1. No category

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How to Deal with the Management
of Prototype Fast Reactor (PFR)
Raffinate
An invitation to participate
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30 September 2004
UKAEA/PP/P(2004)01
CLOSING DATE FOR COMMENT IS 23rd DECEMBER 2004
How to Deal with the Management
of Prototype Fast Reactor (PFR)
Raffinate
An invitation to participate
Introduction
UKAEA’s job at Dounreay is to restore the environment of the site. The Dounreay Site
Restoration Plan (DSRP) sets out the decommissioning and radioactive waste management
activities necessary to restore the site.
In readiness for becoming contractor to the Nuclear Decommissioning Authority (NDA) in
April 2005, the UKAEA is upgrading the DSRP and renaming it as the ‘Life Cycle Base Line’
to be consistent with other nuclear sites. A more detailed description of the main activities
proposed for the next year or two – the Near Term Work Plan – has also been prepared for
the NDA. A summary is available at
http://www.ukaea.org.uk/reports/generalpdf/Dounreay–NTWP–summary–final.pdf.
For many of the individual waste management issues within the overall plan, the detailed
solution has still to be decided. In some cases, a number of different options are available
which will need to be assessed against a range of factors – safety, environmental, financial
and technical – before the final decision is made. As part of this option assessment
process, UKAEA carries out a Best Practicable Environmental Option (BPEO) study for
all issues where there may be a significant impact in the locality of the site, or indeed
further afield.
We want the public to participate in the BPEO assessment and this document outlines the
options and the results of consultations to date for one such issue – the management of
Prototype Fast Reactor (PFR) Raffinate - and invites you to register your views.
UKAEA has attempted to ensure that the information contained here is both sufficient and
appropriate but recognises there will be some who will require further, more in-depth,
information. For that purpose more information is available on our website at
http://www.ukaea.org.uk/dounreay/dsrpnews.htm. If you require additional information
and cannot find it on our website please do not hesitate to contact us at the address given.
The Issue
Background
Dounreay’s historical role as a research and development establishment for fast reactor
technology included plants to reprocess the fuel after it had been irradiated in the reactors.
Most of the nuclear fuel was not used when it was irradiated in this way. Rather than waste
the unused energy in this fuel, plants were built to dissolve the fuel elements in acid and
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separate the unused fuel from the irradiated waste, using a solvent extraction process.
This was known as reprocessing, and recovered the unirradiated metal for reuse as new
reactor fuel.
The acidic wastes (liquors) left behind are known as raffinates, and are grouped into three
distinct categories depending upon which reactor was the source of the fuel:
•
•
•
MTR
Material Test Reactor
DFR
Dounreay Fast Reactor
PFR
Prototype Fast Reactor
1. The overall objective of the BPEO study is to identify the
best overall management strategy.
Heavily shielded underground tanks were built to store the raffinates. In the case of PFR
2. All systems
possible to
options
are overheating.
identified at this stage.
raffinate, tanks were installed complete with cooling
prevent
Reprocessing was stopped in 1996 and today (September 2004) these tanks contain
3. Options
must
with laws in
and
for 78.5%
of comply
the radioactivity
theconventions
total
approximately 1200m3 of raffinate which accounts
therefore
impracticable
options
are
discarded
waste inventory. The safe and secure management of these wastes is one of the highest
at this point. the raffinates; that is to
priority tasks in the DSRP. The key objective is to “immobilise”
convert them to a solid form that is safe for the long-term whether it is storage or disposal.
Classification of the waste
Radioactive waste is classified according to the level of radioactivity and whether or not it
generates significant heat as a result of radioactive decay. Below a certain level of
radioactivity, waste is classified as Low Level Waste (LLW). Above that level, waste is
5. Using the attributes at point 4 evaluation of performance
classified as Intermediate Level Waste (ILW) – unless
it generates significant amounts of
is scored.
heat, in which case it is classified as High Level Waste (HLW). The distinction between
HLW and ILW is therefore heat generation, not the level of radioactivity.
6. generate
Options are
then
compared
key factors.
When it was first produced, the PFR raffinate did
heat,
which
is whytoit identify
was stored
in tanks designed with cooling systems. It was therefore classified as HLW, and if UKAEA
had conditioned the raffinate at that point it would have been vitrified in line with UK
practice. Vitrification is a process whereby the waste
is incorporated into glass. This
7. Determining the BPEO can be carried out through
process has generally been adopted world-wide as
best
practice
for immobilising
stakeholder
workshops,
cascadingwastes
of information.
generating significant heat, though the technology has been found to be complex and
challenging to implement efficiently.
The PFR raffinate has now had a minimum of 10 years storage and no longer generates
the same level of heat. Accordingly, UKAEA has now reclassified the waste as ILW. This is
not a matter of UKAEA policy, but of fact. If PFR raffinate is not reclassified, the next UK
Radioactive Waste Inventory due to be published in October 2005 will be misleading. The
fact that the PFR raffinate no longer generates significant heat also means that it need not
be vitrified if an alternative can be shown to be a better environmental option.
Immobilising the PFR Raffinate
UKAEA is now in a position to move forward with a project to achieve the immobilisation of
Dounreay's PFR raffinate at the earliest opportunity. The work done so far suggests a
practicable and simpler alternative technology to vitrification is to immobilise the PFR
raffinate in cement and store it as solid intermediate level waste, as is already the case for
the less active MTR raffinate. However, before proceeding, we wish to set out the rationale
behind our thinking and invite comments and views from our stakeholders and interested
members of the public on this and the other options being considered. The following
sections of this document provide an overview of the approach we have taken in assessing
the alternatives and discussing them with our stakeholders.
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The Method
For a major environmental project, where society may have an interest and where there
could be a number of possible outcomes, UKAEA is following international best practice
by developing a Best Practicable Environmental Option (BPEO) study. This approach
considers safety, environment, technical, planning and legal aspects for a range of
options in a structured and progressive manner.
The stages in a BPEO Study are:
1.
Define the Objective
The overall objective of the BPEO study is
to assist in the identification of the best
overall management strategy.
2.
Generate Candidate Options
All possible options are identified at
this stage.
3.
Exclude Impracticable Options
Options must comply with laws and
conventions therefore impracticable
options are discarded at this point.
4.
Establish Attributes for Comparing Options
Attributes to be considered include: health and
safety, environment, technical, social, political
and economic and cost.
5.
Evaluate Performance of Options (scoring)
Using the attributes at point 4, evaluation of
performance is scored.
6.
Compare Options
Options are then compared to identify
key factors.
7.
Determine the BPEO
Determining the BPEO can be assisted
through stakeholder workshops or cascading
of information.
The BPEO study develops through a number of stages; from identification of issues
and options through analysis and stakeholder involvement, to recommendations on the
way forward.
The first stages 1 to 5 involve mainly technical work. UKAEA engaged consultants, who are
internationally recognised for their expertise, to carry out a series of studies. This work was
necessary to lay the foundation for developing the BPEO study further through stakeholder
participation.
Throughout the preparation of the preliminary BPEO, UKAEA has endeavoured to identify
the key factors that discriminate between options and the values on which strategic
decisions could rest. The emphasis has been to examine the issues that will be important in
comparing options from a range of perspectives. Due consideration is given to current
government policy.
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The Options for Dealing with PFR Raffinate
(i) The Long List
Twelve principal options were identified. To be chosen from the long list for the short list,
screening criteria was defined based on UK law; international conventions and dose
constraints as set out by the UK regulators. Each option was then considered against
these criteria.
A few of the candidate options, such as direct discharge or disposal to boreholes, failed to
meet these criteria and were screened out as impracticable or illegal. Those screened out
at the early stage were:
• Discharge to sea (after actinide separation) (10Dc)
• Borehole injection (after actnide separation) (10Dd)
• Sea discharge (11)
• Borehole injection (12)
Appendix 1 lists all 12 candidate options, and explains why some were screened out.
Some of the options also gave consideration to sub-options which are also outlined.
(ii) The Short List
The remaining options came through the screening process and can be grouped under the
following headings:
Group 1: Continued storage in a non-passively stable form, with engineered safeguards and
a regime of care and maintenance to ensure safe storage.
1. As a liquid in existing tanks (Do Nothing)
2. As a liquid in newly constructed tanks
3. Temporary immobilisation
Group 2: Generation of a passively stable product that is suitable for indefinite storage or
disposal (taking into account the possibility that it may be necessary to ‘rework’ the product
in future.
4. Immobilisation in ceramics
5. Immobilisation in glass (vitrification)
6. Immobilisation in cement
6a. - as Intermediate Level Waste
6ai: using current Dounreay Cementation Plant (DCP)
6aii: using newly purpose-built cementation plant (DCP2)
6b. - at reduced concentration, such that the product could be categorised as LLW
7. Immobilisation in polymer
Group 3: Generation of a product that would not be susceptible to leakage into the
environment but require additional processing or packaging prior to indefinite storage
or disposal.
8. Evaporate to dryness
9. Calcination
10. Actinide separation followed by an option from 10D and/or 10R).
(10D) management of the actinide-depleted product stream by
10Da - decay store as liquid
10Db - immobilisation in cement
(10R) reduced-scale management of the actinide-rich product stream by
10Ra - indefinite storage as liquid
10Rb - temporary immobilisation
10Rc - immobilisation in cement
10Rd - immobilisation in glass (laboratory scale)
10Re - evaporate to dryness
10Rf - calcination
10Rg - transmutation
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Comparing the Options
The next step in the BPEO assessment is to compare the options against a set of selected attributes.
In order to assess the pros and cons of each option, a range of attributes was chosen that
would allow the options to be compared in a comprehensive and readily understandable
way. International and national guidance suggests five primary categories for attributes:
• Health and Safety
• Environmental impact
• Technical issues
• Social, political and economic considerations
• Cost
One further category – environmental objectives – was considered within this particular
study. This category was introduced to reflect the need to minimise the volume of primary
waste being produced.
These categories encompass a comprehensive range of issues. However, in line with
accepted BPEO methods, they were each divided into a series of sub-attributes so to
provide a means of detailed comparison between the options, as shown below:
Health and
Safety
Environmental
impact
Technical issues Social, political
and economic
issues
Environmental
objectives
Financial cost
1.1 Public Routine
radiation doses
4.1 Air quality
6.1 Maturity of
technology
10.1 Economic
impacts
11.1 Primary waste
volume
12.1 undiscounted
cost
1.2 Public
Radiological
accident
consequences
4.2 Water quality
7.1 Foreclosing
other options
10.2 Culture and
heritage
4.3 Land quality
4.5 Nuisances
1.3 Public NonRadioactive
hazards and risks
2.1 Public collective
doses
4.6 Energy usage
7.2 Cope with
different waste
8.1 Stability of
product
5.1 Preservation
of ecosystem
9.1 Timely
implementation
3.1 Worker Routine
radiation doses
3.2 Worker
Radiological
accident
consequences
3.3 Worker Nonradioactive hazards
& risks
Security of the site was taken into account however no specific attribute was assigned.
Nuclear facilities have strong security defences and since the tragedy of September 11th
there has been even more focus on safety. By its very nature security is hard to explicitly
define however the consequences of an accident similar to terrorist attacks have been
considered in facility safety cases, and therefore was deemed to be included in the scoring
of Attributes 1.2 ad 3.2 “Radiological accident consequences” (public and workers
respectively) and also in the scoring of Attribute 8.1 (Stability of product) with regard to the
potential impact of an attack on the store that would hold the conditioned waste.
The table overleaf summarises how the options were scored against the selected attributes.
Each box outlines the impact of the option, and includes a score to show how the options
perform, relative to the alternatives, against the attribute. A score of 5 is excellent (ideal
performance) while 0 is very poor and indicates unacceptable performance.
5
5
5
5
5
5
3
4
1.1 Public Routine radiation doses
1.2 Public Radiological accident cons
1.3 Public Non-rad hazards & risks
2.1 Public collective doses
3.1 Worker Routine radiation doses
3.2 Worker Radiological accident cons
3.3 Worker Non-rad hazards & risks
6
5
0
0
0
7.1 Foreclosing other options
7.2 Cope with different waste
8.1 Stability of product
9.1 Timely implementation
5
91
12.1 Undiscounted cost
TOTAL
Finance cost
11.1 Primary waste volume
3
3
10.2 Culture and heritage
Environmental objectives
3
10.1 Economic impacts
Socio-economic issues
5
6.1 Maturity of technology
Technical issues
5
5
5
4.4 Visual impact
4.6 Energy usage
5.1 Preservation of ecosystem
5
4.3 Land quality
5
5
4.2 Water quality
93
4
3
3
3
0
5
5
0
5
5
5
4
4
5
5
5
82
1
3
3
3
0
5
0
0
3
3
5
4
4
5
5
5
4
4
5
5
5
81
1
5
3
4
2
2
3
5
1
2
5
4
4
5
4
4
3
4
3
5
4
89
2
5
3
4
4
2
5
5
4
2
5
4
4
5
4
4
3
4
3
5
4
87
3
5
3
3
0
2
5
5
4
2
5
5
5
5
4
4
3
4
3
5
4
4
3
3
4
5
3
5
4
5
4
5
4
4
5
5
5
4
4
5
5
5
1
0
3
4
3
2
5
5
5
3
5
3
4
5
5
5
4
4
5
5
5
100 101 91
4
2
3
3
5
3
4
4
5
4
5
5
5
5
5
5
4
4
5
5
5
86
2
3
3
3
2
1
3
3
1
4
5
4
4
5
5
5
4
4
5
5
5
81
3
5
3
3
4
5
4
1
2
3
5
4
4
5
4
4
2
3
2
5
3
5
2
79
2
5
3
3
4
4
4
1
4
2
5
4
4
5
4
4
2
2
2
5
3
5
2
Polymers
7
5
5
89
3
2
3
3
3
3
4
4
2
4
5
4
4
5
5
5
2
3
5
5
5
5
5
10+10Re Separation + evap
and store
80
2
5
3
3
3
5
4
1
2
3
5
4
4
5
4
4
2
3
2
5
4
5
2
Options were scored on assumed relative cost for the different options.
Process which minimised the volume of waste scored highest whilst Cementation as LLW scored lowest because of the large volume
of wasteform generated.
Options requiring a significant new build were judged to have the greatest economic benefit to the local community and these options
scored the highest.
All scored 3 because no major positive or negative impacts were envisaged
dryness and calcined products would give marginal stability and scored lowest.
Options that retained as a liquid were defined not to meet DSRP timescales and scored lowest, as did vitrification in WVP because of unspecified
delay by BNFL and requirement for approval to transport. Ceramic and polymer options scored low because of significant development work.
Cementation as ILW in DCP and DCP2 scored highest because they could be implemented rapidly. Cementation as LLW would take much longer
because of larger volume of material.
Scoring was based on the amount of R&D required to develop and implement and to the amount of experience applied to similar waste
streams using the technique.
Scoring was applied taking flexibility to change the final wasteform if required in the future into account.
Scoring was considered on the grounds of whether the option could be applied to other waste streams.
The most passively stable products were judged to be immobilisation forms (ceramic, vitrified or cemented as LLW). Evaporator to
High temperature processes were considered more likely to give rise to non-active discharges and were scored at 4 while all other
processes were not considered to impact on air quality.
High temperature processes were considered more likely to give rise to non-active discharges (scrubber liquors, etc.) and were scored
at 4 while all other processes were not considered to impact on water quality.
All scored same because it is assumed that all options would be engineered to have no impact on quality of surrounding land
under normal operating conditions.
Options that could reasonably be expected to be carried out within existing buildings and infrastructure scored highest. A score of 4
was awarded if assumed a new building would be required and/or several additional facilities were required.
Major nuisance would result from construction traffic for new buildings therefore these options scored 4 while Cement as LLW scored
3 due to requirement for large volumes of cement to be transported and larger store.
Scores were generally correlated with temperature requirements for each option.
No significant impact from any of the options.
Higher temperature processes producing powders were more dispersable and scored lowest.
Major hazard would arise from chemical toxicity of the waste and option scores were based on accident consequences attribute.
All options considered to be equal with little dose from any option.
Hot temperature processes pose greater potential doses because of volatility of certain radioelements. Handling of powdered
product from evaporation and calcine may cause higher doses.
Scoring took account of closer proximity of workers and product compared with the public.
Use of high temperature processes, acids and caustics, dust hazards, organic solvents and chemical toxicity were taken into account when scoring this attribute.
All options could be engineered to allow for minimal routine discharges and resultant public dose
Likely migration of radionuclides the higher the temperature/ process thus ceramic, vrtrification, evaporation to dryness & calcination scored lower.
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4.5 Nuisances
5
4.1 Air quality
3
4
5
5
5
Cermics
4
5
5
Vitrification in DVP
5
5
5
Vitrification in WVP
5b
5
5
Cement as ILW in DCP
6ai
5
3
Cement as ILW in DCP2
6aii
5
3
Cement as LLW
6b
5
3
1/10/04
Environmental impact
Continued storge current
1
5
5
New Tanks
2
5
5
Temporary immobilisation
3
Human health and safety
Evaporate
8
Group 3
Calcine
9
Group 2
10D+10Rc Separation & cement
Group 1
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In the BPEO method, each attribute is given a ‘weight’ which reflects how important it is
relative to other attributes. By weighting the score against each attribute, we can convert
them into common values which can be added together to arrive at an overall score for the
relevant option.
The weights are inevitably a matter of judgement. For example, some people might feel
that the social economic impact is much more important to them than cost. They might
reflect this view by giving the social/economic score a weight of 100, compared to a weight
of 10 for cost.
The weights used in this assessment by the Project Team and Stakeholder panels are
detailed in the section below.
Input from Stakeholders Panels
While UKAEA believes the assessment of the BPEO is robust, we are keen to obtain the
views of its stakeholders and to encourage their input to the BPEO assessment itself.
In Stage 6 of the BPEO assessment process, meetings were held so that stakeholders
could be taken through the work already carried out by the Project Team and discuss issues
relating to the BPEO process.
Two stakeholder panels were held to review the options, the assessment process and to
provide feedback on differing views:
•
The internal stakeholder panel was made up of a cross section of people who work
on the Dounreay site. They were chosen from a range of skills, occupations and home
locations and had no direct input to this particular project.
•
The external stakeholder panel was made up of a varied group of people including
members of the Dounreay Local Liaison Committee (DLLC), UK Nirex Ltd, UKAEA
Trade Unions, the Education Authority, NRTE Vulcan, the Liabilities Management Unit,
Highland Council and Dounreay Action Group. Unfortunately, representatives from an
Environmental NGO organisation and the Orkney Island Council had to tender
apologies at very short notice.
Both panels were conducted by Professor Ray Kemp, Galson Sciences Ltd, an independent
facilitator. The objective of the meetings was to be transparent about the decision-making
within UKAEA Dounreay and to hear the views of stakeholders regarding this project. While
acknowledging that this project is at an advanced stage of development it is still considered
important to seek stakeholder views in order to gauge whether any important issues or
considerations had been overlooked, whether more emphasis should be given to certain
issues and to seek opinions on moving forward with this project.
Both panels followed the same approach. The Project Team presented information covering
the background to the project, an overview of the technical studies and an overview of the
preliminary BPEO. During and following these presentations panel members questioned and
discussed any areas of particular interest or concern.
In addition, computer software ‘Hi-View’ was used to capture and display the outcomes of
discussion on attribute weighting. This allowed panel members to review how the software
worked, to see how the Project Team had used a range of weightings to investigate the
sensitivity of the assessment results, and to explore how the ranking options or desirability
of an option are affected by changing assumptions regarding the weighting of different
attributes. The Project Team weightings and weightings suggested by both stakeholder
panels were:
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Attribute Group
Project
Team
Weighting
Technology
position
Environmental
position
Financial
position
Internal
Stakeholder
Panel
External Stakeholder
Panel
1 2
Human Health
Environmental
impact
Technical
Socio-Economic
Environmental
objectives
5
5
10
1
10
10
1
1
5
5
5
5
1
1
5
3
1
10
1
1
1
10
10
1
1
1
3
4
1
1
5
1
3
5
1
Financial cost
5
10
1
10
3
1
1
The individual weightings assigned by the panel members were considered by the group on
an attribute-by-attribute basis and the differences in weightings were discussed. For each
attribute a “group” weighting was agreed. The group weightings were not necessarily the
average of the individual weightings but the outcome of negotiated discussion among the
panel members as recorded. The results should not be interpreted as a final agreed
weighting among the panel members.
Internal Panel
The Panel members generally agreed that the Preliminary BPEO calculations were robust
although it was pointed out that there would have been some benefit in having more time to
consider different attribute scores for the different options. The Project Team noted that
there had been long deliberations regarding the scores and that these had been agreed by
consensus. In addition, subjective judgement had been avoided where possible (Appendix
2 of this paper details the calibration of the scoring used).
External Panel
The conclusion of the panel from investigating the weightings applied was that the result of
the Preliminary BPEO was robust. It was suggested that UKAEA ensure that all briefing
material (used in the panel meetings) was made easily accessible because it would play an
important part in understanding the project. One member was interested to see how
sensitive the result was and by using the sensitivity tool it was demonstrated that the
highest scoring option could be changed albeit that the relative weightings used to achieve
this required to be very high.
Full reports of the stakeholder panels can be found on our website.
Initial Conclusions
Cementing PFR raffinate as ILW appears to be the best option but the difference between
using a newly constructed cementation plant at Dounreay (DCP2) or the existing Dounreay
Cementation Plant (DCP) is only one point. On the basis of the weighted scores DCP2
closely followed by DCP score the highest when using 3 out of the 4 weighting schemes.
These differences whilst pointing towards DCP2 are therefore not considered in themselves
to be sufficient to identify the better option.
Wider considerations were then taken into account when choosing between cementation as
ILW using DCP or the DCP2. UKAEA believe the BEPO is cementation as ILW using a newly
built cementation plant (DCP2) for the following reasons:
•
The difference in the lifecycle costs between the two options is likely to be minimal,
given that the capital cost of the DCP would be offset by lower storage costs. This is
because of the small waste volume generated – DCP2 would be designed with a
higher incorporation rate than is possible with DCP.
•
Use of the DCP would result in timely implementation of a management method for the
PFR raffinate but would delay implementation of management methods for other waste
streams within the DSRP.
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•
In particular, using the DCP would impact on the planned programme of cementation
of the MTR and DFR raffinates, whilst using DCP2 would allow faster overall
management of all the raffinates and other related DSRP programme issues.
•
DCP2 could be designed with greater flexibility to allow a wider envelope of cement
compositions, thus offering greater potential for treating a wider range of other
wasteforms and plant washouts.
•
Relying only on the DCP substantially increases the project risk for a number of
elements of the DSRP due to the lack of redundancy in critical plant capabilities, this
is particularly important considering the likely maintenance and modification regime
that would be required to support the existing plant for a further two decades with the
same situation applying to the existing raffinate storage facilities.
In favouring this option it is assumed that the cemented stable waste form will be safely
stored on the site until a national solution is available.
Next Steps
The next step is to widen the consultation process and seek the views of members of the
public, including Dounreay’s 800 registered stakeholders. All responses received will be
public but respondents’ personal details will be kept private on request.
The BPEO assessment will be reviewed, taking on board all the views and comments given
to UKAEA. Any further work required to clarify points raised will be carried out. A final
recommendation will be prepared in the light of these inputs, for submission to the
regulators and planning authority and made public.
Appendix 1
Brief Description of Options
Group 1
1. Storage in existing tanks
This option assumes that the raffinate stays in the existing tanks. Technically this option could be
continued for the foreseeable future, although the tanks would require a programme of maintenance
and surveillance. This option, by definition, would be only carried out at Dounreay.
2. Storage in new tanks
This option would complement or replace the existing tanks with a suite of newly constructed tanks
and supporting systems, built to modern design standards, to provide an extended storage capability.
3. Temporary immobilisation
This option envisages the ‘solidification’ of the raffinate, thereby removing the potential for the
raffinate to leak or spill from its tank. However, the temporary waste form would be chosen such that
further processing could be undertaken. There are a number of temporary immobilisation methods
that could be applied, including freezing, conversion of the liquid into a gel phase (eg reaction with
sodium silicate) or absorption onto an inert medium (eg vermiculite). The study did not differentiate
between these methods because their environmental and technical characteristics are considered to
be similar to each other.
Group 2
4. Immobilisation in ceramic
A number of ceramic wasteforms have been proposed for the incorporation of highly active
radioactive wastes. Most research has been undertaken on Synroc (synthetic rock), although other
similar inert matrices have been proposed. Synroc is made by mixing mineral oxides with the raffinate
and then calcinating the mixture to remove the water and acid and decompose the nitrates. This
results in a dry product powder that under pressure forms a rock-like wasteform.
5. Immobilisation in glass (vitrification)
This method is the most widely adopted option internationally for these types of waste. Industrialscale plants are operating in several countries including the UK. Specific trials conducted with
simulated PFR raffinates have produced stable vitrified products. This process could be used at
Dounreay or elsewhere with a new vitrification plant constructed for this purpose. Alternatively the PFR
raffinate could be sent for treatment to an existing vitrification plant, such as the one at Sellafield.
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6a. Immobilisation in cement as ILW
Cementation is a widely used immobilisation method for liquid ILW and LLW. UKAEA is cementing
MTR raffinate and will cement DFR raffinate in future. The raffinate is first neutralised, then a blend of
cementitious powders are added to the disposal drum, and mixed using a ‘lost paddle’ (a paddle
fixed within the drum for mixing the raffinate and cement) technique. The resulting mix then sets into a
solid form. This option could be carried out at Dounreay using the existing Dounreay Cementation
Plant (6ai) where currently MTR raffinate is cemented. This would require modification before being
capable of cementing PFR raffinate, or a newly purpose-built cementation plant could be built (6aii).
Potentially, the raffinate could also be sent for treatment to a newly built or existing cementation plant
elsewhere in the UK or overseas.
6b. Immobilisation in cement as LLW
Like 6a above but would involve decreasing the radioactivity concentration in the waste by dilution
with water or dilute acid, such that the resulting wasteform could be classified as LLW. This would give
rise to much larger volumes of solid product.
7. Immobilisation in polymer
Immobilisation of radioactive waste by polymerization is a fairly well developed technology, but one
which is most commonly applied to the encapsulation of solid wastes. The process involves
encapsulating the waste in a solid polymer matrix. For liquid wastes, this is achieved by first forming
an emulsion from the liquid and polymer materials, then allowing the polymer to harden.
Group 3
8. Evaporate to dryness
Existing liquid raffinate volumes held at Dounreay are routinely reduced by evaporation in a
purpose-built evaporator facility. Technically a modified facility could be developed which could
evaporate the PFR raffinate to dryness to create a solid powder form comprising of mainly nitrate
salts. This would then be stored in powder form in specially designed bunkers.
9. Calcination
Calcination is similar to evaporation, but differs in that the waste product is decomposed to a more
thermally stable chemical form by additional heating (the nitrate salts are converted into oxide forms).
Calcination is essentially the first stage in many vitrification technologies, prior to mixing with glass
forming chemicals. A calcination facility would comprise many of the same plant items as a
vitrification plant. This wasteform can, in principle, be stored as a powder without immediate
vitrification.
10. Actinide separation
This option involves passing the liquid PFR raffinate through a novel, industrial scale chemical
process to separate chemically dissimilar components. The benefit is the separation of a small
volume of the actinide long-lived species (nuclides of americium, uranium, plutonium etc) from a
larger volume of the shorter-lived species. This potentially makes the longer term management of
the waste easier. Actinide separation is then followed by an option from 10D and/or 10R below.
10D. Actinide-depleted waste stream (from actinide separation)
The potential options for treating the actinide-depleted product stream are essentially the same as
those that may be applied to the ‘raw’ untreated PFR raffinate. The difference is the reduced activity
concentration of this stream.
10Da: Decay storage as liquid
This option would allow continued decay storage, as a liquid, in existing or new tanks.
10Db: Cementation
After removal of the majority of the actinides by separation, the actinide-depleted
product stream could be cemented.
10R. Actinide-rich waste stream (from actinide separation)
Although smaller in volume, the actinide-rich waste stream would have a higher specific activity than
the original PFR raffinate and this would need to be addressed when considering immobilisation
options. If the actinide-rich waste stream had to be incorporated at a low concentration into a solid,
the volume reduction gained from separation would be lost.
10Ra: Storage as liquid
Continued storage as a liquid may be viable for the actinide-rich waste stream because of the much
smaller volume of liquid to be contained. New tanks would most likely be required to hold this liquid.
10Rb: Temporary immobilisation
Continued storage as a temporarily immobilised product may be viable for the actinide-rich waste stream
because of the much smaller volume of waste to be contained. Of the available technologies freezing
would not be appropriate due to the high heat output of the waste. New tanks would most likely hold
any temporarily immobilised product.
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10Rc: Cementation
The actinide-rich waste stream may potentially be cemented, although the high alpha-emitting
(and beta/gamma) activity concentration may impair successful cementation of a robust wasteform
using traditional processes
10Rd: Vitrify at laboratory scale
Given the much smaller volume of actinide-rich waste stream compared to the original PFR
raffinate volume, vitrification may be possible using small laboratory-scale facilities negating the
need and cost of an industrial-scale DVP. However, the high concentration of radioactive
species in the glass may be a challenge.
10Re and 10 Rf: Evaporate to dryness and calcination
The small volume of actinide-rich waste stream could be reduced further by evaporation to
dryness or calcined. Option 8 and 9 give further details.
10Rg: Transmutation
Nuclear transmutation has been advocated as suitable technology for dealing with radioactive
waste. This would involve irradiating the waste in a specially designed nuclear reactor. Several
strategies could be applied, for example the longest-lived radionuclides could be converted to
shorter-lived nuclides or the most radioactive radionuclides could be converted into less harmful
nuclides. This approach does require further treatment or disposal of secondary wastes that it
would generate, and it would thus have to be combined with one of the other options to produce
a coherent management strategy. This has never been demonstrated to work on an industrial
scale although research on the technology is still ongoing in some countries.
Options Rejected from the Long List
Group 3
10Dc: Discharge to sea (actinide-depleted waste stream (from actinide separtion)
Although the actinide depleted waste stream could be discharged to sea it would result from
discharge of the raffinate over a 50 year period, the estimate dose would be above the current
limit and further more would be inconsistent with the OSPAR objectives.
10Dd: Borehole injection (actinide-depleted waste stream (from actinide separtion)
Although the actinide-depleted waste stream could be discharged to a deep borehole it could
not satisfy the Groundwater Regulation.
Group 4
11 Sea discharge
Discharge to sea, via offshore pipelines, is routinely used for the disposal of many forms of
liquid wastes, such as treated sewage. UKAEA discharge some liquid effluent to sea with very
low levels of residual radioactivity in the effluent. These are substantially lower than the activity
of the PFR raffinate. Dilution of the raffinate to a low concentration could allow the waste to be
released to sea, but this would not be achievable within the DSRP timescales.
12. Borehole injection
Direct disposal of liquid wastes by injection into deep boreholes has been carried out in three facilities
in Russia since the 1960s. This method involves injection into permeable rock formations at depths of
up to 1.5km for HLW and up to 400m for ILW or LLW. Borehole injection could be undertaken at
Dounreay but the rock characteristics are notably different from that at the Russian injection sites.
Transport Issues
Many of the treatment options could be undertaken away from the Dounreay site either at other
facilities in the UK or overseas. The PFR raffinate could be transported in its liquid state or following
solidification (eg by evaporation to dryness or absorption on vermiculite).
Assuming transport occurs in its present liquid state, facilities for export at Dounreay and
receipt at the processing site would have to be constructed. These facilities would involve wet
systems for handling the raffinate, mechanical systems for handling flasks, and service systems for
the operation of the export facility. In addition, similar facilities would be required at the treatment
facility elsewhere that would receive the raffinate.
A suitable flask would also need to be designed and licensed to facilitate the transport of the
raffinate from Dounreay. Transport within the UK would be dependent on gaining all the relevant
authorisations from the national regulators.
Transport overseas would additionally involve authorisations from the host country and,
potentially, the IAEA. Consideration would also need to be given to the long-term fate of the
treated product.
More detailed information on the different options can be found in the preliminary BPEO study which is
available on our website. http://www.ukaea.org.uk/dounreay/dsrpnews.htm.
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Appendix 2 – Calibration for Attribute Scores
Attribute
Sub-attribut
Requirement for intolerable
performance ( score = 0)
Requirement for ideal
performance (score = 5)
1. Public health and safety (individuals):
1.1 Routine radiation doses
Difficult to demonstrate doses <1 mSv yr –1
1.2 Radiological accident consequences. Unacceptably high consequence
1.3 Non-radioactive hazards & risks
Difficult to demonstrate risks <10 –4 yr –1
Easy to demonstrate doses <10 µSv yr –1
Low consequence
Easy to demonstrate risks <10 –6 yr –1
2. Public health and safety (societal, collective doses):
2.1 Routine radiation doses
Difficult to demonstrate doses <100 person Sv Easy to demonstrate doses
<1 person Sv
3. Worker health and safety (individuals):
3.1 Routine radiation doses
Difficult to demonstrate doses <20 mSv yr –1
3.2 Radiological accident consequences. Unacceptably high consequence
3.3 Non-radioactive hazards & risks
Difficult to demonstrate risks <10 –3 yr –1
Easy to demonstrate doses <2 mSv yr –1
Low consequence
Easy to demonstrate risks <10 –5 yr –1
4. Physical environment:
4.1 Air quality
4.2 Water quality
4.3 Land
4.4 Visual impact
4.5 Nuisances (noise, traffic etc)
4.6 Energy usage
Persistent objectionable substances in air
in buildings off the site
Sterilisation of water resource
Sterilisation of substantial area of land
Construction completely out of keeping
with existing landscape
Long-term disturbance/ disruption of local life
Relative scale: unacceptably high
energy usage
No discernible reduction in air quality
No discernible reduction in water quality
No discernible reduction in land quality
No discernible visual impact
No outward signs of the waste
management scheme
Relative scale: lowest energy usage
5. Flora and Fauna:
5.1 Preservation of ecosystems
Complete loss of natural ecosystem
No discernible reduction in quality of the
natural ecosystem
Unproven and not achievable with existing
technology in the timescale of the DSRP.
Established approach, with good track
record and applied to similar waste
streams under similar circumstances to
those of DSRP waste management.
No reasonable potential to rework or apply
different option once complete
Process can only accept PFR raffinate
Easily reworked or different option can
be followed after implementation
Process once developed for the PFR
raffinate easily adapted to other liquid
waste streams.
Product is potentially mobile (e.g. dispersible
in air or water), has only limited stability and
can readily release radionuclides through
leaching/diffusion.
Product is monolithic and demonstrably
stable over long periods and has high
radionuclide retention capabilities.
Cannot be achieved on timescale consistent
with DSRP
Can be achieved within 10 years
(by 2012)
6. Viability:
6.1 Maturity of technology
7. Flexibility:
7.1 Foreclosing other options
7.2 Ability to cope with different
waste streams
8. Stability:
8.1 Stability of product
9. Timescale:
9.1 Timely implementation
10. Local Community:
10.1 Economic impacts
10.2 Culture and heritage
Collapse of local economy
Major enhancement to the local economy
Collapse of local community through depopulation Major enhancement of local community
11. Environmental Objectives:
11.1 Primary waste volume
Relative scale: unacceptably high volumes
of waste generated
Relative scale: lowest total volumes of
waste
Not applicable (see text).
Smallest cost of options
12. Overall Cost:
12.1 Undiscounted cost
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References
UKAEA recognises that some interested stakeholders will require more in-depth information
to help form a judgement on the approach taken to identifying the BPEO. If you require
additional information and cannot find it on our website please contact us at the address
given – we will be happy to help.
1.
Public Participation Newsletter No 4
How to Deal with the Management of Prototype Fast Reactor (PFR) Raffinate
May 2004
2.
D3900(04)P027
Preliminary Best Practicable Environmental Options Study for the
Management of PFR Raffinate.
30 July 2004
3.
Information pack as given to Internal and External Stakeholder Panel
00: Contents of pack
01: Agenda
02: Executive summary
03: Draft Internal options report
04: Summary of options
05: Scoring of options
06: Sample questions (for panel members to consider)
07: Justification for Classifying PFR Raffinate as ILW
08: Current Arrangements and Requirements for the Conditioning, Packaging and
Storage of Intermediate Level Radioactive Waste: Joint RWMAC/NuSAC Report
09: Public Participation newsletter no 4 (see reference 1).
10: Glossary
11: Feedback questionnaire
4.
Poster information used at internal/external stakeholder panel meetings.
5.
0426-2v1
PFR Raffinates BPEO: Internal Stakeholder Panel Report
Galson Sciences Ltd: 27 July 2004
6.
0426-2
PFR Raffinates BPEO: External Stakeholder Panel Report
Galson Sciences Ltd: 27 July 2004
7.
Downloadable spreadsheet with scores.
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Your Invitation to Participate – BPEO Assessment Questionaire
To contribute to the assessment of the options for the management of PFR raffinate, please consider and
respond to the following questions. Please note these questions are for guide only – if you wish to submit a
fuller response we will be happy to receive it.
Q1:
Do you agree with the process used, i.e. the BPEO method?
Q2:
Do you think any options have been missed?
Q3:
Do you agree that we screened out the correct options before the short list?
Q4:
Do you think we should have screened out any of the remaining options earlier in the process?
Q5::
Do you have any views on the attributes chosen?
Q6:
Do you have any views on the scoring of options?
Q7:
Do you have any views on the weightings of attributes?
Q8:
What is your opinion of the robustness of our preliminary conclusions?
Q9:
Any other comments?
Name:
Address:
Organisation (if any):
Tel No:
Email:
Please put a tick in the box if you wish your personal details to be kept private
❑
Please post completed form to:
Mrs June Love
Dounreay Communications
Freepost SCO3151
UKAEA, Dounreay
Caithness, KW14 7TZ
Tel:
01847 806082
Fax:
01847 806900
Email: [email protected]
Or complete our electronic form on our website at www.ukaea.org.uk/dsrpnews.htm.
ALTERNATIVE FORMATS OF THIS PUBLICATION, INCLUDING LARGE PRINT AND AUDIO CASSETTE,
CAN BE MADE AVAILABLE ON REQUEST.