The problem of joining the International Thermonuclear Experimental Reactor (ITER) vacuum vessel (VV) sectors, considering the tolerance requirements of the blanket attachments, and the time required for TIG welding, continues to stimulate EU R&D into power beam welding techniques which can yield fewer passes, less welding time and lower distortion. The previous work on reduced pressure e-beam welding showed that penetration varied with position, fit-up, distance and pressure and single-pass weld control was deemed to be not reliable enough so the work direction changed to an all-e-beam welding procedure where the root weld is carried out with rest-current-control and the fill passes by wire-fill. In addition, a novel method of increasing the possible single-pass weld thickness for overhead positions is investigated demonstrated and now patented. Another solution may be offered with wire-fill NdYAG laser welding, which has demonstrated useable and stable results and proved improved performance over TIG. Preliminary work has shown even further advantages with the introduction of hybrid MIG/Laser welding.

The ITER modules are connected to the vacuum vessel wall mechanically, electrically and hydraulically in a way suitable for remote handling with access from the frontside only. In order to validate the design and operation of the attachment systems for the 1998 ITER design, EFDA directed three Associations (ENEA, Brasimone, (ÖAW Seibersdorf and CEA, Arceuil) in tasks including process investigations and the design, procurement and testing of three ITER-representative mock-ups. ENEA, Brasimone procured and provides the site for the largest rig, the Blanket Module Carrier, which provides 6-axis movements of a 4 ton module mock-up to simulate the mounting of a typical ITER module to a vertical wall. ÖAW Seibersdorf designed an ITER remote-handling-compatible, water-hydraulically-operated bolting tool, which ENEA, Brasimone procured and used in a test programme. CEA, Arceuil developed and tested a special bore tool using a NdYAG laser for cutting and welding the hydraulic connectors. The overall programme demonstrated the concept viability and highlighted problem areas of the assembly procedure of the blanket module-to-wall attachment. Aspects of the work still require further attention to refine and finally validate the techniques especially with regard to the ITER-FEAT design.

The effects of age, dam age, type of birth and rearing on weaning weight, clean fleece weight, hogget weight, fibre diameter and yield were estimated for 751 Corriedale rams aged 16-19 months, over three years. Twin born and reared rams were 20% lighter at weaning and 4% at hogget weighing than singles and cut 4% less wool. All characters except yield increased with the age of the ram, the effect being greatest for weaning weight with a regression coefficient of 0.17 kilogram per day of age. Of particular interest was fibre diameter, which increased with age; the regression coefficient was 0.026 pm per day of age. Clean fleece weight also increased with age; the regression coefficient was 0.0061 kilogram per day of age. The phenotypic correlation between clean fleece weight and fibre diameter was very high (0.45), other correlations were within previously published estimates. The relation between eight qualitative characters (head type, face cover, back cover, belly cover, wool quality, standard of feet, body size and classer grade) and three productive characters (clean fleece weight, weaning weight and hogget weight) was studied. Clean fleece weight was not correlated with face cover but was negatively correlated with belly cover (-0.30) and positively correlated with classer grade (0.41).

ABSTRACTProgeny of younger dams grow more slowly than those of older dams. When the environmental effects of dam age are not allowed for in selection for growth rate, selection differentials and genetic responses to selection are reduced.In a model herd, with cows aged 2 to 8 years, it was found that neglecting the dam age effects reduced genetic gains by about 15% when selection is for weaning weight, and by 11 to 7 % when selection is at an age of 12 to 20 months. Much of the reduction occurs because of the selection of higher proportions from genetically inferior groups.If genetic differences among dam age groups are small the reduction is only 7% at weaning and less at older ages. The effect of ignoring calf age was also estimated. It was found that if calves born within a period of 33 days were compared and calf age was neglected, the response to selection for weaning weight would be reduced by about 6%.

Returns on investments in open or closed nucleus breeding schemes to improve clean wool production were examined using Hill's approach of examining the flow of genes through the population.

Individual selection on the basis of adjusted yearling weight records (policy 1) was compared with selection of proven sires based on progeny test results ('progeny test selection'). The major assumptions in the comparisons were that herd sizes were 100 recorded cows, and that each herd used four joining groups. It was assumed that 25 herds cooperated in using two reference sires in artificial breeding to link progeny test data from young bulls in natural service, thereby increasing selection intensity without the loss in accuracy normally suffered in a single multi-sired herd. In the progeny test comparisons, preselection of young bulls for progeny testing (policy 2) was also compared with random selection among young bulls for progeny testing (policy 3). This paper contains a limited number of comparisons only, in order to indicate the possible extent of selection pressure with different policies. Comparisons in terms of annual genetic progress ranked the policies in the order 2 (greatest), 1, 3, with policy 2 being better than 3 by 90-110%. The advantage of policy 2 over policy 1 was 26-38%. In all cases, using bulls first as yearlings was preferable to 2 1/4 years in terms of annual genetic gain. With individual selection, keeping bulls for 1 year compared with 2 or 3 years had little effect on annual gain, as the rise in selection intensity balanced the rise in generation interval. Inbreeding change per year was more affected, lower rates resulting from bulls being used for 1 year only. Inbreeding rates were small with progeny test selection as described here, as long as proven sons came from young bulls as well as proven sires. The effect of selection intensity under progeny test selection with preselection becomes diluted to 25% in its contribution to annual genetic change. Thus some degree of assortative mating may be useful, or wider use of proven sires relative to young sires. With preselection the break-even number of cooperating progeny test herds was low (three herds), compared with equal rates of genetic gain from individual selection.

A computer model was used to investigate the costs and returns from selecting pigs on growth rate and backfat thickness. The cases considered were (1) a closed herd with all parents selected from within the herd; and (2) a base herd where only females were homebred.

Records of post-weaning growth for 1134 heifers and 375 bulls from 11 Victorian beef cattle herds were analysed for the effects of sex, age of dam, age of calf, season of birth and herd/year on postweaning gain (PWG) and yearling weight (YLG WT). Age of dam had a significant effect on PWG and YLG WT for each sex, but the effect on heifer PWG was small. Suitable corrections for the effect of age of dam on heifer YLG WT were made using weaning weight adjusted for age of dam effects plus gain from weaning to yearling. Post-weaning management of young bulls and heifers was very different. Averaged over all herd/years, bulls were 37.5 per cent heavier than heifers at yearling age and grew 57.5 per cent faster between the two post-weaning dates, The environmental effects on PWG and YLG WT were therefore different for each sex. The effects of calf age and season were significant for each dependent variable except YLG WT for bulls and PWG for bulls respectively. The interaction between calf age and season was significant for heifers only.