Initial characterization of the Cornell Cold Neutron Source
A device to moderate reactor spectrum neutrons to subthermal energies and filter out photons and higher energy neutrons has been designed, constructed and tested at Ward Laboratory, Cornell University. The Cornell Cold Neutron Source, which houses a chamber containing an organic moderator (mesitylene), the cryogenic cooling apparatus, and the first three one-meter long neutron guide elements, is physically inserted into a beamport in the reactor biological shield. The remaining 10 guide elements, which act as the filter, are mounted on a horizontal I-beam, and surrounded with suitable radiation shielding. The elements are horizontally displaced from the beamport axis in a combination curved/straight layout to eliminate directly transmitted radiation. The guide penetrates the reactor bay wall, terminating in a dedicated room to provide a location for low background experiments. Out-of-reactor bench thermal tests were conducted on the cryorefrigerator itself, then on a shortened version of the cryogenic cooling apparatus, and finally on the full scale system using heaters to simulate reactor induced nuclear heating in upstream cryogenic components. Temperature results, measured by silicon diodes, were close to predicted values. In-reactor tests were conducted to benchmark thermal performance, and to ascertain reliability of temperature and flux measurement systems. Type E thermocouples were selected for temperature measurement in the hostile reactor environment; although they depart from standard output at cryogenic temperatures due to inhomogeneities in the wire, crucial thermocouples located on the moderator chamber are calibrated against the in situ gas thermometer formed with the chamber as the sense bulb and a canister of known volume as the gas reservoir. In-reactor trials demonstrated reproducibility of thermocouple results. Moderator temperatures of 11 K at zero reactor power up to 28.5 K at 500 kW were obtained. Time-of-flight measurements were taken at 10 kW at the exit of the third guide element, where little filtering action has occurred, to ascertain the flux spectrum for both warm and cooled mesitylene moderator configurations. Acceptance diagram analysis was employed to estimate neutron conductance to the end of the guide, leading to a prediction of the exit thermal equivalent flux of 3.8 {times} 10{sup 6} n/cm{sup 2}-s at 480 kW.
- Research Organization:
- Cornell Univ., Ithaca, NY (United States)
- Sponsoring Organization:
- USDOE Office of Energy Research, Washington, DC (United States)
- DOE Contract Number:
- FG02-92ER75780
- OSTI ID:
- 656948
- Report Number(s):
- DOE/ER/75780-2-Pt.3; TRN: 98:010586
- Resource Relation:
- Other Information: TH: Thesis (Ph.D.); PBD: Jan 1998
- Country of Publication:
- United States
- Language:
- English
Similar Records
The Cornell University cold neutron beam facility
Cryogenic engineering and thermometry for an in-core apparatus