IEC TR 62283:2010 pdf – ptical fibres – Guidance for nuclear radiation tests.
5.4 High-energy physics experiments
Usually. In high-energy physics, electrons or protons with energies as high as several 100 GeV (protons) are used to study elementary particles. In order to increase the reaction energy it is common that two beams collide within a reaction zone which is surrounded by huge detectors analyzing the reaction products. The accelerator tube and the inner parts of the detectors will become highly radioactive, especially it protons collide.
The secondary radiation that threatens the accelerator control instruments and the detector read-out equipment mainly consists of pions (mean energy several 100 MeV), gamma rays and, at radii >50 cm, of neutrons with maximum energies up to more than 100 MeV. but a mean energy of only about I MeV to 2 MeV, The radiation intensities strongly depend on the operating conditions (particle energy, beam current), the distance from the beam line, and the emission angle (maximum in beam direction). Particularly in the beam cleaning sections, high radiation levels may occur.
The annual total dose can be of the order of iO Gy to 106 Gy end the neutron fluence can reach values from 1013 cm 2 to 1015 cm 2, The dose and dose rates are typical and may vary, depending on the specific application,
5.5 Space environments
Close to the earth the dominating radiations are solar protons, trapped protons and trapped electrons. “Trapped means trapped by the magnetic field of the earth, within the Van Allen Belts.
The electrons are concentrated in an inner zone (ending at about 2.4 earth radii) and an outer zone (between about 2,8 earth radii and 12 earth radii). Their maximum energy is about 7 MeV. They can be stopped, for example, by about 10 mm Al. During the slowing down process in matter, they produce penetrating X-rays (Brenisstrahlung).
The proton flux decreases with increasing distance from earth. The maximum energy Is several 100 MeV. For example, the range of 300 MeV protons in Al is about 24 cm. More than 90 % of the protons have energies below 100 MeV.
In a geostationary orbit (for example. 15 east) the total annual dose behind 3 mm Al is nearly 600 Gy. of which about 550 Gy is caused by trapped electrons and about 50 Gy by solar protons. In a low earth orbit (LEO), height 1 000 km and 70 inclination, the total annual dose of about 823 Gy (behind 3 mm Al) is composed of about 400 Gy trapped electron contribution, about 420 Gy trapped proton contribution and 3 Gy solar proton contribution.
Additionally to the above-mentioned radiation types, cosmic rays are an additional type of space radiation. The primary cosmic rays are a low flux of high energetic particles (about 85 % protons, 14 % alpha particles and about 1 % heavier nuclei). Their contribution to the total dose, however, is negligible.
Particle fluences for certain orbits and dose values can be calculated, for example, with the SPENVIS system 151. The dose and dose rates are typical and may vary depending on the specific application.
5.6 MedIcine
For radiography purposes (diagnostics) X-rays with energies <100 keV are used. With modern image intensifier techniques dose values ‘ciO3 Gy are sufficient to take a series of expressive pictures. Irradiation of tumours is made with 0Co gamma rays, high energy electrons (20 MeV to 30 MeV), high energy protons (60 MeV to 300 MeV) or heavy Ions (for example 12C. 2 GeV to 4 GeV). and thermal or fast neutrons. Dose values within the tumour can reach several Gy per "session". The dose and dose rates are typical and may vary depending on the specificapplication. 5.7 Military environments The radiation emitted from a nuclear weapon can be divided into prompt (gamma) radiationemitted during the explosion phase within a time of about 10- s,and a delayed component(gammas and fast neutrons) becoming effective after times of up to 1 min. Despite the factthat the contribution of prompt radiation to the total dose is less than 10 %, this componentcan be very destructive because of its high dose rate (for example, 1 Gy within 10-8 s, i.e. adose rate of 108 Gy/s). Therefore,special tests with pulsed radiation sources (for example,flash X-ray generators) would have to be performed to simulate this radiation component. Total dose and neutron fluence depend on weapon strength (explosive force), the weapontype (contribution of fusion energy), and the distance from the explosion site. The radiationemission for a given explosive force can be increased by increasing the fusion contribution("neutron bomb"or "radiation enhanced weapon").According to the "balanced hardening"principle,fibre cables should not withstand extremely high radiation dose values near thecenter of the explosion,where heat and shock wave will destroy the cable anyway.