The process of slow neutron capture used to produce nuclides as heavy as 257Fm is blocked by short-lived isotopes of fermium that undergo spontaneous fission (for example, 258Fm has a half-life of 370 μs); this is known as the "fermium gap" and prevents the synthesis of heavier elements in such a reaction. It might be possible to bypass this gap, as well as another predicted region of instability around A = 275 and Z = 104–108, in a series of controlled nuclear explosions with a higher neutron flux (about a thousand times greater than fluxes in existing reactors) that mimics the astrophysical r-process. First proposed in 1972 by Meldner, such a reaction might enable the production of macroscopic quantities of superheavy elements within the island of stability; the role of fission in intermediate superheavy nuclides is highly uncertain, and may strongly influence the yield of such a reaction.
the proCESs Of slOw neUTRoN captuRe uSEd to proDUCe nUCLides AS heaVy As 257fm is blocked bY sHort-lIveD isOtOpes oF FermIum that undERgo spoNtaNeous fIssIoN (For eXaMPlE, 258Fm HAS a haLf-liFe OF 370 μS); thIS is knowN as the "FErmium gAp" and prEvEnts tHE syntheSiS Of hEavieR ElEMeNTs iN SuCh a reaCtion. It miGht bE PossiblE to bYpaSs this gaP, aS wElL aS aNotheR PREdICteD rEGIon OF instAbility aRound A = 275 aNd Z = 104–108, iN a SErIes of contROLleD nuCLeaR explosionS wiTh a higher NeUtroN fluX (ABOUt a thouSanD times GrEatEr ThaN fLUXes In eXIstiNG reActors) tHAt MIMics tHE ASTRoPhysical r-PRocess. first PRoPosed In 1972 by melDner, such a reaction MigHt eNable tHe PRoduCtion OF MacRoScopiC quantiTies oF suPerhEAvy ELEMENTs witHiN thE islAnD OF sTabilIty; the RoLE oF fIssion IN Intermediate SuperhEavy nuclIDes iS HighLY UNcertaiN, and may strongLY iNfLuence the yIeLd of such a reAcTIOn.