Material selection radiation

Hemmerich, K. J., Polymer Materials Selection for Radiation-Sterilized Products, MD DI, Feb. 2000. 

The intensity of the selected radiation is measured by devices in which the radiation either interacts with the materials in the detector (e.g., electron release, thermal heating) or generates induced currents due to the electromagnetic field of the radiation. 

Avrami and Voreck (Ref 192) reported on a transient radiation test in which a group of nine expls and proplnts in expln-proof irradiation capsules were subjected to a transient burst of energy of about 1 millisecond duration which resulted from fission of about 10 atoms of. One set of nine capsules was attached to the KIWI reactor pressure vessel and another group on the support structure as part of the KIWI-B4-E excursion expt conducted by Los Alamos Scientific Laboratory at the Nevada Test Site. The materials selected were TATB, DATB and TACOT as the secondary expls, HNS as the booster expl, Pb styphnate as the primary expl, BlkPdr as the igniter, and three composite proplnts. Each capsule contained 3.6 grams of the selected material... 

Stability of a material refers to its mechanical and chemical inertness under the conditions to which it will be subjected. Nuclear plants have a variety of environments to which materials are subjected. Some of these environments, such as high temperatures, high acid, high radiation, and high pressure, can be considered extreme and harsh therefore, the stability of the materials selected for service in these areas is a major consideration. 

Materials selected for the surveillance program are those judged most likely to be controlling with regard to radiation embrittlement according to the recommendations of Regulatory Guide 1.99, Revision 2. 

Various polymers are used in over 1,000 different parts of all shapes and sizes, from instrument panels and interior trim to bumpers and radiator grilles, fuel tanks and engine parts. The material selection for a particular application will depend primarily on the ability to meet the required specification and also on polymer price and total systems cost. The total systems cost includes the cost of the polymer, processing cost and tooling and assembly cost, and is a prime consideration for cost-conscious car manufacturers. 

In order for the internally insulated hot leg piping concept to have adequately performed hydraulically, thermally, and structurally, appropriate materials would need to have been selected In addition, the chosen materials would need to have met all system requirements and constraints. Final selection of the reactor plant materials would not have occurred for several years due to radiation testing and other long term materials testing however, preliminary material selection would have been required in the near term to support conceptual design and proof of principal testing. Material development efforts would have been required for the outer pipe, insulation, and liner. 

One of the variants for creating a given axial/radial gradient of the refractive index involves simultaneous treatment of the polymeric sample surface by <-radiation, while a mask from a material absorbing radiation, for example, lead, is placed between the y-radiation source and the sample. Therewith, the axial/radial distribution of the mask thickness is selected so that the real distribution of radiation by length/radius of the sample corresponds to the experimentally found doses required to achieve the given axial/radial change of the refractive index. 

It was not intended to include valves and operators in a shielded volume or space other than the reactor shield. Again, prudent plant arrangement would be used to attempt to provide some shielding for the valves and reduce the service life levels. However, preliminary maximum values of 0.833 giga rad (1x10 rad) and 1x10 neutrons/cm over a 20 year service life were initially Identified for valve applications. Radiation levels of this magnitude would dictate material selections for construction of the valve and operator and mandate that operators and associated electronics be radiation hardened. 

Environmental Considerations for Instrumentation and Control. The significant effect radiation has upon many materials must be a central focus during the materials selection and testing phase of any future effort. 

Materials selected for thermal control must perform after exposure to long periods of radiation. 

ORNL/LTR/NR-PROM1/05-21, Radiation Transport Analyses to Support the Reactor Shield Materials Selection, Bucholz, J.A., et al., ORNL report, August 2005. 

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