[en] The response of ZCAL, the E866 Downstream Calorimeter, to changes in gold beam position was examined during the October 1995 running period. Motion in the x direction was achieved by physically moving ZCAL: in the y direction by pitching the beam. These new results for gold incident on a heavily radiation-damaged ZCAL differ substantially from previous data for silicon impinging on a relatively undamaged calorimeter

[en] The anticipated range of particle energies at the LHC, coupled with the need for precision, low noise calorimetry makes severe demands on the dynamic range of the calorimeter readout. A common approach to this problem is to use shapers with two or more gain scales. In this paper, the authors describe their experience with a new approach in which a preamplifier with dynamic gain compression is used. An unavoidable consequence of dynamic gain adjustment is that the peaking time of the shaper output signal becomes amplitude dependent. The authors have carried out a test of such a readout system in the RD3 calorimeter, a liquid argon device with accordion geometry. The calibration system is used to determine both the gain of the individual channels as well as to map the shape of the waveform as a function of signal amplitude. A new procedure for waveform analysis, in which the fitted parameters describe the impulse response of the system, permits a straightforward translation of the calibration waveform to the waveform generated by a particle crossing the ionization gap. They find that the linearity and resolution of the calorimeter is equivalent to that obtained with linear preamplifiers, up to an energy of 200 GeV

[en] A laser interacting with a relativistic electron beam behaves like a virtual wiggler of an extremely short period equal to half of the laser wavelength. This approach opens a route to relatively compact, high-brightness x-ray sources alternative or complementary to conventional synchrotron light sources. Although not new, the laser synchrotron source (LSS) concept is still waiting for a convincing demonstration. Available at the BNL Accelerator Test Facility (ATF), a high-brightness electron beam and the high-power CO₂ laser may be used as prototype LSS brick stones. In a feasible demonstration experiment, 10-GW, 100-ps CO₂ laser beam will be brought to a head-on collision with a 10-ps, 0.5-nC, 50 MeV electron bunch. Flashes of collimated 4.7 keV (2.6 angstrom) x-rays of 10-ps pulse duration, with a flux of ∼ 10¹⁹ photons/sec, will be produced via linear Compton backscattering. The x-ray spectrum is tunable proportionally to the e-beam energy. A rational short-term extension of the proposed experiment would be further enhancement of the x-ray flux to the 10²² photons/sec level, after the ongoing ATF CO₂ laser upgrade to 5 TW peak power and electron bunch shortening to 3 ps is realized. In the future, exploiting the promising approach of a high-gradient laser wake field accelerator, a compact ''table-top'' LSS of monochromatic gamma radiation may become feasible

[en] The Cross-Section Evaluation Working Group (CSEWG) is a long-standing committee charged with the responsibility for organizing and overseeing the U.S. cross-section evaluation effort. It's main product is the official U.S. evaluated nuclear data file, ENDF. The current version of this file is Version VI. All evaluations included in ENDF are reviewed and approved by CSEWG and issued by the U.S. Nuclear Data Center, Brookhaven National Laboratory. CSEWG is comprised of volunteers from the U.S. nuclear data community who possess expertise in evaluation methodologies and who collectively have been responsible for producing most of the evaluations included in ENDF. In 1992 CSEWG added the Measurements Committee to its list of standing committees and subcommittees. This action was based on a recognition of the importance of experimental data in the evaluation process as well as the realization that measurement activities in the U.S. were declining at an alarming rate and needed all possible encouragement to avoid the loss of this resource. The mission of the Committee is to maintain a network of experimentalists in the U.S. that would provide needed encouragement to the national nuclear data measurement effort through improved communication and facilitation of collaborative activities. In 1994, an additional charge was added to the responsibilities of this Committee, namely, to serve as an interface between the more applied interests represented in CSEWG and the basic nuclear science community. This annual report is the second such document issued by the Committee. It contains voluntary contributions from eleven laboratories in the U.S. which have been prepared by members of the Committee and submitted to the Chairman for compilation and editing. It is hoped that the information provided here on the work that is going on at the reporting laboratories will prove interesting and stimulating to the readers

[en] This manual covers procedures and technology currently in use at the Environmental Measurements Laboratory. An attempt is made to be sure that all work carried out will be of the highest quality. Attention is focused on the following areas: quality assurance; sampling; radiation measurements; analytical chemistry; radionuclide data; special facilities; and specifications

[en] In Nov. 1990, fuel damage occurred durin refuel'mg in Ontario Hydro's Darlington Unit 2 Generating Station. The fatigue damage to the end plates was determined to be a result of acoustic pressure pulsations caused by the main coolant pumps. The pumps generated a pressure pulse in the coolant at 150 Hz, due to the 30 Hz pump rotation frequency multiplied by the five pump impeller vanes. Furthermore, the acoustic response of the piping amplified the pressure pulses in the headers and feeders. Thus pulsation amplitudes greater than 40 kPa (0-to-peak) reached the fuel. This system response had not been anticipated in the primary heat transport system design, nor was the fuel designed for such pressure pulse conditions. Thus, a small number of fuel channels was subject to unexpectedly high levels of pressure pulsations. The realization that all fuel channels have some potential for pressure pulsations, required that these conditions be incorporated into the tests qualifying new fuel or new channel hardware designs. As a result, methods were developed to test fuel in conditions similar to those experienced in reactor, and to develop techniques to determine acceptable fuel behavior. (author)

[en] Post-irradiation examinations (PIE) were conducted on prototype 43-element CANDU fuel bundles that overheated during test irradiations in the NRU reactor. PIE revealed that the bundles remained physically intact, but on several elements the Zr-4 sheath collapsed into axial gaps between the pellet stack and end caps, between adjacent pellets within the stacks, and into missing pellet chips and cracks. Helium pressurization tests showed that none of the collapsed elements leaked. Hydride blisters were discovered on a few elements, but the source of the hydrogen was not linked to a breach of the cladding or end caps. These defects were attributed to primary hydriding. Microstructural changes in the fuel and cladding indicate that the cladding-was briefly exposed to temperatures in the range 600-800^oC and pressures above 11.2 MPa. The results show that Zr-4 cladding behaves in a highly ductile manner during such transient, high-temperature and high-pressure excursions. (author)

[en] The analysis performed for this paper was applied during the 1995 PLGS outage. Because of problems replacing the channel closure plug on channel 001, it was necessary to drain the channel and replace the closure plug manually. This analysis was used to demonstrate that the procedure did not result in any threat either to fuel sheath integrity or to subsequent return to power for the fuel in channel 001. During the 1995 outage at Point Lepreau Generating Station (PLGS), the fuel channels underwent a Spacer Location and Relocation (SLAR) procedure. The SLAR tool is used during the defuelling of the channel. However, this tool restricts coolant flow in the channel. It was possible that the fuelling machine ram could have become jammed during this process, inhibiting flow in the fuel channel. To determine the possible consequences of this, an assessment was made of the heatup rate of the fuel bundles at decay powers in stagnant coolant. The goal was to determine a waiting period to allow for decay heat sources to diminish before beginning SLAR such that the maximum bundle temperature would not exceed a pre-defined limit. An interim limit of 600 degrees Celsius was initially used. The work reported in this paper addresses whether that limit can be supported. The goal was to ensure that there will be no fuel failures for the set of possible scenarios. While this analysis was undertaken for the accident scenario described above, it is generally applicable for any situation in which a bundle which is at decay power levels is expected to heat up to steam

[en] CANDU reactors are well-suited to utilize carrier fuels to burn excess Pu or actinide waste, because of their excellent neutron economy and fuel-management capabilities. The selection process for determining a good candidate(s) for the carrier matrix is in its early stages. SiC appears to be an excellent choice, because of its high thermal conductivity and resistance to oxidation and interaction with water coolant even at high temperatures, as well as its lack of neutron absorption. Resistance to fission-fragment damage and other issues relevant to its use as a fuel for CANDU reactors are being investigated. (author)

[en] A new analytical solution for the diffusion of fission-gas atoms inside the UO₂ fuel grain has been obtained. This solution and a related numerical procedure model fission-gas atom migration to the grain boundary under varying conditions of temperature and fission power and including the grain growth process. This new formulation is presented and its improvements and advantages are outlined. The fission-gas release results obtained with a developmental version of ELESIM, which incorporates this new model, as well as some other improvements, are presented. (author)