JP0450435 JAERI - Corif 2004 - 006 10. Disposal and recycling 10.1 ChaflengesforDisposalofln-adiatedBeryllium G.R. Longhurst, M. L. Carboneau, C. K. Mullen, J. W. Sterbentz Idaho National Engineering and Envirorimental Laboratory P.O. Box 1625, Idaho Falls, Idaho 83415-3860, USA Beryllium is used as a neutron reflector in many research reactors around the world. Additionally, it is being considered as a plasma-facing material for the International Thermonuclear Experimental Reactor and for use as a neutron multiplier in tritium breeding blankets. Because of swelling associated with helium production under irradiation, it must be replaced at regular intervals in applications were dimensional tolerances must be maintained. Though dimensional tolerance will be less significant in fusion reactors,. beryllium still will require disposal at the end of life or as cleanup of sputtered beryllium is necessary. Disposal or recycling of that beryllium is influenced by a number of factors, among which is its radioisotopic inventory. Tritium inventories have been known for years, but it has recently been discovered that activation of minor impurities including nitrogen, iobium, and uranium have the potential to change the waste classification for disposal. Recycling of beryllium with significant radioisotopic inventory has yet to be developed. Beryllium from different sources has widely differing uranium impurity levels, but nitrogen content and other impurities are determined more by processing methods. Other factors influencing radiological characteristics of irradiated beryllium are the neutron energy spectrum and the temperature at which it is irradiated. Research is needed to explore techniques for mitigating consequences of radioisotopic inventories in disposal or recycling of irradiated beryllium. 1. OVERVIEW disposal sites 2 A greater problem exists when Although considerable attention and concern the concentration of transuranic isotopes is high have lately been directed to issues surrounding enough that the waste becomes classified as health hazards from contact with beryllium [1], an transuranic or TRU. Tat results when alpha- emerging issue, and the subject of this report, is the emitting isotopes with atomic numbers greater than disposal of beryllium following irradiation. The 92 and half-lives greater than 20 years have International Thermonuclear Experimental Reactor concentrations of 100 nCi/g or greater. (ITER) plans to use beryllium as a plasma-facing A number of fission research reactors around surface and as a neutron multiplier in tritium the world make use of beryllium as a neutron breeding blankets. Beryllium exposed to the plasma reflector. In the U.S., the Advanced Test Reactor will be sputtered and re-deposited in crevices and (ATR), the High Flux Isotope Reactor (HFIR), and pockets around the machine. Eventually, it will the Missouri University Research Reactor MURR) require removal and disposal. Blanket beryllium are the operating reactors with the most significant will also require end-of-life disposal. inventories of irradiated beryllium. Over time, the Previously, irradiated beryllium was considered (n, 2n) and (n, cc) reactions, always accompanying to be low-level radioactive waste. Sites that accept the use of beryllium in reactors, generate substantial low-level radioactive waste have limits on concen- amounts of4 He , 3He, and 3H. The accumulation of trations and total inventories of radionuclides they these gases, which are insoluble in beryllium, can accept. There is little radiological risk from causes the beryllium to swell. That requires 'OBe or 3H formed when beryllium is irradiated with periodic replacement and eventual disposition of neutrons unless the beryllium corrodes. In that case, these irradiated beryllium components. While radioisotopes will b e r eleased i n p roportion t o t he fusion reactor first walls and blankets will not see fraction of beryllium corroding. Recent quite as much neutron fluence as fission reactor investigations have shown that radioisotopes 14C, reflectors, the beryllium in them will still become 2311pU, 4 'Am, and other transuranics are also activated and may become TRU waste. generated because of impurities in the berylliuni, Problems with disposal have only recently come such as nitrogen and uranium. In addition, Au to light because of analyses performed to impurity transmutes to Hg. These isotopes may characterize beryllium from the ATR. It is become a problem if they exceed limits in the waste instructive to review the work leading to the finding acceptance criteria at low-level radioactive waste that such material may be TRU. - 225 - JAERI-Conf 2004-006 NORTH Outer Shim Control Cylinder R l tor 010R) Shim ing ue (Di Figure 1. Advanced Test Reactor cross-section ad one of the beryllium reflector blocks. 1.1 Advanced Test Reactor (20-24 in) in diameter depending on how many The ATR reflector consists of w edge-shaped removable beryllium sleeves are ins talled. The first blocks and 16 outer shim control cylinders permanent reflector was removed in 1983. The (OSCCs). These must be replaced at approximately second was replaced in 2000. n addition to te I 0-year i ntervals. 0 ne su ch block a nd t he r elative reflector, there are several beryllium plugs cm placement of these blocks in the ATR core are (2 in) in diameter and 61 cm 24 i) long that are shown in Figure 1. Each block has a mass of about used as fillers when test holes are not occupied. 81.2 kg 179 lb) after machining. Hence a set of Presently, one of the removed reflectors is stored in blocks would contain 650 kg (1,432 lb) of an above-ground vault constructed of lead and beryllium. Each block is 129.5 cm (51 in) long 31, stainless steel, and the other is in the HFIR spent- Within each of the reflector blocks are 2 outer fuel pool. shim control cylinders (OSCCs). The OSCCs are essentially right circular cylindrical colurrins 18.4 1.3 Missouri University Research Reactor cm 7.25 in) in diameter and 119 cm 46.8 in) long, The other large operating reactor in the U.S. comprised of tree xial segments. They hold witl a beryllium reflector is the Missouri University hafnium plates used to control reactor flux. OSCC Research Reactor (MURR) at the University of mass, excluding the mass of attached hafnium Missouri, Columbia. Its reflector is a monolithic components, is 57 kg 125 lb). The combined mass sleeve 50.2 cm 19.75 in) in outside diameter, 69 of the beryllium in each core is about 1570 kg cm 2.73 in) thick, and 94 cm 37 in) in height. It is (3,458 lb). replaced at 8-year intervals on the basis of INEEL Since ATR operations began, this beryllium has and HFIR reported critical neutron fluences. MURR been r eplaced 5 t imes, a nd the 6 th r eflector s et i s operators did see cracking and swelling of their first soon to be replaced. reflector in 1981. There is one reflector in the MURR pool now awaiting disposal 4]. 1.2 High Flux Isotope Reactor The High Flux Isotope Reactor (HFIR) at Oak 1.4 Other Reactors Ridge National Laboratory is another research Around te world there are 31 operating reactor tat uses a beryllium reflector. The reactors with Be reflectors 5]. Nineteen of these permanent reflector is nominally an annular having p ower I evels a bove I M Wth a re I isted i n cylinder, about 122 cm 48 in) in diameter, 61 cm Table . (24 in) high with a central cavity about 50-60 cm - 226 - JAERI-Conf 2004-006 Table . Reactors with power levels above IO MWh having beryllium reflectors operating in 2000. Rated Thermal Power Flux Fast Flux DateOn Reactor Location (MWth) (n/cm2s) (n/cm2s) Line ATR INEEL, ID, USA 250 5.30E+14 1.50E+15 Jul-67 HFETR Chenadu, Sichuan, China 125 6.20E+14 1.7013+15 Jan-79 BR-2 Mol, Belgium 100 1.20E+15 8.40E+14 Jun-61 HFIR ORNL, TN, USA 100 1.50E+14 1.30E+15 Aug-65 MIR-M I Dirnitrovgrad, Russia 100 5.OOE+14 Dec-66 SM-2 Dimitrovgrad, Russia 100 5.OOE+15 2.OOE+15 Oct-61 OSIRIS Saclay, France 70 2.70E+14 1.60E+14 Sep-66 R-2 Nykoping Sweden 50 4.OOE+14 4.OOE+14 May-60 RSG-GAS-30 Jarkata. Indonesia 30 5.OOE+14 3.OOE+14 Jul-87 SILOE Grenoble, France 25 5.0013+14 5.OOE+14 Mar-63 SAFARI-1 Pretoria, South Africa 20 2.50E+14 4.OOE+14 Mar-65 Trigia-II Pitesti, Romania 14 2.60E+14 2.60E+14 Nov-79 BER-2 Berlin, Germany 10 9.OOE+13 4.50E+12 Apr-91 EWA Otwock, Poland 10 1.00E+14 1.30E+14 Jun-58 MURR Columbia, MO, USA 10 6.OOE+14 1.00E+14 Oct-66 RBT-10/1 Riar, Russia 10 7.40E 3 6.90E+13 Dec-83 RBT-10/2 Riar, Russia 10 7.40E+13 6.90E 3 Dec-84 SAPHIR Wuerenlingen, Switzerland 10 1.20E+14 1.OOE+14 Apr-57 WWR-M Kiev, Uraine 10 1.50E+14 7.OOE+13 Dec-60 Lower-power reactors do not have the same and countries in Central Africa. The variability in neutron fluence or beryllium replacement frequency impurity content is illustrated in Table 2 where as the higher-power reactors. There are also impurities of concern to the present investigation decomissioned reactors, such as the Materials Test are listed for four different types of beryllium: one Reactor (MTR) and the Engineering Test Reactor (TShG) from Kazakhstan 6 the standard US (ETR) at the INEEL and the NASA Plum Brook grade Brush Wellman S-65 7], material from early Reactor at Sandusky, Ohio with beryllium reflectors ATR reflectors ftirnished by Kawecki Beryllium, still awaiting disposal.