Review of TDR Chapter 12 on Radioactive Wastes and Emissions

1. Review of TDR Chapter 12“Radioactive wastes and emissions” • PatrikCarlsson • with support from • P. Jacobsson, T. Hansson, L. Zanini, S Norlinder

2. General comments - 1 • Clearly a lot of good work in WP 11 is underlying the chapter. Clear that work is still ongoing and progressing. More results are coming? • WP11 contributors are to be congratulated to the work. Very specific and deep expert knowledge is clearly needed for it. • It deals with an important area and it is related to and underpinning safety, licensing and the information ESS give to authorities and the public. • How does it relate to the chapter on Safety and our licensing applications? The scope of the chapter must be defined and also the reason for including it in the TDR. • Why not describe the environmental impact in general? A possible answer is that the production of radioactive waste and emissions has such a defining influence on the design of the facility. • Clearly the HSE group is very interested in the results! TDR Internal Review, Lund, October 2012

3. General comments - 2 • Content is overlapping with safety chapter 11. • Introductory texts could guide the reader in many places. • In particular text on H-3 is sensitive from a communications perspective. • Landfills of very low level waste? TDR Internal Review, Lund, October 2012

4. General comments - 3 • References are made to reports, but the reports are missing and are not named. • There are many references to future work and studies for quite important matters. Is this work expected to be completed in the near future? (It is important not only for TDR but for progress of ESS). • The text is repetitive at several places – it is clear that several authors are involved. • The English is good in many parts. In some parts it is bad and in a few sentences are incomprehensible. • Isotope notation is inconsistent. • Numbers are formatted inconsistently. TDR Internal Review, Lund, October 2012

5. Comments – 12.1 • Chapter 12.1 actually covers what is stated in chapter 11.2 (Safety). This should be coordinated. • Chapter 12.1.1 • “The calculations shall be based upon measured dispersion data and knowledge of the circumstances in the most affected area during the time period concerned. ESS has declared that it will abide by the intention of this regulation [MS]”. Incorrect? Note, Sture Nordlinder believes this is right. Peter agrees with Thomas that this is not an exact formulation by the SSM and that it should be removed from the text. • The release of liquid waste to the municipal sewage water treatment is regulated in SSMFS 2010:2. SSM has replied that this regulation is not valid for ESS. Remove the sentence. TDR Internal Review, Lund, October 2012

6. Comments – 12.1 • Chapter 12.1.2 • “In most cases, these ESS limits are stricter than those required by Swedish law.”This is not correct, coordinate with HSE. • “…. for each exposure pathway: direct radiation, inhalation and ingestion.”The term Pathway is used with a different meaning, compared to page 15-16. • “A preliminary application process for the application under the Radiation Protection Act is described in an SSM memorandum [Lillhök].”Replaced with another official document. TDR Internal Review, Lund, October 2012

7. Comments – 12.2 • Chapter 12.2.1 • “… integrated equivalent dose from full beam loss outside the predicted shields has to comply with exposure limits in case of a cut-off time of 50 ms.”Is this the latest knowledge provided by the Accelerator division? • “…estimate of the required shielding in the HEBT zone was performed. Calculations have shown that two meters of iron block followed by 40 cm of ordinary concrete layer will be required to shield the bending magnet in the linac-to-target connection zone. … The proposed thickness of the shielding guarantees an integrated dose in case of accident below the acceptable limit with sufficient margin to cut-off the beam.”Is this also based on 50 ms? • “To be on the safe side, the ESS accelerator design has to include protective measures to isolate the soil from groundwater in order to prevent the exchange of contaminated water.”Check this, existing documents indicate the opposite opinion. • A preliminary evaluation of the activity released in the atmosphere from the linac tunnel accounting only for the air change rate inside the entire tunnel volume was also carried out. It was found from this conservative analysis that a more realistic model will be required to aid in the design of the ventilation system inside the accelerator tunnel. There is a calculation from Studsvik showing that the dose is very low. TDR Internal Review, Lund, October 2012

8. Comments – 12.2 • “Supplementary studies related to the shielding against skyshine as well as the analysis of the consequences of failures and severe accidents have to be performed.”When is this expected to be completed? It is important for the chapter and for the work. • Table 12.2 is hard to understand when two different sums are presented at the bottom of the table. Should be clear what do we mean. • InstrumentsFor the first beamline shielding calculations, a generic source term is intended to be obtained that will capture the specifics of the high energy component of the direction of the beamlines with regard to the incident proton beam. Reference is then made to results in report 12.2.1.5. The text would benefit from expanding on the results in the reference • Source terms for environmental analysisRadioactive inventories associated with the linac tunnel and surroundings as well of the majority of the target station components have already calculated under conservative operation conditions. Reference is needed to report. The HSE group is interested in more elaborate studies showing the majority of the the inventory at ESS. • The release and diffusion of the radioisotope products depend of many parameters and require experiments reproducing the ESS conditions. Agree, but needed already 2013, because it will define the requirements for the three safety barriers. • “In this stage of the design project, only qualitative assessment of the above processes can be done based mainly….”We have already given some figures, right? Check with HSE group if unclear. TDR Internal Review, Lund, October 2012

9. Comments – 12.2 • Chapter 12.2.2 • Conclusion and outlook The INCL4.6-Abla07 reaction model gives good results for residual production yields on tungsten in the ESS energy range, i.e. most of the time calculations fit experimental data within a factor of two. The conclusion would then be that there is a need to include this uncertainty for the results. Has this been done so far? • “…the model will also be benchmarked to experiments carried out with thick targets.”When? • It is good to discuss the validity of INCL4.6-Abla07 model used in the calculations. One could show a validation curve of cross section vs mass number for experimental data and calculations, showing in which mass regions the calculations are less valid. That (and a more detailed analysis) would give an idea whether experimental validation on thick targets is required or not. • “The total activity after 3.6 years of irradiation, 156 days off-beam, 208 days on-beam and a cooling of 9 years is 9.251E+15 Bq (see right side of the figure ??).”Why 9 years of cooling? Is it baseline conditions? TDR Internal Review, Lund, October 2012

10. Comments – 12.2 • Figure on target seems to be up-side-down • Why is there a focus on alpha emitters only in the text? Explain why or give results on beta and gamma as well. TDR Internal Review, Lund, October 2012

11. Comments – 12.3 • 12.3.1 • All radioactive waste from ESS will be handled and disposed of within the Swedish system for management of radioactive waste. There is a nice picture of this from SKB that I can provide you with (HSE group). Figure on swedish system should be enlarged if kept. • “… judgement on waste classification can only be made after specific waste type descriptions have been prepared for each type of waste. … having reliable information about the nuclide inventory, dimensions and material information is key to planning for waste transport, treatment, conditioning, and disposal.”Can these specific descriptions, nuclide inventories, etc be provided in the next draft? It is important info for the Radiation Safety Authority. • 12.3.2 • “This solution has the advantage of saving time and gaining public acceptance more easily.”There is probably no correlation between existing transport flasks and the public acceptance. Maybe there is a correlation to authorities acceptance, but is something different. TDR Internal Review, Lund, October 2012

12. Comments – 12.3 • 12.3.3 • This chapter should come together with 12.3.1, i.e. the strategy of ESS of how to handle waste (Studsvik, SKB etc.) • “Approval for SFL cannot be expected until the facility has been built.”According to other sources, preliminary “waste acceptance criteria” (WAC) for SFL might be expected in 2016 according to existing plans. • Will we have a landfill dump on site for VLLW? TDR Internal Review, Lund, October 2012

13. Comments – 12.4 • This section provides an overview of works undertaken and the main results achieved on the topic of the operational emissions and wastes. The study pertains to the entire ESS facility, including the accelerator complex, target station with the hot cells, neutron lines and experiments. Presented where? • One of the main goals of the investigation is to survey the existing literature on chemical reactivity and speciation regarding the activated tungsten target and its surroundings.Is this really the main goal? What about contributions? • 12.4.1 • “At the operating temperatures of the ESS target, ranging from 500 to 600 C (REF12.4.2, 3,5), the majority of spallation radionuclides produced have slow diffusion through tungsten material. Therefore one can conclude that these isotopes remain inside the target.”On what timescale? Slow is not equal to “zero movement”. • “The amount of tungsten dust released from surfaces is a subject of investigation. Previous experience comes from gas- cooled fission reactors [REF12.4.14] and tungsten first-wall experiments in fusion reactors.”What are the similar parameters that could be compared with fission reactors? TDR Internal Review, Lund, October 2012

14. Comments – 12.4 • “Due to low diffusion coefficients, radioactive impurities in the dust are not released unless the dust is subjected to high temperatures or excessive oxidation [REF12.4.10].“On what timescale? • 12.4.2 • “The spent wheel is retracted into the hot cells for preparation for final disposal, all the while controlling H-3, dust, and volatiles.”How? • “The effluent from the hot cells shall be released by the facility stack after high efficiency (99.999%) particulate filtration.”Is 99.999 % realistic to achieve? Is there a reference? • “The collimators and beam dumps can be seen as a marginal extension (<5% in total activity) compared to the target itself, and the H-3 release profile will likely be the same.”Assuming the same release profile does not seem correct. A justification is needed. TDR Internal Review, Lund, October 2012

15. Comments – 12.4 • “ • 12.4.3 • “The controlled release of this [H-3]H2 to the atmosphere is feasible under selected atmospheric conditions, preventing high local concentrations.”The ambition should be to avoid the necessity of “selected conditions”, and instead expect that releases will be needed for all conditions. • “Due to activation during operation, the moderator and pre-moderator cooling water will contain H-3. The liquid hydrogen phase through activation will contain small amount of H-3 (about 1E+10 Bq). … The total production of H-3 in the linac system cooling water will be less than 1 TBq/y, which is minimal compared to the H-3 generated in the monolith cooling circuits.”The numbers are not obvious. Here is a clear need for a reference, confirming the numbers. • For reducing the amount of Be, reflector updates of the baseline design are underway. In the new design, the amount of Be reflector waste will be substantially reduced. This is important, do we know this? Can we refer to something? TDR Internal Review, Lund, October 2012

16. Comments – 12.5 • “.. possibly routine releases which might exceed predefined dose limits for potentially affected populations.”Can we not stick within our/SSM’s limits? Rewrite this! • “In the work that has been completed so far, the aim of the analysis has been to establish and demonstrate the calculation methodologies.”Should also include a first estimation of the results. • “It resulted from calculations that the representative inhabitant may have an intake of 2.9 10-8 Bq of tritium per year per Bq released per year. The above estimated value corresponds to an annual dose of 5.2 10-19 Sv/Bq.”Can the dose in mSv be presented? Reference needed. • “The following external dose contributions were evaluated: ….”Why is summarized results in mSv not presented table 12.6? Table 12.5 and 12.6 are unnecessary. What do they say? • 12.5.2 • This chapter should completely be replaced by text that has already been communicated to SSM. There is a preliminary dose assessment made from Sture N/Studsvik that has been reported to SSM. TDR Internal Review, Lund, October 2012

17. Comments – 12.6 • This have to be coordinated with other docs/work on decommissioning. • “… ESS has chosen immediate dismantling as its decommissioning reference …” • Have we taken such a decision? • 12.6.1 • “The radiation level of the ESS structure in shutdown conditions (after the removal of the last target) will not exceed that of the operating facility so it will not pose a significant threat”Not correct? since workers might need to perform other activities than during operation. • 12.6.3 • “Detailed activation calculations for the rotating tungsten target, the LINAC assemblies and the beam dumps with high energy protons and spallation-generated neutrons are required in order to compile an appropriate source term. “This was expected within the TDR. I think results are available? • 12.6.5 • Costing input does not belong in TDR. Move to other document. • Take out the very strong words on methods not appropriate. TDR Internal Review, Lund, October 2012

18. Comments – 12.6 • 12.6.6 • “Every structural material which can be activated by the primary protons and the generated neutrons should be analysed prior to installation…”Not enough to analyze before installation. Should be analyzed before decisions are taken in the design phase. TDR Internal Review, Lund, October 2012

19. RECOMMENDATIONS • Let the ESS HSE group have the final say on the text. Possibly include it as a “subchapter” in the Safety chapter and consider whether to change scope of Safety paper. • Define the scope of the paper. Why is it important? Why is it in the TDR? For next draft. Coordinate with Safety chapter and HSE group. • Expand on the parts describing the instruments, samples and the in some cases also the accelerator for next draft3. • Put for next draft more details on the calculations of activation and shielding of the linac, such as • a figure with the geometry used in the calculations, • a figure with results of the shielding calculations for the linac (example thickness os shielding on x axis, dose rate outside shielding on Y axis), • a table with results of activities of most important isotopes at shutdown and after some selected decay time • Put for next draft a table with the activities of the most important isotopes, at shutdown and at selected decay times for the target. TDR Internal Review, Lund, October 2012