Surface dose rate variations in planar and curved geometries of 106Ru/106Rh plaque sources for ocular tumors

2021 ◽  
Vol 89 ◽  
pp. 200-209
Author(s):  
A.K. Bakshi ◽  
Vandana Shrivastava ◽  
Arghya Chattaraj ◽  
Kasthuri Samuel ◽  
T. Palani Selvam ◽  
...  
Keyword(s):  
2018 ◽  
Vol 108 ◽  
pp. 34-40 ◽  
Author(s):  
Jon B. Hansen ◽  
Wesley S. Culberson ◽  
Larry A. DeWerd

Author(s):  
J. A. Mason ◽  
W. Hage ◽  
R. Price ◽  
A. C. Tolchard ◽  
A. C. N. Towner

The paper describes an automated non-destructive assay (NDA) system for the measurement and characterization of radioactive waste. The Waste Characterisation System (WCS) can be adapted to measure a variety of drum sizes: 60, 220 (55 gallon) and 440 liter, the latter with a maximum weight of 1500 kg (1.5 tonnes). The NDA system includes a Tomographic Segmented Gamma Scanner (TSGS) and an active/passive neutron Differential Die-away (DDA or DDT). The system can assay a wide variety of waste types in a range of waste matrices. The assay stations are linked by a heavy duty roller conveyor which incorporates a 20 drum buffer store, a load cell (built into the conveyor), bar code readers and a dose rate measurement station. The Tomographic Segmented Gamma Scanner (TSGS) combines conventional high resolution gamma spectrometry and a tranission source to interrogate a waste drum in vertical slices (segments) as for Segmented Gamma Scanner (SGS) measurements. However, in the case of the TSGS, while the drum is rotated, it is also moved in the horizontal direction leading to an enhanced ability to correct the gamma ray energies, from the nuclides of interest, for the attenuation of the matrix. The TSGS can also be operated as a conventional SGS for the measurement of homogeneous waste drums. The DDA is a very sensitive active neutron interrogation method that uses thermalised neutrons from a pulsed source within the chamber to irradiate a waste drum. Prompt neutrons from fissile material present in the waste (e. g. 239Pu, 235U) are detected and provide a measure of the fissile content in the drum. In passive mode, the DDA determines the even Pu nuclides exhibiting significant spontaneous fission (e.g. 240Pu). Measurement accuracy depends on correction algorithms to compensate for self-shielding and matrix effects in waste drums containing hydrogenous materials. In addition, the DDA will be provided with the Fission-Fission Neutron Correlation Analysis System (FFnC) which is an absolute technique eliminating the need for matrix dependent mass calibrations, and allowing separate U and Pu determination using delayed neutron counting. The FFnC technique will be tested for the first time on the WCS. The NDA system incorporates integrated stations to determine the weight and dose rate of each drum, the former built into the conveyor the latter as part of the TSGS. Six Geiger Muller tubes measure the surface dose at three positions on the drum side, one at 1 metre from the drum and one each measuring the surface dose of the top and bottom of the drum. The assay instruments are linked to a heavy duty conveyor system onto which up to 20 waste drums can be loaded for delivery to the various measurement stations, thus permitting unattended, automated operation. Once measured, the drums remain on the conveyer in a holding system waiting to be unloaded. Automation is provided using a programmable logic controller (PLC) and associated computers. A central computer and associated software is used for data acquisition and management.


1990 ◽  
Vol 17 (3) ◽  
pp. 416-421 ◽  
Author(s):  
Mohamed M. Ali ◽  
Faiz M. Khan
Keyword(s):  

2015 ◽  
Vol 103 ◽  
pp. 120-127 ◽  
Author(s):  
Sudhir Kumar ◽  
P. Srinivasan ◽  
S.D. Sharma ◽  
Sanjay Kumar Saxena ◽  
A.K. Bakshi ◽  
...  

2011 ◽  
Vol 175 (1) ◽  
pp. 343-350 ◽  
Author(s):  
Y. F. Chen ◽  
R. J. Sheu ◽  
S. H. Jiang ◽  
J. N. Wang ◽  
U. T. Lin

Author(s):  
Roger Nelson ◽  
Alton D. Harris

The U.S. Department of Energy (DOE) is responsible for waste management from nuclear weapons production and operates the Waste Isolation Pilot Plant (WIPP) for permanent disposal of defense-generated transuranic waste (TRU), as authorized by Congress in 1979. Radioactive waste in the U.S. has historically been managed in one of two ways depending on its penetrating radiation dose rate. Waste with surface dose rates above 200 millirem/hour (0.002 sievert/hour) and waste that has been managed remotely (remote-handled). In 1992, Congress passed the WIPP Land Withdrawal Act, which created the regulatory framework under which DOE was to operate the facility, and authorized disposal of waste up to 1,000 rems/hour (10 Sievert/hour). Subsequently, DOE submitted applications to the Environmental Protection Agency (EPA), at the Federal level, for certification to operate WIPP, and to the New Mexico Environment Department (NMED), at the State level, for a hazardous waste permit. Both applications described the characterization methods that DOE proposed to use to ensure only compliant waste was shipped to WIPP. No distinction was employed in these methods concerning the surface dose rate from the waste. During the applications review, both regulatory agencies came to the conclusion in their approval that DOE had not demonstrated that remote-handled transuranic (RH-TRU) waste could be adequately characterized. Therefore, WIPP was only granted approval to begin waste disposal operations of waste with surface dose rates less than 200 millirem/hour (0.002 sievert/hour) — or contact-handled transuranic (CH-TRU) waste. Emplacement of CH-TRU waste in WIPP began March 26, 1999. However, WIPP was designed for disposal of both CH- and RH-TRU waste, with the RH-TRU waste in canisters emplaced in the walls of the underground disposal rooms and CH-TRU waste in containers in the associated open drifts. Therefore, as disposal rooms filled with CH-TRU waste, the space along the walls for RH-TRU waste disposal was lost. This made removal of the regulatory prohibition on RH-TRU waste a very high priority, and DOE immediately began an iterative process to change the two regulatory bases for RH-TRU waste disposal. These changes focused on how DOE could rely on CH-TRU characterization methods for adequate characterization of RH-TRU waste. On January 23, 2007, the first shipment of RH-TRU waste was finally received at WIPP. The revised EPA certification and NMED permit now both consider all waste characterization methods to be equally effective when applied to either CH- or RH-TRU waste, as DOE maintained in the original applications over 10 years ago.


2019 ◽  
Vol 46 (5) ◽  
pp. 2430-2443 ◽  
Author(s):  
Jon B. Hansen ◽  
Wesley S. Culberson ◽  
Larry A. DeWerd

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