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APPENDIX III 63
T A B L E XI ( c o a t . )
S ite C r it ic a l m a te r ia l C r it ic a l e x p osu re c a te g o r y E xp osed g rou p
M in istry o f D e f e n c e (N a v y D e p a rtm e n t)
C h a th a m R iver m u d /s ilt G a m m a d ose to w h o le b o d y G e n e r a l p u b lic (h o u seb o a t d w e lle rs)
F a sla ne M u d /s ilt G a m m a d ose to w h o le b o d y B oatyard w orkers
R osyth S ilt G a m m a d o se to w h o le b o d y D r e d g e rm e n
Liquid discharges from Dounreay contaminate a variety of
potential seafoods to a small fraction of the DWL, but the authorization
is largely based upon the activity that collects upon salmon
fisherm en's nets and the resultant dose to the hands of the fishermen
handling these nets. During 1969 very little fishing was carried
out, but monitoring of experimental nets in 1968 showed the average
dose to the hands of fewer than ten fishermen during the 1968 fishing
season to be about 70 mrem compared with a dose lim it of 3750
mrem allocated to the fishing season.
The critical group with respect to gaseous discharges is often
infants who drink cow s' milk and measurements of activity in milk
near Windscale indicate doses in 1969 not exceeding 30 mrem to
mineral bone due to 90Sr and 3 m rem to whole body due to 137Cs,
including the contribution due to fall-out. The critical group for
krypton releases from the reprocessing plant at Windscale com prises
the few mem bers of the population who live within about 1 km of the
plant. A conservative calculation shows the upper limit of exposure
of this critical population due to the 1970 UK power programme to
be 4 m rem /a (skindose), and of a larger population of a few thousand
within about 6 km to be 1-2 m rem /a (skin dose). Dose rates to
gonads are about 1% of these values.
Doses to m em bers of the general public due to burial of solid
waste at Drigg and Ulnes Walton are negligible because the substratum
is of clay and any water draining from the site runs into
non-potable water courses. The amounts of waste disposed of into
the Atlantic Deeps are too small to have an appreciable effect on
the environment.
The average dose rate due to 1®6Ru in the GI tract of the whole
group of 26 000 laverbread eaters, whose consumption was about 1 0%
of that of the critical group, was about 60 m rem /a during 1962-1967,