The SGHWR

Table 6.2 makes a direct comparison of some design features. Here the SGHWR and PFR figures are for the actual prototypes with indication of proposed operating improvements. 

Only the SGHWR and RBMK under comparison have a direct cycle of light water coolant to the turbine and therefore the admission of somewhat radioactive steam. Both of these types have additional circulation... 

The UKAEA reactors are not formally licensed by the Nil, although they are required to maintain a standard of safety equivalent to that of licensed sites. Dr Peckover of SRD explained how SRD monitored the safety of operations and reported independently to the Chairman of the Authority on this. Nevertheless, as for all industrial plant in the UK, the responsibility for safety lay with the line management on the site concerned. A convenient table contrasting important characteristics of the SGHWR and the Chernobyl... 

Although the results obtained in full-system decontaminations at Candu plants as well as at the SGHWR reactor proved to be encouraging, there are sufficient... 

The greater part of this conference is to be devoted to the SGHWR. Delegates will... 

J>. I now take great pleasure in wishing this conference well and in expressing the hope that you all have a controversial and profitable round of discussions in the course of the next few days. I myself believe that the SGHWR will find its own place as a supplier of electric power both, in the United Kingdom and around the world. 

The origins of the SGHWR system can be traced back to the middle of 1957 when the Initial design study of the advanced gas cooled reactor (AGR) was reviewed within the UKAEA. It was decided that, while all promised well, It would only be prudent to have some alternative advanced thermal reactor system under study. Accordingly, the features of a power reactor were broken down Into five main headings - fuel, cladding, coolant, moderator and form of construction. The solutions selected for the AGR were considered and possible alternatives put down which could be evaluated for this, so far, unidentified new system. 

As indicated, this work involved the efforts of a number of establishments within the Authority and culminated in a proposal to build a 100 MWe prototype of the SGHWR system at Wlnfrlth. Construction of this reactor started in May, I963 as already noted, and it successfully achieved full power in January of this year. 

The subsequent papers presented to this symposium describe the development programme the UKAEA has mounted to back the SGHWR system, the design and operating experience of the Wlnfrlth SGHWR and the Authority s proposals for fully commercial stations. We believe this reactor system will prove to be a very attractive one to electricity utilities both at home and abroad. 

The SGHWR fuel elements operate In a boiling H2O environment and are contained in circular pressure tubes. Compatibility considerations led to the early selection of UOp as the fuel material, a decision that has never been seriously challenged except In the context of a natural feed reactor. 

As a compromise between total can strain and gas release, fuel pins have been designed to permit some interference between UO2 pellets and can at peak rating positions at full power. The SGHWR reference fuel design limit is 0.5/ for... 

Fuel pellet details for the SGHWR reference design... 

The main fuel pin Irradiation experiments In the SGHWR fuel development have been in the X-6 loop in the NRX reactor at Chalk River. These experiments are summarized in Table 5. Apart from length,... 

I would therefore like to know If It Is possible to repair defects In the thermal shield In the SGHWR concept. 

One major advantage claimed for the SGHWR reactor is its suitability for load following. This would, of course, involve a considerable amount of power cycling in the fuel elements. Could the Author say how much data are available on this point, and what is the maxiimam member and amplitude of the cycles which have been withstood by fuel under irradiation ... 

In the early days of the SGHWR project it was realized that the nuclear performance of the reactor would be dominated by the choice of lattice parameters. Since the parasitic absorption present in the structural materials tends to be fixed by asking the mechanical designer to minimize his requirements, the nuclear designer has essentially three main parameters at his disposal ... 

The SGHWR project has been able to make use of the extensive experience of oxide fuel irradiation behaviour obtained in the course of the AGR programme. This experience has been correlated into the SUPATRICE code which follows the life history of a fuel pin subjected to a specified irradiation history. Fuel temperatures, fission gas pressures and clad strains are calculated through life. 

The basic dynamic properties of the SGHWR system are discussed first in terms of possible control actions, followed by the practical requirements for normal regulation and protection against fault conditions. 

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