I assume your flag means 'our AF' is the USAF . Actually the RB-45 units deeply penetrating the Soviet Union were RAF.Interestingly, our AF regularly flew recon missions over the USSR in B45s until the Mig 15 became operational and then the B47 took over that mission. There were some hairy moments between the B47s and Mig 15s but, as I recall, no B47s were ever downed.
One USAF RB-45 was downed, the only one lost in combat, by Soviet MiG-15's over North Korea, December 4 1950, the first verifiable 'jet kill' by MiG-15's (several earlier claims against US jet fighters are not reflected in US records), and first jet fighter to down a jet bomber, bomber-type anyway.
At least 3 RB-47's were downed during the Cold War, two by MiG's and one by SAM's.
This is a decent list of incidents on the web
Intrusions, Overflights, Shootdowns and Defections During the Cold War and Thereafter
Two books are "Spyflights of the Cold War" by Lashmar and "By any Means Necessary" by Burrows.
Note most of those incidents happened on the peripheries of the USSR, flights not really intended to violate Soviet air space, or only marginally, sometimes accidentally. Many of the a/c intercepted were in intl airspace as the US claimed at the time. The British effort (with US cooperation) was in contrast to fly deep into the Soviet Union, as were of course the U-2 flights later.
Joe