1. Selected comments and recommendations of the International Advisory Committee - Comments/replies from IOWG Resulting actions
V. Mertens
IOWG
Reference:
FCC Review :

2. Civil engineering
R4.3. A detailed plan for additional ground investigation should be drawn up and integrated into the overall baseline schedule. The campaign should be planned such that data is available as early as possible in the project lifecycle (in order to identify where major layout changes may be required). However, the investigation should not occur before there is reasonable confidence in a baseline layout in order to avoid expending resource investigating an area that later falls outside the perimeter of the project. The campaign should be phased so that information necessary to freeze the layouts and shaft locations is carried out first with additional future campaigns for determining the data necessary for detailed design to commence of the specific shafts, tunnels and caverns. Note that the schedule may be different for the h-h machine and the e-e machine since the h-h machine schedule is driven largely by magnet R&D whereas the e-e machine may allow for an earlier start to civil engineering works.
ILF is developing a detailed plan for this (phase III of consulting studies), yielding estimates for cost, duration, and best timing. This exploration shall probably start early in the TDR phase, independent on whether a lepton machine will be built before a hadron machine or not, to be ready in time.

3. Civil engineering
R4.5. In order to avoid the necessity to excavate one or two electrical alcoves in the tunnel under Lake Geneva, an option for a larger spacing of the alcoves in this region should be studied and compared (schedule and cost) with the current layout (i.e. with alcoves formed under the lake).
If the refined study for the electrical network requires alcoves under the lake, the extra cost of moving them to the side will be studied. Latest tendencies in the study seem to indicate that these alcoves could be reduced (or even suppressed). It must still be studied to which extent electronics must be located in a radiation-shielded place near the equipment (smaller alcove) and whether these could also be displaced away from the lake.

4. Civil engineering
R4.6. Although not identified as a showstopper, it would be worthwhile prior to CDR to undertake the necessary calculations to determine the feasibility of a 35 m span cavern within the range of rock conditions and overburden likely (for example with a sandstone roof and a Marl roof). These calculations could include a more precise assessment of the minimum thickness of the rock pillar between the Experimental Cavern and the Service Cavern.
Such a study shall be launched, probably with civil engineering consultant AMBERG, considering a geologically favourable and an unfavourable situation, close to the real expected conditions at points A, B, G, and L. Note the remark under C4.7 that the rock pillar will probably be replaced by a concrete separation.

5. Civil engineering
R4.8. The CDR should include at least some technically feasible solutions for the disposal of the 10 million cubic metres of spoil arising from the excavations and a roadmap to defining a final solution or combination of solutions. This should also address possible solutions to deal with rock contaminated with hydrocarbons.
This is planned to be explored with CETU (see remark under C4.11). Indications on this aspect are also among the deliverables of the collaboration with “FIML - Fraunhofer Institut für Materialfluß und Logistik”. ILF will produce figures on the average output per type of material and per shaft.
R4.9. Consideration should be given to including at least an allowance for civil works modifications for the HE-LHC as it seems unrealistic to imagine nothing would be required.
It will be studied to which degree the infrastructure required for FCC-hh is compatible with the LHC/HL-LHC structures (see remark under C4.9). A survey is going on to understand/compile the system requirements. Spaces for cooling, ventilation and electrical distribution should not be significantly different; a potential evolution for cryogenics and magnet powering will be checked. It is assumed that continued maintenance will leave the technical infrastructure in directly exploitable condition.

6. Civil engineering
R4.10. In the case a second campus would be required for providing access and/or services (see chapter on “Infrastructures”), preliminary siting studies should also be undertaken for this in the CDR.
The FIML study will indicate requirements from magnet assembly and testing. Remote experimental point G will probably require a limited amount of amenities like canteen, dormitories and a visitor centre plus services like a fire station. The driving times and frequencies from and to the different points, and their impact on exploitation, will be studied in more detail. A separate “campus” could lead to different cultures and loss of synergies resp. difficulties in working together, and should be avoided. An intermediate solution might be required for the installation phase.
R4.11. Possible interferences with exploited aquifers, and ways to mitigate them, should be explicitly addressed in the CDR.
First-level clarification will be carried out with external consultants CETU and Cerema (see remark under C4.13).

7. Civil engineering
R4.12. The CDR should address, at some level, the likely impact on the local environment and local populations at and close to the shaft locations and surface works associated with the project. Mitigation measures, perhaps based on CERN’s previous experience with LEP and LHC should be developed in the CDR.
This study is going on with ECOTEC for the sites in Switzerland and will be launched with Cerema for the sites in France (see remark under C4.15).

8. Infrastructure, Integration, Energy
R5.1. Discuss underground safety in all sections of the tunnel and caverns, not only the current “smooth” section.
Selected areas will be covered in a qualitative way. Foreseen safety features include general principles like bypasses around high-radiation areas, no confined spaces (dead tunnel ends), or multiple access/escape paths.
R5.2. Study machine integration in complex areas of the tunnel – e.g. insertions and injection/extraction areas for FCC-hh, RF straights for the two storage rings and the booster ring of FCC-ee – and show corresponding 2-D cross-sections in the CDR.
Most critical areas will be covered in CDR, like the RF straights and extraction zones, with space reservations for beam line elements and major civil engineering features.
R5.3. Present a credible solution for HE-LHC integration in the existing tunnel.
The presented transport and handling solution will be checked for feasibility and cost.
R5.4. Produce bottom-up nominal power estimates also for FCC-he and HE-LHC.
For FCC-he the estimate will be taken from LHeC. HE-LHC can orientate itself mainly on LHC; the power consumption of the cryogenics plants will be studied.

9. Infrastructure, Integration, Energy
R5.5. In case of large variations of power consumption with beam parameters or physics performance, also produce power tables at several representative levels of these parameters, including the injector chain.
The beam and RF parameter tables will be used to evaluate the power at different FCC-ee energies.
R5.6. Study the possibilities for higher energy efficiency and better power management, in particular load shedding during peak periods and possible recovery of waste heat, and enhance the findings in the text of the CDR.
See remarks under C5.8. The internal grid optimisation is being studied. The potential for recovery of waste heat will be studied together the energy efficiency coordinator. In the TDR phase this could be further studied in the framework of an EU project.

10. Infrastructure, Integration, Energy
R5.7. Analyze energy storage options with a stronger effort; this is also desirable given the long timescale of the project and the foreseeable development on the energy market; an interesting option is possibly the combination of a fast reacting SMES with a slow but large capacity storage using liquid H2, a proposal by KIT called LIQHYSMES; this system has the capacity to allow energy management on a large scale (hours) even at FCC power levels; the cost might still be too high at the presented level but the concept has synergies with CERN activities like s.c. magnets and cryogenics.
See remarks under C5.8. The indicated reference will be looked at. Present preference for local storage of electrical energy is rather for batteries (tbc). In the TDR phase this could be further studied in the framework of an EU project.