How to reduce Shutdown Dose Rates in ITER Diagnostics Equatorial Ports
- Departamento de Ingenieria Energetica, ETSII - UNED, Calle Juan del Rosal 12, Madrid 28040 (Spain)
- Fircroft Engineering Services LTD (United Kingdom)
- ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex (France)
- Budker Institute of Nuclear Physics, Novosibirsk (Russian Federation)
- Project Center ITER, Kurchatov sq.1, Building 3, 123182 Moscow (Russian Federation)
The ITER vacuum vessel presents 54 access ports, arranged in three levels, where port plugs are inserted hosting different types of systems: test blanket modules, antennas, vacuum pumps, neutral beam injectors and diagnostics. At the equatorial level, nine out of the eighteen access ports present diagnostics port plugs, in which the diagnostics systems are deployed into three DSMs (Diagnostics Shield Modules). The DSMs, being a major constituent in volume of the port plugs, must help to fulfill the design target of Shutdown Dose Rates (SDDR) corresponding to 100 μSv.h{sup -1} after 10{sup 6} s of cooling time for planned in-situ maintenance operations in the port interspace. Additionally, the DSMs are largely responsible for the port plug drained weight limit of 45 T, which imposes limitations to the shielding technology. Up to now, all the proposed DSM designs combine differently stainless steel, water and/or B{sub 4}C as shielding to accommodate a maximum of 1.1 m{sup 3} of DSM bulk shield, contained into a L 1845 x W 518 x H 2011 mm stainless steel box weighting 5.8 T for each DSM. These proposals show insufficient shielding properties with respect to SDDR, while none of them satisfies currently the weight limit. However, during 2016, a new DSM concept has been developed, named 'modular DSM', with significant engineering advances and changes. The DSM length has been increased by 500 mm, up to 2345 mm. The SS box has been reduced to the minimum structure required, presenting the same weight while being larger and hosting a larger volume of bulk shielding inside. Thus, the volume of bulk shielding has been enlarged up to 1.5 m{sup 3} per DSM. The shielding technology is based on B{sub 4}C bricks deployed in SS trays that are attached to the vertical plates. This results in a bulk shielding made of 65% of B{sub 4}C, 10% SS and 25% void, with effective density of 2.4 g.cm{sup -3}. In summary, the modular DSM, without a weight increase, hosts extra 0.5 m3 of bulk shielding along an additional 500 mm of length, to be used with a light but highly neutron absorber, what allows fitting the weight limit of 45 T for the port plug once drained. From now, the non-modular DSMs will be referred as 'short DSMs'. The modular DSM's advantages with respect to the short DSM versions have shown that the DSMs design can be improved in generic approach, i.e. when the penetrations of the systems are not taken into consideration. A mention apart is required when port specific penetrations are considered. Provided that they will be an important radiation transmission path, their presence could significantly diminish the improvement. To clarify this issue, in this work we have carried out a nuclear analysis of the ITER equatorial port no. 11 integration considering the modular DSM. It is a first plasma port hosting the following 6 major diagnostics systems: Neutral Particle Analyzer (NPA), H-α monitor, Low Field Side (LFS) reflectometry, Visible - Ultraviolet divertor (VUV div), Visible - Ultraviolet core survey (VUV CS) and X-rays Crystal System (XRCS). For the baseline case, a SDDR matrix has been derived assigning responsibilities to the different EP no. 11 individual systems in terms of neutron flux transmission through them, and the related activation due to that neutron flux (activation of itself, but also of the rest of systems taken one by one). Different EP no. 11 configurations have been studied in addition to the baseline case. For example, the backfill of the port plug penetrations to protect all the empty space not required for systems sight. Another issue is the determination of the role of the Co impurity content minimization from 0.05 wt.% to 0.03 wt.% recently proposed. In this summary, only some results related to the baseline are given.
- OSTI ID:
- 23047399
- Journal Information:
- Transactions of the American Nuclear Society, Vol. 116; Conference: 2017 Annual Meeting of the American Nuclear Society, San Francisco, CA (United States), 11-15 Jun 2017; Other Information: Country of input: France; 11 refs.; available from American Nuclear Society - ANS, 555 North Kensington Avenue, La Grange Park, IL 60526 (US); ISSN 0003-018X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
61 RADIATION PROTECTION AND DOSIMETRY
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
BORON CARBIDES
CRYSTALS
DENSITY
DESIGN
DOSE RATES
FAR ULTRAVIOLET RADIATION
ITER TOKAMAK
NEUTRAL PARTICLE ANALYZERS
NEUTRON ABSORBERS
NEUTRON FLUX
PLASMA
SHIELDING
SHUTDOWN
STAINLESS STEELS
VACUUM PUMPS
X RADIATION