Radiochemical analysis of fission products in the Dragon reactor. Part I. Design and operation of the system. Project DRAGON

Technical Report · Thu Aug 15 04:00:00 EDT 1963

OSTI ID:4108065

Acciarri, P.; Mitchell, E. J.

One of the major objectives of the Dragon Reactor experiment is to study fission product control. This is important because, contrary to most other nuclear reactors, the fuel elements are not contained in a metal cladding. The initial concept of the fuel element was one in which fission products were emitted from the fuel. Their control was effected by passing a fraction of the coolant gas (the "purge stream") over the fuel inserts and into a fission product control system in which fission products would be adsorbed on active charcoal. Because of the very high activities, it was deemed necessary to somewhat delay the fission products within the fuel elements prior to entering the control system. The fuel inserts were therefore enclosed in low permeability graphite fuel boxes and in addition the purge stream was made to pass through an active charcoal bed incorporated into the bottom of each fuel element. By these means it was hoped to produce at least a one hour delay before the fission products entered the fission product control system. This particular concept has certain inherent disadvantages, and was therefore superseded - at least for the first Dragon fuel charge - by the introduction of coated particle fuel. The current object is to develop coated particle fuel capable of retaining all but a fraction of the order of 10^-6 of the gaseous fission products, to the stage where FIFA (Fissions per Initial Fissile Atom) burn-ups in excess of 100% can be attained. If this becomes possible, then there might be no need for a purge flow and the associated complex fission product control system in future reactors. However, the only realistic means of developing such fuel involves testing under operational conditions in the Dragon Reactor. To this end a programme to develop and define the limits of such fuels has been laid down. A vital part of this programme is the measurement of fission products released from fuel elements at various locations within the core. The measurement will be performed by gamma counting and gamma spectrometry of the purge flow. This method was chosen because of its simplicity and adaptability for remote control and because the feasibility of the principles has already been demonstrated in the Pluto Loop. (See Part 2 of this report.) In this report a description of the methods chosen and the equipment used is given. The importance of flexibility has been emphasised, since it is appreciated that certain components cannot be optimised until operational experience has been obtained. It will be shown that the proposed system is capable of recording the activities of certain isotopes of krypton and xenon within the range 10^-2 to 10^-6 fractional fission product release with the assumption of no delay in the fuel. With one hour delay in the fuel the system will record in the order of 100% release of these gaseous isotopes. The system has been designed such as to allow the introduction of new or modified apparatus if this should subsequently be found desirable.

• Research Organization: Atomic Energy Establishment (AEE), Winfrith, England (United Kingdom)
• Sponsoring Organization: Atomic Energy Establishment (AEE)
• NSA Number: NSA-24-041021
• OSTI ID: 4108065
• Report Number(s): DP-Report--207(Pt.1)
• Country of Publication: United Kingdom
• Language: English

Related Subjects

DETERMINATION
DRAGON
FISSION PRODUCTS
FISSION PRODUCTS/release from Dragon fuel elements
measurement by $gamma$ counting and $gamma$ spectrometry
FUEL ELEMENTS
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GAMMA SPECTROMETERS
HIGH-TEMPERATURE GAS- COOLED REACTOR EXPERIMENT/fission product release from core of
$gamma$ counting and $gamma$ spectrometric measurement of
KRYPTON ISOTOPES
KRYPTON ISOTOPES/release from Dragon fuel elements
measurement by $gamma$ counting and $gamma$ spectrometry
N38160* --Power Reactor Development--Auxiliary & Emergency Systems
REACTORS
XENON ISOTOPES
XENON ISOTOPES/release from Dragon fuel elements
measurement by $gamma$ counting and $gamma$ spectrometry