More interesting was this paper I found. It speaks of MRR's (or PNE peaceful nuclear explosions) and how and why they release tritium as a "nuisance". The paper is extremely long but this section was interesting:
here is the link but the MRR piece is below:
nuclearweaponarchive.org/Nwfaq/Nfaq4-5.html4.5.4 Minimum Residual Radiation (MRR or "Clean") Designs
It has been pointed out elsewhere in this FAQ that ordinary fission-fusion- fission bombs (nominally 50% fission yield) are so dirty that they merit consideration as radiological weapons. Simply using a non-fissile tamper to reduce the fission yield to 5% or so helps considerably, but certainly does not result in an especially clean weapon by itself. If minimization of fallout and other sources of residual radiation is desired then considerably more effort needs to be put into design.
Minimum residual radiation designs are especially important for "peaceful nuclear explosions" (PNEs). If a nuclear explosive is to be useful for any civilian purpose, all sources of residual radiation must be reduced to the absolute lowest levels technologically possible. This means elimination neutron activation of bomb components, of materials outside the bomb, and reducing the fissile content to the smallest possible level. It may also be desirable to minimize the use of relatively hazardous materials like plutonium.
The problems of minimizing fissile yield and eliminating neutron activation are the most important. Clearly any MRR, even a small one, must be primarily a fusion device. The "clean" devices tested in the fifties and early sixties were primarily high yield strategic three-stage systems. For most uses (even military ones) these weapons are not suitable. Developing smaller yields with a low fissile content requires considerable design sophistication - small light primaries so that the low yields still produce useful radiation fluxes and high-burnup secondary designs to give a good fusion output.
Minimizing neutron activation form the abundant fusion neutrons is a serious problem since many materials inside and outside the bomb can produce hazardous activation products. The best way of avoiding this is too prevent the neutrons from getting far from the secondary. This requires using an efficient clean neutron absorber, i.e. boron-10. Ideally this should be incorporated directly into the fuel or as a lining of the fuel capsule to prevent activation of the tamper. Boron shielding of the bomb case, and the primary may be useful also.
It may be feasible to eliminate the fissile spark plug of a MRR secondary by using a centrally located deuterium-tritium spark plug similar to the way ICF capsules are ignited. Fusion bombs unavoidably produce tritium as a by- product, which can be a nuisance in PNEs.
Despite efforts to minimize radiation releases, PNEs have largely been discredited as a cost-saving civilian technology. Generally speaking, MRR devices still produce excessive radiation levels by civilian standards making their use impractical.
MRRs may have military utility as a tactical weapon, since residual contamination is slight. Such weapons are more costly and have lower performance of course.
This leads to another reason why PNEs have lost their attractiveness - there is no way to make a PNE device unsuitable for weapons use. "Peaceful" use of nuclear explosives inherently provides opportunity to develop weapons technology. As the saying goes, "the only difference between a PNE and a bomb is the tail fins".
4.5.5 Radiological Weapon Designs This is the opposite extreme of an MRR. Earlier several tamper materials were described that could be used to tailor the radioactive contamination produced by a nuclear explosion - tantalum, cobalt, zinc, and gold. Uranium tampers produce contamination in abundance - but quite a lot of energy too. In some applications it may be desired that the ratio of contamination to explosive force be increased, or tailored to a narrower spectrum of decay times compared to fission by-products.
Practical radiological weapons must incorporate the precursor isotope directly into the secondary. This is because the high compression of the secondary allows the use of reasonable masses of precursor material. In an uncompressed state, the thickness of most materials required to capture a substantial percentage of neutrons is 10-20 cm, leading to a very massive bomb. A layer of 1 cm or less will do as well when compressed by radiation implosion.
Some radioisotopes that would be very attractive for certain applications are difficult to produce in a weapon. A case in point is sodium-24, an extremely prolific producer of energetic gammas with a half-life of 14.98 hours. This isotope produces a remarkable 5.515 MeV of decay energy, with two hard gammas per decay (2.754 MeV and 1.369 MeV) and might be desired for very short-lived radiation barriers. The most obvious precursor, natural Na- 23, has a minuscule capture cross section for neutrons in the KeV range (although it is a significant hazard from induced radioactivity in soil after low altitude nuclear detonations). The best for precursor candidate for Na-24 is probably magnesium-24 (78.70% of natural magnesium) through an n,p reaction.
