Internal Review of TDR – Target Station

1. Internal Review of TDR – Target Station Håkan Danared European Spallation Source Lund, 11 October 2012

2. Contents of Target Chapter, Reviewers Håkan Danared Tom Shea Jan Molander John Weisend Christine Darve Håkan Danared

3. Section 3.1 General Description

4. Findings • Section 3.1 contains • System requirements, 3 pages • Target system general layout, 8 pages • Quality assurance and risk analysis, 1 page • Global simulation of target station system, 3 pages • Target station control system, 3 pages • Target station operations and maintenance, 4 pages • Material properties, 5 pages • All with “green status”, as of 3 October

5. Comments – 1 Sections 3.1.1 and 3.1.2 give a good introduction to the layout-out and features of the target building. Section 3.1.1 mentions 2 x 22 instruments instead of 2 x 24 in several figures, in a layout quite different from in chapter 2. Figures 3.1-3.3 are important and give a good overview, but colours are too similar so it is difficult to identify the different parts of the building. Text size of legends in these figures is too small or resolution too low. Adding a scale would be helpful. The style of 3.1.2 is different from much of the target chapter in that it has more bullet points and less full sentences. Should this be adjusted? Sections 3.1.3 and 3.1.4 are very well written. Section 3.1.5 has been cross-checked with ICS, and some changes have been made (not reviewed here). Error in sub-section header “Target station systems operating domains Associated actions Mechanical design criteria”? Same sub-section difficult to understand. Same S-Action1 triggered in both normal and off-normal situations? “Swedish nuclear authority” should be Swedish Radiation Safety Authority.

6. Comments – 2 Section 3.1.6 has almost only bullet points and has repetitions that could be formulated differently. Much is definitions – what is the “take home message”? Should be realigned with rest of chapter? Its heading is “operations and maintenance”, but nothing is mentioned about what maintenance is needed. Section 3.1.7 is well written. Fig. 3.15 is not referenced in the text. “Beam window” is mentioned – is that beam entrance window? Generally speaking, there are numerous language issues, typos, non-ascii characters and sub/superscripts that have disappeared, missing references, etc., and the entire chapter should be polished within TD before going to a review by a native English speaker. The chapter is more or less written for experts, which is perhaps expected and reasonable. However, the style seems to differ between chapters and suffers perhaps from a lack of directives on this point.

7. Recommendations Use more distinctive colour legends in figures 3.1-3.3. Check size of texts in all figures and make sure all texts are readable. Improve readability of 3.1.6 and align its structure with rest of document. For entire chapter: Define acronyms at first use, plus in a list at the end, or avoid them (why call the beam dump a PBDS?) Don’t capitalize “important words” or do it consistently (Target or target, Collimator or collimator?) Be consistent in use of “proton beam window”/“beam entrance window”/“beam window” Please use spell-checker!

8. Section 3.2 Neutronics

9. Findings The section describes neutronics calculations that have been performed in support of ESS target systems design. Optimization of Beam profile on target and of the moderator system has been performed using well-defined figures of merit. In subsection 3.2.6 “Optimization of TMR System”, subsubsection “Advanced moderators” is incomplete. Section 3.2.8, “Neutronic support for engineering design” is incomplete.

10. Comments From the beginning through subsection 3.2.6, the section (3.2) reads very well and generally meets all of the goals for the TDR. Editing for grammar is still required. Writing style is not consistent across subsections. Non of the beam profiles in Table 3.13: “Optimisation results” are physically realistic. The text comments on the pencil beams, and also on the fact that window scattering is not included, but the table caption should contain appropriate caveats. Section 3.2.7, “Beam extraction” contains limited technical design information and reads more like more like a backgrounder. The 47 µA/cm2 peak current may not be consistent with latest baseline.

11. Comments (HD) A figure illustrating the TMR system at the beginning of section 3.2 would be helpful. What is “Surf.” in table 3.12?

12. Recommendations Edit for grammar, style, etc. Complete missing subsections and update figures and tables as required. Check that beam parameters are consistent across chapters. Complete section 3.2.8, “Neutronic support for engineering design. Rewrite section 3.2.7, “Beam extraction” to include design information.

13. Section 3.3.1–3.3.2 Monolith Structure: Monolith, Target wheel unit

14. Findings – 1 • Section 3.3.1 Monolith • p. 39 second bullet describes a Base plate manufactured with high accuracy. To which tolerances and will this work with low tolerances shield blocks? • p. 39 fourth bullet mentions a backpack shielding block. Please explain what this is? • p. 39 Liner, end of first part describes a seal weld not intended to transfer loads. How will this work? • p. 39 Liner, second part and figure 3.28. The function of the double seal and where it actually is situated is not clear • p. 40 Liner The last sentence could need some more explanation • p. 40 Monolith … second part, do we need high density grout? • p. 40 Monolith … third part describes requirement for the grout not to overheat. What kind of temperature variations could be expected for the grout? • p. 41 Monolith … second sentence below figure 3.29 describes a support. Should the word support be replaced with supposed?

15. Findings – 2 • Section 3.3.2 Target Wheel Unit • p. 45 After heat analysis, second part states that shielding surrounds target. Text could need some development • p. 47 Mechanical … Please explain how a nut will relax stresses • p. 48 Mechanical … Should it be half this thickness? • p. 54 Target Shaft row five, the comma should be placed after the word too? • p. 54 Target Shaft row 15, arranges should be arranged? • p. 55 Seal row eight below figure 3.50. Please revise “will be has to be”

16. Comments • References to publications are all missing • Many figures are small in size and some of them are therefore difficult to understand • Some figures are placed far away from text referring to them

17. Comments (HD) Labeling of parts shown in figures, like fig. 3.27 and many others, would be very helpful Does the rotating seal of the target wheel deserve a more detailed description? First paragraph of section 3.3.2: Direct view of what? After heat analysis, line 6: is really 40–60% of the 5 MW deposited in the shielding? The mechanical analysis shows stresses etc.: what are the conclusions, the “take home messages”, from the different analyses? Table 3.23 is not referenced in the text. Do the quantities in the first column need to be defined? What does fig. 3.48 show? Some fraction of the BEW? Where in fig. 3.53 is the SNS system shown?

18. Recommendations Some technical descriptions could be hard to follow for non-experts and would possibly gain from short introductions Chapter 3.3.1 Monolith could possibly be improved by a rather large figure pointing out the most important discussed details

19. Section 3.3.3–3.3.7 Monolith Structure: Moderator system, PBW system, Beam ports and beam extraction system, Irradiation ports, Tune-up dump

20. Findings These sections are part of the Monolith Structure Description They describe the Moderator andReflector System, Proton BeamWindow, Beam Ports, Beam Extraction System, Irradiation Ports and Tune Up Dump These sections comprise 32 pages and containnumerous figures and tables

21. Comments – 1 The descriptions in these sections are well organized and generally quite readable. There are however numerous language errors and typos that need to be fixed to improve the section These sections make good use of color figures and tables to convey information The figures are readable, clear and add value to the content There appears to be very little extraneous information in these sections so reduction in length without reducing valuable content would be difficult

22. Comments – 2 There is an inconsistency in the way we describe the hydrogen in the moderators. In some cases it is described as a liquid (or LH2) in some cases as supercritical, in some cases as cryogenic and in some cases as a supercritical liquid. We need to decide a consistent usage for the TDR Technically, the hydrogen is above its critical pressure but not above its critical temperature. Thus is is really a very subcooled liquid rather than a supercritical fluid (supercritical liquid is an oxymoron) Thus I would propose we use either liquid hydrogen or cryogenic hydrogen. However, we should make clear its operating point (20 K and 15 Bar)

23. Comments (HD) Is the data on the 1 year lifetime of the proton beam window obsolete? We hear that fatigue issues are more severe than this. What does “more than 5 MW proton beam power” mean in the 4th paragaph of section 3.3.4? Labeling the components shown in figures would be very helpful. Is it true that graphite in beam dumps/stops is discouraged because of 14C production? Fig. 3.72 should have units on the axes.

24. Recommendations • Correct all indicated language errors and typos in time for the November 1st draft • Reexamine section to eliminate any remaining passive voice or improper tense usage by the November 1st draft • Summarize in the beginning of section 3.3.3, the sizes and locations of the heat deposited into the cryogenic hydrogen system. This will improve clarity so that there is no confusion between the 20 kW total heat deposited into the complete hydrogen system and the ~ 8 kW deposited into a single moderator. Accomplish this by November 1st • Determine ESS wide how to refer to the hydrogen in the moderators (Liquid hydrogen, supercritical hydrogen, cryogenic hydrogen) and use this consistently throughout the TDR

25. Section 3.4 Fluid circuits

26. Findings Long document of 100 pages, 107 figures and 38 tables. A very comprehensive and fluid document to emphasize the good TD work. Distribution of the ToC is adequate

27. Comments A very comprehensive document to emphasize the good work. The TDR mission has been reached, except for the interface with other chapters and the complete handling of risk description. Good detailed analysis (e.g. CFD results, fatigue). More references to the original work is needed or should be published. Spelling and syntax errors must be addressed. Complete the references, tables and figure definitions.

28. Comments (HD) Fig. 3.76 has too small text. Are numbers on pressure in target wheel consistent within and between sections? Sub-section “Seal” in section 3.3.2 states 3.6 bar in and 3.0 bar out. Section 3.4.2 states 4 bar outlet pressure of helium pump, and compression ratio 1.5.

29. Recommendations – 1 Word-smoothing or smithing necessary Add link to other TDR chapters, e.g. defined rules, standards and call for the safety chapter. Shouldn’t 3.2.8 “Neutronic support for engineering design” be detailed with chapter “6- Integration” or better in “11- Safety”. Safety should be considered as a support to the design of the target equipment. 3.5.1 “active cell” should be linked to chapter 12 (and reverse). When written “is treated in a specific chapter” , say which chapter you are talking about. It happens several times. Zoning concept (chp 3.1.2) should be consistent with chapter 6. Table 3.3 refers to barrier numbers that are inconsistent with what is said in chapter 6. Reference to “Quality Assurance and risk analysis” must refer to chapter 8.2.

30. Recommendations – 2 Don’t use acronyms in chapter title (e.g. chap 3.6.2. LBE Target, PWB and chap 3.2.6) Don’t use large letter for the 3.3 and 3.6. sub-section titles. Apply consistent principles Missing paragraph in 3.6.2. Use SI unit (e.g. bar  MPa, 12L/s  12 l/s (p113)). In chapter 3.4.1, should close loops and “open loop” be most relevant title? Figure 3.77 is too small Correct section titles listed in chapter 3.4.2. page 78: 2300m3.hr-1, should read 2300 m3.hr-1 page85: 99 % Para should read para

31. Section 3.5 Handling and logistics

32. Findings • Section 3.5 contains • Active cells, 6 pages • Casks and associated handling devices, 4 pages • All with “green status”, as of 3 October

33. Comments • This section is very well written. The figures are very clear with relevant details clearly labeled. • Minor details are • What is “band graphite saw blade”? • What is the airlock referred to in the second line of sub-section “Maintenance cell?” • What is meant by “first opening” and “second opening” mentioned under “Confinement”? • Where are activated shielding blocks put during exchange of components?

34. Recommendation Add figures like the ones in this section to other sections

35. Section 3.6 Comparative target concepts

36. Findings • Section 3.6 contains • Water cooled rotating tungsten target, 6 pages • LBE target, 23 pages • All with “yellow status” or “red status”, as of 3 October.

37. Comments With “yellow status” indicating “not ready for review”, only a few general comments are given: An introduction and a conclusion to this section would be logical. A schematic diagram of the water-cooled rotating tungsten target would be useful. The LBE section reads more like a research paper than as a design report.

38. Recommendation Shorten or rework the LBE section so that it reads more like a design report.