Databank

POSIVA Report 1996-16

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Name:

Käytetyn polttoaineen loppusijoitus Suomen kallioperään. Paikkakohtaisen turvallisuusanalyysin edellytykset ja mahdollisuudet

Language:

Finnish

Page count:

82

ISBN:

951-652-015-4; 1239-3096

Summary:

Working report: FINAL DISPOSAL OF SPENT FUEL IN THE FINNISH BEDROCK,
SCOPE AND REQUIREMENTS FOR SITE-SPECIFIC SAFETY ANALYSIS



The decision made by the Ministry of Trade and Industry (KTM) in 1994 ordered Teollisuuden
Voima Oy (TVO) to report the results from site investigations and to present new site-specific repository
layouts, together with safety assessments, for scrutiny by the authorities at the end of year 1996. Finnish
Centre for Radiation and Nuclear Safety (STUK) has later stated that the reporting should also include an
outline for the safety analysis to be made in the year 2000.
As a consequence of the 1994 amendment to the Nuclear Energy Act the spent fuel accumulating
from the Imatran Voima Oy’s (IVO) Loviisa Power Plant will also be disposed of in Finland. TVO and
IVO have, therefore, agreed on co-operation in final disposal of spent fuel, and established a new
company, Posiva Oy, for that purpose. The R & D and technical planning work made by Posiva now take
into account the spent fuel from both TVO and IVO power plants, but the present programme is largely
based on the programme started by TVO.
This report is a summary of the research conducted in the period 1993 to 1996 into safety of spent
fuel final disposal. The principal goal of the research in this period, as set in 1993, was to develop a
strategy for site-specific safety analysis. At the same time efforts were to be continued to gather data and
validate the technical approach for the analysis. The work aimed at having the data needed for the analysis
available at the end of year 1998.
A safety assessment update, TILA-96, prepared by VTT Energy, is published as a separate report.
The assessment is based on the TVO-92 safety analysis, but takes into account the knowledge acquired
after 1992 on safety aspects of the disposal system and the data gathered from the site investigations made
by TVO and. from the beginning of 1996, by Posiva. Since the site investigations are still ongoing and
much of the data gathered still pending interpretation, only limited amount of new site-specific
information has been available for the present assessment.. However, TILA-96 confirms the main
conclusions of TVO-92 on the safety of final disposal and shows that the safety margins are even larger
than indicated by TVO-92.
The present view on incorporating site-sepcific factors in safety analysis is largely based on the
experience obtained in the work for TILA-96 and the conclusions made in the TILA-96 report..
Accordingly, the efforts towards making the analysis site-specific must be balanced with the overall
objective of keeping to conservative models and assumptions.Since the variability within one site can be
as large as the identified differences between the sites, possible differences between the sites cannot be
compressed to any single, objective, safety index.
The Finnish approach to final disposal is based on isolation of the waste using a canister with a long
expected life-time. The investigations made to date have not brought out differences between sites which
would have bearing on the life-time of the canisters. The implications of the very saline groundwaters
observed at Olkiluoto have to be clarified, though. In general, site-specific comparisons could be
meaningful mainly for the case of initially defect canisters.
In addition to general views on site-specific safety analysis the report describes the outline for the
future research into safety of final disposal. The purpose is to integrate the research into safety and the
investigations of site properties in one large project of site assessment.
FINAL DISPOSAL OF SPENT FUEL IN THE FINNISH BEDROCK,
SCOPE AND REQUIREMENTS FOR SITE-SPECIFIC SAFETY ANALYSIS



The decision made by the Ministry of Trade and Industry (KTM) in 1994 ordered Teollisuuden
Voima Oy (TVO) to report the results from site investigations and to present new site-specific repository
layouts, together with safety assessments, for scrutiny by the authorities at the end of year 1996. Finnish
Centre for Radiation and Nuclear Safety (STUK) has later stated that the reporting should also include an
outline for the safety analysis to be made in the year 2000.
As a consequence of the 1994 amendment to the Nuclear Energy Act the spent fuel accumulating
from the Imatran Voima Oy’s (IVO) Loviisa Power Plant will also be disposed of in Finland. TVO and
IVO have, therefore, agreed on co-operation in final disposal of spent fuel, and established a new
company, Posiva Oy, for that purpose. The R & D and technical planning work made by Posiva now take
into account the spent fuel from both TVO and IVO power plants, but the present programme is largely
based on the programme started by TVO.
This report is a summary of the research conducted in the period 1993 to 1996 into safety of spent
fuel final disposal. The principal goal of the research in this period, as set in 1993, was to develop a
strategy for site-specific safety analysis. At the same time efforts were to be continued to gather data and
validate the technical approach for the analysis. The work aimed at having the data needed for the analysis
available at the end of year 1998.
A safety assessment update, TILA-96, prepared by VTT Energy, is published as a separate report.
The assessment is based on the TVO-92 safety analysis, but takes into account the knowledge acquired
after 1992 on safety aspects of the disposal system and the data gathered from the site investigations made
by TVO and. from the beginning of 1996, by Posiva. Since the site investigations are still ongoing and
much of the data gathered still pending interpretation, only limited amount of new site-specific
information has been available for the present assessment.. However, TILA-96 confirms the main
conclusions of TVO-92 on the safety of final disposal and shows that the safety margins are even larger
than indicated by TVO-92.
The present view on incorporating site-sepcific factors in safety analysis is largely based on the
experience obtained in the work for TILA-96 and the conclusions made in the TILA-96 report..
Accordingly, the efforts towards making the analysis site-specific must be balanced with the overall
objective of keeping to conservative models and assumptions.Since the variability within one site can be
as large as the identified differences between the sites, possible differences between the sites cannot be
compressed to any single, objective, safety index.
The Finnish approach to final disposal is based on isolation of the waste using a canister with a long
expected life-time. The investigations made to date have not brought out differences between sites which
would have bearing on the life-time of the canisters. The implications of the very saline groundwaters
observed at Olkiluoto have to be clarified, though. In general, site-specific comparisons could be
meaningful mainly for the case of initially defect canisters.
In addition to general views on site-specific safety analysis the report describes the outline for the
future research into safety of final disposal. The purpose is to integrate the research into safety and the
investigations of site properties in one large project of site assessment.

Keywords:

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Käytetyn polttoaineen loppusijoitus Suomen kallioperään. Paikkakohtaisen turvallisuusanalyysin edellytykset ja mahdollisuudet (pdf) (4.4 MB)


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