D2O, moderator

Inventory of D2O moderator in reactor core = 7.72 X 10 g Average thermal-neutron flux in moderator = 1.01 X 10 n/(cm -s)... 

From tbe above data it is shown that a minimum criti cal mass can be as low as about 200 grams of 94 39 and be capable of sustaining a reaction in a D2O moderator unity. The fissionable isotope density in the liquid has infinite DjO reflector. Not less than about 300... 

M. C. Edlund and L. C. Noderer, An harmonics method applied to D2O moderated reactors, ORNL-54-3-120 (1954). 

The calculated values of the By activation thermal disadvantage factor are si 2% highsr than the measured values for both the light- and heavy-water lattices. The calculated values of p , the ratio of epi- to subcadmium captures in 111, are in fairly good agreement with the measurements. The calculations of 6 , the ratio of the fissions in h to those in U, do not agree well with the three values that were measured in the D2O moderator. 

I sent experiments, critical D2O moderator and lattice parameters (6, p, and 6 )... 

As a member of the CANDU family, the CANDU 300 design closely follows that of the larger CANDU 600 and CANDU 950 nuclear power plants and is is illustrated in Figure A key CANDU features include a pressure tube reactor, heavy water (D2O) moderator, natural uranium fuel, and on-power refuelling. 

A thermal heterogeneous reactor, fuelled with enriched uranium. D2O moderated and cooled, D2O and partial graphite reflectors. 

An array of so-called moderator displacement or Interlattice tubes located between the pressure tubes within the calandrla were provided. These tubes could be emptied if necessary to bring an excessively positive void coefficient into the desired range. An excessively negative void coefficient could be corrected by increasing the H2O impurity in the D2O moderator. In the event, the calculations of void coefficients have proved to be very accurate and it has not been necessary to resort to either of these measures. Interlattice... 

Similar tests with the H2O coolant and D2O moderator raised to full operating temperatures (280°C and 65°C respectively) by electrical heat gave... 

The Niederaichbach nuclear plant Is a prototype of a COg cooled, D2O moderated pressure tube reactor, with an output of 100 MWe (refs 6). If construction proceeds according to schedule the plant will be commissioned in 1970. A noteworthy feature of this reactor Is the high coolant temperature of 550°C at the reactor outlet, requiring, of course, steel as canning material for the fuel. 

Because of inherent technical characteristics, D2O moderation, and distributed channels with flexible fueling, HWRs have a great deal of fuel cycle flexibility, and this has been the subject of significant research and development by AECL and others. The combination of relatively high neutron efficiency (provided by heavy water moderation and careful selection of core materials), online fueling capability, and simple fuel bundle design mean that HWR reactors can use not only natural and enriched uranium, but also a wide variety of other fuels. These include ... 

With a uranium enrichment plant not yet available, the Soviets focused on designing reactor types that could be fueled with natural uranium. These included heavy water (D2O) moderated combined with gas cooling, graphite moderated and water cooled, and finally graphite moderated and gas cooled reactors. 

H2O or D2O moderator ing plant Elimination of D2O requirement (H2O moderator) Low fissile-material inventory (D2O moderator) enriched uranium with no regeneration) compared to homogeneous breeders and converters... 

In summary, it would appear that Pu could be obtained from material available early in the nuclear fuel cycle. Both graphite and heavy water seem viable as moderator materials. When considered simply in terms of production rate versus uranium investment, the D2O-moderated system would seem to be more efficient, although its design contains more complexities from the neutronic perspective. Graphite, on the other hand, may be more... 

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