I'm afraid there's no way to get "normal" negatives from Tech Pan at EI 100+ -- regardless of the developer used. It's very tricky The best you can do for film already exposed is get microfilm-like high contrast with a document film developer like Technidol. If you use a low contrast developer like H&W Control (recipe to mix your own is readily available), SPUR, or one of the low contrast Caffenol derivatives, you'll get anywhere from EI 25 to EI 40 or so, which is a minimum of about two stops underexposed.
The best I can recommend is to use either a Rodinal derivative at 1:100 (sorry, don't have a time for this one, but for this EI I'd start at 30 minutes) or Caffenol LC+C (formula below) and increase development time by 50% to try to push the contrast enough to get usable mid-tones without going into document film contrast where there are no midtones.
Caffenol LC+C (speed enhancing low contrast microfilm developer)
8 oz Water
4 tsp (level) Arm & Hammer Washing Soda
.26 g (4 grain) Ascorbic acid or erythorbic acid (supplement or technical, 97%)
2 tsp (slightly rounded) Folger's Coffee Crystals
Mix 1/4 tsp (1 g) ascorbic acid powder in one quart water, and use 8 ounces for the developer, if you don't have a scale that will read low enough. Use with microfilms to give increased speed with pictorial contrast. No detectable stain.
Film (EI) Time (at 20° C) Agitation Interval
Copex Rapid (64, pictorial) 15 3 min
ADOX CMS 20 (EI 20, pictorial) 15 3 min
This developer, at this time, should give EI 25-32 for Tech Pan (I've never shot that film, so this is an educated guess). I'd increase development to 22-25 minutes, still agitating with five inversions every third minute, to try to push that enough to get EI 100 -- that should at least get images. There will be no shadow detail, and the highlights may run too dense to print or scan -- but it may be the best you can do for Tech Pan already shot at EI 100.