1304:
reaction was unique, as far as is currently known, to the Oklo ore bodies. It is also possible that other natural nuclear fission reactors were once operating but have since been geologically disturbed so much as to be unrecognizable, possibly even "diluting" the uranium so far that the isotope ratio would no longer serve as a "fingerprint". Only a small part of the continental crust and no part of the oceanic crust reaches the age of the deposits at Oklo or an age during which isotope ratios of natural uranium would have allowed a self sustaining chain reaction with water as a moderator.
1172:
812:
629:
2967:
2957:
2937:
50:
346:
1136:; all five have been found trapped in the remnants of the natural reactor, in varying concentrations. The concentrations of xenon isotopes, found trapped in mineral formations 2 billion years later, make it possible to calculate the specific time intervals of reactor operation: approximately 30 minutes of criticality followed by 2 hours and 30 minutes of cooling down (exponentially decreasing residual
2947:
1333:. Therefore, increasing oxygen levels during the aging of the Earth may have allowed uranium to be dissolved and transported with groundwater to places where a high enough concentration could accumulate to form rich uranium ore bodies. Without the new aerobic environment available on Earth at the time, these concentrations probably could not have taken place.
1303:
The Oklo uranium ore deposits are the only known sites in which natural nuclear reactors existed. Other rich uranium ore bodies would also have had sufficient uranium to support nuclear reactions at that time, but the combination of uranium, water, and physical conditions needed to support the chain
567:
is exactly what happens in a nuclear reactor. A possible explanation was that the uranium ore had operated as a natural fission reactor in the distant geological past. Other observations led to the same conclusion, and on 25 September 1972 the CEA announced their finding that self-sustaining nuclear
333:
isotope. Normally the concentration is 0.72% while these samples had only 0.60%, a significant difference (some 17% less U-235 was contained in the samples than expected). This discrepancy required explanation, as all civilian uranium handling facilities must meticulously account for all fissionable
1354:
and elevated temperatures to a few hundred degrees
Celsius. Most of the non-volatile fission products and actinides have only moved centimeters in the veins during the last 2 billion years. Studies have suggested this as a useful natural analogue for nuclear waste disposal. The overall
1125:. After cooling of the mineral deposit, the water returned, and the reaction restarted, completing a full cycle every 3 hours. The fission reaction cycles continued for hundreds of thousands of years and ended when the ever-decreasing fissile materials, coupled with the build-up of
1390:-93), 198 kilograms (437 lb) of caesium-135 (since decayed to barium-135, but the real value is probably lower as its parent nuclide, xenon-135, is a strong neutron poison and will have absorbed neutrons before decaying to
1488:
Several studies have analysed the relative concentrations of radioactive isotopes left behind at Oklo, and most have concluded that nuclear reactions then were much the same as they are today, which implies that
1648:
Gauthier-Lafaye, F.; Holliger, P.; Blanc, P.-L. (1996). "Natural fission reactors in the
Franceville Basin, Gabon: a review of the conditions and results of a "critical event" in a geologic system".
1117:
took place, producing heat that caused the groundwater to boil away; without a moderator that could slow the neutrons, however, the reaction slowed or stopped. The reactor thus had a negative
1906:
Petrov, Yu. V.; Nazarov, A. I.; Onegin, M. S.; Sakhnovsky, E. G. (2006). "Natural nuclear reactor at Oklo and variation of fundamental constants: Computation of neutronics of a fresh core".
1168:
and thus scientists were able to determine the neutronics of this reactor by calculations based on those isotope ratios almost two billion years after it stopped fissioning uranium.
2970:
1614:
379:
mined at Oklo showed anomalous results compared to those obtained for uranium from other mines. Further investigations into this uranium deposit discovered uranium ore with a
1821:
De Laeter, J. R.; Rosman, K. J. R.; Smith, C. L. (1980). "The Oklo
Natural Reactor: Cumulative Fission Yields and Retentivity of the Symmetric Mass Region Fission Products".
2101:
2765:
803:
by neutron capture. This excess must be corrected (see above) to obtain agreement between this corrected isotopic composition and that deduced from fission yields.
1156:
if not allowed to absorb neutrons. While caesium-135 is relatively long lived, all caesium-135 produced by the Oklo reactor has since decayed further to stable
194:
371:
259:
2160:
1370:
is about 4.6 kilograms (10 lb). Over its lifetime the reactor produced roughly 100 megatonnes of TNT (420 PJ) in thermal energy, including
1205:
made up about 3.1% of the natural uranium, which is comparable to the amount used in some of today's reactors. (The remaining 96.9% was non-fissile
3011:
1307:
Another factor which probably contributed to the start of the Oklo natural nuclear reactor at 2 billion years, rather than earlier, was the
2094:
1374:. If one ignores fission of plutonium (which makes up roughly a third of fission events over the course of normal burnup in modern human-made
568:
chain reactions had occurred on Earth about 2 billion years ago. Later, other natural nuclear fission reactors were discovered in the region.
1805:
2406:
2323:
2399:
1959:
Davis, Edward D.; Hamdan, Leila (2015). "Reappraisal of the limit on the variation in α implied by the Oklo natural fission reactors".
2605:
1744:
Meshik, A. P.; et al. (2004). "Record of
Cycling Operation of the Natural Nuclear Reactor in the Oklo/Okelobondo Area in Gabon".
2054:
266:
Oklo is the only location where this phenomenon is known to have occurred, and consists of 16 sites with patches of centimeter-sized
3021:
2087:
1144:
is the strongest known neutron poison. However, it is not produced directly in appreciable amounts but rather as a decay product of
1435:
might have changed over the past 2 billion years. That is because α influences the rate of various nuclear reactions. For example,
713:
content, we can subtract the natural neodymium and gain access to the isotopic composition of neodymium produced by the fission of
397:
concentration as low as 0.44% (almost 40% below the normal value). Subsequent examination of isotopes of fission products such as
2940:
2915:
2780:
2858:
2692:
2530:
2294:
1857:
1382:
amount to roughly 129 kilograms (284 lb) of technetium-99 (since decayed to ruthenium-99), 108 kilograms (238 lb) of
538:
years being almost two orders of magnitude shorter than the time elapsed since the reactor operated, it has decayed to roughly
530:
must have also been present in higher than usual ratios during the time the reactor was operating, but due to its half life of
290:
of thermal power during that time. During that era, life on Earth consisted of little more than aquatic single-cell organisms.
2059:
2016:
2848:
2697:
2155:
2622:
2455:
299:
2055:
The natural nuclear reactor at Oklo: A comparison with modern nuclear reactors, Radiation
Information Network, April 2005
2702:
2411:
2165:
1858:"2 billion year old natural analogs for nuclear waste disposal: the natural nuclear fission reactors in Gabon (Africa)"
659:
The neodymium found at Oklo has a different isotopic composition to that of natural neodymium: the latter contains 27%
2996:
2960:
2922:
2760:
2587:
2525:
2350:
2254:
2140:
1336:
It is estimated that nuclear reactions in the uranium in centimeter- to meter-sized veins consumed about five tons of
1329:
was at least 3% or higher at all times prior to reactor startup. Uranium is soluble in water only in the presence of
899:
concentration than otherwise naturally occurring (27–30% vs. 12.7%). This anomaly could be explained by the decay of
187:
3026:
2808:
2487:
1502:
180:
2460:
2991:
2785:
2394:
2177:
89:
72:
3006:
3001:
2950:
2875:
2775:
2687:
94:
375:(CEA) began an investigation. A series of measurements of the relative abundances of the two most significant
2654:
1292:
in natural uranium is only 0.72%. A natural nuclear reactor is therefore no longer possible on Earth without
2905:
2880:
2494:
2271:
1746:
1429:
1308:
2770:
1683:
Davis, E. D.; Gould, C. R.; Sharapov, E. I. (2014). "Oklo reactors and implications for nuclear science".
1114:
219:
2800:
2755:
2217:
2145:
1797:
1379:
151:
146:
546:
its original value and thus basically nothing and below any abilities of current equipment to detect.
342:
is why people mine uranium, a significant amount "going missing" was also of direct economic concern.
2750:
2735:
2028:
1978:
1925:
1869:
1830:
1755:
1702:
1657:
1615:"Nature's Nuclear Reactors: The 2-Billion-Year-Old Natural Fission Reactors in Gabon, Western Africa"
1579:
1540:
1105:
The natural nuclear reactor at Oklo formed when a uranium-rich mineral deposit became inundated with
307:
695:
is not produced by fission; the ore contains both fission-produced and natural neodymium. From this
2910:
2885:
2670:
2264:
2132:
1375:
1122:
439:
424:
376:
156:
118:
67:
2790:
2627:
2554:
2365:
1994:
1968:
1941:
1915:
1726:
1692:
406:
234:, where self-sustaining nuclear reactions have occurred in the past, are verified by analysis of
937:. In the bar chart, the normal natural isotope signature of ruthenium is compared with that for
2069:
1175:
Change of content of
Uranium-235 in natural uranium; the content was 3.65% 2 billion years ago.
811:
628:
2122:
1801:
1771:
1718:
1595:
1567:
1171:
1165:
1110:
1035:
1008:
852:
443:
303:
127:
41:
963:
with thermal neutrons. The fission ruthenium has a different isotope signature. The level of
519:
concentration present at the time the reactor was active would have long since decayed away.
3016:
2036:
1986:
1933:
1877:
1838:
1834:
1789:
1763:
1710:
1665:
1587:
1548:
1507:
1118:
420:
339:
283:
246:
2610:
2450:
2389:
2868:
2828:
2355:
2282:
2111:
2073:
1161:
1068:
942:
938:
490:
271:
242:
223:
215:
161:
2360:
2065:
NASA Astronomy
Picture of the Day: NASA, Oklo, Fossile Reactor, Zone 15 (16 October 2002)
2032:
1982:
1929:
1873:
1759:
1706:
1661:
1583:
1544:
1034:. On the timescale of when the reactors were in operation, very little (about 0.17
2843:
2823:
2818:
2813:
2563:
2470:
2439:
2421:
1311:. Uranium is naturally present in the rocks of the earth, and the abundance of fissile
1149:
1126:
982:
335:
166:
1881:
1669:
1591:
49:
2985:
2299:
1998:
1945:
1842:
1730:
1409:
1180:
901:
1179:
A key factor that made the reaction possible was that, at the time the reactor went
1132:
Fission of uranium normally produces five known isotopes of the fission-product gas
419:
did not deviate significantly in its concentration from other natural samples. Both
17:
2574:
2079:
1531:
Kuroda, P. K. (1956). "On the
Nuclear Physical Stability of the Uranium Minerals".
1437:
1413:
1383:
1094:
505:
286:, and continued for a few hundred thousand years, probably averaging less than 100
1767:
345:
2632:
2222:
2015:
Bentridi, S.E.; Gall, B.; Gauthier-Lafaye, F.; Seghour, A.; Medjadi, D. (2011).
1417:
1356:
1293:
1153:
1106:
508:
induced (n,2n) reactions in nuclear reactors. In Oklo any possible deviation of
315:
267:
227:
62:
2040:
1990:
1937:
873:
in more than trace quantities over the time since the reactors stopped working.
1894:
1714:
1157:
1145:
1137:
1020:
986:
279:
1722:
2343:
2333:
1253:
1141:
878:
402:
398:
99:
2838:
2064:
1775:
1599:
815:
Isotope signatures of natural ruthenium and fission product ruthenium from
632:
Isotope signatures of natural neodymium and fission product neodymium from
349:
Geological situation in Gabon leading to natural nuclear fission reactors
2863:
2712:
2707:
2647:
2316:
2244:
2227:
2212:
2187:
1478:
1371:
1297:
2853:
2833:
2232:
2207:
1920:
1512:
1387:
1184:
405:
also showed anomalies, as described in more detail below. However, the
275:
235:
212:
1552:
1416:(long since decayed to zirconium), and 185 kilograms (408 lb) of
1121:
of reactivity, something employed as a safety mechanism in human-made
2642:
2637:
2617:
2597:
2582:
2465:
2202:
2182:
2150:
1330:
313:
samples from the Oklo mine showed a discrepancy in the amount of the
2019:[Inception and evolution of Oklo natural nuclear reactors].
1895:
New
Scientist: Oklo Reactor and fine-structure value. June 30, 2004.
1481:
isotopes in samples from Oklo can be used to calculate the value of
1093:(quickly followed by beta decay) can only have occurred during high
2192:
1973:
27:
Naturally occurring uranium self-sustaining nuclear chain reactions
2679:
2535:
2338:
2328:
1697:
1170:
1133:
810:
627:
344:
254:
238:
1428:
The natural reactor of Oklo has been used to check if the atomic
334:
isotopes to ensure that none are diverted to the construction of
249:
of those fission products). This was first discovered in 1972 in
2540:
2429:
2239:
2197:
1473:, and since the rate of neutron capture depends on the value of
287:
250:
2083:
981:
in the fission product mixture is low because fission produces
2513:
2377:
263:(CEA) under conditions very similar to Kuroda's predictions.
274:
reactions are thought to have taken place approximately 1.7
48:
1412:(since decayed to silver), 86 kilograms (190 lb) of
1274:, and thus decays more rapidly, the current abundance of
1097:
and thus ceased when the fission chain reaction stopped.
1643:
1641:
1639:
1637:
1635:
1007:
would only be produced in appreciable quantities by
2898:
2799:
2729:
2678:
2669:
2596:
2562:
2553:
2512:
2505:
2485:
2438:
2420:
2376:
2281:
2263:
2131:
2017:"Génèse et évolution des réacteurs naturels d'Oklo"
1309:
increasing oxygen content in the Earth's atmosphere
877:Similar investigations into the isotopic ratios of
833:which had been subjected to thermal neutrons. The
1113:for the neutrons produced by nuclear fission. A
677:, while that of Oklo contains less than 6%. The
438:concentrations significantly different from the
1424:Relation to the atomic fine-structure constant
1152:). Xenon-135 itself is unstable and decays to
2766:Small sealed transportable autonomous (SSTAR)
2095:
1408:in some cases), 28 kilograms (62 lb) of
650:which had been subjected to thermal neutrons.
188:
8:
1568:"The Workings of an Ancient Nuclear Reactor"
1129:, no longer could sustain a chain reaction.
222:occur. The conditions under which a natural
2946:
2743:
2675:
2559:
2509:
2502:
2278:
2102:
2088:
2080:
195:
181:
29:
1972:
1919:
1696:
1685:International Journal of Modern Physics E
1164:in xenon-135 decays extremely slowly via
570:
1523:
1160:. Meanwhile, xenon-136, the product of
39:
2693:Liquid-fluoride thorium reactor (LFTR)
1056:will have occurred. Other pathways of
226:could exist were predicted in 1956 by
2698:Molten-Salt Reactor Experiment (MSRE)
941:ruthenium which is the result of the
489:and due to it being both consumed by
294:Discovery of the Oklo fossil reactors
7:
2703:Integral Molten Salt Reactor (IMSR)
1823:Earth and Planetary Science Letters
1011:of the very long-lived (half life
624:Fission product isotope signatures
25:
1592:10.1038/scientificamerican1105-82
1359:from the fission of five tons of
372:Commissariat à l'énergie atomique
300:Tricastin uranium enrichment site
260:Commissariat à l'énergie atomique
2966:
2965:
2956:
2955:
2945:
2936:
2935:
2786:Fast Breeder Test Reactor (FBTR)
1613:Mervin, Evelyn (July 13, 2011).
1420:(long since decayed to barium).
1183:1.7 billion years ago, the
302:at Pierrelatte, France, routine
230:. The remnants of an extinct or
1650:Geochimica et Cosmochimica Acta
1566:Meshik, A. P. (November 2005).
855:) has not had time to decay to
209:natural nuclear fission reactor
3012:Radioactive waste repositories
2776:Energy Multiplier Module (EM2)
1140:) to complete a 3-hour cycle.
232:fossil nuclear fission reactor
1:
1882:10.1016/S1631-0705(02)01351-8
1768:10.1103/PhysRevLett.93.182302
1670:10.1016/S0016-7037(96)00245-1
1455:captures a neutron to become
478:being enriched together with
2576:Uranium Naturel Graphite Gaz
1856:Gauthier-Lafaye, F. (2002).
1843:10.1016/0012-821X(80)90135-1
1619:blogs.scientificamerican.com
881:at Oklo found a much higher
2923:Aircraft Reactor Experiment
1533:Journal of Chemical Physics
257:by researchers from French
3043:
2761:Liquid-metal-cooled (LMFR)
2041:10.1016/j.crte.2011.09.008
1991:10.1103/physrevc.92.014319
1938:10.1103/PHYSREVC.74.064610
1503:Deep geological repository
1485:from 2 billion years ago.
152:Shunga-Francevillian event
2931:
2886:Stable Salt Reactor (SSR)
2781:Reduced-moderation (RMWR)
2746:
2588:Advanced gas-cooled (AGR)
2118:
2021:Comptes Rendus Geoscience
1794:Chemistry of the Elements
1792:; Earnshaw, Alan (1997).
1715:10.1142/S0218301314300070
1539:(4): 781–782, 1295–1296.
851:(an extremely long-lived
767:lead to the formation of
270:. There, self-sustaining
95:Francevillian A Formation
90:Francevillian B Formation
3022:Nuclear reactors by type
2951:List of nuclear reactors
2791:Dual fluid reactor (DFR)
2407:Steam-generating (SGHWR)
2941:Nuclear fusion reactors
2906:Organic nuclear reactor
2112:nuclear fission reactor
1862:Comptes Rendus Physique
1835:1980E&PSL..50..238D
1747:Physical Review Letters
1578:(5): 82–86, 88, 90–91.
1477:, the ratio of the two
1430:fine-structure constant
1109:, which could act as a
220:nuclear chain reactions
1380:fission product yields
1176:
874:
651:
366:
278:years ago, during the
241:of uranium and of the
218:where self-sustaining
84:Geology and localities
53:
1798:Butterworth-Heinemann
1790:Greenwood, Norman N.
1174:
983:neutron rich isotopes
814:
631:
353:Nuclear reactor zones
348:
338:. Furthermore, since
147:Great Oxidation Event
141:Evolutionary concepts
52:
2771:Traveling-wave (TWR)
2255:Supercritical (SCWR)
2070:הכור הגרעיני של הטבע
2060:Oklo Fossil Reactors
1376:light water reactors
1123:light water reactors
298:In May 1972, at the
18:Oklo Fossil Reactors
2141:Aqueous homogeneous
2033:2011CRGeo.343..738B
1983:2015PhRvC..92a4319D
1930:2006PhRvC..74f4610P
1874:2002CRPhy...3..839G
1760:2004PhRvL..93r2302M
1707:2014IJMPE..2330007D
1662:1996GeCoA..60.4831G
1584:2005SciAm.293e..82M
1572:Scientific American
1545:1956JChPh..25..781K
1223:and roughly 55 ppm
985:which subsequently
853:double beta emitter
731:. The two isotopes
572:
440:secular equilibrium
425:reprocessed uranium
377:isotopes of uranium
157:Huronian glaciation
119:Francevillian biota
42:Francevillian basin
34:Part of a series on
2997:Geography of Gabon
2961:Nuclear technology
2027:(11–12): 738–748.
1691:(4): 1430007–236.
1493:was the same too.
1386:(since decayed to
1177:
875:
652:
571:
493:and produced from
427:will usually have
407:trace radioisotope
367:
54:
3027:Nuclear chemistry
2979:
2978:
2971:Nuclear accidents
2894:
2893:
2725:
2724:
2721:
2720:
2665:
2664:
2549:
2548:
2481:
2480:
1961:Physical Review C
1908:Physical Review C
1807:978-0-08-037941-8
1656:(23): 4831–4852.
1553:10.1063/1.1743058
1166:double beta decay
1009:double beta decay
621:
620:
467:. This is due to
359:Uranium ore layer
304:mass spectrometry
247:daughter nuclides
205:
204:
132:
16:(Redirected from
3034:
2992:Nuclear reactors
2969:
2968:
2959:
2958:
2949:
2948:
2939:
2938:
2881:Helium gas (GFR)
2744:
2739:
2676:
2560:
2510:
2503:
2498:
2497:
2279:
2275:
2274:
2104:
2097:
2090:
2081:
2044:
2003:
2002:
1976:
1956:
1950:
1949:
1923:
1903:
1897:
1892:
1886:
1885:
1868:(7–8): 839–849.
1853:
1847:
1846:
1818:
1812:
1811:
1800:. p. 1257.
1796:(2nd ed.).
1786:
1780:
1779:
1741:
1735:
1734:
1700:
1680:
1674:
1673:
1645:
1630:
1629:
1627:
1625:
1610:
1604:
1603:
1563:
1557:
1556:
1528:
1508:Geology of Gabon
1472:
1471:
1470:
1463:
1462:
1454:
1452:
1451:
1444:
1443:
1407:
1406:
1405:
1398:
1397:
1369:
1367:
1366:
1353:
1352:
1351:
1344:
1343:
1328:
1327:
1326:
1319:
1318:
1291:
1290:
1289:
1282:
1281:
1273:
1272:
1271:
1264:
1263:
1251:
1250:
1249:
1242:
1241:
1233:
1231:
1230:
1222:
1221:
1220:
1213:
1212:
1204:
1203:
1202:
1195:
1194:
1119:void coefficient
1092:
1090:
1089:
1081:
1079:
1078:
1067:production like
1066:
1064:
1063:
1055:
1054:
1053:
1046:
1045:
1033:
1031:
1030:
1018:
1016:
1006:
1005:
1004:
997:
996:
980:
979:
978:
971:
970:
962:
961:
960:
953:
952:
936:
935:
934:
927:
926:
918:
916:
915:
908:
907:
898:
897:
896:
889:
888:
872:
871:
870:
863:
862:
850:
849:
848:
841:
840:
832:
831:
830:
823:
822:
802:
801:
800:
793:
792:
784:
783:
782:
775:
774:
766:
765:
764:
757:
756:
748:
747:
746:
739:
738:
730:
729:
728:
721:
720:
712:
711:
710:
703:
702:
694:
693:
692:
685:
684:
676:
675:
674:
667:
666:
649:
648:
647:
640:
639:
573:
566:
565:
564:
557:
556:
545:
543:
537:
535:
529:
527:
526:
518:
516:
515:
503:
501:
500:
488:
486:
485:
477:
475:
474:
466:
464:
463:
455:
453:
452:
437:
435:
434:
421:depleted uranium
418:
416:
415:
396:
395:
394:
387:
386:
369:Thus the French
340:fissile material
332:
330:
329:
322:
321:
284:Paleoproterozoic
245:(and the stable
243:fission products
197:
190:
183:
124:
30:
21:
3042:
3041:
3037:
3036:
3035:
3033:
3032:
3031:
3007:Nuclear fission
3002:Nuclear physics
2982:
2981:
2980:
2975:
2927:
2890:
2795:
2740:
2733:
2732:
2717:
2661:
2592:
2567:
2545:
2517:
2499:
2492:
2491:
2490:
2477:
2443:
2434:
2416:
2381:
2372:
2286:
2269:
2268:
2267:
2259:
2173:Natural fission
2127:
2126:
2114:
2108:
2074:Hebrew language
2051:
2014:
2011:
2006:
1958:
1957:
1953:
1905:
1904:
1900:
1893:
1889:
1855:
1854:
1850:
1820:
1819:
1815:
1808:
1788:
1787:
1783:
1743:
1742:
1738:
1682:
1681:
1677:
1647:
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1633:
1623:
1621:
1612:
1611:
1607:
1565:
1564:
1560:
1530:
1529:
1525:
1521:
1499:
1469:
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1396:
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1365:
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1360:
1350:
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1325:
1323:
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1321:
1317:
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1312:
1288:
1286:
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1268:
1267:
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1259:
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1229:
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1225:
1224:
1219:
1217:
1216:
1215:
1211:
1209:
1208:
1207:
1206:
1201:
1199:
1198:
1197:
1193:
1191:
1190:
1189:
1188:
1162:neutron capture
1150:parent nuclides
1148:(or one of its
1127:neutron poisons
1103:
1088:
1086:
1085:
1084:
1083:
1077:
1075:
1074:
1073:
1072:
1069:neutron capture
1062:
1060:
1059:
1058:
1057:
1052:
1050:
1049:
1048:
1044:
1042:
1041:
1040:
1039:
1029:
1027:
1026:
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1024:
1014:
1012:
1003:
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1000:
999:
995:
993:
992:
991:
990:
977:
975:
974:
973:
969:
967:
966:
965:
964:
959:
957:
956:
955:
951:
949:
948:
947:
946:
939:fission product
933:
931:
930:
929:
925:
923:
922:
921:
920:
914:
912:
911:
910:
906:
904:
903:
902:
900:
895:
893:
892:
891:
887:
885:
884:
883:
882:
869:
867:
866:
865:
861:
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858:
857:
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839:
837:
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752:
751:
750:
745:
743:
742:
741:
737:
735:
734:
733:
732:
727:
725:
724:
723:
719:
717:
716:
715:
714:
709:
707:
706:
705:
701:
699:
698:
697:
696:
691:
689:
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687:
683:
681:
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673:
671:
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657:
646:
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642:
638:
636:
635:
634:
633:
626:
563:
561:
560:
559:
555:
553:
552:
551:
550:
541:
539:
533:
531:
525:
523:
522:
521:
520:
514:
512:
511:
510:
509:
499:
497:
496:
495:
494:
491:neutron capture
484:
482:
481:
480:
479:
473:
471:
470:
469:
468:
462:
460:
459:
458:
457:
451:
449:
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447:
446:
433:
431:
430:
429:
428:
414:
412:
411:
410:
409:
393:
391:
390:
389:
385:
383:
382:
381:
380:
365:
336:nuclear weapons
328:
326:
325:
324:
320:
318:
317:
316:
314:
311:
296:
272:nuclear fission
224:nuclear reactor
201:
172:
171:
162:Lomagundi event
142:
134:
133:
113:
105:
104:
85:
77:
28:
23:
22:
15:
12:
11:
5:
3040:
3038:
3030:
3029:
3024:
3019:
3014:
3009:
3004:
2999:
2994:
2984:
2983:
2977:
2976:
2974:
2973:
2963:
2953:
2943:
2932:
2929:
2928:
2926:
2925:
2920:
2919:
2918:
2913:
2902:
2900:
2896:
2895:
2892:
2891:
2889:
2888:
2883:
2878:
2873:
2872:
2871:
2866:
2861:
2856:
2851:
2846:
2841:
2836:
2831:
2826:
2821:
2816:
2805:
2803:
2797:
2796:
2794:
2793:
2788:
2783:
2778:
2773:
2768:
2763:
2758:
2756:Integral (IFR)
2753:
2747:
2741:
2730:
2727:
2726:
2723:
2722:
2719:
2718:
2716:
2715:
2710:
2705:
2700:
2695:
2690:
2684:
2682:
2673:
2667:
2666:
2663:
2662:
2660:
2659:
2658:
2657:
2652:
2651:
2650:
2645:
2640:
2635:
2620:
2615:
2614:
2613:
2602:
2600:
2594:
2593:
2591:
2590:
2585:
2580:
2571:
2569:
2565:
2557:
2551:
2550:
2547:
2546:
2544:
2543:
2538:
2533:
2528:
2522:
2520:
2515:
2507:
2500:
2486:
2483:
2482:
2479:
2478:
2476:
2475:
2474:
2473:
2468:
2463:
2458:
2447:
2445:
2441:
2436:
2435:
2433:
2432:
2426:
2424:
2418:
2417:
2415:
2414:
2409:
2404:
2403:
2402:
2397:
2386:
2384:
2379:
2374:
2373:
2371:
2370:
2369:
2368:
2363:
2358:
2353:
2348:
2347:
2346:
2341:
2336:
2326:
2321:
2320:
2319:
2314:
2311:
2308:
2305:
2291:
2289:
2284:
2276:
2261:
2260:
2258:
2257:
2252:
2251:
2250:
2247:
2242:
2237:
2236:
2235:
2230:
2220:
2215:
2210:
2205:
2200:
2195:
2190:
2185:
2175:
2170:
2169:
2168:
2163:
2158:
2153:
2143:
2137:
2135:
2129:
2128:
2120:
2119:
2116:
2115:
2109:
2107:
2106:
2099:
2092:
2084:
2078:
2077:
2067:
2062:
2057:
2050:
2049:External links
2047:
2046:
2045:
2010:
2007:
2005:
2004:
1951:
1921:hep-ph/0506186
1898:
1887:
1848:
1829:(1): 238–246.
1813:
1806:
1781:
1754:(18): 182302.
1736:
1675:
1631:
1605:
1558:
1522:
1520:
1517:
1516:
1515:
1510:
1505:
1498:
1495:
1468:
1460:
1449:
1441:
1425:
1422:
1403:
1395:
1364:
1349:
1341:
1324:
1316:
1287:
1279:
1269:
1261:
1252:has a shorter
1247:
1239:
1228:
1218:
1210:
1200:
1192:
1115:chain reaction
1102:
1099:
1087:
1076:
1061:
1051:
1043:
1028:
1002:
994:
976:
968:
958:
950:
932:
924:
913:
905:
894:
886:
868:
860:
846:
838:
828:
820:
808:
805:
798:
790:
780:
772:
762:
754:
744:
736:
726:
718:
708:
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690:
682:
672:
664:
656:
653:
645:
637:
625:
622:
619:
618:
615:
612:
609:
606:
603:
600:
596:
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592:
589:
586:
583:
580:
577:
562:
554:
524:
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498:
483:
472:
461:
450:
432:
413:
392:
384:
364:
363:
360:
357:
354:
350:
327:
319:
309:
295:
292:
282:period of the
203:
202:
200:
199:
192:
185:
177:
174:
173:
170:
169:
167:Origin of Life
164:
159:
154:
149:
143:
140:
139:
136:
135:
123:
122:
114:
111:
110:
107:
106:
103:
102:
97:
92:
86:
83:
82:
79:
78:
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75:
70:
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59:
56:
55:
45:
44:
37:
36:
26:
24:
14:
13:
10:
9:
6:
4:
3:
2:
3039:
3028:
3025:
3023:
3020:
3018:
3015:
3013:
3010:
3008:
3005:
3003:
3000:
2998:
2995:
2993:
2990:
2989:
2987:
2972:
2964:
2962:
2954:
2952:
2944:
2942:
2934:
2933:
2930:
2924:
2921:
2917:
2914:
2912:
2909:
2908:
2907:
2904:
2903:
2901:
2897:
2887:
2884:
2882:
2879:
2877:
2874:
2870:
2867:
2865:
2862:
2860:
2857:
2855:
2852:
2850:
2847:
2845:
2842:
2840:
2837:
2835:
2832:
2830:
2827:
2825:
2822:
2820:
2817:
2815:
2812:
2811:
2810:
2807:
2806:
2804:
2802:
2801:Generation IV
2798:
2792:
2789:
2787:
2784:
2782:
2779:
2777:
2774:
2772:
2769:
2767:
2764:
2762:
2759:
2757:
2754:
2752:
2751:Breeder (FBR)
2749:
2748:
2745:
2742:
2737:
2728:
2714:
2711:
2709:
2706:
2704:
2701:
2699:
2696:
2694:
2691:
2689:
2686:
2685:
2683:
2681:
2677:
2674:
2672:
2668:
2656:
2653:
2649:
2646:
2644:
2641:
2639:
2636:
2634:
2631:
2630:
2629:
2626:
2625:
2624:
2621:
2619:
2616:
2612:
2609:
2608:
2607:
2604:
2603:
2601:
2599:
2595:
2589:
2586:
2584:
2581:
2579:
2577:
2573:
2572:
2570:
2568:
2561:
2558:
2556:
2552:
2542:
2539:
2537:
2534:
2532:
2529:
2527:
2524:
2523:
2521:
2519:
2511:
2508:
2504:
2501:
2496:
2489:
2484:
2472:
2469:
2467:
2464:
2462:
2459:
2457:
2454:
2453:
2452:
2449:
2448:
2446:
2444:
2437:
2431:
2428:
2427:
2425:
2423:
2419:
2413:
2410:
2408:
2405:
2401:
2398:
2396:
2393:
2392:
2391:
2388:
2387:
2385:
2383:
2375:
2367:
2364:
2362:
2359:
2357:
2354:
2352:
2349:
2345:
2342:
2340:
2337:
2335:
2332:
2331:
2330:
2327:
2325:
2322:
2318:
2315:
2312:
2309:
2306:
2303:
2302:
2301:
2298:
2297:
2296:
2293:
2292:
2290:
2288:
2280:
2277:
2273:
2266:
2262:
2256:
2253:
2248:
2246:
2243:
2241:
2238:
2234:
2231:
2229:
2226:
2225:
2224:
2221:
2219:
2216:
2214:
2211:
2209:
2206:
2204:
2201:
2199:
2196:
2194:
2191:
2189:
2186:
2184:
2181:
2180:
2179:
2176:
2174:
2171:
2167:
2164:
2162:
2159:
2157:
2154:
2152:
2149:
2148:
2147:
2144:
2142:
2139:
2138:
2136:
2134:
2130:
2125:
2124:
2117:
2113:
2105:
2100:
2098:
2093:
2091:
2086:
2085:
2082:
2075:
2071:
2068:
2066:
2063:
2061:
2058:
2056:
2053:
2052:
2048:
2042:
2038:
2034:
2030:
2026:
2023:(in French).
2022:
2018:
2013:
2012:
2008:
2000:
1996:
1992:
1988:
1984:
1980:
1975:
1970:
1967:(1): 014319.
1966:
1962:
1955:
1952:
1947:
1943:
1939:
1935:
1931:
1927:
1922:
1917:
1914:(6): 064610.
1913:
1909:
1902:
1899:
1896:
1891:
1888:
1883:
1879:
1875:
1871:
1867:
1863:
1859:
1852:
1849:
1844:
1840:
1836:
1832:
1828:
1824:
1817:
1814:
1809:
1803:
1799:
1795:
1791:
1785:
1782:
1777:
1773:
1769:
1765:
1761:
1757:
1753:
1749:
1748:
1740:
1737:
1732:
1728:
1724:
1720:
1716:
1712:
1708:
1704:
1699:
1694:
1690:
1686:
1679:
1676:
1671:
1667:
1663:
1659:
1655:
1651:
1644:
1642:
1640:
1638:
1636:
1632:
1620:
1616:
1609:
1606:
1601:
1597:
1593:
1589:
1585:
1581:
1577:
1573:
1569:
1562:
1559:
1554:
1550:
1546:
1542:
1538:
1534:
1527:
1524:
1518:
1514:
1511:
1509:
1506:
1504:
1501:
1500:
1496:
1494:
1492:
1486:
1484:
1480:
1476:
1453:
1434:
1431:
1423:
1421:
1419:
1415:
1411:
1410:palladium-107
1389:
1385:
1381:
1377:
1373:
1358:
1334:
1332:
1310:
1305:
1301:
1299:
1295:
1255:
1186:
1182:
1173:
1169:
1167:
1163:
1159:
1155:
1151:
1147:
1143:
1139:
1135:
1130:
1128:
1124:
1120:
1116:
1112:
1108:
1100:
1098:
1096:
1070:
1037:
1022:
1010:
988:
984:
944:
940:
917:
880:
854:
813:
806:
804:
654:
630:
623:
616:
613:
610:
607:
604:
601:
598:
597:
593:
590:
587:
584:
581:
578:
575:
574:
569:
549:This loss in
547:
507:
492:
445:
441:
426:
422:
408:
404:
400:
378:
374:
373:
361:
358:
355:
352:
351:
347:
343:
341:
337:
331:
312:
305:
301:
293:
291:
289:
285:
281:
277:
273:
269:
264:
262:
261:
256:
252:
248:
244:
240:
237:
233:
229:
225:
221:
217:
214:
210:
198:
193:
191:
186:
184:
179:
178:
176:
175:
168:
165:
163:
160:
158:
155:
153:
150:
148:
145:
144:
138:
137:
130:
129:
121:
120:
116:
115:
109:
108:
101:
98:
96:
93:
91:
88:
87:
81:
80:
74:
71:
69:
66:
64:
61:
60:
58:
57:
51:
47:
46:
43:
38:
35:
32:
31:
19:
2809:Sodium (SFR)
2736:fast-neutron
2575:
2172:
2121:
2024:
2020:
1964:
1960:
1954:
1911:
1907:
1901:
1890:
1865:
1861:
1851:
1826:
1822:
1816:
1793:
1784:
1751:
1745:
1739:
1688:
1684:
1678:
1653:
1649:
1622:. Retrieved
1618:
1608:
1575:
1571:
1561:
1536:
1532:
1526:
1490:
1487:
1482:
1474:
1432:
1427:
1414:strontium-90
1384:zirconium-93
1335:
1306:
1302:
1178:
1131:
1104:
1095:neutron flux
876:
658:
548:
506:fast neutron
456:relative to
370:
368:
297:
265:
258:
231:
208:
206:
126:
117:
63:Preservation
33:
2844:Superphénix
2671:Molten-salt
2623:VHTR (HTGR)
2400:HW BLWR 250
2366:R4 Marviken
2295:Pressurized
2265:Heavy water
2249:many others
2178:Pressurized
2133:Light water
1418:caesium-137
1357:mass defect
1294:heavy water
1234:.) Because
1154:caesium-135
1107:groundwater
1038:) decay to
228:Paul Kuroda
2986:Categories
2628:PBR (PBMR)
1974:1503.06011
1519:References
1158:barium-135
1146:iodine-135
1138:decay heat
1021:molybdenum
987:beta decay
306:comparing
280:Statherian
268:ore layers
125:(Also see
2680:Fluorides
2344:IPHWR-700
2339:IPHWR-540
2334:IPHWR-220
2123:Moderator
2110:Types of
1999:119227720
1946:118272311
1731:118394767
1723:0218-3013
1698:1404.4948
1372:neutrinos
1254:half-life
1142:Xenon-135
1111:moderator
1101:Mechanism
879:ruthenium
807:Ruthenium
655:Neodymium
403:ruthenium
399:neodymium
356:Sandstone
100:Oklo Mine
2713:TMSR-LF1
2708:TMSR-500
2688:Fuji MSR
2648:THTR-300
2488:Graphite
2351:PHWR KWU
2317:ACR-1000
2245:IPWR-900
2228:ACPR1000
2223:HPR-1000
2213:CPR-1000
2188:APR-1400
1776:15525157
1600:16318030
1497:See also
1479:samarium
1378:), then
1298:graphite
1187:isotope
1181:critical
1023:isotope
128:Akouemma
3017:Uranium
2854:FBR-600
2834:CFR-600
2829:BN-1200
2495:coolant
2422:Organic
2307:CANDU 9
2304:CANDU 6
2272:coolant
2233:ACP1000
2208:CAP1400
2146:Boiling
2029:Bibcode
2009:Sources
1979:Bibcode
1926:Bibcode
1870:Bibcode
1831:Bibcode
1756:Bibcode
1703:Bibcode
1658:Bibcode
1624:July 7,
1580:Bibcode
1541:Bibcode
1513:Mounana
1388:niobium
1185:fissile
1019:years)
943:fission
362:Granite
276:billion
236:isotope
216:deposit
213:uranium
112:Fossils
73:History
2899:Others
2839:Phénix
2824:BN-800
2819:BN-600
2814:BN-350
2643:HTR-PM
2638:HTR-10
2618:UHTREX
2583:Magnox
2578:(UNGG)
2471:Lucens
2466:KS 150
2203:ATMEA1
2183:AP1000
2166:Kerena
1997:
1944:
1804:
1774:
1729:
1721:
1598:
1331:oxygen
442:of 55
239:ratios
2916:Piqua
2911:Arbus
2869:PRISM
2611:MHR-T
2606:GTMHR
2536:EGP-6
2531:AMB-X
2506:Water
2451:HWGCR
2390:HWLWR
2329:IPHWR
2300:CANDU
2161:ESBWR
1995:S2CID
1969:arXiv
1942:S2CID
1916:arXiv
1727:S2CID
1693:arXiv
1256:than
1134:xenon
617:1.06
614:0.98
611:1.01
608:1.00
605:1.00
602:0.99
532:2.348
255:Gabon
211:is a
68:Biota
2876:Lead
2859:CEFR
2849:PFBR
2731:None
2541:RBMK
2526:AM-1
2456:EL-4
2430:WR-1
2412:AHWR
2356:MZFR
2324:CVTR
2313:AFCR
2240:VVER
2198:APWR
2193:APR+
2156:ABWR
2072:(in
1802:ISBN
1772:PMID
1719:ISSN
1626:2017
1596:PMID
989:and
785:and
749:and
599:C/M
594:150
591:148
588:146
585:145
582:144
579:143
423:and
401:and
251:Oklo
40:The
2864:PFR
2655:PMR
2633:AVR
2555:Gas
2493:by
2461:KKN
2395:ATR
2310:EC6
2270:by
2218:EPR
2151:BWR
2037:doi
2025:343
1987:doi
1934:doi
1878:doi
1839:doi
1764:doi
1711:doi
1666:doi
1588:doi
1576:293
1549:doi
1296:or
1082:or
1071:in
1036:ppb
1013:7.1
945:of
919:to
576:Nd
540:1.4
504:by
444:ppm
2988::
2598:He
2564:CO
2440:CO
2361:R3
2035:.
1993:.
1985:.
1977:.
1965:92
1963:.
1940:.
1932:.
1924:.
1912:74
1910:.
1876:.
1864:.
1860:.
1837:.
1827:50
1825:.
1770:.
1762:.
1752:93
1750:.
1725:.
1717:.
1709:.
1701:.
1689:23
1687:.
1664:.
1654:60
1652:.
1634:^
1617:.
1594:.
1586:.
1574:.
1570:.
1547:.
1537:25
1535:.
1464:Sm
1445:Sm
1399:Cs
1300:.
1091:Tc
1080:Ru
1065:Ru
1047:Ru
1032:Mo
1017:10
998:Ru
972:Ru
928:Ru
909:Tc
890:Ru
864:Ru
842:Mo
794:Nd
776:Nd
758:Nd
740:Nd
704:Nd
686:Nd
668:Nd
544:10
536:10
308:UF
288:kW
253:,
207:A
2738:)
2734:(
2566:2
2518:O
2516:2
2514:H
2442:2
2382:O
2380:2
2378:H
2287:O
2285:2
2283:D
2103:e
2096:t
2089:v
2076:)
2043:.
2039::
2031::
2001:.
1989::
1981::
1971::
1948:.
1936::
1928::
1918::
1884:.
1880::
1872::
1866:3
1845:.
1841::
1833::
1810:.
1778:.
1766::
1758::
1733:.
1713::
1705::
1695::
1672:.
1668::
1660::
1628:.
1602:.
1590::
1582::
1555:.
1551::
1543::
1491:α
1483:α
1475:α
1433:α
1368:U
1345:U
1320:U
1283:U
1265:U
1243:U
1232:U
1214:U
1196:U
1015:×
954:U
824:U
722:U
641:U
558:U
542:×
534:×
528:U
517:U
502:U
487:U
476:U
465:U
454:U
436:U
417:U
388:U
323:U
310:6
196:e
189:t
182:v
131:)
20:)
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