ISO 15080:2001 pdf download

ISO 15080:2001 pdf download.Nuclear facilities – Ventilation penetrations for shielded enclosures.
containment enclosure
enclosure designed to prevent leakage of products contained in the internal environment under consideration into the external environment, or the penetration of substances of the external environment into the internal environment, or both simultaneously
NOTE This is a generic term to designate all kinds of enclosures, including glove boxes, or cells of different dimensions used for handling or storing radioactive materials by means of handling devices.
3.2
shielded enclosure
containment enclosed by an additional shielding wall intended to provide complementary shielding against penetrating radiation
NOTE This additional shielding wall can be integral with, mounted on, or independent of the containment enclosure wall. The choice and thickness of the protection material depend on the type of radiation (beta, gamma or neutron) and the type of handling required.
3.3
static service penetration
(for a shielded enclosure)
device used in a containment enclosure wall for the introduction or the extraction of fluids such as air, water, gas, water vapour, or the transmission of energy
3.4
ventilation penetration
(for a shielded enclosure)
device installed on a ventilation network and mounted on a shielded enclosure wall, intended to ensure the shielding continuity of the enclosure wall and the required passage of the air or gas through this enclosure wall
4 Design of ventilation penetrations
4.1 General principles
The general and detailed design principles for ventilation penetrations for shielded enclosures, specified in this International Standard, can be divided more generally into two categories of guidance, which apply to the two following systems of ventilation penetrations for shielded enclosures already in use:
the first corresponding to the most important conventional systems, which are used worldwide, and the second corresponding to an alternative method, which is called the “cast iron helix technique”.
Ventilation penetrations for shielded enclosures shall be designed to maintain the quality of the containment and the efficiency of the shielding of the shielded enclosure, in order to protect the operators against ionizing radiation and radioactive contamination.
The quality of the containment shall be particularly good where the level of internal radioactive contamination of the shielded enclosure is high. In this last case, the junction between the wall penetrations and the inner line of the shielded enclosure shall be leaktight.
Static penetrations shall be carried out in order to reproduce the shielding efficiency ensured by the structure of the shielded enclosure. When a local lessening of the shielding is unavoidable, additional shielding shall be placed on the radiation leakage line, inside, outside or directly included in the enclosure wall.
This additional shielding shall ensure that the cross-section of the shielding efficiency of the wall penetration taken in all directions provides the same level of shielding in units of mass as the shielding wall.
The design of the additional shielding is dependent upon:
— the intensity and the position of the source (or sources) of radiation;
— the diameter of the wall penetrations; the thickness of the shielding wall.
The design of the additional protection shall be conducted on a case-by-case basis.
When neutrons are simultaneously emitted with gamma radiation, it is necessary, depending on the neutron energy, to add an additional shielding material more effective for neutrons. Special calculations shall be made for the dimensioning of the systems ensuring the wall penetrations.
The designer could refer to the manual on safety aspects of the design and equipment of Hot Laboratories (see reference [3] in the Bibliography).
4.2 Conventional ventilation penetrations
Where the ventilation duct crosses the wall directly, it is necessary to add shielding in order to minimize radiation leakage (see Figure 1).
Shielding shall be designed to prevent direct streaming through the ventilation penetration. The duct shall not be located on the direct path of the radiation compared to the position of the operators.
Where the ventilation duct penetrates the wall in a zigzag, the duct-mounting appliance shall be enclosed in a material providing the same level of protection as the shielding wall. In general, the material shall be at least three times more dense than the wall, if it is made in concrete with a density of 2,2 tIm3 (see Figure 2).
Annex C gives other examples of conventional duct penetrations for shielded enclosures.
4.3 Cast iron helix technique
4.3.1 General considerations.