Pebble-bed fuel

Similar to Helium-Cooled Reactors Prismatic or Pebble-Bed Fuel)... 

Pebble-Bed-Fuel Liquid-Salt-Cooled High-Temperature Reactors... 

The Pacific North-West National Laboratory (PNNL) of the USA develops the concept of a small light water reactor with coated particle based pebble bed fuel directly cooled by lateral flow of light water coolant this reactor, which has a long core lifetime and is refuelled without opening the reactor vessel cover, is tentatively named the Atoms for Peace Reactor (AFPR). 

BRINKMANN, H.U., DUWE, R., GANSER, B., MEHNER A.-W., REBMANN, A., Contributions towards the development of a packaging concept for the final disposal of spent HTGR pebble bed fuel". Nuclear Engineering and Design 118 (1900) 107- 113. 

Molten salt cooled small reactor with pebble-bed fuel MARS (RRC Kurchatov... 

Non-conventional designs CHTR, ELENA, Pebble-bed fuel molten salt coolant fixed bed reactor MARS... 

Small PWRs FBNR - fixed bed modular PWR one of fuel options considered is a pebble bed fuel... 

Reactor styie Pebble bed fuel Prismatic core pin-in-block fuel... 

Reactor style Pebble bed fuel Pebble bed fuel... 

HTGRs with pebble bed fuel and continuous refuelling (PBMR, HTR-PM) provide a relatively small reactivity margin for fuel bum-up (Level 1 in Table 4), resulting in the reactor capacity to survive, without core damage, an unprotected transient overpower caused by the ejection of a control rod. 

The GT-MHR shares certain technologies and design approaches with other prismatic block or pebble bed fuel high temperature gas cooled reactor designs described in this report, e.g. GTHTR300 (Japan), PBMR-AOO (South Africa), HTR-PM (China), etc. 

Reactor type Pebble bed fuel helium coolant graphite moderator... 

SiHcon carbide s relatively low neutron cross section and good resistance to radiation damage make it useful in some of its new forms in nuclear reactors (qv). SiHcon carbide temperature-sensing devices and stmctural shapes fabricated from the new dense types are expected to have increased stabiHty. SiHcon carbide coatings (qv) may be appHed to nuclear fuel elements, especially those of pebble-bed reactors, or siHcon carbide may be incorporated as a matrix in these elements (153,154). 

The Arbeitsgemeinschaft Versuchsreaktor (AVR) and Thorium High-Temperature Reactor (THTR-300) were both helium-cooled reactors of the pebble-bed design [29,42,43]. The major design parameters of the AVR and THTR are shown in Table 10. Construction started on the AVR in 1961 and full power operation at 15MW(e) commenced in May 1967. The core of the AVR consisted of approximately 100,000 spherical pebble type fuel elements (see Section 5). The pebble bed was surrounded by a cylindrical graphite reflector and structural carbon... 

Fig. 14. HTGR fuel elements (a) prismatic core HTGR fuel element (b) cross section of a spherical fuel element for the pebble bed HTGR. Reprinted from [88], 1977 Ameriean Nuelear Soeiety, La Grange Park, Illinois.

Alternative reactor types are possible for the VHTR. China s HTR-10 [35] and South Africa s pebble bed modular reactor (PBMR) [41] adopted major elements of pebble bed reactor design including fuel element from the past German experience. The fuel cycles might be thorium- or plutonium-based or potentially use mixed oxide (MOX) fuel. 

In terms of safety, two issues are regularly debated. First, the issue of nuclear waste and, second, concerns over potential terrorist attacks on nuclear power plants. The first objection may be overcome through the introduction of new types of power plants, such as the pebble-bed modular reactor.This type of reactor uses graphite balls flecked with tiny amounts of uranium, rather than conventional fuel rods. With the fuel encased in graphite and impermeable silicon carbide, the theory is that the waste should be relatively easy to dispose of.The terrorism fears are less easily addressed and may ultimately stall the construction of new plants in countries such as the U.S., where these worries are greatest. 

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