Wardray Premise

Premadex® Neutron Shielding

Part of the Wardray Premise Total Radiation Shielding Package



For Neutron shielding, we can provide the complete analysis and solution of Neutron and Photon shielding problems from definition through design to construction, installation and final testing.

Premadex® was developed in conjunction with the Health Protection Agency, Harwell, specifically for neutron shielding. It is the product of collaborative research by experts in Neutron Physics, Radiation Shielding and Chemical Engineering.

Based on an organo-lithium salt, it is very rich in hydrogen for the most efficient neutron moderation. The lithium content, which is distributed on a molecular level for maximum effect, is adequate to prevent the significant production of secondary gamma rays.

Premadex® is a slightly waxy, lightweight solid material. It is non-flammable, has good ageing characteristics and can be cut to shape or poured molten into prefabricated shielding assemblies.

Premadex® is an ideal shield wherever neutrons are found. Typical areas of application include Particle Accelerator Facilities, Neutron Source Containers, Glovebox Construction, Nuclear Facilities and Room-Scatter Attenuation.

Premadex® Lined Maze Entrance
Premadex® Lined Maze Entrance
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Room-Scatter Attenuation

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Typical building materials reflect neutrons to a high degree. For example, approximately half the number of fast neutrons striking a concrete surface will be re-emitted.

This leads to a substantial build up of scattered neutrons in a room; the intensity being inversely proportional to the internal surface area.

An appropriate surface layer of Premadex® in a concrete room reduces the scattered neutron dose rate to around one third of its original level.

Neutron Shielding Detail
Neutron Shielding Detail
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Accelerator Facilities

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Particle Accelerators are used increasingly in medicine, science and industry. High-energy electron linear accelerators and cyclotrons are routinely involved in radiotherapy, isotope production, activation analysis and form the basis of many research facilities.

Premadex® can play an important role in the solution of all radiological problems arising from neutron production within accelerator facilities.

To control neutron leakage from treatment rooms, Premadex® can be used to line the maze entrance replacing the need for a heavy shielding door. Alternatively, when a door is necessary it can be included in the design for neutron attenuation.

Neutron Shielding Installations

These are some of the major Neutron Shielding projects that Wardray Premise have undertaken for Linear Accelerator installations:

  • Christie Hospital, Manchester (two projects)
  • Coventry New Hospitals.
  • Ipswich Hospital (two projects)
  • Mid Kent Oncology Centre (two projects)
  • Mount Vernon Hospital
  • Norfolk and Norwich Hospital
  • Beatson Oncology Centre, Glasgow
  • Walsgrave Hospital, Coventry.
Power Operated Neutron Shielded Doors
Power Operated Neutron Shielded Doors
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Neutron Source Containers

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Premadex® is the most cost-effective material available for the construction of lightweight transport and storage shielding containers for highly active neutron sources such as Americium Beryllium (α,n) and Californium-252 (sf).

Its use eliminates the problem of secondary gamma rays and allows gamma shielding to be concentrated at the core of the assembly. This can result in substantial reductions in the overall weight of neutron source containers.

In the oil industry, the non-flammable nature of Premadex® is an important safety consideration. In the offshore environment, a lightweight Premadex® container also provides significant handling benefits.

Shipping cask used to transport radioactive neutron sources
Shipping cask used to transport radioactive neutron sources
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The illustration on the right is a custom made bunker with a 2.5 tonne hydraulic powered door for storing Cf252 and Am241Be sources. This was built for a leading multi-national oilfield technology company.

Designed by Wardray Premise Ltd, it is lined with 400mm to 600mm Premadex® Neutron Shielding and meets current UK legislative requirements and national standards

Storage Bunker for Neutron Sources
Storage Bunker for Neutron Sources
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Completed Contracts

These are some of the contracts completed for neutron source storage containers:

  • British Nuclear Fuels plc
  • Health Protection Agency
  • Ministry of Defence
  • Atomic Energy Authority
  • BP Chemical Limited
  • Atomic Weapons Establishment, Aldermaston
  • FW Frost Limited, Norwich
  • Halliburton Manufacturing and Services Limited
  • Reeves Technologies Limited
  • Baker Hughes Inteq Limited

Glove Box Construction

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Where gloveboxes are intended for handling neutron emitting radioisotopes, especially for fissionable materials, consideration must be given not only to basic shielding performance of wall materials but also to the internal scattering characteristics.

Where a critical risk is present, a lower scattered flux means greater safety. Hence the performance of Premadex® as a neutron shielding material is complemented by its low neutron reflectivity and good thermal neutron absorption.

Its choice for glovebox shielding also combines the important benefits of simple, reliable and economical shielding design.


Read More: Composition and technical characteristics of Premadex®