository Ltd)
Ellie Robinson (LLW Repository Ltd)
Andy Bicknell (LLW Repository Ltd)
1 ) Background
2 ) System Dynamics Model
3 ) Model Impact
4 ) Conclusions
5 ) Bibliography
Radioactive waste management da
My)
¢ Nuclear material has a wide range of applications in the UK.
* Radioactive waste is a by-product of these activities and much be treated and
managed appropriately to ensure safe disposal
* Radioactive waste is categorised into four categories, based on radioactivity:
- High Level Waste (HLW)
- Intermediate Level Waste (ILW)
- Low Level Waste (LLW)
- Very Low Level Waste (VLLW)
* The current long-term management policy for all ILW is for it to be disposed of at
a Geological Disposal Facility (GDF).
* The current planning assumption is that the GDF will be available in 2040.
Radioactive Waste in the UK da
My)
* Every 3 years the NDA collects data from waste producers and publishes an
inventory of the radioactive waste currently in storage and predicted to arise
over the next 100 years.
¢ The inventory data shows that VLLW makes up more than half of the
radioactive waste in the UK but over 80% of the radioactivity is contained ina
relatively small volume of HLW.
Volume of Radioactive Waste in the UK Activity of Radioactive Waste in the UK
3,000,000 3,500,000
VLLW, 2,720,000 HLW, 3,200,000
2,500,000 3,000,000
2,500,000
2,000,000
2,000,000
1,500,000
Volume (m?)
Activity (TBq)
1,500,000
1,000,000
1,000,000
500,000 500,000
VLLW, 14 LW, 93
Activity (TBq)
Source: Radioactive Wastes in the UK: A summary of the 2016 Inventory
Low Level Waste Repository w ga io
»
* The Low Level Waste Repository in West Cumbria is the UK's
principal national facility for the disposal of solid low level
radioactive waste.
* It is managed and operated by the LLWR, a consortium of
AECOM, Studsvik and Areva, on behalf of the NDA.
¢ In December 2017, the LLWR were required to present a
Business Case to support the Third Term Contract Option.
* As part of the Business Case, the LLWR wanted to propose
potential opportunities to be explored during the Third Term.
Scope of Analysis da
My)
* The primary purpose of the analysis was to determine an As-ls baseline cost
estimate to inform the Business case.
* In addition, it has been identified that some Intermediate Level Waste near the
LLW/ILW boundary could potentially be safely disposed of at the LLWR prior to the
availability of the Geological Disposal Facility.
* Initial analysis was required to demonstrate if there are any potential cost savings
to be realised from this opportunity and if further analysis is worth perusing
during the Third Term.
* Decision Analysis Services Ltd were commissioned to develop a cost model to
inform the value for money argument in the business case.
Model Purpose ca
My)
An initial high level cost model was required to support gaining economic approval for the
LLWR’s Third Term Contract Option Business Case. The Business Case includes development of
potential options for enhancing the operations at the LLWR, which include the capability to
dispose of some ILW at the LLWR.
* The model is required to enable cost estimates and volume
projections associated with the baseline case and other potential
disposal proposed options.
¢ The initial focus is on waste generated from Sellafield, Harwell and
Winfrith
¢ The model timeframe is 2016 to 2140.
¢ The model will allow for “what-if” calculations and enable the
impact of the uncertainty associated with key parameters to be
determined.
* The model must be scalable to allow greater levels of detail to be
added to the model following the initial assessment of the
alternative options.
Justification for using System Dynamics da
My)
¢ System Dynamics was selected to develop the economic model for the following
reasons:
- Long modelling time horizon,
- Potentially large degree of segmentation, which may be increased in future model iterations,
- Flexible and scalable modelling environment,
- Continuous processes, such as radioactive decay, can be represented
- Complex feedback processes, such as controls on disposal options can be incorporated,
- Delays, for example time for treatment capacity to come on line can be included,
- Monte Carlo and multiple scenario runs can be incorporated into system dynamics models to
allow the evaluation of uncertainty,
- Aggregation (for example of waste into different categories and transportation assets into
types of assets is acceptable).
Model Development
| LLW Repository Ltd
MAY 2017 * Stakeholder Workshops OCTOBER 2017
* Specification written «
and signed-off
* Vensim and Excel
* Based on best practises, eg
mass balances, units etc
Model Scoping
Model Construction ;
Detailed user
documentation
Model Documentation
Model Testing
* Independent testing
based on test
specification
* Rapid analysis for
LLWR Business Case
Model Architecture
My)
Data Inputs
Excel
System
Dynamics
model
Vensim
Model
Outputs
PowerPoint
Model Data
My)
7
Data Inputs
~
System
Dynamics
model
System Dynamics Model Overview ‘i da
<== LLW Repository Ltd
fm
I
!
I
I
I
Is waste suitable for !
surface disposal at I
LLWR? I
! ILW Stored goes to GDF (post 2040)
ILW ILW Pre-2040 = ee
ILW Stored
Generated
ILW Stored goes to LLWR
Re-classification
Re-permitting
Augmentaton
New surface facility
ILW goes to LLWR
Re-classificaton
Re-permitting
Augmentation
New sutace facili
ey LLW LLW goesto LLWR
Generated
Alternative Treatment
and Disposal
6 Current ILW Route
@--=====>@ |LW Route when GDF in service
o———® Current LLW Route
o—————® Potential new ILW route to LLWR
System Dynamics Model Detail
a
: a — * Separate Stock and Flow diagrams covering waste
E: ae generation, waste storage, transport constraints and
Ce | * = ~ associated cost estimates.
* Model segmented by:
: ¢ Waste Stream (>1000)
eee ¢ Waste Type (HLW, ILW, LLW, VLLW)
¢ Site (Sellafield, Harwell, Winfrith, Elsewhere)
¢ Scenario Estimates (Minimum, Most Likely, Maximum).
Vani iil
¢ Model calculates costs and waste disposal and storage
profiles over time.
¢ Each simulation takes seconds to run and is simulated in
batches.
System Dynamics Model Sample Outputs
My)
System
Dynamics
model
7
Sample Outputs
Time Series
Bar charts
Uncertainty
———
Tabular
La}
[a
~~ =
Ne
>»
3. Model Impact
Model Impact ca
My)
* The model was used to determine the cost and benefits for the third term
contract option Business Case.
* The model provided a “whole system view” of the Business Case and the different
underlying datasets and assumptions.
¢ The rapid simulation runtime allowed multiple options to be explored and the
impact of varying the underlying assumptions to be tested.
* As each of the variables were available for analysis it was possible to present the
model results in different ways.
Base Business Case options for analysis da
=
~
As Is: “Business as Usual” — ILW disposed of in line with current strategy;
S
\
Re-classification: The focus would be would be working with consigners upstream to help characterise
and segregate suitable wastes to allow disposal of those fractions of ILW waste streams which can be re-
classified as LLW in the current vault system.
y,
Disposal by Safety Case and Re-Permitting: Modify the current LLWR Environmental Safety Case to
allow disposal of suitable ILW waste streams in the current vault system by removing the constraints of
the current LLW definition limits (4&12 GB/te).
y,
~
Vault Augmentation: Modify the current vault system (emplacement strategies, additional shielding,
semi-remote handling etc.) to allow a larger range of Higher Activity waste stream to be disposed (i.e.
those requiring shielding).
y,
\
Potential Future Options
(Not current UK Policy)
New Surface Facility: Disposal of Higher Activity waste streams following build of a new, purpose built
surface facility similar to Centre de LAube which includes shielding, roof and remote handling.
Example Analysis 1
Waste Generation over time
Volume of Waste Generated by Waste Type
VLLW
—| uw
—| ww
2016 2032 «2048 «= 2064-2080 = 2096-2112
Model Time Base (Years)
LW
Liaw
iw.
VELW
Volume of Waste Generated by Site
__-| Setaniela
Elsewhere
he |__
a
teh Harwell
2016 -2032,—~=—««2048= 2064 = 2080 += 2096.—S 212 Winrth
‘Model Time Base (Years)
The model enables large sets of data to be processed
and presented in a easy to understand format.
Profiles the waste generation over time which can be
broken down by waste type, site and waste stream.
Monte-Carlo analysis can be used to determine the
uncertainty associated with the projections of waste
generation.
NOTE: Model results are currently embargoed due to commercial sensitivities.
Example Analysis 2 7 ga o
»
How different waste disposal options vary based on diversion from the GDF
* The model enables profiles of waste over time to
be determined at different stages of the waste
management process.
¢ Diversion from final disposal at GDF means that
there is a lower requirement for on-site storage
M3
* This reduces volumes of waste requiring
packaging, transportation and disposal when the
0 GDF becomes available, and reduces risks
2016 2047 2078 2109 2140 associated with GDF availability.
Model Time Base (Years)
Ass ns Limited A
| i Construct New Surface Facility
NOTE: Model results are currently embargoed due to commercial sensitivities .
Example Analysis 3
My)
How different options vary based on Whole Life Cost
= ¢ Different options will have different associated
> an costs
ae + For example
an * Packaging Costs: Potential opportunity to
a _ : “ ” package some ILW in an alternative, cheaper
— container.
* Disposal Fees: the fee to dispose waste at the
GDF is currently unknown, itis estimated to
be up to 160% greater than the LLWR
disposal fee therefore cost savings can be
realised for every m3 of waste diverted from
the GDF to the LLWR.
NOTE: Model results are currently embargoed due to commercial sensitivities .
4. Conclusions
4. Conclusions da
My)
¢ The model was effective in supporting Business Case development as it
allowed rapid analysis of the “As-Is” option.
¢ Lots of work is continuing to underpin our findings around the alternative
options.
¢ Although UK policy does not currently support the approach of diversion of
ILW to LLWR, this work provides insights into the benefits of taking it
forward.
¢ The NDA are deciding if and how to take this (and other options) forward.
¢ The model can be reused to undertake this analysis, and will be improved
for example to include addition consigner sites, additional disposal facilities
and more detailed waste segmentation.
5. Bibliography
Bibliography (NOT FOR PRESENTATION) da
My)
* Cave, S (2014). CfWI technical paper series no. 0008, Developing robust system-dynamics-based workforce models: A best-practice approach, London: CfWI Publications.
http://www.wales.nhs.uk/sitesplus/documents/1096/Technical%20Paper%20N0%208%20-%20BP%20to%20developing%20SD%20based%20WF%20models1.pdf
* Cave, Sién with John Peters and Alison Gray (2016) Simulation and analysis to support decision making in the treatment and handling of radioactive waste
https://www.systemdynamics.org/assets/conferences/2016/proceed/papers/P1131.pdf
+ Forrester J. W. 1961. Industrial Dynamics. The MIT Press, Cambridge, Massachusetts, 1961.
* Jacobson, Jacob with Steven Piet, A. Yacout, G. Matthern and Anton Moisseytsev (2005) Modeling the Nuclear Fuel Cycle
https://www.systemdynamics.org/assets/conferences/2005/proceed/papers/JACOB317.pdf
* Keating E. K. (1999) Issues to consider while developing a System Dynamics model. http://metasd.com/wp-content/uploads/2010/03/SDModelCritique.pdf
* Love, Gregory with Chris Glazner, Sam Steckley and Kristin Lee (2011) Nuclear Waste Management: Strategic Framework for Large-Scale Government Programs: Addressing Legacy
Waste from the Cold War https://www.systemdynamics.org/assets/conferences/2011/proceed/papers/P1350.pdf
* Malczynski, Leonard with Jacob Jacobson (2008) Very Large System Dynamics Models - Lessons Learned
https://www.systemdynamics.org/assets/conferences/2008/proceed/papers/MALCZ214.pdf
* NDA Report No, DSSC 412-01, Geological Disposal, Generic Disposal Facility Design, December 2016 _https://rwm.nda.gov.uk/publication/geological-disposal-generic-disposal-
facility-designs/
* NDA Radioactive Wastes in the UK: Context and Methodology Report https://ukinventory.nda.gov.uk/wp-content/uploads/sites/18/2014/01/2016UKRWMI-Context-and-
methodology. pdf
¢ Randers J. 1980. Guidelines for Model Conceptualization. In Elements of the System Dynamics Method, ed. by J. Randers. Portland, OR: Productivity Press.
* Sterman J. D. (2000) Business Dynamics. McGraw-Hill Higher Education.
* UK Radioactive Waste Inventory https://ukinventory.nda.gov.uk/the-2016-inventory/2016-uk-data/
”»
Appendix A: What is System Dynamics cc
| LLW Repository Ltd
System Dynamics is a modelling approach that enables complex systems to be better
understood, and their behaviour over time to be projected using computer simulation
Qualitative Graphical description of the cause and effect relations that define system
behaviour
* Holistic view of how the system of interest operates
Generated through facilitated workshops and interviews
Graphical representation brings together the knowledge held by all stakeholders
Identifies ownership, bottlenecks, intervention points
* Standard diagramming conventions called Stock Flow Diagrams or Causal Loop Diagrams
Quantitative Computer simulation to calculate the behaviour of the system over time
Time based simulation
Quantifies the potentially complex feedback mechanisms that drive behaviour
oo * Enables alternative scenarios to be quantified and so make informed strategic decisions
_A
* “Drill-in” to key performance drivers and detail to mitigate risk and understand implications of alternative
interventions
Stakeholder can be provided with management simulation tools that they can use to test out their own
interventions
