Efficiency of generation of optical centers in KS-4V and KU-1 quartz glasses at neutron and gamma irradiation

Room temperature post-irradiation measurements of diffuse reflectance and electron paramagnetic resonance spectroscopies were made to characterize the long-lived radiation-induced species formed from the gamma irradiation of solid KCl, MgCl2, and ZnCl2 salts up to 100 kGy. The method used showed results consistent with those reported for electron and gamma irradiation of KCl in single crystals. Thermal bleaching of irradiated KCl demonstrated accelerated disaggregation of defect clusters above 400 K, due to decomposition of Cl3−. The defects formed in irradiated MgCl2 comprised a mixture of Cl3−, F-centers, and Mg+ associated as M-centers. Further, Mg metal cluster formation was also observed at 100 kGy, in addition to accelerated destruction of F-centers above 20 kGy. Irradiated ZnCl2 afforded the formation of Cl2− due to its high ionization potential and crystalline structure, which decreases recombination. The presence of aggregates in all cases indicates the high diffusion of radicals and the predominance of secondary processes at 295 K. Thermal bleaching studies showed that chloride aggregates’ stability increases with the ionization potential of the cation present. The characterization of long-lived radiolytic transients of pure salts provides important information for the understanding of complex salt mixtures under the action of gamma radiation.

Gamma radiation-induced defects in KCl, MgCl2, and ZnCl2 salts at room temperature.

Influence of electron irradiation on the band gap and microhardness of TlInS
 2
 , TlInSSe and TlIn
 0.99
 Cr
 0.01
 S
 2
 single crystals

The neutron fluxes and the intensity of γ radiation are measured in 26 channels of a WR-SM reactor and its thermal column. The fast neutron fluxes in the channels are determined using Ni, Fe, Co, Au, and Mn element monitors with different threshold energies, together with a theoretical calculation using the MCNP-4C program. The energy distribution of the neutron flux inside the fuel assembly is obtained for selected channels around the core. The flux of neutrons with energies >1 MeV is in the range (0.5-43).10 12 cm -2 sec -1 , depending on the location of the channel. A linear correlation is discovered between the induced optical absorption at the 215 nm line (E' center) of SiO 2 -BaO glass and the fast neutron flux in the channels. The γ-ray intensity in the thermal channel is estimated for the reactor during operation (∼38.4 Gy/sec) and 24 hours after it is shut down (∼24. 7 Gy/sec ) using the E' centers induced in pure quartz glasses. The observed difference in the efficiency with which oxygen defects are formed during dry and wet irradiation of glass owing to the radiolysis of water must be taken into account when developing radiation technology and during the burial of radioactive waste.

Determination of the neutron flux and γ radiation in the core of operating and shut-down reactors using quartz glasses and element monitors

Nanostructures formed in pure quartz glass under irradiation in the reactor core

The absorption spectra, photoluminescence spectra, and microhardness of LiF crystals exposed to gamma radiation from a shutdown reactor and a 60Co source at a dose rate of 7.65 Gy/s are investigated. The structure of these crystals is determined using x-ray diffraction analysis. It is revealed that the Li sublattice contains not only point and complex radiation-induced defects but also 28-nm LiOH particles induced by gamma radiation. It is shown that the formation of defects occurs more efficiently upon exposure to radiation from a shutdown reactor than from a 60Co source.

Formation of nanodefects in LiF crystals under gamma irradiation

The characteristics of quartz glass for separate dosimetry of γ radiation from a VVR-SM reactor in the presence and absence of neutron fluxes are investigated. Comparing the absorption and photoluminescence spectra of samples irradiated with γ rays from a stopped reactor and mixed with neutron and γ radiation from an operating reactor shows that in both cases oxygen defects are produced and the dose dependences are linear. The dosimetric bands are stable with respect to light and temperatures up to 400°C. The stationary γ-ray flux from the reactor, after the reactor is stopped, is calibrated according to a known source of γ-ray source 60Co and is ≈15 Gy/sec.

Reactor radiation dosimetry using fused quartz

The microhardness and photoluminescence spectra excited with 337-nm laser radiation in commercial SiO2 glasses (UV windows, substrates with BaTiO3 film coatings) exposed to 60Co gamma radiation and a mixed neutron flux from the reactor are investigated. It is revealed that initial samples contain nanocrystalline phases. An increase in the microhardness and the intensity of the excitonic UV luminescence due to 60Co gamma irradiation and the quenching of the photoluminescence associated with the nonbridging oxygen centers result from healing of Si-O dangling bonds and microcracks in the surface layer at the nanocrystal-glass matrix and substrate-coating interfaces. It is demonstrated that reactor irradiation leads to the phase transformation of SiO2 cristobalite into tridymite and BaO into BO2, as well as to the decomposition of BaTiO3 and BaCO3. This brings about a decrease in the microhardness and photoluminescence quenching.

The influence of irradiation on the microhardness and photoluminescence of SiO2

The absorption and photoluminescence of LiF crystals, irradiated by γ radiation from a stopped reactor and a wet repository, are studied and compared with the corresponding spectra obtained by irradiation with 60Co γ rays with known power. The contribution of neutron and γ radiation of the reactor to the formation of point and complex radiation defects is determined. The dose dependences of the optical bands are used to determine the intensity of the γ radiation from the reactor and the repository.

Determination of γ-ray flux in a stopped vvr-sm reactor from the color-center formation in LiF

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