(Radiation) skyshine describes the
ionizing radiation
Ionizing radiation (or ionising radiation), including nuclear radiation, consists of subatomic particles or electromagnetic waves that have sufficient energy to ionize atoms or molecules by detaching electrons from them. Some particles can travel ...
emitted by a
nuclear technical or
medical
Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care practic ...
facility, reaching the facility's surroundings not directly, but indirectly through
reflection Reflection or reflexion may refer to:
Science and technology
* Reflection (physics), a common wave phenomenon
** Specular reflection, reflection from a smooth surface
*** Mirror image, a reflection in a mirror or in water
** Signal reflection, in ...
and
scattering
Scattering is a term used in physics to describe a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including ...
at the
atmosphere
An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...
back to
earth's surface
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surface ...
. This effect can happen when the shielding barrier around the source of radiation is open at the top.
This effect can also happen when the shielding in the vault room of a
linear particle accelerator
A linear particle accelerator (often shortened to linac) is a type of particle accelerator that accelerates charged subatomic particles or ions to a high speed by subjecting them to a series of oscillating electric potentials along a linear b ...
in
radiation therapy
Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radia ...
is not sufficient to reduce the intensity of the primary incident beam down to a very low level.
For example, a member of the public may be positioned outside of such a room or vault in a nearby parking lot. For a radiation therapy facility with limited shielding in the vault ceiling, even if the radiation is directed straight upward through the ceiling into the atmosphere, there can still be a significant amount of radiation scattering off of the atmosphere backward and at an angle. This skyshine can be measured by a
medical physicist A medical physicist is a health professional with specialist education and training in the concepts and techniques of applying physics in medicine and competent to practice independently in one or more of the subfields (specialties) of medical physi ...
at the position of the pedestrian standing on the ground in the nearby parking lot. Such radiation is generally measured in terms of exposure-rate or dose-rate. It has been shown that this downward intensity is heavily dependent on the shape of the beam. Regardless of whether the upward incident beam is shaped like a circle, square or rectangle, specific calculation formalism has been described.
The intensity of radiation measured at the surface immediately surrounding the facility increases with growing distance from the shielding barrier to reach a maximum and then fall again continuously with further increasing distance. Depending on the energy of the scattering radiation, the intensity maximum is reached at different distances from the vault. For example,
x-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...
s emitted from
linear accelerator
A linear particle accelerator (often shortened to linac) is a type of particle accelerator that accelerates charged subatomic particles or ions to a high speed by subjecting them to a series of oscillating electric potentials along a linear beam ...
s reached maxima of 18
MeV
In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the measure of an amount of kinetic energy gained by a single electron accelerating from rest through an Voltage, electric potential difference of one volt i ...
at a distance of 13.6 m and 6 MeV at 4.6 m in studies.
Between 1967 and 1975 significant
radiation damage
Radiation damage is the effect of ionizing radiation on physical objects including non-living structural materials. It can be either detrimental or beneficial for materials.
Radiobiology is the study of the action of ionizing radiation on living ...
of the surroundings was caused by radiation skyshine at and near the
AVR reactor
The AVR reactor (german: Arbeitsgemeinschaft Versuchsreaktor) was a prototype pebble-bed reactor, located immediately adjacent to Jülich Research Centre in West Germany, constructed in 1960, grid connected in 1967 and shut down in 1988. It was a ...
in
Jülich
Jülich (; in old spellings also known as ''Guelich'' or ''Gülich'', nl, Gulik, french: Juliers, Ripuarian: ''Jöllesch'') is a town in the district of Düren, in the federal state of North Rhine-Westphalia, Germany. As a border region betwe ...
, Germany, which, in its original
BBC #REDIRECT BBC #REDIRECT BBC
Here i going to introduce about the best teacher of my life b BALAJI sir. He is the precious gift that I got befor 2yrs . How has helped and thought all the concept and made my success in the 10th board exam. ...
...
construction, lacked a top shielding barrier.
In 2011, the skyshine effect reached media attention in the controversy around the
repository after higher levels of radiation were measured outside the facility, despite it being shielded by a shielding wall.