Journal of NUCLEAR SCIENCE and TECHNOLOGY, 6 (8), p. 474~477 (August 1969).

Production of "C and 'Be by TRIGA-II Research Reactor

Yoshiaki MARUYAMA*, Teruo MANRI* and Kazuhide KOMIYA*

Received February 20, 1969

"C has been produced by irradiating for 30 min in the pneumatic tube of a MICA-II research reactor about 700 mg of metaboric acid (HBO,), using the "B(p,n)11C reaction initiated by neutron-hydrogen recoil. The fast neutron flux (>1 MeV) was 9 X 10" n/cm2• sec. The "C pro- duced was separated from the irradiated target by distillation of CO,. The yield of "C at the end of irradiation was 0.27 mCi. 'Be also was produced by irradiating for 15 hr 1 g of hydroxide in the central experi- mental tube of the reactor, through the "Li(p,n)7Be reaction initiated by neutron-hydrogen recoil. The fast neutron flux was 2.2 x 10" n/cm2. sec. Separation of carrier-free 'Be from the irradiated target was obtained by co-precipitation with ferric hydroxide. The yield of 'Be was 0.2 ,mCi. For determining the influence on the 'Be yield brought by differences in the chemical com- position of target, irradiations were carried out on lithium compounds containing hydrogen, such as , lithium hydroxide hydrate, lithium and . Among these four lithium compounds, lithium hydroxide provided the highest yield of 'Be per gram of target.

the n(p n)"C reaction initiated by neutron- I. INTRODUCTION hydrogen recoils. It is now well established that secondary CO2 distillation was applied to separte "C reactions occur in a nuclear reactor. The from the irradiated terget. tritons generated by the 81.A.(n,a)3H reaction 'Be captures electrons and decays with a cause such nuclear reactions as "0(t,n)"F half-life of 53.61 days to produce 'Li. Roy and 26mg(t,p)28mgc2i. The protons and deute- et al.(6) have further shown that 'Be can be rons generated by neutron-hydrogen or generated by irradiating Li compounds con- neutron-deuterium collisions can also cause taining H in a reactor, using the 'Li(p, n)'Be secondary reactions such as "0(p, n)"P" and reaction. In the present work, 'Be was pro- "0(d , n)"F' in a nuclear reactor. These duced by irradiating lithium hydroxide in reactions can be used to produce certain light reactor, making use of the 'Li(p, n)7Be reac- radionuclides in a nuclear reactor. For tion initiated by neutron-hydrogen recoils. example, "F is produced by irradiating Li The yield of 'Be was expected to change with compounds containing 0 in a reactor, using the chemical composition of the target, and the eLi(n, a)31-1 and "0(t, n)"F reactions. in order to find the influence of this composi- The present work was undertaken for the tion on 'Be yield, different Li compounds purpose of producing "C and 'Be in a containing H, such as lithium hydroxide, TRIGA-II research reactor, by means of (p, n) lithium hydroxide hydrate, lithium acetate and reactions initiated by neutron-hydrogen re- lithium citrate were irradiated. The co-pre- coils. These radioisotopes are produced com- cipitation method with ferric hydroxide was mercially by cyclotron irradiation, using the applied to separate carrier-free 'Be from the (p, n) reaction on Li or B. irradiated targets. "C is a positron emitter decaying with a half-life of 20.4 min and producing "B. Roy II. EXPERIMENTAL et al.-) have shown that "C can be produced 1. Target Material and Irradiation in a reactor by the 81_,i(n,a)31-1 and "B(t , 2n) "C reactions . In the present work, "C has For the production of "C, commercial pure been produced by irradiating metaboric acid * Atomic Research Laboratory of Musashi Institute of in the TRIGA-II research reactor, through Technology, Ozenji, Kawasaki-shi, Kanagawa-ken.

56 — Vol 6 , No. 8 (Aug. 1969) 475 metaboric acid (HBO2) was used as target was co-precipitated with the ferric hydroxide. material without further purification. About This sample was centrifuged at 4,000 cpm for 700mg of metaboric acid was weighed accu- 5 min, and the supernatant discarded. The rately, sealed in cylindrical polyethylene cap- precipitate was dissolved in 20 ml of 1 N sule (4 ram diam., 50 mm long) and irradiated hydrochloric acid and precipitated by the same for 30 min in the pneumatic tube of a TRIGA-II procedure as before. research reactor. The precipitate was dissolved in a mini- For producing 'Be, commercial reagent mum amount of hydrochloric acid and passed grade lithium hydroxide was used for target through an H-form cation exchange column without further purification. About 1 g of of Diaion SK 1(1.0 cm diam., 6 cm high). After lithium hydroxide was sealed in the same washing the column with 5 m/ of distilled cylindrical polyethylene capsule as before, and water, the 'Be adsorbed on the resin was irradiated for 15 hr in the central experimental eluted with 0.5 N hydrochloric acid at a flow tube of the reactor. rate of 1 m//min. The thei mai and fast neutron fluxes in the In a preliminary column experiment for pneumatic tube of the reactor were 1.1 x 1012 elution curve determination, the eluate was and 9 x 10"n/cm2 sec respectively. At the cent- collected in a number of fractions, and the ral experimental tube of the reactor, these activity of each fraction counted with scintil- neutron fluxes were 4.2 x 10'2 and 2.0 X 10'2n/ lation counter. The elution curve of 'Be is cm2-sec respectively. The fast neutron fluxes shown in Fig. 1. were determined by measuring the 32P pro- duced by the 32S(n,p)32P reaction, adopting a value of 60 mb for the cross section of 32S.

2. Purification of "C "C was separated and purified by a meth - od similar to that reported by Roy et al.") After cooling for 5 min, the irradiated metabo- ric acid was transferred to a round-bottomed distillation flask with funnel for introducing liquid deagents in drops, where the acid was dissolved in 20 m/ of distilled water. As carrier for C, about 10 mg of sodium car- bonate were added to the solution, and 5 ml of concentrated sulfuric acid dripped in from the funnel. Fig. 1 Elution curve of Be The CO, released upon addition of the acid was distilled in a current of air by heating III. RESULTS AND DISCUSSION gently. The distillate was passed through The radiochemical purity of the irradiated anhydron tube to absorb water, and the CO, metaboric acid was determined from its g-ray was absorbed in 20 m/ of 3 N potassium spectrum and decay curve. Active impurities hydroxide solution. could be detected after cooling for 30 min. 3. Purification of 'Be The major inclusions were "No and "Br, After cooling for 2 weeks, the irradiated formed from the impurities contained in the lithium hydroxide was taken out of the poly- irradiated target. The chemical form of "C ethylene capsule and dissolved in 10 m/ of 6 N dissolved in the sulfuric acid solution was hydrochloric acid containing about 30 mg of determined by a method similar to that re- ferric chloride. Ferric hydroxide was preci- ported by Roy ei al.") From this experiment, pitated with a slight excess of concentrated it was concluded that "C existed almost ammonium hydroxide. In this process, 'Be entirely in the form of CO2.

57 — J. Nucl. Sci. Technol., 476

The active as well as inactive impurities contained in the target were eliminated by CO2 distillation, as described in the previous section. The r-ray spectrum of the purified sample only exhibited a photopeak at 0.51 MeV which decayed with a half-life of 20 min. The chemical yield for the purification of "C was about 95 %. The time taken for the purification of "C was about 10 min. The "C yield at the end of irradiation was calculated from the chemical yield, the abundance of the r-ray and the efficiency of the scintillation spectrometer. The experimental results are shown in Table 1. The radioactivities were measured Fig. 2 Excitation function of with a Hitachi 400 channel pulse height ana- "B(p lyzer with 14x2 NaI (T1) crystal. , n)"C reaction

Table 1 Yield of "C The radiochemical purity of the irradiated lithium hydroxide was determined by r-ray spectrum. The long-lived impurities were observed, after cooling for 2 weeks. The major inclusion was 'Cs, formed from im- purities contained in the irradiated salt. Active impurities such as the 'Cs, as well as inactive impurities contained in the Li compound were eliminated by the procedure described in Chap. ll, Sec. 2. Metaboric acid covered with Cd and boron The only photopeak found in the r-ray oxide were irradiated to obtain proof that spectrum of the final product was at 0.48 "C is produced by the "B(p ,n)"C reaction MeV. It decayed with 52 day half-life, which initiated by neutron-hydrogen recoils. The indicated belonging to 'Be. Carrier-free 'Be experimental results are shown in Table 1. was co-precipitated almost completely with Comparison of the "C yield obtained from ferric hydroxide. Percent recovery of the the neutron irradiation of metaboric acid with 'Be on the ferric hydroxide was 99. and without Cd show that "C is produced by Lithium hydroxide, lithium hydroxide reactions involving fast neutrons. In addi- hydrate, lithium acetate and lithium citrate tion, the low yield of "C obtained from boric were irradiated for the purpose of determining oxide shows that H atoms contribute to the the influence of target composition on 'Be production of "C. yield. Irradiation of H-containing substances with The yields of 'Be at the end of irradiation fast neutrons produces knock-on protons of were calculated for each target from the appreciable energy through collision with the chemical yield, the abundance of r-rays and H atoms. These protons may cause second- the efficiency of the scintillation spectrometer. ary reactions such as 180(p, n)"F"). The experimental resulte are shown in Table On the basis of these experimental results, 2, from which it is seen that, among the four it would appear reasonable to conclude that Li compounds, lithium hydroxide provides the the reaction "B(p, n)"C is the predominating highest 'Be yield per gram of target. one for the production of "C. The excitation function of the reaction "B(p,n)"C is shown in Fig. 2(7).

58 — Vol. 6 No. 8 (Aug. 1969) 477

Table 2 Yield of Be

IV. CONCLUSION research from the Ministry of Education. REFERENCES Carbon-II and 'Be were produced in a TRIGA-II research reactor, by using the (1) MARUYAMA,Y.: J. Nucl. Sci. Technol., 4[4], (p, n) reaction initiated by neutron-hydrogen 185 (1967). recoils. The experimental results have shown (2) WEISS, A.J., HILLMAN,M.: BNL-6607, (1963). that none of the reactions produce large (3) AUMANN,D.C., BORN,H.J.: Int. J. Appl, Ra- amounts of these radioisotopes in a reactor, diat. Isotop., 16, 727 (1965). (4) AMIEL,S., PEISACH,M.: Anal. Chem., 34[10] though the reactions might be used in reactor 1305 (1992). to produce trace amounts of these radio- (5) ROY, J.C., HAWTON,J. J. : Can. J. Phys., 39, isotopes. 1528 (1961). ACKNOWLEDGMENT (6) ROY, J.C., BRESESTI,M., HAWTON,J.J.: ibid., 38, 1428 (1960). This research was supported in part by (7) NORTON,M. H., NORMAN,F.R. : Phys. Rev., a grant in aid for fundamental scientific 88 [1] 19 (1952).

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