After a year of experiments and different methods I have now found a development method I am so satisfied with I won’t try to improve it. So I will write it down here, for safekeeping.
Expose with 1 stop over per decade of expiration. So if it expired in 1998, that is two stops extra.
Svema CO32 is ISO32, so by this rule of thumb you should aim for something around ISO8. I shot a roll of 16mm at ISO12 and it turned out fine too, but you can probably reduce development time with a minute if you do ISO8.
I developed in D76 stock, D76 1+1 and HC110. All turned out fine.
With D76 stock I did 13 minutes in 24c. I think results are better at 24c than 20c. Just reduce development time accordingly. I also added 5ml of Benzotriazole (BZT) 1% in 500ml, that is 1 part per 100 should be BZT 1%. You can probably increase this, and prolong development time accordingly. BZT is a restrainer that helps with the base fog.
After this, fix for normal times for your fixer, and here now comes the trick. After fix, bleach the negs in Povidone-iodine (PVP-I). This is the orange stuff they use in hospitals to clean cuts. You can get it in stronger version and larger bottles from veterinary supply stores. You want at least 5%, anything less and you will not bleach it in a reasonable amount of time.
Let the negs sit in the PVP-I for at least 12 minutes. I found that after this you get benefits but diminishing returns.
Now fix the negs again, for your normal amount of time.
Wash, dry, and we are done.
For 35mm this is totally not worth it. If you want to experiment with russian film, get something that was black and white to begin with. However, there is a good supply of expired 16mm films out there in the old Soviet bloc, and this can be a cheap and cool way to do some cine stuff.
I also tried to bleach with citric acid, without results.
I tried to bleach before dev, and got blank negs.
I tried weaker bleach, shorter times, no difference.
Without the BZT the base fog was greater.