Irradiation simulation techniques

Irradiation simulation techniques for the study of reactor pressure vessel (RPV) embrittlement... 

The effect of ionising radiation is described in Section 4.2. Most often, accelerated tests are carried out using gamma radiation from an isotope source or an electron beam from an accelerator. Radiation from nuclear reactors can also be used but will be a mixed radiation which may or may not be suitable for the simulation. The penetration of an electron beam is inherently limited which means that only relatively thin samples can be treated. Hence, gamma irradiation is the more versatile technique. With thin samples, such that penetration limits are not a problem, there are conversion factors to approximately equate the various radiations and energies to an equivalent gamma dose. 

Ion beams are useful to simulate the environment in space, where semiconductor devices are exposed to high-energy heavy-ion impact. Incorrect operation of semiconductor devices such as single-event upset results from the heavy-ion irradiation. The cocktail ion families of MjQ = 4 and 5, available at the JAERI AVF cyclotron facility [24], are frequently utilized to investigate the tolerance of the semiconductor devices to the radiation, and to survey highly radiation-tolerant semiconductor devices appearing in the market. Efficiency of the radiation-tolerance testing for thousands of kinds of semiconductor devices has been totally improved by the cocktail acceleration technique. 

The experimental technique devised in this work is based on a NAA method. Neutron irradiation of solid waste forms of simulated HLW (see Table II) produces activation of the elements in the sample. The activation products can be readily measured before and after leaching by radiochemical and/or instrumental techniques. In order to be useful for these purposes, the activation product must have a sufficiently energetic and abundant radiation (either 6 or y) to be easily detected, as well as a sufficiently long half-life several days or more) to be useful for relatively... 

Instrumental Techniques. Ion beam irradiation of samples was performed by focusing 2.1 MeV He2+ ions, using an Ionex Tandetron accelerator, to a spot size of approximately 4 mm2. Ion beam currents were held constant at 10 nA. Radiation effects were determined by varying the total charge on the sample between 0 and 20 pC. RBS spectra were collected with the samples at an angle of 45° with respect to the incident beam additional instrumental details can be found elsewhere (20). Spectral simulations were performed using the RUMP method designed by Doolittle (21). 

Figure 12.2 SOFeX depth profiles of biomass (PN)-specific NO/ uptake rates, determined during 24-h incubations in Plexiglas acrylic incubators under simulated in-situ light and temperature conditions. Ultra-clean trace-metal techniques were used for sample collection within and outside (control waters) of the Fe-enriched patch north and south of the Antarctic Polar Front zone. The/-values [f = Fn03/(1 n03 + 1 nH4 + F n02 + F Urea)] were determined at the isolume depths of 47 and 16% surface irradiance, using tracer-level isotopic enrichments, and are not corrected for the effects of isotopic dilution. Error bars represent the range of duplicate samples (n = 2). Corrected from Coale et al. (2004).

ISO 9370 (Table 5.1) contains valuable information and recommendations on important characteristics for the instruments used and provides a guide for selection and use as well as calibration procedures of these radiometers. The guide includes natural and simulated exposure testing. Instrumental techniques include the continuous measurement of irradiance in specific wavelength bands and the accumulation (or integration) of instantaneous data to provide a total radiant exposure (dosage). 

Chemical durability. Leaching studies on synthetic monazite containing 20 wt % simulated Savannah River waste (MCC-1 leach test, 28 days at 90°C) showed release rates of uranium to be on the order of 0.001 g/m d (Sales et al. 1983). The leach rate of the host matrix of a synthetic monazite, LaP04, containing simulated waste remained low even after the material had been transformed to an amorphous state by irradiation with 250 keV Bi ions (Sales et al. 1983). Perhaps, the most interesting aspect of the work by Sales et al. (1983) was the variety of techniques used to measure the leach rate. In addition to the standard MCC-1 leach test, they also used changes in the ionic... 

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