Two studies [40, 62] considered a nuclear-laser device that operates in pulsed — periodic mode with a 1 Hz frequency and a pulse duration of about 1 ms (Fig. 11.11). The schematic (Fig. 11.12) shows the photon path from its origin in the NOC to its absorption in the laser material. The gas medium is excited in the NOC by fission fragments escaping from the fissile material: uranium aerosol particles of several microns in diameter. Luminescent photons reflected by particles from the fissile material and NOC walls pass through the window and are then transmitted to the active laser medium using a light-conducting tube. The laser medium is manufactured as a plate and is a so-called “active mirror” (see, for example, [63]). A design analysis [40] of different configurations for the “con­tainer-tube” shows that the extraction efficiency of the light radiation from the NOC container and its transport to the laser medium may reach 70-80 %.

Amplifier based on an adaptive mirror

Fig. 11.12 Schematic of the transmission of luminescent radiation from the NOC container to the laser medium [40]

The reactor core consists of two parts which contain a mixture of aerosol uranium fuel (2-5 qm UO2 particles) and a luminescent gas medium. Between the parts of the core, there are three disks that contain 235U, 10B, and Be and rotate at different frequencies. These disks, which are modulators of the core reactivity, are used to realize the pulsed operation mode of the reactor. We note that a similar method for obtaining periodic bursts of fissions using external reactivity modula­tion is used in IBR-type pulsed reactors [64]. The parameters of the proposed reactor in studies [40, 62] are: core volume 2.3 m3; uranium load 0.5 g/cm3; pulse repetition frequency 1 Hz; average power 400 kW (170 W/cm3); and the peak neutron flux density 2 x 1016 cm-2 s-1.

Using light-conducting tubes, the luminescent radiation from the two parts of the reactor core is withdrawn beyond the biological shielding. Two flat mosaic blocks of laser elements are installed at the ends of the light-conducting tubes. Each of
these blocks consists of tens of “active mirrors” manufactured from 0.5 cm thick GSGG:Cr3+:Nd3+ crystals up to 20 cm in diameter. The suggested luminescent media is a gas mixture based on excimer alkali molecules with an assumed conversion efficiency of 30 %. Under these conditions, the estimated peak power of the laser radiation is 12 MW (average power is 12 kW) with a 3 % total conversion efficiency of the nuclear energy released in the reactor core into laser radiation.