The Ministry of Employment and the Economy required in 2003 that the parties under the nuclear waste management obligation shall, either sepa- rately, jointly or through Posiva submit a status re- port on the preparation of the construction licence application for the encapsulation and final disposal facility during 2009. STUK issued a statement of the report to the Ministry of Employment and the Economy in late 2010. In addition to the statement, STUK sent the observations made during review of the draft application and its opinion regarding fulfilment of the safety requirements to Posiva in June 2011. In this safety evaluation report regard- ing the preliminary application documents, STUK has gone through the safety requirements regard- ing final disposal (Government Decree 736/2008) and assessed, as its conclusion, the situation re- garding fulfilment of the requirements. STUK is of the opinion that the plant can be implemented so that it meets the safety requirements, but achiev- ing the required standard of design following the suggested time schedule will be challenging. The following is a summary of the issues STUK consid- ers most critical for the construction licence ap- plication:
• Formation of scenarios meeting STUK’s re- quirements and describing the entire final dis- posal system, analysis of the release and migra- tion of radionuclides in these scenarios, as well as a comprehensive analysis of uncertainty
factors.
• In its documentation, Posiva has not explained how the parts of the final disposal system will reach the target status and how they will meet the set performance requirements (performance analyses). Deficiencies are obvious, particularly with regard to the buffer, in understanding the processes affecting performance and in demon- strating the planned performance of the buffer. • Demonstration of the development work and
functionality of the bedrock classification sys- tem as well as demonstration of the final dis- posal tunnels and holes in Onkalo.
• The documentation submitted by Posiva does not shed any light on how the defence-in-depth principle and single failure tolerance of sys- tems, for example, have been taken into account in plant design work.
In 2011, STUK monitored in particular the prog- ress made in the above issues in Posiva’s work, and safety issues were discussed in many subject- specific meetings between STUK and Posiva. One of STUK’s key tasks in 2011 was to start prepara- tions for processing Posiva’s construction licence application for the disposal facility of spent nuclear fuel to be submitted in 2012. In the first stage of the preparatory work, the first version of the review plan was compiled on the basis of safety requirements and areas and subjects of review composed of them. External international experts also assisted in producing the review plan, and the work was observed by representatives of the Swedish Radiation Safety Authority (SSM).
During 2011, STUK actively monitored Posiva’s design work for the encapsulation plant and dis- posal facility, particularly the situation in system design. Posiva is developing its process and system descriptions to the standard required for the con- struction licence application. This requires devel- oping Posiva’s organisation and operations to meet the safety requirements of nuclear facilities, and STUK is of the opinion that Posiva should, for ex- ample, pay attention to ensuring the availability of sufficient resources as well as to the guidance and quality assurance of design work.
During 2011, STUK has monitored the research and development work on the final disposal sys- tem, and that on the canister and bentonite buffer in particular. Posiva has several projects in prog-
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ress aimed at demonstrating the performance of the buffer. STUK’s oversight focussed on the defini- tion of functions and goals set for the buffer and on the associated open questions regarding safety. In 2011, STUK began the review of the detailed buffer plan and the freezing-thawing analysis related to the penetration of permafrost. These reviews will be completed in early 2012.
STUK has assessed the documentation on Posiva’s disposal canister manufacturing, weld- ing and inspection techniques and sent to Posiva, in June, the resulting statement on the status of development work regarding the manufactur- ing, welding and inspection techniques of disposal canisters. It can be stated as a conclusion on the assessment work that the descriptions, quality re- quirements and acceptance criteria regarding the manufacturing, welding and inspection techniques of disposal canisters have become more specific compared to what was presented earlier. In the opinion of STUK, the descriptions, quality require- ments and acceptance criteria must be further developed and specified for the construction licence application documents so that the impacts of dif- ferent stages of the manufacturing, welding and inspection techniques on the operational and long term safety of the disposal canisters are shown comprehensively enough. In addition, STUK began the review of documents concerning the design and corrosion resistance of canisters; this review will be completed in early 2012.
Regarding disposal scenarios, STUK analysed Posiva’s safety analysis methodology for scenario analysis. The focus of STUK’s oversight in this area was on assessing the international situation
and knowledge regarding the formation of sce- narios and on assessing the safety requirements. Furthermore, STUK began its own comparable scenario analysis work that can be used as support when analysing the scenarios presented by Posiva in the construction licence application.
STUK has monitored Posiva’s development work on the bedrock classification system by as- sessing the results of the project and the efforts to demonstrate its functionality, by overseeing the research work carried out in Onkalo and by analys- ing development subjects with Posiva. Testing of the bedrock classification system was an important part of the implementation of Onkalo’s demon- stration facilities, and Posiva produced detailed descriptions of the bedrock in the area for the pur- pose of indicating in advance the suitability of the subject rock volume for final disposal. In its over- sight work, STUK paid particular attention to the reliability of descriptions and the bedrock criteria set in the classification system.
As a summary, it can be stated that STUK presented in 2011 its views to Posiva regarding the open safety questions raised in the prelimi- nary application documentation and monitored in particular the research, development and design/ planning work related to these areas. At this stage, Posiva is concentrating its efforts in preparing the construction licence documentation to be submit- ted at the end of 2012, and it has therefore sub- mitted less preliminary documentation to STUK. Consequently, STUK’s regulatory activities mainly consisted of plan assessments, inspection visits and analysis of observations jointly with Posiva.
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