1959 incident Sodium Reactor Experiment

1 1959 incident

1.1 limited experience
1.2 before incident
1.3 wash cell explosion
1.4 run 14 (july 12–july 26, 1959)

1959 incident
limited experience

the sodium reactor experiment designed , constructed gain experience in use of uranium fuel in reactor used produce electricity. fuel elements in sodium reactor experiment operating under untried conditions. fuel-design limits based on theoretical limits, not operating experience. cladding materials likewise untested, little or no operating experience.

before incident

during operation of sodium reactor experiment operators conducted several test cycles (known “runs”) correct , modify facility support systems, conduct reactor physics experiments , generate electricity. during run three, sodium reactor experiment became first nuclear reactor in united states produce power commercial power grid. during run eight, black residue (believed decomposed tetralin) noticed on fuel elements removed reactor. fuel elements washed in wash cell, , returned reactor. reactor returned operation high-temperature testing. several anomalous temperature readings noticed during next few runs, while operators attempted understand behavior , cause. @ end of run 13, obvious had occurred impaired heat-transfer characteristics of system. decided tetralin leak had reoccurred, , cause of trouble. reactor sodium purged gaseous nitrogen, remove volatile contamination.

wash cell explosion

following run 13, attempt made wash fuel element in wash cell. during operation, explosion occurred of sufficient magnitude lift shield plug out of wash cell. believed tetralin-related decomposition products caused substantial amount of sodium trapped in fuel rod elements blocking drain holes. there no reported injuries or fatalities associated wash-cell explosion. result of explosion, no further washing of elements done. measurements within reactor building indicated extremely high radioactivity levels throughout building. within several days radioactivity in high bay had been reduced normal levels, except area around wash cells.

partially melted fuel rod after july 1959 incident


run 14 (july 12–july 26, 1959)

shortly after reactor restarted, radiation monitors inside reactor building showed sharp increase in airborne radioactivity within reactor building. reactor remained operating, while attempts made determine radioactivity coming from. airborne radioactivity returned normal.

on july 13, reactor experienced series of temperature , radiation fluctuations (known excursions , because unexpected departure expected conditions). power level rose 4 mw 14 mw (70 percent of full power) on period of 2 minutes. excursion required operators manually override malfunctioning automatic-control switch, , reactor shut down. switch repaired, , reactor restarted. following day, monitors again indicated elevated airborne radioactivity levels within reactor building. source traced 2 locations @ reactor core loading face, sealed; airborne radioactivity within reactor building reduced. reactor restarted, operators noted unusual behavior on next few days. reactor increased power faster expected, , temperature difference between reactor bottom (where sodium entered) , reactor top (where sodium exited) unusually high. radioactivity within reactor increased. operators investigated, performing several exercises understand , correct reactor behavior.

on july 23, decided shut reactor down because of high fuel temperature , unacceptable top-bottom reactor temperature differential. while moving elements dislodge foreign material (and lower exit temperatures), noticed 4 reactor elements stuck. on july 26 reactor shut down, , first damaged fuel element observed. there no reported fatalities @ time of incident.

on july 29, 1959, ad hoc investigative committee established study incident , make recommendations. on august 21, 1959, van nuys news published story headline “parted fuel element seen @ atomics international”. article stated, “…a parted fuel element observed” , “the fuel element damage not indication of unsafe reactor conditions. no release of radioactive materials plant or environs occurred”. investigative committee released “sre fuel element damage, interim report” on november 15, 1959; final report made in 1961. introductory material in both documents includes statement, ”this report has been distributed according category ‘reactors-power’ given in standard distribution lists unclassified scientific , technical reports”, noting total of 700 copies printed. documents not labeled “secret”.