Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Minimizing the background radiation in the new neutron time-of-flight facility at CERN: FLUKA Monte Carlo simulations for the optimization of the n_TOF second experimental line
2013 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

At the particle physics laboratory CERN in Geneva, Switzerland, the Neutron Time-of-Flight (n_TOF) facility has recently started the construction of a second experimental line. The new neutron beam line will unavoidably induce radiation in both the experimental area and in nearby accessible areas. Computer simulations for the minimization of the background were carried out using the FLUKA Monte Carlo simulation package.The background radiation in the new experimental area needs to be kept to a minimum during measurements. This was studied with focus on the contributions from backscattering in the beam dump. The beam dump was originally designed for shielding the outside area using a block of iron covered in concrete. However, the backscattering was never studied in detail. In this thesis, the fluences (i.e. the flux integrated over time) of neutrons and photons were studied in the experimental area while the beam dump design was modified. An optimized design was obtained by stopping the fast neutrons in a high Z material and by adding a hydrogenous material for neutron moderation. In addition, a material with high neutron absorption cross-section was used to stop the slow neutrons. The neutron and photon backscattering were decreased between one and two orders of magnitude depending on the energy range of the neutron beam.Furthermore, the neutron-induced radiation dose levels in the nearby ISR tunnel were estimated. Being a permanent workplace puts strict limits on the acceptable equivalent dose rate. The aim of this study was to reinforce the existing shielding in the ISR tunnel in order to reach below 0.5 uSv/h. A problem in this study was the crane operating in the tunnel, which puts restrictions on the height of the shielding wall. As a consequence, two shielding scenarios were explored. In the scenario where the crane could be blocked, the optimal design was to build a 160 cm thick concrete shielding wall reaching up to the roof. In the scenario where the crane was kept in operation, the wall could only be made 4 m high and the optimal design was to keep the wall 160 cm thick and add iron plates to slow down fast neutrons. In both scenarios the average equivalent dose was below or on the limit of 0.5 uSv/h.

Place, publisher, year, edition, pages
2013. , 96 p.
Keyword [en]
Physics Chemistry Maths
Keyword [sv]
Fysik, Kemi, Matematik
Identifiers
URN: urn:nbn:se:ltu:diva-49545Local ID: 6e099d65-6017-4401-acf1-1dd71336bfa0OAI: oai:DiVA.org:ltu-49545DiVA: diva2:1022892
Subject / course
Student thesis, at least 30 credits
Educational program
Engineering Physics and Electrical Engineering, master's level
Supervisors
Examiners
Note
Validerat; 20130610 (global_studentproject_submitter)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

Open Access in DiVA

fulltext(30779 kB)260 downloads
File information
File name FULLTEXT02.pdfFile size 30779 kBChecksum SHA-512
dc3a1e97870f19c2c7382746b9b6767567947447d1f41f1f5cb2475dd81bc63a40720fd9800a706d4007388875925d774c246d2bff6950cfe2b294a797a83fb3
Type fulltextMimetype application/pdf

Search outside of DiVA

GoogleGoogle Scholar
Total: 260 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

urn-nbn

Altmetric score

urn-nbn
Total: 48 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf