Pneumatic Rabbits

The pneumatic rabbits provide the Materials Testing Reactor with facilities to irradiate small samples of material in the high-neutron fields of the reactor. The horizontal holes that constitute the pneuntatic rabbit facilities are HR-1, 2. 3, and 4- However, any beam hole can be adapted to provide additional shuttle facilities. Holes HR-3 and 4 are of 4 in. I.D. and extend inward only to the reactor tank. Holes HR 1 and 2, which are 1 in. in diameter, extend completely through the reactor and pass within 1 in. of the. active lattice (see Fig. 2.D).  

The only parts of these facilities which actually exist in the construction are the holes and liners and the vacuum exhaust lines within the reactor. It is intended that the HR-1 hole always be used for -through shuttles, i.e., shuttles that pass directly through the reactor. The equipment for this hole and the HR-3 and 4 holes will bedesigned and set up by the experimenters, and it is therefore not discussed further. 

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Irradiation I. The samples and standards (with appropriate flux monitors) are individually exposed to a neutron flux of 1 X 1013 neutrons cm"2 sec-1 for periods of V2 min for fly ash and 1 min for coal via a pneumatic rabbit system. The samples are irradiated and counted individually because of the short half-life of the (n/y) products of some of the elements and the requirement of counting at a specific time after irradiation. A copper flux monitor is irradiated with each sample to allow... 

ORNL would design channels for the pneumatic rabbits. ANL would... 

In addition to the thimble holes, tank section D is pierced by the aluminum bar containing the HR 1 and HB-2 pneumatic rabbit holes and by the HT-1 facility. The aluminum bar containing the rabbit holes is shown in Figs. 2.D and 2.4.A. It reaches to the bottom of the reflector merely to simplify the beryllium machining and stacking. The rabbit holes themselves pass just undeir the extension of HG-9 and within 1 in. of the east face of the active lattice. 

Scott, D., Pneumatic Rabbits in the X-Pile, ORNL CF-47-11-35, October 31, 1947. 

Scott, D., Status of the Pneumatic Rabbit Design in the High Flux Pile, ORNL CF-48-6-134, June 9, 1948. 

A sample recycling pneumatic rabbit system must be made available for CESIAA. It is essential that the recycling system be installed as close as possible to the reactor so that the sample transfer time is minimal. Consideration must be given to the type and level of radiation in the surrounding areas so that the gamma ray spectrum of a sample is not influenced by the background radiation. 

Several major differences existed between this scheme and one compatible with the PBR facilities. The PBR did not have an operating pneumatic transfer irradiation facility, nor was there a sophisticated y-ray spectrum analysis and data reduction computer program available. Irradiation facilities at PBR were hydraulic. Aluminum capsules (rabbits) were used to contain and transfer samples to and from the core. 

The selected samples were sent to the University of Maryland. They were opened in a Class 100 clean room and half of each filter was cut from the holder with a stainless steel scalpel, folded and transferred to an acid-washed polyethylene bag. The bags were placed into pneumatic tube sample carriers ("rabbits") along with standards and flux monitors, and irradiated in the National Bureau of Standards (NBS) reactor at a flux of 5 x 10 n/cm -sec. Gamma-ray spectra of the irradiation products were observed with Ge r-ray detectors using procedures discussed by... 

Provision was made in the rabbit to hold either a metal target on edge or a small cylindrical container of a salt of the element to be bombarded. After bombardments of approximately a minute were made In this Jiffy probe, the doors of the cyclotron were opened immediately the target blown out of the probe Into a lead carrier which was manually carried to the laboratory for processing. Later arrangements were made to transport the rabbit to the laboratory with a pneumatic tube. ... 

Pneumatic tube systems are also useful for rapid transference of samples irradiated In a reactor (17 ). In one such facility the sample to be Irradiated Is placed In lusteroid or polyethylene capsules and Is Inserted In a polyethylene rabbit which runs through the pneumatic tube to the side of the reactor. After Irradiation, the rabbit is returned to a hood in which chemical operations can be performed, is quickly opened and the sample removed. The pneumatic tube system la operated by vacuum rather than by compressed air to minimize... 

A typical run procedes as follows The nitrite pill,-H, is placed in the rabbit, E, and is sealed in with, a thin piece of paper, G, held on by Scotch tape. The rabbit is placed in the pneumatic tube with the pill ejector, P, end down. 

Research Centre of Casaccia (Italy). Two different irradiation facilities are used, namely, the pneumatic transfer (so-called Rabbit) and the rotating rank facility (so-called Lazy Susan). 

Typically, a set of samples of a few milligrams up to gram amounts are individually wrapped in aluminum foil and packed into the irradiation container. Pneumatic transfer systems are usually used for transport of samples to the irradiation position. Figure 2 shows a schematic representation of a typical irradiation position. The sample rabbit is rotated by air-blow so as to obtain a quasihomogeneous activity distribution. Excessive heat is removed from the sample by the air-jet. Exposure periods depend upon the half-lives of the expected product activities for a typical multielement trace analysis, irradiation times of a few hours are sufficient. 

Hgure 2 Typical bremsstrahlung exposure position schematic representation. 1 = Sample and reference material 2=sample rabbit 3=tangential airflow injection inlet 4=pneumatic tube 5=compressed air inlet for sample rabbit retransfer 6 = bremsstrahlung converter assembly 7=electron beam window (Ti) 8 = accelerator tube. 

Irradiations for conventional INAA, PNAA, and RNAA are usually performed using a pneumatic sample transfer system (rabbit system) normally available in the reactor. In some cases, a hydraulic system is employed. For ENAA, samples can be irradiated in specially built pneumatic sites fitted with thermal neutron shields (e g., Cd, B, Gd). The samples may also be wrapped in one of these shields and placed in a conventional rabbit system. 

Using the operator information books provided, determine how long you must irradiate a 28 ml sample of pure argon gas in the rabbit (pneumatic) tube to produce an activity of 1000 microcuries (22.4 liters= 1 mole of a gas)... 

WHICH ONE of the following gases is used to propel the rabbit in the pneumatic tube system ... 

When short-lived radionuclides are used, it is important that the sample is available as soon as possible after the irradiation. Moreover the radiation level at the target station directly after the irradiation may be very high, so that entering the shielded target area and manual removal of the sample holder from the beam transport system must be avoided. Therefore a pneumatic transfer system such as the one described by Strijckmans (39) can be used. This system allows samples mounted on a copper rabbit to be send from the sending station to the irradiation station situated in a room shielded with thick concrete walls. 

Fig. 11-20 illustrates the operation of the system and shows the rabbit. Initially all electro-pneumatic valves (V) are closed and the turbine and the pump are off. The following sequence is then carried out under control of a microprocessor ... 

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