5. Deuteron disintegration in condensed matter

5. Deuteron disintegration in condensed matter - DEUTERON...

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Unformatted text preview: DEUTERON DISINTEGRATION IN CONDENSED MATTER © M. Ragheb 9/20/2007 INTRODUCTION 150 M-A [MeV] 150 100 50 50 0 0 -50 -50 -100 -100 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 100 Mass Number A 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 M-A [MeV] We discuss the possibility of deuteron disintegration in condensed matter through photonuclear and wave polarization reactions known as the Oppenheimer Phillips process and the possibility of nucleosynthesis that originates outside stellar environments. Deuteron disintegration could provide a source of neutrons leading to transmutation that would drive the surrounding elements to regions of higher stability as closed nuclear shells or nuclei with the magic numbers. Mass Nu m be r A Fig. 1: The mass defect diagram for the naturally occurring (left) and the artificially created and naturally occurring isotopes (right) shows local minima as well as a major minimum around nickel and iron. Evidence is presented about deuteron disintegration occurring in natural nuclear reactors as part of the Oklo phenomenon leading to an anomalous value of the deuterium D to hydrogen H ratio (D/H) from the natural occurrence value of 150 ppm to the observed value of 127 ppm. We calculate an estimate of the deuteron disintegration constant under the conditions of the Oklo phenomenon as 7.47 x 10-14 sec-1. We discuss the possibility of fissile breeding using deuteron disintegration, the maintenance of a subcritical source driven systems, and present deuteron disintegration as a possible source of heating in comets and in the Earth’s mantle and outer core; complementary to the radioactive decay of K40, Th232 and the uranium isotopes. The suggested nucleosynthesis process amounts to an increase of pseudo nuclear entropy process, decreasing the D/H ratio in condensed matter, concentrating the occurrence of condensed matter around the local minima corresponding to the closed nuclear shells at the magic numbers, and at the major minimum corresponding to the most stable elements such as nickel and iron, in the mass defect versus mass number curve for both the natural and artificial nuclides. The proposed mechanism may have been observed as different manifestations of low intensity nuclear reactions, sometimes referred to as cold fusion earlier on reported by Fleishman and Pons and by Jones et. al. and later pursued by numerous authors. MAGIC NUMBERS NUCLIDES Neutron capture from deuteron disintegration could encourage the migration of the surrounding nuclides to regions of high stability and high abundance with respect to the neighboring nuclides. These are characteristics for nuclei for which the magic numbers for N or Z are 2, 8, 20, 28, 50, 82, and 126. The magic nuclei are more tightly bound and require more energy to be excited than the non magic nuclei. These correspond to closed shell in the structure of the nucleus in the same way that we encounter closed electronic shells in the structure of the atom. The frequency of the stable isotones, which are nuclides with an equal number of neutrons is shown as a function of the neutron number N = A - Z. Higher frequencies of occurrences correspond to the magic numbers. . 8 Stable Isotones Number 7 6 5 4 3 2 1 96 91 86 81 76 71 66 61 56 51 46 41 36 31 26 21 16 11 6 1 0 Neutron Number N Fig. 2: The frequency of the stable isotones as a function of the neutron number N. Higher frequencies correspond to the magic numbers N = 20, 28, 50 and 82. UNIQUE CHARACTERISTICS OF THE DEUTERON The deuteron 1D2 possesses unique characteristics compared to the other stable nuclei in nature: 1. It is the only known existing two-particle nuclear bound system. 2. It has the lowest Binding Energy (BE) among all other nuclei. Table ** compares the BE per nucleon and the total binding energy of the deuteron to the other nuclei. 3. Deuterons do not possess any excited states that are stable with respect to decomposition . 4. In the deuteron nucleus, the constitutive neutron and the proton spend about one half of the time outside the range of the nuclear forces. Using the expression for the nuclear radius: 1 R = 1.25 A 3 [ fm ] where: A is the mass number of the nucleus, (1) 1 fm = 1 Fermi = 10-13 cm the radius of the deuteron will be: R = 1.25 x 2 1 3 = 1.57[ fm ] compared with the separation distance between the neutron and the proton at 4 fm. 5. The charge distribution of the deuteron nucleus is very unsymmetrical. 6. The separation between the center of mass and the center of charge in the deuteron is the most extreme among other nuclei. These characteristics suggest that even though the deuteron is stable with respect to natural radioactive decay, it is a very loose particle that may break up if it existed under conditions that will further enhance the instabilities in its nuclear structure to the point of disintegration. Table 1: Binding Energy per nucleon (B/A) and total Binding Energy (BE) of typical nuclides. Nuclide 2 1D 3 1T 3 2He 4 2He 6 3Li 7 3Li 9 4Be Average per nucleon BE/A, [MeV/nucleon] 1.11 2.83 2.57 7.08 5.33 5.60 6.47 - BE, [MeV] 2.22 8.48 7.72 28.30 32.00 39.20 58.19 8.50 ORIGIN OF DEUTERIUM It is believed that virtually all the deuterium in the universe was created in nuclear reactions in the first 2 minutes after the Big Bang. This left the universe with a Deuterium to Hydrogen ratio (D/H) of 27 parts per million (ppm). This matches both theoretical calculations and measurements conducted by the Wilkinson Microwave Anisotropy Probe (WMAP) satellite probe launched by NASA to measure the afterglow remnant of the Big Bang. Through the process of nucleosynthesis, the D/H ratio, according to various models, should have fallen into the range of 10-15 ppm. Measurements in the 1970s by the Copernicus satellite revealed that the ratio D/H varies from one site to another in the Milky Way galaxy. This contradicted the view that hydrogen is well mixed within the galaxy and therefore the same D/H ratio should be expected throughout the galaxy. Fig. 3: Dust cloud star AE Aurigae contains deuterium. NASA Photopgraph. In 2006, observations with NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) looked for the signature of deuterium in ultraviolet light coming from various locations in the galaxy. Attention was directed to dusty and relatively undisturbed regions by searching for low levels of gaseous silicon and iron. The reasoning was that these elements condensed into solid dust grains that would have deuterium attached to them. The measurements estimated that the D/H ratio in these dusty locations was 5 ppm. Other observations found D/H ratio levels at 23 ppm in environments where the dust was likely to vaporize at the vicinity of hot stars and supernovae. The current belief is that the galaxy’s overall D/H ratio is the higher value of 23 ppm, with the lower value of 5 ppm thought to be only as an illusion caused by the deuterium hiding on silicon and iron dust grains. The higher observed ratio of D/H at 23 ppm compared with the theoretically expected D/H of 10-15 percent resulting from stellar nucleosynthesis, suggests that an unexpectedly large 85 percent of the hydrogen gas in our galaxy has never been inside a star. An explanation of the higher ratio suggests that the galaxy has absorbed much more pristine gas that is unaltered by the stars than previously thought. This could have occurred by the Milky Way galaxy absorbing other small galaxies which processed their gas at a slower rate than the Milky Way galaxy. DEUTERIUM IN METEORITES Some meteorites contain organic molecules that date back to the birth of the planets about 4.56 billion years ago. It is observed that these organic molecules in interplanetary dust are unusually rich in deuterium and the isotope nitrogen15. The conclusion is that they are just as primitive as the solar system. The D/H ratio in the comets Halley, Hyakutake and HaleBopp averaged 320 ppm or 320 / 23 = 13.9 times that in the solar system. In the atmospheres of the gaseous planets Jupiter and Saturn the D/H ratio is about 20 ppm. Earth’ sea water has a D/H ratio of 160 ppm; an enrichment of 160 / 23 = 6.95 times relative to its value in the solar nebula. The interesting fact is that the D/H ratio on Earth at 160 ppm has lost ½ its deuterium compared with the one in the comets. DEUTERIUM WAVE POLARIZATION, THE OPPENHEIMERPHILLIPS PROCESS Early on in the study of nuclear reactions, it was observed that (D , p) reactions occur at deuteron energies well below the Coulomb barrier of a target nucleus. Moreover, the cross sections are considerably larger than those for the corresponding (D , n) reactions. These reactions were observed in the accelerator bombardment of the bismuth209 isotope, which occurs with a 100 percent natural abundance, with deuterons resulting in the production of polonium210 as an alpha emitter, the latter eventually decaying into the stable isotope lead206: 1 D 2 + 83 Bi 209 → 1 H 1 + 83 Bi 210 83 84 Bi 210 → −1 e0 + 84 Po 210 Po 210 → 2 He + 82 Pb 4 (2) 206 This reaction appeared favored, emitting protons, to what was thought to be the favored reaction, emitting neutrons, through compound nucleus formation: 1 D 2 + 83 Bi 209 → 0 n1 + 84 Po 210 210 → 2 He 4 + 82 Pb 206 84 Po (3) These two observations were at odd with what would be expected from the compound nucleus model for nuclear reactions, which suggests that there should not be reactions below the Coulomb barrier and that neutron emission should predominate over proton emission from the compound nucleus formed. Oppenheimer and Phillips explained this apparent anomaly based on the peculiar properties of the deuteron. The deuteron is a loosely bound nuclear structure with a binding energy of only 2.23 MeV. This can be calculated as: BE = [ Z .M ( p ) + N .M (n ) − M ']x931.5 (4) or: BE = [ Z .M ( H ) + N .M (n ) − M ]x931.5 (5) M(p) = mass of proton M(n) = mass of neutron where: M(H) = neutral atom mass of hydrogen M' = mass of bare nucleus M = mass of neutral nuclide Thus for the deuteron: BE = [ M ( H ) + M (n) − M ( D )]x 931.5 = 2.2246 MeV where: M(D) = 2.01410179 amu M(n) = 1.00866497 amu M(H) = 1.00782504 amu This actually determined experimentally from the threshold for the photodisintegration reaction of the deuteron into a proton and a neutron: γ + 1 D2 → 1 H1 + 0 n1 (6) and combined with the mass spectrographic data for the masses of H and D to determine the neutron mass, since no accurate method for a direct measurement of the neutron mass is known. The deuteron binding energy is evidently low compared with that of other nuclei: 8.48 MeV for the triton 1T3; 7.72 MeV for 2He3, 28.3 Mev for the alpha particle 2He4, 32 MeV for 3Li6, 39.2 MeV for 3Li7, and about 8.5 MeV for the average nucleon in a nucleus. The absence of excited states of the deuteron, its low binding energy, and its large size (the neutron and the proton spend about one half the time outside the range of the nuclear force) result from the weakness of the nuclear force when viewed in the context of its small range. Moreover, the charge distribution of the deuteron is very unsymmetrical. Its center of mass and its center of charge do not coincide as they do in the case of the alpha particle. A large separation of about 4 x 10-13 cm exists between the constituents proton and neutron, which actually spend most of their time outside the range of their attractive mutual force. Oppenheimer explained the preponderance of proton emission over the expected neutron emission on the basis of a quantum mechanical model of the deuteron a s a wave function with a proton and a neutron component. As the deuteron wave function approaches the Coulomb barrier of a nucleus, a polarization effect occurs repelling away the charged proton component, but not affecting the neutral neutron component. As the deuteron gets closer to the nucleus, the neutron component of the wave function can be captured by the nucleus, leaving the proton component unaffected. The net effect appears as a neutron capture process where the neutron is passed on from the deuteron to the nucleus, with the proton left free. The process only invokes polarization and does not involve any tunneling process through the Coulomb barrier. VOLKOFF AND BETHE CALCULATIONS Volkoff calculated the ratio of the Oppenheimer-Phillips penetrability to the Gamov-Condon-Gurney penetrability of the nucleus potential barrier which invokes tunneling through the Coulomb barrier. He considered ratio for different nuclei of charge Z as a function of the deuteron energy in MeV. His most interesting observation was that the ratio increases for lower deuteron energies, as well as for higher values of Z. Hans Bethe also calculated the same ratio for various nuclear charges Z as a function of the deuteron energy. He also observed that his calculations predict a higher ratio at lower deuteron energies, even below the deuteron binding energy. The work of Volkoff and Hans Bethe suggests that at low deuteron energy, the Oppenheimer-Phillips process will predominate over classical tunneling of the Coulomb barrier. In addition it increases as the nuclear charge increases, suggesting its higher preponderance in the heavy elements compared with the light elements. NATURAL SOURCES OF GAMMA RAYS Neutrons can originate from natural environmental causes such as cosmic ray showers. They can also originate from energetic gamma rays from natural sources such as thallium208, a member of the thorium232 natural decay chain, which emits gamma rays at an energy above the thresholds for 1D2 as well as 4Be9. In fact the maximum photon energy from Tl208 is 2.614 MeV above the deuteron binding energy threshold of 2.26 MeV, and it occurs with an intensity of 100 percent. Fig. 4: Gamma rays emissions from the 81Tl208 isotope. Table 2: Gamma ray energies and their relative intensities in Tl208. Isotope 81Tl 208 * Gamma ray photons energy keV 211.40 233.36 252.61 277.358 277.72 485.95 510.77 583.191 587.7 650.1 705.2 722.04 748.7 763.13 821.2 860.564 883.3 927.6 982.7 1004 1093.9 1125.7 1160.8 1185.2 1282.8 1381.1 1647.5 1744.0 2614.533 Relative Intensity, Percent* 0.18 0.31 0.70 6.36 0.050 22.8 85.2 0.04 0.036 0.022 0.203 0.043 1.83 0.040 12.53 0.031 0.132 0.205 0.005 0.40 0.005 0.011 0.017 0.052 0.007 0.002 0.002 100.0 For absolute intensity multiply by 0.9916 PHOTO NUCLEAR AND DEUTERIUM BERYLLIUM DISINTEGRATION One can consider the interaction by a few high energy gamma photons from common naturally occurring gamma ray sources such as 81Th208 through photo-nuclear (γ , n) reactions as a cause of deuteron disintegration. For instance one can consider the interaction of energetic gamma photons with beryllium9 , which possesses a relatively loose last neutron, through the reaction: γ + 4 Be9 → 0 n1 + 2 He4 + 2 He4 (7) In fact, the binding energy of the last neutron in the 4Be 9 nucleus is just 1.6 MeV. This can be calculated as follows: BE ( 4 Be9 ) = {[ M ( 2 He 4 ) + M ( 2 He 4 ) + M ( 0 n1 )] − M ( 2 He 4 )}x 931.5 = 1.5734 MeV The threshold energy for this reaction, which is also the binding energy of the last neutron in the 4Be9 nucleus is: 4 EthBe = 1.666 ± 0.002 MeV 9 The emitted neutrons would then be absorbed in the other surrounding elements. The resulting helium could be the one observed in some experiments. With the exception of deuterium and beryllium, the binding energy of the last neutron for other nuclei lies between 5 and 13 MeV. If 4Be9 is used we can write a neutron capture reaction: X ( Z , A) + 4 Be9 → [C ( Z , A + 1)] + 2 He4 + 2 He4 If deuterium is the target nucleus, if say beryllium deuteride is used, the following reaction could occur: 1 D 2 + 4 Be9 + → 2 He4 + 2 He 4 + 1T 3 which is a charged particle neutronless reaction. PHOTO NUCLEAR DEUTERON DISINTEGRATION One can also consider the photo disintegration reaction of the deuteron: γ + 1 D2 → 1 H1 + 0 n1 (8) The generated neutrons could activate some other elements in the sample creating some radioactive species and causing transmutations. As an example, in heavy water cooled and moderated reactors such as the Canadian Deuterium Uranium (CANDU) design, those neutrons are absorbed in deuterium itself leading to the production of tritium through the reaction: 0 n1 + 1 D2 → 1T 3 + γ (9) The binding energy of the deuteron is known to be equal to: 1 EthD = 2.226 ± 0.003 MeV 2 Gamma photons from 81Th208 with an energy of 2.614 MeV are capable of disintegrating the deuteron with its lower biding energy of 2.226 MeV without the need to invoke any other phenomena such as tunneling through the Coulomb barrier, nor for that matter electron shielding to surmount the barrier. DEUTERON FISSILE BREEDING Through deuteron disintegration, it is possible to consider the nuclear transmutations through neutron capture of the fertile isotopes into fissile ones. This would not need the achievement of a critical configuration in a nuclear reactor or the use of particles accelerators as neutron sources. The relevant nuclear reactions with the Th232 isotope would be: 1 D 2 + 90Th 232 → 90Th 233 + 1 H 1 Th 233 → −1 e0 + 91 Pa 233 90 91 (10) Pa 233 → −1 e0 + 92U 233 The relevant nuclear reactions with the U238 isotope would be: 1 D 2 + 92U 238 → 92U 239 + 1 H 1 92 U 239 → −1 e0 + 93 Np 239 93 Np 239 → −1 e0 + 94 Pu 239 (11) DEUTERON DISINTEGRATIONJ IN NATURAL REACTORS, THE OKLO PHENOMENON Under the time span conditions of the Oklo phenomenon, the produced fissile isotope would have further decayed through the reaction: 94 Pu 239 → 2 He4 + 92U 235 The overall reaction would then be: (12) 1 D 2 + 92U 238 → 92U 239 + 1 H 1 92 U 239 → 93 Np 239 → 94 Pu 239 → 2 He 4 + 92U 235 −1 e0 + 93 Np 239 −1 e0 + 94 Pu 239 (13) __________________________________ 1 D 2 + 92U 238 → 2 −1 e0 + 2 He 4 + 1 H 1 + 92U 235 Notice that the helium produced here would result from a radioactive decay process rather than a fusion process. Deuteron disintegration can also lead to the fissioning of the produced fissile isotopes generating elements in the middle of the periodic table such as: 1 D2 + 92 U 235 → 1 D2 + 94 Pu 239 → 1 D2 + 92 U 233 → 36 Kr 97 + 54 53 Ba137 +2 0 n1 + 1 H1 (14) Xe136 + 38 Sr 97 +3 0 n1 + 1 H1 (15) 56 I137 + 39Y 96 +3 0 n1 + 1 H1 (16) The presence of neutrons from these reactions could lead to the establishment of a source S driven subcritical system generating a neutron flux: φ = S + kS + k 2 S + k 3S + k 4 S + ... = S (1 + k + k 2 + k 3 + k 4 + ...) (17) where k is the multiplication factor. For a subcritical system, k is less than unity and we can write: φ= S , ∀ k <1 1− k (18) This provides an alternative explanation for the occurrence of the Oklo phenomenon as a subcritical rather than a critical system. DEUTERON DISINTEGRATION FOR FUSILE BREEDING In the same way that fissile breeding could be achieved through the process of deuteron disintegration, fusile breeding could be achieved using lithium through the tritium breeding reaction: 1 D 2 + 3 Li6 + → 2 He4 + 1T 3 + 1 H1 (19) The generated proton could interact with deuterons leading to: 1 H1 + 1 D2 → 2 He3 +γ (20) The proton could also interact with the produced tritium, further producing helium through the reaction: 1 H1 + 1T 3 → 2 He 4 +γ (21) ENHANCED RADIOACTIVITY AND MUON CATALYSED FUSION For a while no one thought that a nuclear property such as the half lives of radioactive isotopes or the fusion rate can be altered by environmental factors. Otto Reifenschweiler showed in 1994 that the activity of tritium absorbed in titanium particles could be reduced by 40 percent at temperatures in the range of 115-275 o C. Muon catalyzed fusion was predicted in 1947, and there was an agreement between theory and experiments that showed that a small temperature change can considerably alter the fusion rate. REFERENCES 1. M. Ragheb and G. H. Miley, “Deuteron Disintegration in Condensed Media,” Journal of Fusion Energy, Vol. 9, No. 4, pp. 429-435, 1990. 2. Magdi Ragheb and George H. Miley, “On the Possibility of Deuteron Disintegration in Electrochemically Compressed D+ in a Palladium Cathode,” Fusion Technology, Vol. 16, pp. 243-247, Sept. 1989. 3. M. Shaheen , M. Ragheb, “Anomalous Deuteron to Hydrogen Ratio in Naturally Occurring Fission reactions and the Possibility of Deuteron Disintegration,” Journal of Radioanalytical and Nuclear Chemistry, Articles, Vol. 158, No.2, pp. 323-342, 1992. 4. M. Ragheb and S. Behtash, “Symbiosis of Coupled Systems of Fusion D-He3 Satellites and Tritium and He3 Generators,” Nucl. Sct. Eng., 88, p. 16, 1984. 5. M. Ragheb, G. H. Miley, J. F. Stubbins, and C. Choi, “Alternate Approach to Innertial Confinement Fusion with Low Tritium Inventory and High Power Densities,” J. Fusion Energy, 4, 5, p. 339, 1985. 6. M. Fleishman and S. Pons, “Electrochemical Induced Nuclear Fusion of Deuterium,” J. Electroanal. Chem., 261, p. 301, 1989. 7. S. E. Jones et. Al. “Observation of Cold Fusion in Condensed Matter,” Nature, 338, p. 737, Apr. 1989. 8. G. Friedlander, J. W. Kennedy, and J. M. Miller, Nuclear and Radiochemistry, p. 310, John Wiley and Sons, New York, 1964. 9. J. R. Oppenheimer and M. Phillips, “Note on the Transmutation Function of Deuterons,” Phys. Rev., 48, p. 500, 1935. 10. F. W. Walker, G. J. Kirouac, and F. M. Rourke, “Chart of the Nuclides,” Knolls Atomic Power Laboratory, 2005. 11. C. M. Lederer and V. S. Shirley, Eds., Table of Isotopes, John Wiley and Sons, Inc., New York, 1978. 12. I. Kaplan. Nuclear Physics, p. 487, Addison-Wesley Pubishing Co., Inc., Reading Massachussetts, 1966. 13. R. D. 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