(1)J a n u a r y 2 0 1 4
P O S I V A O Y
O l k i l u o t o
F I - 2 7 1 6 0 E U R A J O K I , F I N L A N D
P h o n e ( 0 2 ) 8 3 7 2 3 1 ( n a t . ) , ( + 3 5 8 - 2 - ) 8 3 7 2 3 1 ( i n t . )
F a x ( 0 2 ) 8 3 7 2 3 8 0 9 ( n a t . ) , ( + 3 5 8 - 2 - ) 8 3 7 2 3 8 0 9 ( i n t . )
P o s i v a O y
Safety Case for the Disposal of
Spent Nuclear Fuel at Olkiluoto
Tekijä(t) – Author(s)
Posiva Oy
Toimeksiantaja(t) – Commissioned by
Posiva Oy
Nimeke – Title
SAFETY CASE FOR THE DISPOSAL OF SPENT NUCLEAR FUEL AT OLKILUOTO
FEP SCREENING AND PROCESSING
Tiivistelmä – Abstract
TURVA-2012 is Posiva’s safety case in support of the Preliminary Safety Analysis Report
(PSAR) and application for a construction licence for a repository for disposal of spent nuclear
fuel at the Olkiluoto site in south-western Finland. This report presents and applies the
methodology by which Posiva’s TURVA-2012 FEP list
−
as described in
Features, Events and
Processes
and
used in
Performance Assessment
,
Formulation of Radionuclide Release Scenarios,
Assessment of Radionuclide Release Scenarios for the Repository System, Biosphere Assessment
and
Models and Data for the Repository System
−
is shown to be as comprehensive as necessary
at the current stage of the spent nuclear fuel management programme.
The main part of the work, i.e. screening methodology and processing of the selected FEPs, has
been conducted within earlier safety assessments, and has been applied to TURVA-2012 and to
previous safety assessments, but never formally presented before this report. A full screening of
Nuclear Energy Agency 2.1 FEP database is carried out again for this report and reported in detail
to confirm the comprehensiveness of the TURVA-2012 FEP list. Except for the first stages of the
screening process, surface environment FEPs are, however, not considered in this report.
Avainsanat - Keywords
FEPs, screening, disposal system, regulatory framework, assessment, scenario driver
.
ISBN
ISBN 978-951-652-241-1
ISSN
ISSN 1239-3096
Sivumäärä – Number of pages
148
Kieli – Language
English
Posiva Oy
Olkiluoto
FI-27160 EURAJOKI, FINLAND
Puh. 02-8372 (31) – Int. Tel. +358 2 8372 (31)
Julkaisuaika – Date
Tekijä(t) – Author(s)
Posiva Oy
Toimeksiantaja(t) – Commissioned by
Posiva Oy
Nimeke – Title
TURVALLISUUSPERUSTELU KÄYTETYN YDINPOLTTOAINEEN
LOPPUSIJOITUKSELLE OLKILUODOSSA - FEPIEN VALINTA JA PROSESSOINTI
Tiivistelmä – Abstract
Posivan rakentamislupahakemukseen liittyen tuotettu PSAR (Preliminary Safety Analysis Report)
-raportti perustuu osaltaan TURVA-2012-pitkäaikaisturvallisuusperusteluun, joka on tehty
käy-tetyn ydinpolttoaineen loppusijoitusta varten Olkiluodon kallioperään rakennettavalle
loppu-sijoituslaitokselle. Tässä raportissa esitetään metodologia, joka on ollut käytössä FEP-listan
(ilmiöt, tapahtumat ja prosessit) muodostamisessa TURVA-2012-turvallisuusperustelua varten.
TURVA-2012:n FEP-lista on kuvattu tarkemmin raportissa
Features, Events and Processes.
FEP-listan käyttö turvallisuusperustelussa on kuvattu raporteissa
Performance Assessment
,
Formulation of Radionuclide Release Scenarios,
Assessment of Radionuclide Release Scenarios
for the Repository System, Biosphere Assessment
sekä
Models and Data for the Repository
System.
Tämän raportin tarkoitus on kuvata FEPien valinta ja prosessointi turvallisuusperustelua
varten ja osoittaa että TURVA-2012:n FEP-lista on riittävän kattava ja vastaa käytetyn
polttoaineen loppusijoitusohjelmassa meneillään olevan vaiheen tarpeita.
Tässä raportissa esitetyn työn pääosa koskee FEP-valintaprosessin metodologiaa, joka on ollut
käytössä myös turvallisuusarvioiden aiemmissa vaiheissa ja jota on käytetty myös
muodos-tettaessa TURVA-2012:n FEP-listaa. Tätä metodologiaa ja prosessointia ei ole kuitenkaan
aiemmin järjestelmällisesti kuvattu. FEPien valinnan pohjana on käytetty NEAn (Nuclear Energy
Agency) 2.1 FEP-tietokantaa. Tässä raportissa esitetään FEPien valinta ja prosessointi, minkä
perusteella on tarkasteltu TURVA-2012:n FEP-listan kattavuutta. Lukuun ottamatta FEPien
valintaprosessin alkuvaihetta, pintaympäristön FEPit eivät ole mukana lopullisessa tarkastelussa.
Avainsanat - Keywords
FEPit, loppusijoitusjärjestelmä, viranomaisvaatimukset, turvallisuusarvio.
ISBN
ISBN 978-951-652-241-1
ISSN
ISSN 1239-3096
Sivumäärä – Number of pages
148
Kieli – Language
Englanti
Posiva Oy
Olkiluoto
FI-27160 EURAJOKI, FINLAND
Puh. 02-8372 (31) – Int. Tel. +358 2 8372 (31)
Julkaisuaika – Date
TABLE OF CONTENTS
ABSTRACT
TIIVISTELMÄ
TERMS AND ABBREVIATIONS ... 3
FOREWORD ... 5
1
INTRODUCTION ... 7
1.1
Background ... 7
1.2
The KBS-3 method ... 7
1.3
Posiva’s programme for developing a KBS-3 repository at Olkiluoto ... 8
1.4
Regulatory context for the management of spent nuclear fuel ... 11
1.5
Safety concept and safety functions ... 11
1.6
TURVA-2012 Safety Case portfolio ... 15
1.7
Quality assurance ... 17
1.8
Scope and objectives of the present report ... 19
1.9
Structure ... 19
2
METHODOLOGY FOR FEP SCREENING AND PROCESSING ... 21
2.1
Overall methodology ... 21
2.2
FEP screening and processing steps ... 22
2.3
Identification and screening of FEPs for potential significance ... 22
2.3.1
The initial FEP list ... 22
2.3.2
Relevance screening ... 22
2.3.3
Initial aggregation and component-wise classification of the FEPs .. 23
2.3.4
Significance screening ... 23
2.4
Mapping remaining Project FEPs to the TURVA-2012 FEP list ... 24
2.5
Cross-checking ... 24
3
SCREENING AND PROCESSING OF THE FEPS ... 25
3.1
FEP lists included in the work ... 25
3.2
Relevance screening results ... 25
3.3
Preliminary aggregation of FEPs and classification under disposal system
components ... 25
3.4
Significance screening results ... 26
4
MAPPING REMAINING PROJECT FEPS TO THE TURVA-2012 FEP LIST ... 27
5
CROSS-CHECKING AGAINST OTHER RELEVANT FEP SOURCES ... 29
5.1
Cross-checking against the Swedish SR-Site ... 29
5.2
Cross-checking against the Canadian Fourth Case Study ... 32
5.3
Comparison with FEPs in Process Report 2007-12 ... 34
6
CONCLUSIONS AND THE WAY FORWARD ... 37
6.1
Comprehensiveness of TURVA-2012 FEP list ... 37
6.2
The way forward ... 37
REFERENCES ... 39
APPENDIX A. FULL TURVA-2012 FEP LIST ... 43
APPENDIX B. MAPPING OF THE TURVA-2012 FEPS TO NEA FEPS AFTER
SCREENING PROCESS ... 49
APPENDIX C. CROSS-CHECK AGAINST SR-SITE ... 111
TERMS AND ABBREVIATIONS
CLA
Construction Licence Application.
DiP (Government)
Decision-in-Principle.
EBS
EPM
Engineered Barrier System, which includes canister, buffer,
back-fill and closure.
Equivalent Porous Medium.
FEPs
Features, Events and Processes.
GD Government
Decree.
IAEA
International Atomic Energy Agency.
ISAM
Integrated Safety Assessment Methodology.
KBS-3
An abbreviation of
kärnbränslesäkerhet
(nuclear fuel safety)
ver-sion 3. The KBS-3 method for implementing the spent nuclear
fuel disposal concept based on multiple barriers.
KBS-3H
(Kärnbränslesäkerhet 3-Horisontell). Design alternative of the
KBS-3 method in which several spent nuclear fuel canisters are
emplaced horizontally in each deposition drift.
KBS-3V (Kärnbränslesäkerhet
3-Vertikal). The reference design alternative
of the KBS-3 method, in which the spent nuclear fuel canisters are
emplaced in individual vertical deposition holes.
KTM
Finnish Ministry of Trade and Industry.
NDT Non-Destructive
Testing.
NEA
Nuclear Energy Agency.
NWMO
Nuclear Waste Management Organization (in Canada).
OL3 Olkiluoto
3
reactor.
OL4
Fourth reactor to be constructed at Olkiluoto. Expected to be
simi-lar to OL3 in TURVA-2012 safety case.
ONKALO
Underground research facility constructed at Olkiluoto.
OSD
Olkiluoto Site Descriptive model.
POTTI
Database at Posiva with site-investigation data.
PSAR
Preliminary Safety Analysis Report – a part of the construction
licence application.
QA Quality
Assurance.
QC
Quality Coordinator; Quality Control.
R1
Relevance screening criterion 1. The Project FEP is defined by a
heading without any description of what is meant by the heading.
R2
Relevance screening criterion 2. The Project FEP is related to
as-sessment methodology. These FEPs are handled elsewhere in the
TURVA-2012 safety case.
R3
Relevance screening criterion 3. The Project FEP is not relevant
for the context of the TURVA-2012 safety case, especially in
re-spect to the national regulatory requirements and guidelines.
R4
Relevance screening criterion 4. The Project FEP is not relevant
for the KBS-3V type repository design for spent nuclear fuel
dis-posal.
R5
Relevance screening criterion 5. The Project FEP is not relevant
for the present-day Olkiluoto site characteristics and likely future
site characteristics evolving in response to climatic changes and
other external factors.
Repository
system
Spent nuclear fuel, canister, buffer, backfill (deposition tunnel
backfill + deposition tunnel end plug), closure components and
host rock. Excludes the surface environment.
RSC
Rock Suitability Classification. The aim of the RSC is to define
suitable rock volumes for the repository, deposition tunnels and
deposition holes.
RTD
Research, Technical development and Design.
S1
Significance screening criterion 1. The FEP has insignificant
im-pact on safety functions and radiation protection criteria.
S2
Significance screening criterion 2. The FEP has low probability to
occur and low impact on safety functions and radiation protection
criteria.
S3
Significance screening criterion 3. The FEP itself has considerably
more serious consequences than any potential radiological
conse-quences from the spent nuclear fuel.
SAFCA
Safety Case project.
SKB
Swedish Nuclear Fuel and Waste Management Company.
SR-Site
SR-Site safety assessment for a repository in Forsmark.
STUK
Finnish Radiation and Nuclear Safety Authority.
TEM
Finnish Ministry of Employment and the Economy, previously
Ministry of Trade and Industry (KTM).
TKS-2009
Finnish equivalent for RTD (see RTD). RTD programme for
2010
−
2012.
TURVA-2012
Posiva’s safety case supporting the construction licence
applica-tion submitted in 2012 for the Olkiluoto spent nuclear fuel
dis-posal facility. TURVA means safety.
VAHA
Requirements management system at Posiva.
VVER-440 Pressurised
water
reactor type at Loviisa.
YJH
Finnish abbreviation for Nuclear Waste Management.
FOREWORD
The participants in the project group for screening in/out discussions in this report are
listed below:
Hagros, Annika (Saanio & Riekkola, SROY)
Hellä, Pirjo (SROY)
Hjerpe, Thomas (Facilia AB)
Pitkänen, Petteri (Posiva Oy)
Koskinen, Lasse (Posiva Oy)
Laine, Heini (SROY)
Marcos, Nuria (SROY)
Pastina, Barbara (SROY)
Snellman, Margit (SROY)
1 INTRODUCTION
1.1 Background
On assignment by its owners, Fortum Oyj and Teollisuuden Voima Oyj, Posiva Oy will
manage the disposal of spent nuclear fuel from the Loviisa and Olkiluoto nuclear power
plants. At Loviisa, two pressurised water reactors (VVER-440) are in operation; at
Olkiluoto, two boiling water reactors are operating and one pressurised water reactor is
under construction. Plans exist also for a fourth nuclear power unit at Olkiluoto. At both
sites there are facilities available for intermediate storage of the spent nuclear fuel
be-fore disposal.
In 2001, the Parliament of Finland endorsed a Decision-in-Principle (DiP) whereby the
spent nuclear fuel generated during the operational lives of the operating Loviisa and
Olkiluoto reactors will be disposed of in a geological repository at Olkiluoto. This first
DiP allowed for the disposal of a maximum amount of spent nuclear fuel corresponding
to 6500 tonnes of uranium (tU) initially loaded into the reactors. Subsequently,
addi-tional DiPs were issued in 2002 and 2010 allowing extension of the repository (up to
9000 tU) to also accommodate spent nuclear fuel from the operations of the OL3 reactor
and the planned OL4 reactor. OL4 spent nuclear fuel is handled in the TURVA-2012
safety case assuming it to be similar to OL3 spent nuclear fuel.
1.2 The KBS-3 method
The 2001 DiP states that disposal of spent nuclear fuel shall take place in a geological
repository at the Olkiluoto site, developed according to the KBS-3 method. In the
KBS-3 method, spent nuclear fuel encapsulated in water-tight and gas-tight sealed
me-tallic canisters with a mechanical load-bearing insert is emplaced deep underground in a
geological repository constructed in the bedrock. According to the DiP, the repository
shall be located at minimum depth of 400 m. In Posiva’s current repository design, the
repository is constructed on a single level and the floor of the deposition tunnels is at a
depth of 400
−
450 m in the Olkiluoto bedrock.
Posiva’s reference design in the construction licence application is based on vertical
emplacement of the spent nuclear fuel canisters (KBS-3V; Figure 1-1). Currently, an
alternative horizontal emplacement design (KBS-3H) is being jointly developed by the
Swedish Nuclear Fuel and Waste Management Company (SKB) and Posiva.
The KBS-3V design is based on a multi-barrier principle in which copper-iron canisters
containing spent nuclear fuel are emplaced vertically in individual deposition holes
bored in the floors of the deposition tunnels (see inset in Figure 1-1). The canisters are
to be surrounded by a swelling clay buffer material that separates them from the
bed-rock. The deposition tunnels and the central tunnels and the other underground openings
are to be backfilled with materials of low permeability.
Figure 1-1. Schematic presentation of the KBS-3V design.
1.3 Posiva’s programme for developing a KBS-3 repository at Olkiluoto
The Olkiluoto site, located on the coast of south-western Finland (Figure 1-2), has been
investigated for over 20 years. During the past few years, key activities in the
pro-gramme have been related to:
completion of the investigations for site confirmation at Olkiluoto both through
analyses of data from surface-drilled characterisation holes and surveys and studies
carried out in the ONKALO underground research facility,
the design of required surface and disposal facilities,
the development of the selected disposal technology to the level required for the
construction licence application, and
demonstration of the long-term safety of the disposal of spent nuclear fuel including
the preparation of a safety case (Section 1.6) presented as a portfolio of reports,
including the present report.
Posiva’s ongoing RTD (research, development and technical design) phase has been
introduced in the TKS-2009 report (Posiva 2009) for the years 2010
−
2012, which also
provides insight into developments from previous RTD phases. In 2012 a new RTD
programme (YJH-2012) for 2013
−
2015 was published (Posiva 2013). In Figure
1-3, a
general timeline of Posiva’s programme is presented.
Figure 1-2. Olkiluoto Island is situated on the coast of the Baltic Sea in south-western
Finland. Photograph by Helifoto Oy.
Figure 1-3.
Overall schedule for nuclear waste management relating to the Loviisa and
Olkiluoto reactors until 2020. The target is to begin disposal of spent nuclear fuel around
2020.
The repository will be located in the bedrock of Olkiluoto Island taking into account the
host rock properties as well as the restrictions set by urban planning in the Eurajoki
Municipality. In Figure 1-4 the current reference layout is presented.
Figure 1-4. The current reference layout (green). Dark grey areas are not suitable for
deposition tunnels based on Rock Suitability Classification (RSC), which has been
de-veloped by Posiva. Red ovals denote respect distances to drillholes. The red line
sur-rounding the repository shows the area reserved for the repository in urban planning.
1.4 Regulatory context for the management of spent nuclear fuel
According to the law, the Finnish Ministry of Employment and the Economy (TEM;
previously the Ministry of Trade and Industry, KTM) decides on the principles to be
followed in waste management of spent fuel and other nuclear waste.
The schedule for the disposal of spent nuclear fuel was established in the KTM’s
Deci-sion 9/815/2003. According to this DeciDeci-sion, the parties under the nuclear waste
man-agement obligation shall, either separately, together or through Posiva Oy, prepare to
present all reports and plans required to obtain a construction licence for a disposal
fa-cility for spent nuclear fuel as stated in the Nuclear Energy Decree by the end of 2012.
The disposal facility is expected to become operational around the year 2020.
The legislation concerning nuclear energy was updated in 2008. As part of the
legisla-tive reform, a number of the relevant Government Decisions were replaced with
Gov-ernment Decrees. The Decrees entered into force on 1
st
December 2008. The
Govern-ment Decision (478/1999) regarding the safety of disposal of spent nuclear fuel, which
particularly applied to the disposal facility, was replaced with Government Decree
736/2008, issued 27 November 2008.
Currently, the valid Regulatory Guides pertaining to nuclear waste management are
Guides YVL D.1
−
D.5 issued by the Radiation and Nuclear Safety Authority (STUK) in
2013. Guide YVL D.1 deals with nuclear non-proliferation control, D.2 with the
trans-port of nuclear material and nuclear waste, D.3 with the processing, storage and
encap-sulation of spent nuclear fuel, D.4 with nuclear waste management and
decommission-ing activities and D.5 with the disposal of nuclear waste. As these Guides were
pub-lished in late 2013, the version of YVL D.5 used in the preparation of the TURVA-2012
safety case (see Section 1.6) was Draft 4 (17.3.2011, in Finnish only).
1.5 Safety concept and safety functions
The long-term safety principles of
Posiva’s
planned repository system are described at
Level 2 of the VAHA (VAHA is
Posiva’s
requirement management system) as follows:
1.
The spent nuclear fuel elements are disposed of in a repository located deep in the
Olkiluoto bedrock. The release of radionuclides is prevented with a multi-barrier
disposal system consisting of a system of engineered barriers (EBS) and host rock
such that the system effectively isolates the radionuclides from the living
environ-ment.
2.
The engineered barrier system consists of
a)
canisters
to contain the radionuclides for as long as they could cause significant
harm to the environment,
b)
buffer
between the canisters and the host rock to protect the canisters as long as
containment of radionuclides is needed,
c) deposition
tunnel backfill and plugs
to keep the buffer in place and help restore
the natural conditions in the host rock,
d) the
closure
, i.e. the backfill and sealing structures
to decouple the repository from
the surface environment.
3.
The host rock and depth of the repository are selected in such a way as to make it
possible for the EBS to fulfil the functions of containment and isolation described
above.
4.
Should any of the canisters start to leak, the repository system as a whole will hinder
or retard releases of radionuclides to the biosphere to the level required by the
long-term safety criteria.
The safety concept, as depicted in Figure 1-5, is a conceptual description of how these
principles are applied together to achieve
safe disposal
of spent nuclear fuel in the
con-ditions of the Olkiluoto site. Due to the long-term hazard of the spent nuclear fuel, it has
to be isolated from the surface environment over a long period of time. The KBS-3
method provides
long-term isolation and containment
of spent nuclear fuel by a
sys-tem of multiple barriers, both engineered and natural, and by ensuring a sufficient depth
of disposal (the key safety features of the system in Figure 1-5). All of these barriers
have their roles in establishing the required long-term safety of the repository system.
These roles constitute the
safety functions
of the barriers (see Table 1-1). The surface
environment is not given any safety functions; instead it is considered as the object of
the protection provided by the repository system.
Most radionuclides in the spent nuclear fuel are embedded in a ceramic matrix (UO2)
that itself is resistant to dissolution in the expected repository conditions. The slow
re-lease of radionuclides from the spent nuclear fuel matrix is part of Posiva’s safety
con-cept. Moreover, the near-field conditions should contribute to maintain the low
solubil-ity of the matrix.
Figure 1-5. Outline of the safety concept for a KBS-3 type repository for spent nuclear
fuel in a crystalline bedrock (adapted from Posiva 2003). Orange pillars and blocks
indicate the primary safety features and properties of the disposal system. Green pillars
and blocks indicate the secondary safety features that may become important in the
event of a radionuclide release from a canister.
Retention and retardation of
radionuclides
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SAFE DISPOSAL
LONG-TERM ISOLATION AND CONTAINMENT
FAVOURABLE, PREDICTABLE BEDROCK
AND GROUNDWATER CONDITIONS WELL-CHARACTERISED MATERIAL
PROPERTIES
Implementation of the KBS-3 method entails the introduction of a number of additional
barriers because of engineering, operational safety or long-term safety needs. Long-term
safety needs arise, for example, because implementation involves the construction of a
system of underground openings, including access tunnels and shafts, that would
sig-nificantly perturb the safety functions of the host rock unless backfilled and sealed at
closure of the disposal facility. These closure components with long-term safety
func-tions include:
backfill of underground openings, including the central tunnels, access tunnels,
shafts, and other excavations, and
drillhole plugs, mechanical plugs, long-term hydraulic plugs at different depths and
plugs near the surface.
The safety functions of the engineered barrier system (EBS) components and host rock
are summarised in Table 1-1. In the TURVA-2012 safety case documentation, the spent
nuclear fuel, EBS and the host rock are jointly termed the
repository system
, whereas
the term
disposal system
is used when the repository system and the surface
environ-ment are both considered (see Figure 1-6).
Table 1-1. Summary of safety functions assigned to the barriers (EBS components and
host rock) in
Posiva’s
KBS-3V repository.
Barrier
Safety functions
Canister
Ensure a prolonged period of containment of the spent nuclear fuel. This
safety function rests first and foremost on the mechanical strength of the
canister’s cast iron insert and the corrosion resistance of the copper
sur-rounding it.
Buffer
Contribute to mechanical, geochemical and hydrogeological conditions that
are predictable and favourable to the canister,
Protect canisters from external processes that could compromise the safety
function of complete containment of the spent nuclear fuel and associated
radionuclides,
Limit and retard radionuclide releases in the event of canister failure.
Deposition
tunnel
backfill
Contribute to favourable and predictable mechanical, geochemical and
hydrogeological conditions for the buffer and canisters,
Limit and retard radionuclide releases in the possible event of canister
failure,
Contribute to the mechanical stability of the rock adjacent to the deposition
tunnels.
Host rock
Isolate the spent nuclear fuel repository from the surface environment and
normal habitats for humans, plants and animals and limit the possibility of
human intrusion, and isolate the repository from changing conditions at the
ground surface,
Provide favourable and predictable mechanical, geochemical and
hydro-geological conditions for the engineered barriers,
Limit the transport and retard the migration of harmful substances that could
be released from the repository.
Closure
Prevent the underground openings from compromising the long-term
isola-tion of the repository from the surface environment and normal habitats for
humans, plants and animals.
Contribute to favourable and predictable geochemical and hydrogeological
conditions for the other engineered barriers by preventing the formation of
significant water conductive flow paths through the openings,
Limit and retard inflow of water to and release of harmful substances from
Figure 1-6. The components of the disposal system.
1.6 TURVA-2012 Safety Case portfolio
A safety case for a geological disposal facility documents the scientific and technical
understanding of the disposal system, including the safety barriers and safety functions
that these are expected to provide, results of a quantitative safety assessment, the
proc-ess of systematically analysing the ability of the repository system to maintain its safety
functions and to meet long-term safety requirements, and provides a compilation of
evi-dence and arguments that complement and support the reliability of the results of the
quantitative analyses.
As stated in Guide YVL D.5, A01:
Compliance with the requirements concerning
long-term radiation safety, and the suitability of the disposal method and disposal site, shall
be proven through a safety case that must analyze both expected evolution scenarios
and unlikely events impairing long-term safety. The safety case comprises a numerical
analysis based on experimental studies and complementary considerations insofar as
quantitative analyses are not feasible or involve considerable uncertainties
(Govern-ment Decree GD 736/2008).
The TURVA-2012 safety case portfolio is based on the safety case plan published in
2008 (Posiva 2008), which updates an earlier plan published in 2005 (Vieno & Ikonen
2005). In the updated safety case plan, further details are provided on quality assurance
and control procedures and their documentation, as well as on the consistent handling of
different types of uncertainties. Since 2008, the safety case plan has been iterated based
on the feedback received from the authorities, and the contents of the safety case
portfo-lio TURVA-2012 are now as presented in Figure 1-7. In this report, all TURVA-2012
portfolio reports are referenced using the report title in
italics
. The full titles and report
numbers are listed at the beginning of the reference list.
Main reports
Main supporting documents
Site Description
Biosphere Description
Understanding of the present state and past
evolution of the host rock
Understanding of the present state and evolution of
the surface environment
Models and Data for the
Repository System
Biosphere Data Basis
Description of climate evolution and definition of release scenarios
Models and data used in the performance
assessment and in the analysis of the
radionuclide release scenarios
TURVA-2012
Synthesis
Description of the overall methodology of analysis, bringing together all the lines of arguments for safety, and the
statement of confidence and the evaluation of compliance with long-term safety constraints
Design Basis
Performance targets and target properties for the repository system
Production Lines
Design, production and initial state of the EBS and the underground openings
Description of the Disposal System
Analysis of releases and calculation of doses and activity fluxes.
Complementary Considerations
Supporting evidence incl. natural and anthropogenic analogues
Data used in the biosphere assessment and
summary of models
Biosphere Assessment: Modelling reports
Description of the models and detailed modelling of surface environment
Assessment of Radionuclide
Release Scenarios for the
Repository System
Biosphere Assessment
Summary of the initial state of the repository system and present state of the surface environment
Features, Events and Processes
General description of features, events and processes affecting the disposal system
Performance Assessment
Analysis of the performance of the repository system and evaluation of the fulfillment of performance
targets and target properties
Formulation of Radionuclide Release Scenarios
Figure 1-7. TURVA-2012 safety case portfolio including report names (coloured boxes)
and brief descriptions of the contents (white boxes). Disposal system = repository
sys-tem + surface environment.
The main reports and supporting documents of the TURVA-2012 portfolio have been
described in the introduction to other main reports and will not be repeated here.
This FEPs screening and processing report is not in the portfolio. The FEP screening
and processing methodology, although applied in TURVA-2012, has not been formally
reported until now, though an auditing of the FEPs taken into account in previous safety
assessment was reported by Vieno & Nordman (1997) and discussions on what FEPs
should be taken into account in a safety case took place during the compilation of
Rasi-lainen (2004) and of Miller & Marcos (2007). This report presents also an audit against
the NEA Version 2.1 Project Databases. The reasoning on why the FEPs are screened
out of the final list is also presented.
In the review of the pre-licensing documentation, STUK emphasises the need for
aggre-gating/disaggregating FEPs, and this has been taken thoroughly into account
.
1.7 Quality
assurance
The quality assurance (QA) procedures for the safety case (SAFCA) portfolio (see
Fig-ure 1-7) have been carried out following
Posiva’s
quality management system, which
complies with the ISO 9001:2008 standard and considers relevant regulatory
require-ments. Even though the quality assurance is based throughout on management
accord-ing to the standard ISO 9001:2008, a graded approach proposed for nuclear facilities is
adopted, i.e. the primary emphasis is on the quality control of the safety case,
particu-larly for those activities that have a direct bearing on long-term safety, whereas standard
quality measures are applied in the supporting work. This means, in practice, that the
main safety case reports are subjected to stricter quality demands than general research
activities. The input from Posiva’s own RTD activities and other research also fulfil the
ISO 9001 quality standards.
The general quality guidelines of Posiva are also applied; the composition and quality
management of portfolio reports and the recruitment of expert reviewers are carried out
according to the respective guidelines. In addition, special attention is paid to the
man-agement of the processes that are applied to produce the safety case and its foundations,
which is the basis for the whole safety case process and organisation of the work. The
purpose of this enhanced process control is to provide full traceability and transparency
of the data, assumptions, models, calculations and results. The safety case production
process is a part of Posiva’s RTD process and is linked to Posiva’s Production lines,
Facility design and other main processes. The main customer is the Strategy process and
the Licensing sub-process. The aim of the safety case production process is to produce
the long-term safety documentation for the construction licence application. The safety
case production process is owned by the research manager of Posiva’s Long-term Safety
Unit in Posiva’s Research Department.
The overall plan, main goals and constraints for the safety case production process are
presented in the Safety case plan (Posiva 2008). The details of how the Safety case plan
2008 is being implemented are described in the SAFCA project plan. The work is
man-aged and coordinated by a SAFCA core group and supervised by a steering group.
The safety case production process is divided into four main sub-processes:
Conceptu-alisation and Methodology, Data Handling and Modelling, Safety Assessment, and
Evaluation of Compliance and Confidence.
The Data Handling and Modelling sub-process constitutes the central linkage between
Posiva’s main technical and scientific activities and the production of the safety case. It
is a clearinghouse activity between the supply of, and demand for, quality-assured data
for the safety case. Data are produced by Posiva’s planning, design and development
processes for the EBS (Engineered Barrier System), by the site characterisation process
for the geoscientific data and through the biosphere description of the Olkiluoto area.
A SAFCA quality co-ordinator (QC) has been designated for the activities related to the
quality assurance measures applied to the production of the safety case contents. The
QC is responsible for checking that the instructions and guidelines are followed, and
improvements are made in the process as deemed useful or necessary. The QC is also
responsible for the coordination of the external expert reviews, maintenance of
sched-ules, review and approval of the products, and the management of the expert elicitation
process. The QC also leads the quality review of models and data used in the Data
Han-dling and Modelling sub-process. Regular auditing of the safety case production process
is done as part of Posiva's internal audit programme.
Data sources and quality aspects of the sources are documented according to a specific
guideline. Individual data and databases are approved through a clearance procedure
supervised by the SAFCA Quality Co-ordinator. The process owner checks and
ap-proves the data and the QC checks and apap-proves the procedure. Data used may also be
approved using other Posiva databases such as VAHA or POTTI and the respective
ap-proval processes. A clearance procedure has been applied to all key data used in the
performance assessment (i.e. showing compliance with performance targets and target
properties), and in the safety assessment (i.e. radionuclide transport and dose
calcula-tions).
The control and supervision of the safety case products (i.e. main portfolio reports) has
been done in two steps, first an internal review by safety case experts and subject-matter
experts within
Posiva’s
RTD programme and then the second step by external expert
reviewers. A group of external experts covering the essential areas of knowledge and
expertise needed in the safety case production has been set up. The review process is
based on review templates, which record each review comment and how it has been
addressed. Upon completion, this template is checked and approved according to the
quality guidelines of Posiva.
An expert elicitation process has been applied to specific cases when the understanding
or data basis is conflicting and consensus is needed for the selection of key data (e.g.
future climate scenarios, solubility and sorption data). This expert elicitation process has
been initiated, recruited, documented and managed by the SAFCA Quality
Co-ordinator.
QA issues are discussed further in the
Synthesis
. Quality assurance and quality control
measures related to the production and operation of the repository are discussed in detail
in the Production Line reports (
Canister, Buffer, Backfill, Closure
and
Underground
Openings
).
1.8 Scope and objectives of the present report
This report documents the screening and processing of features, events and processes
(FEPs) starting from NEA Version 2.1 Project Databases that has been carried out
within TURVA-2012. The main objective is the FEP screening process that has been
used to show that Posiva’s FEP list, as described in
Features, Events and Processes
, is
adequate for the current stage of the spent nuclear fuel management programme. The
disposal system, as defined in Figure 1-6 includes the spent nuclear fuel, the engineered
barriers surrounding it, the host rock, and the surface environment. The disposal system
will evolve over time. The evolution of the disposal system will depend on:
-
the initial state of the system (relevant features are summarised in
Description of the
Disposal System
),
-
a number of processes acting within the disposal system, and
-
external influences (events and processes) acting on the system.
The focus of the present report is on the FEPs related to the repository system and
ex-ternal FEPs. The processing for the FEPs related to the surface environment is here
lim-ited to the initial step, the relevance screening (Chapter 3). This is due, on the one hand,
to the lack of resources and, on the other hand, to the emphasis given by the Finnish
regulator STUK, to the FEPs related to the repository system.
1.9 Structure
The structure of the present report is as summarised below.
Chapter 2 presents the overall FEP screening and processing methodology.
Chapter 3 presents the outcome of the relevance and significance screening steps
performed on the NEA Version 2.1 Project Databases.
Chapter 4 presents the further processing of the screened in FEPs and the mapping
of the TURVA-2012 FEP list to the screened in FEPs.
In Chapter 5 a cross-checking of the TURVA-2012 FEP list is performed against
FEP lists developed in other relevant projects and FEPs in Posiva’s 2007 Process
Report (Miller & Marcos 2007).
Chapter 6 concludes on the advantages and challenges of the TURVA-2012 FEPs
classification and provides a discussion on comprehensiveness.
2 METHODOLOGY FOR FEP SCREENING AND PROCESSING
2.1 Overall
methodology
A central feature of Posiva’s TURVA-2012 safety case is the formulation and analysis
of a set of scenarios that, collectively, represent the envelope of future evolutions for a
KBS-3V type disposal facility at the Olkiluoto site. The definition and formulation of
scenarios is supported by the identification and consideration of all potentially relevant
features, events and processes (FEPs) that, on the one hand, characterise the system, and
on the other hand might occur during system evolution, and that have the potential to
affect long-term safety. These FEPs are discussed in detail in
Features, Events and
Processes
. Focusing on FEPs when developing the scenarios is in line with international
recommendations regarding the development, operation and closure of disposal
facili-ties and international best practice applied. For example, the Specific Safety
Require-ments on Disposal of Radioactive Waste (IAEA 2011) states in Requirement 15 on Site
characterization for a disposal facility that:
The site for a disposal facility shall be characterized at a level of detail sufficient
to support a general understanding of both the characteristics of the site and how
the site will evolve over time. This shall include its present condition, its probable
natural evolution and possible natural events, and also human plans and actions
in the vicinity that may affect the safety of the facility over the period of interest. It
shall also include a specific understanding of the impact on safety of features,
events and processes associated with the site and the facility.
More specifically, the Specific Safety Guide on The Safety Case and Safety Assessment
for the Disposal of Radioactive Waste (IAEA 2012) states (5.42):
Regardless of the method used for developing the scenarios, all features, events
and processes that could significantly influence the performance of the disposal
system should be addressed in the assessment.
Posiva’s methodology for scenario formulation, related to the repository system, follows
a ‘top-down’ approach in first identifying the safety functions that are required of the
repository system, then considering the effects of single FEPs or combinations of FEPs
on those functions to check that the scenarios are comprehensive (
Formulation of
Ra-dionuclide Release Scenarios
, Section 2.5). However, Posiva’s methodology for the
FEP screening component in the overall FEP processing is more closely related to the
‘bottom-up’ approach for scenario development described, for example, in the ISAM
project (IAEA 2004). When using this method, a comprehensive list of features, events
and processes is developed as a starting point. This may involve the use of generic lists
of features, events and processes (internationally agreed lists, regulations, etc.) and the
determining of site- and system-specific features, events and processes (as discussed
above). This is followed by a screening process to exclude features, events and
proc-esses from further considerations that are either irrelevant for the KBS-3 concept or
considered to have insignificant impact on the long-term safety of the disposal system.
Criteria for screening features, events and processes may include rules relating to
regu-lations and/or to the probability of occurrence or consequences of events and processes.
The sections below describe the step-wise FEP screening method, and further
process-ing, applied in demonstrating that the TURVA-2012 FEP list for the repository system
and external events and processes is comprehensive enough.
2.2 FEP screening and processing steps
Features, events and processes that might occur, and that have the potential to affect
long-term safety under certain conditions are accounted for in the safety assessment in
the TURVA-2012 safety case. These FEPs are presented and discussed in
Features,
Events and Processes
. This section describes the identification and screening of FEPs
and their further processing and cross-checking that was conducted in order to assess
the comprehensiveness of the TURVA-2012 FEP list. The work has been conducted in a
structured step-wise manner mainly relying on expert judgement. Each step in the
proc-ess is elaborated in the sub-sections below and they are summarised as follows:
1.
Selecting an initial comprehensive FEP list to use as a starting point.
2.
Performing a
relevance screening
based on a set of screening criteria aiming at
screening out FEPs not relevant for the KBS-3 concept or the TURVA-2012 safety
case.
3.
Performing an initial aggregation of FEPs with an identical heading or meaning, and
the classification of the FEPs under the components of the disposal system (or as
ex-ternal if they are exex-ternal to the system).
4.
Performing a
significance screening
based on a set of screening criteria aiming at
screening out FEPs clearly insignificant for long-term safety.
5.
Mapping the FEPs not screened out in previous steps to the TURVA-2012 FEP list.
This step contains, for example, the aggregation and disaggregation of FEPs to
fol-low Posiva’s FEP nomenclature.
6.
Cross-check the final TURVA-2012 FEP list against FEP lists developed in other
relevant projects.
2.3 Identification and screening of FEPs for potential significance
2.3.1 The initial FEP list
The FEP screening is based on the FEP list from NEA 2.1 Project Databases
(NEA 2006), which was the latest NEA FEP database available in 2011 when the FEPs
in
Features, Events and Processes
were compiled.
2.3.2 Relevance
screening
A relevance screening, aiming to screen out FEPs not relevant for a KBS-3V type
re-pository or the TURVA-2012 safety case, is performed on the FEPs in the NEA Version
2.1 Project Databases, below denoted as Project FEPs. A set of criteria has been set out
to facilitate this screening. A Project FEP is screened out if at least one of the five
fol-lowing screening criteria is fulfilled:
R1 The Project FEP is defined by a heading without any description of what is
meant by the heading.
R2
The Project FEP is related to assessment methodology. These FEPs are handled
elsewhere in the TURVA-2012 safety case.
R3
The Project FEP is not relevant for the context of the TURVA-2012 safety
case, especially in respect to the national regulatory requirements and
guide-lines.
R4
The Project FEP is not relevant for the KBS-3V type repository design for
spent nuclear fuel disposal.
R5
The Project FEP is not relevant for the present-day Olkiluoto site
characteris-tics and likely future site characterischaracteris-tics evolving in response to climatic
changes and other external factors.
2.3.3 Initial aggregation and component-wise classification of the FEPs
The second step in the process includes:
the initial aggregation of the Project FEPs screened in that have identical heading or
meaning. At this stage, the individual project-specific FEP descriptions are,
how-ever, kept in the documentation for the benefit of the experts carrying out the next
screening step (Section 2.3.4).
the classification of the aggregated FEPs under the component(s) of the disposal
system, i.e. spent fuel, canister, buffer, backfill, auxiliary components, geosphere or
surface environment or they are classified as “external” if they are related to
condi-tions external to the disposal system. A FEP is classified under several components
if it is not obvious that it only relates to one component (e.g. “soil moisture and
evaporation” is only mapped to surface environment, whereas “diffusion” is
classi-fied to all components of the disposal system).
2.3.4 Significance
screening
The third step in the process is to conduct a screening evaluation of the Project FEPs not
screened out in the relevance screening, aiming at screening out FEPs clearly
insignifi-cant for long-term safety. A set of criteria regarding a FEP’s impact on safety functions
and radiation protection criteria (these are doses and activity fluxes; there are FEPs
af-fecting e.g. exposure pathways that have an impact on the end points regarding radiation
protection criteria, but these FEPs have no impact on safety functions) has been defined
to facilitate this screening. A Project FEP is screened out if at least one of the following
significance screening criteria is fulfilled:
S1 The FEP has insignificant impact on safety functions and radiation protection
criteria.
S2 The FEP has low probability to occur and low impact on safety functions and
radiation protection criteria.
S3 The FEP itself has considerably more serious consequences than any potential
radiological consequences from the spent nuclear fuel.
2.4 Mapping remaining Project FEPs to the TURVA-2012 FEP list
The outcome of the steps in the FEP screening and initial processing described above is
a list of NEA Project FEPs potentially safety relevant for a KBS-3V repository at the
Olkiluoto site. These FEPs have been aggregated and classified under relevant
compo-nents of the disposal system or as external FEPs. This list is mapped to TURVA-2012
FEPs to check that they include all FEPs relevant for the KBS-3V system at Olkiluoto.
The full TURVA-2012 FEP list is presented in Appendix A. An explanation is given,
when necessary, in case a remaining NEA Project FEP has not a clear corresponding
TURVA-2012 FEP.
2.5 Cross-checking
The final step is to cross-check the TURVA-2012 FEP list against relevant sources to
increase the confidence in that no important FEPs have been omitted. Of importance is
to cross-check against FEP lists developed in other relevant projects, especially the lists
underpinning safety assessments performed by SKB for a KBS-3V type repository for
spent nuclear fuel disposal. A cross-check against the FEP list in Miller & Marcos
(2007) is also included.
3 SCREENING AND PROCESSING OF THE FEPS
3.1 FEP lists included in the work
The screening process was based on the NEA FEP list (NEA Version 2.1 Project
Data-base), which is a compilation of FEPs included in several spent nuclear fuel disposal
programmes around the world (i.e. Goodwin et al. 1994, NAGRA 1994, DOE 1996,
Chapman et al. 1995, Miller et al. 2002, Miller & Chapman 1993, Bronders et al. 1994).
Other FEP lists or sources of information used are discussed in Chapter 5 where the
final list is cross-checked against relevant literature. Cross-checking includes data from
SKB’s SR-Site (SKB 2010a) (Section 5.1), NWMO’s Fourth Case Study (Garisto 2012)
(Section 5.2) and comparison to earlier work done by Posiva (Section 5.3).
3.2 Relevance screening results
Relevance screening was performed following the protocol presented in Section 2.3.2.
The number of Project FEPs in version 2.1 of the NEA FEP database is large, in total
there are 1671 FEPs (Electronic Appendix 1, NEA version 2.1 Project Database). In
order to make the relevance screening more efficient, a workshop exercise was carried
out by a group of safety assessment experts.
This screening process is documented in Electronic Appendix 1 (NEA version 2.1
Pro-ject Databases – Relevance screening_final), where screening decisions based on
R-criteria (see Section 2.3.2) are listed. The final table shows the result of the initial
work-shop as well as including additional screening decisions that were revised during further
steps, i.e. cross-check, of the work.
The relevance screening resulted in 1154 FEPs being screened in and 517 FEPs being
screened out; the latter were divided among the individual screening criteria:
R1: 119 FEPs screened out
R2: 88 FEPs screened out
R3: 89 FEPs screened out
R4: 111 FEPs screened out
R5: 110 FEPs screened out.
3.3 Preliminary aggregation of FEPs and classification under disposal
system components
A preliminary aggregation of the FEPs and their classification under components of the
disposal system (or as external to the system) was done before moving to the
Signifi-cance screening phase. The protocol for the process is described in Section 2.3.3. The
aggregation was done to collate FEPs that were duplicates in the NEA FEP list in order
to simplify the following steps. FEPs were then classified under the following
compo-nents (reflecting those discussed in
Features, Events and Processes
):
canister
buffer
backfill
auxiliary components
geosphere
surface environment
external FEPs.
The aggregation was documented in an Excel file which was used as a basis for the
Sig-nificance screening. Hence the, aggregation is shown also in the documentation of the
Significance screening results and is not duplicated here (see Section 3.4 and Electronic
Appendix 2, NEA version 2.1 Project Databases – Significance screening and
justifica-tions).
After the preliminary aggregation, the number of FEPs in the list was 735. It should be
noted that some of these FEPs (168 in total) were exclusively related to the surface
en-vironment, and these FEPs were not further processed.
3.4 Significance screening results
The Significance screening was performed in accordance to the protocol presented in
Section 2.3.4. The significance screening requires a deeper process understanding
com-pared with the relevance screening. Hence, the screening involved various subject
mat-ter experts for the different components of the disposal system and exmat-ternal conditions.
Initial screening was carried out by a group of experts in a significance screening
work-shop, and the justifications for screening out FEPs were written later by individual
ex-perts. The components included in the significance screening were all those listed above
(Section 3.3), except for the surface environment.
The Significance screening was documented in an Excel file on top of the initial
aggre-gation of the FEPs (Section 2.3.3). As noted above FEPs that relate only to the surface
environment (168 FEPs in total) are shown in the Excel sheet but they were not further
processed. Thus, 567 FEPs remained to be screened in this phase. The screening
deci-sions based on the Significance criteria and justification for “OUT” screening decideci-sions
are presented in Electronic Appendix 2 (NEA version 2.1 Project Databases –
Signifi-cance screening and justifications).
The significance screening resulted in 491 FEPs being screened in and 76 FEPs being
screened out. The latter were divided among the individual screening criteria:
S1: 55 FEPs screened out
S2: 16 FEPs screened out
S3: 5 FEPs screened out.
See Electronic Appendix 2 for justifications why these FEPs were screened out in this
phase (column “Justification”).
4 MAPPING REMAINING PROJECT FEPS TO THE TURVA-2012 FEP LIST
After the screening phase (Chapter 3), the resulting FEP list (comprising 491
screened-in FEPs) was divided to component-wise lists, which were then used screened-in the mappscreened-ing
against Posiva’s FEPs to show that the TURVA-2012 FEP list is comprehensive
enough. The full TURVA-2012 FEP list is given in Appendix A.
Initial mapping was done by the project group for each component included in this
phase (spent fuel, canister, buffer, backfill, auxiliary components, geosphere and
exter-nal). The results were cross-checked within the project group. Mapping of the FEPs is
documented in Appendix B (Tables B-1 to B-7). In the mapping, FEP names from the
TURVA-2012 (
Features, Events and Processes
) were used. Project FEPs not included
in the TURVA-2012 FEP list were marked as “NA” (Not Applicable) in the mapping
tables with a note (justification or explanation).
The number of Project FEPs not applicable (NA) to the components was 21 for the
FUEL (FU), 24 for the CANISTER (CA), 11 for the BUFFER (BU), 15 for the
BACK-FILL (BA), 12 for the AUXILIARY COMPONENTS (A), 5 for the GEOSPHERE (G)
and 2 for EXTERNAL (E). The main reasons were that the Project FEP did not occur
in the component itself, being in most cases treated in interaction matrices (e.g. Table
3-4, p. 54 in
Features, Events and Processes
). In other cases the Project FEP was not
found as a TURVA-2012 FEP, but its consequences were treated under other relevant
FEPs of TURVA-2012, belonging to the same component or to others.
5 CROSS-CHECKING
AGAINST
OTHER RELEVANT FEP SOURCES
In this chapter, the TURVA-2012 FEP list is compared with other relevant FEP lists
produced after the compilation of NEA’s Project Databases Version 2.1 but before the
publication of
Features, Events and Processes
in 2012. The FEP lists considered here
include those related to the following safety assessments for deep geological
reposito-ries in crystalline environments:
Sweden’s SR-Site (SKB 2010a),
Canada’s Fourth Case Study (Garisto 2012).
The purpose of this section is to cross-check whether all FEPs from these safety
assess-ments are also included in the TURVA-2012 FEP list, and if not, the reasons for their
omission are explored. The cross-checking is done by going through the entire FEP list
in question and by mapping the FEPs to one or (if necessary) several FEPs of the
TURVA-2012 FEP list (Tables C-1 and D-1 in Appendices C and D). If a FEP cannot
be mapped to any TURVA-2012 FEP, the reason for the omission is documented.
Fur-thermore, all TURVA-2012 process FEPs (excluding the surface environment FEPs) are
mapped to process FEPs in the above-mentioned assessments (Tables C-2 and D-2 in
Appendices C and D).
5.1 Cross-checking against the Swedish SR-Site
The SR-Site FEP catalogue (SKB 2010a) has been mapped to TURVA-2012 FEPs in
Appendix C to check the comprehensiveness of the TURVA-2012 FEP list. All SR-Site
FEPs that could not be mapped directly to any TURVA-2012 FEP are shown in Table
5-1. It came out that the FEP lists are fairly similar with the few exceptions mentioned
in Table 5-1. Differences are mainly due to the fact that assessment methodology issues
(including quality control issues) are not treated as FEPs in TURVA-2012 but are
han-dled elsewhere in the safety case and/or in other documents presented for the
construc-tion licence applicaconstruc-tion (CLA). Also, a few irrelevant FEPs (e.g. earth currents,
lique-faction of bentonite) have been excluded from Posiva’s FEP list already before
TURVA-2012, but they are included in the SR-Site FEP catalogue, even if concluded to
be irrelevant in the assessment.
Table 5-1. SR-Site FEPs (SKB 2010a, Tables 5-1...5-12, Sections 5.6, 5.7 and 5.8 and
Appendix 2) that were not found in the TURVA-2012 FEP list (see Table C-1). FEPs
that were excluded from the SR-Site assessment (shown in grey in Table C-1) are not
included here, nor any surface environment FEPs.
FEP
number in
SR-Site
FEP name in SR-Site
Note
ISGen02
Effects of phased
op-eration
Operation schedule is handled elsewhere in TURVA-2012 (e.g.
waste emplacement schedule used in thermal dimensioning).
ISGen03
Incomplete closure
Out of the scope of the post-closure safety case TURVA-2012 that
assumes the disposal facility to be properly closed.
ISC01
Mishaps – canister
Canister handling accidents discussed in
Performance
Assess-ment
but not included as a FEP, as any canister damaged during
operation is assumed to be replaced. Operational safety is outside
the scope of TURVA-2012.
ISC02
Design deviations –
canister
Initial penetrating defect(s) assumed in several radionuclide re-
lease scenarios.
ISBu01
Mishaps – buffer
Out of scope of TURVA-2012. It is assumed that quality control
(QC) measures are successfully applied to buffer production and
emplacement. QC issues are related to assessment methodology
and are handled elsewhere in TURVA-2012.
ISBu02
Design deviations –
buffer
Out of scope of TURVA-2012. It is assumed that quality control
(QC) measures are successfully applied to buffer production and
emplacement. QC issues are related to assessment methodology
and are handled elsewhere in TURVA-2012.
ISBfT01
Mishaps – backfill in
tunnels
Out of scope of TURVA-2012. It is assumed that quality control
(QC) measures are successfully applied to backfill production and
emplacement. QC issues are related to assessment methodology
and are handled elsewhere in TURVA-2012.
ISBfT02
Design deviations –
backfill in tunnels
Out of scope of TURVA-2012. It is assumed that quality control
(QC) measures are successfully applied to backfill production and
emplacement. QC issues are related to assessment methodology
and are handled elsewhere in TURVA-2012.
ISBP01
Mishaps – bottom plate
in deposition holes
The bottom plate is not a component in Posiva’s current repository
design.
ISBP02
Design deviations –
bottom plate in
deposi-tion holes
The bottom plate is not a component in Posiva’s current repository
design.
ISPg01
Mishaps – plugs
Out of scope of TURVA-2012. It is assumed that quality control
(QC) measures are successfully applied to the production and
emplacement of closure plugs (auxiliary components). QC issues
are related to assessment methodology and are handled
else-where in TURVA-2012.
ISPg02
Design deviations –
plugs
Out of scope of TURVA-2012. It is assumed that quality control
(QC) measures are successfully applied to the production and
emplacement of closure plugs (auxiliary components). QC issues
are related to assessment methodology and are handled
else-where in TURVA-2012.
