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J L Muñiz

Publications and source records attributed to J L Muñiz.

8 recordsLinked to original sources
PubMed2004

A new area multidetector dosemeter for mixed n-gamma fields.

A new instrument to assess neutron ambient doses has been designed and constructed. In its design, spectrometric capabilities have been implemented that allow to take into account the energy spectrum of the neutron field in the evaluation of the operational magnitude, ambient dose equivalent, H*(10). This dosemeter is based on the moderation-absorption technique and can be employed over a wide range of energies from thermal to 20 MeV. It consists of a spherical shaped polyethylene moderator with a set of thermoluminescence dosemeters (TLDs) inserted in different positions of its interior to evaluate the external neutron energy spectrum. At this moment the system uses pairs 6LiF:Mg,Ti (TLD-600) and 7LiF:Mg,Ti (TLD-700) thermoluminescence dosemeters for a better gamma discrimination. The dosemeter response matrix was calculated using the MCNP4C Monte Carlo code (MC). The viability of the dosemeter for area dosemetry has been examined experimentally showing its capabilities over a wide range of energies.

Algorithms↗
PubMed2002

The use of passive environmental TLDs in the operation of the Spanish early warning network 'REVIRA'.

As required by different international agreements, the regulatory body in Spain (Consejo de Seguridad Nuclear) implemented in 1992 a national automatic network (REVIRA) that continuously monitors radiation levels in order to give early warning of incidents having potential transboundary implications. The detector for environmental gamma-radiation dose rate is an active instrument based on a Geiger-Müller counter. However, the use of passive environmental dosemeters provides an additional low-cost dose estimate with an independent centralised calibration and even better basic features than active instruments. Since 1999, all 25 REVIRA stations have been monitored with passive TL environmental dosemeters based on LiF:Mg,Cu,P and operated according to the procedures established at Ciemat. This paper presents the obtained results and the further analysis considering differences in aspects such as photon energy response, inherent background or response to cosmic rays. The benefits of the use of passive environmental dosemeters in early warning networks are discussed.

Air Pollution, Radioactive↗
PubMed2002

Experience gained from the Ciemat External Dosimetry Service participation in several environmental dosimetry intercomparisons.

This paper summarises the experience gained by the Ciemat External Dosimetry Service (EDS) in the environmental dosimetry intercomparisons organised by the US Department of Energy. During the three latest intercomparisons. important dosimetry aspects such as energy calibration, energy response, dosimetric quantities and signal stability have been tested by the Ciemat EDS on up to seven different thermoluminescent (TL) materials, including hypersensitive phosphors, and employing several dosimetric systems. In last year's intercomparison, in addition to TL dosemeters the Ciemat EDS sent a set of silicon diode active dosemeters, usually used as personal dosemeters, to be tested in environmental conditions without intervention for more than 3 months. All the results obtained from different dosemeters have undergone an exhaustive analysis process in order to find some conclusions that may help to increase the knowledge of field performance of these devices in real but controlled environmental conditions.

Equipment Design↗
PubMed2002

Evaluation of the peripheral dose to uterus in breast carcinoma radiotherapy.

The absorbed dose outside of the direct fields of radiotherapy treatment (or peripheral dose, PD) is responsible for radiation exposure of the fetus in pregnant women. Because the radiological protection of the unborn child is of particular concern in the early period of the pregnancy, the aim of this study is to estimate the PD in order to assess the absorbed dose in the uterus in a pregnant patient irradiated for breast carcinoma therapy. The treatment was simulated on an Alderson-Rando anthropomorphic phantom, and the radiation dose to the fetus was measured using an ionisation chamber and thermoluminescence dosemeters. Two similar treatments plans with and without wedges were delivered, using a 6 MV photon beam with two isocentric opposite tangential fields with a total dose of 50 Gy, in accordance with common established procedures. Average field parameters for more than 300 patients were studied. Measurements showed the fetal dose to be slightly lower than 50 mGy, a level at which the risk to the fetus is uncertain, although several authors consider this value as the dose threshold for deterministic effects. The planning system (PS) underestimated PD values and no significant influence was found with the use of wedge filters.

Breast Neoplasms↗
PubMed1997

A study of LiF GR-200 for radiotherapy mailed dosimetry.

A study of the measurement performance of LiF GR-200 for radiotherapy mailed dosimetry is presented. The study was carried out in the practical working conditions of a mailed system where a lengthy delay between dosimeter preparation and the final readout can occur. Prompt and delayed TL measurements were employed to determine, among other characteristics, the reusability and the stability during storage at room temperature. From the results obtained it can be concluded that GR-200, although producing dose results adequate for mailed dosimetry, does not improve the performance attainable with LiF TLD-100.

Calibration↗
PubMed1995

Application of glow curve analysis methods to radiotherapy mailed dosimetry with LiF TLD-100.

This paper presents the results obtained in a study of LiF TLD-100 performance for mailed dosimetry in radiotherapy, using glow curve analysis of TL evaluation and reusable chips. An excellent reusability is assured by a simple thermal treatment of 1 h at 400 degrees C followed by a controlled and reproducible cooling to room temperature that accurately reproduces the sensitivity of the detectors. Particular attention was devoted to studying sensitivity changes during room temperature storage of TLD-100 detectors. These changes can be one of the major sources of uncertainty in mailed dosimetry, where long intervals can occur between detector preparation, irradiation and readout. Based on the features of the individual peak evolution during storage a rather simple method to correct for these sensitivity modifications is proposed. The analysis of the different influential factors permitted us to estimate a combined uncertainty for the measurement of absorbed doses within the 0.5-4 Gy range of 1.0%.

Humans↗
PubMed1992

Application of glow curve analysis methods to improve TLD-100 dose reassessment performance.

This paper presents a method of improving the TLD-100 dose reassessment performance. This method consists of applying numerical analysis techniques for evaluating the TLD-100 phototransferred thermoluminescence (PTTL) glow curve. From this analysis, a simple procedure for estimating the ultraviolet background components usually present in phototransferred thermoluminescence (TL) signals has been established. This procedure has been implemented in a computer program which performs the automatic evaluation of the glow curves and extracts the dose information contained in the PTTL curves. The use of this computer-aided evaluational method has enabled the extension of the working range of estimated absorbed dose down to 0.2-0.5 mGy with very adequate operational quality for doses even below the conventionally admitted lower reestimation limit (approximately 2 mGy). Because TL readout is a destructive process, the ability to reestimate doses can be important in any kind of dosimetric activity, such as operational dosimetry programs. The other commonly used dosimeter, film, uses a nondestructive readout and, therefore, presents some advantages over TLD when dose reassessment is necessary. With the reported improvements in the TLD-100 dose reassessment performance, the full range of absorbed doses covered by film dosimetry can now be reliably reassessed using TLD-100 dosimeters.

Gamma Rays↗