Let's say a double-dipper gets $10 K per year in a 401k LANS match. Note that these double-dippers don't present an imminent pension cost threat to LANS since they are already on UCRP. However, if they get laid off it will cause an immediate lump-sum severence payout of around $80k and that will hit this year's budget. If LANS lays off a non-UCRP worker with many years of service, they'll be looking at both high severance costs and an immediate hit to the pension fund if the worker start pulling on TCP1 (which seems likely given the poor state of real estate in Los Alamos).
From LANS' fiscal point of view, it would be far cheaper and more cost effective if they went after the young'ins. Salary compression at LANL only serves to strengthen this motive. I would be especially worried if I was a newbie staffer who is non-vested with less than 5 years of service at LANL.
I know this may come as a shock to some people, but LIFO is exactly what I would be expecting LANS to implement if they are looking at the RIF in a cold hearted 'dollars-only' manner.
If you're young or a recently hired worker, then you have good cause to be worried about this RIF.