F.H. Ruddy

Proton and alpha particle response characteristics of CR-39 polymer for reactor and dosimetry applications

Proton and alpha particle response characteristics of CR-39 polymer for reactor and dosimetry applications have been investigated. The investigation included measurement of track etch rate as a function of proton and alpha particle energy. A calibration curve of track diameter versus proton energy is presented. The promising capabilities for reactor proton spectrometry and passive fast-neutron personnel dosimetry techniques are discussed.

Optical efficiency for fission-fragment track counting in Muscovite Solid-State Track Recorders

In order to determine absolute fission rates from thin actinide deposits placed in direct contact with Muscovite Solid-State Track Recorders, it is necessary to know the efficiency with which fission-fragment tracks are recorded. In this paper, a redetermination of the optical efficiency, i.e., the fraction of fission events recorded and observed in the Muscovite, is reported. The value obtained from a well-calibrated thin deposit of /sup 252/Cf and Muscovite etched about 90 min. in 49% HF at room temperature, is 0.9875 +- 0.0085. Manual counting was used. Preliminary results from a deposit of /sup 242/Pu are also reported, along with preliminary comparisons of track counting with an automated system. Reasons for the discrepancy of the optical efficiency reported here with an earlier measurement are also reported. 5 references, 1 figure, 3 tables.

Applications of solid state track recorder neutron dosimetry for fuel debris location in the three mile island unit 2 makeup and purification demineralizers

Abstract As a result of the Three Mile Island Unit 2 (TMI-2) accident on March 28, 1979, fuel debris was dispersed into the primary coolant and auxilliary systems of the reactor. The presence of fuel may be traced by using the neutron activity which is associated with the burn-in of higher actinides (about 300 neutrons/sec/kgU). Solid state track recorder (SSTR) neutron dosimetry is the most sensitive technique for measuring low neutron fluxes. Hence, neutron dosimetry is being performed at TMI-2 to locate fuel debris and subsequently aid the reactor recovery effort. Herein, the results of a scoping measurement on the fuel content of TMI-2 Makeup Demineralizer A are reported along with relevant calibration measurements. The total amount of fuel estimated in Demineralizer A, 1.7 kg, corresponds to a total neutron source of about 500 neutrons/sec. At the detector positions, data were obtained with neutron fluxes as low as 10-3 n/sec/cm2, demonstrating the extreme sensitivity of the SSTR method.

Solid-State Track Recorder Materials for Use in Light-Water-Reactor Pressure Vessel Surveillance Exposures

Solid-state track recorders (SSTR) have been used extensively in reactor neutron dosimetry. Further applications of SSTR in the U.S. breeder reactor, light water reactor, and magnetic fusion energy reactor programs have been planned. Extension of high-accuracy SSTR techniques to high-fluence irradiations requires careful attention to many experimental details. One very important aspect of this work is the selection of materials that comprise the SSTR. A variety of solid state track recorder materials has been examined for light-water-reactor pressure vessel surveillance applications. Emphasis has been placed on SSTR characteristics which are most relevant to high-fluence irradiations. The SSTR materials investigated include eleven different types of muscovite mica from worldwide geographical locations and different commercial suppliers, synthetic and natural quartz crystals, and quartz glass. Activatable impurities are appreciable only in the case of mica SSTR, and relative isotopic impurity concentrations are reported. Fissionable impurity concentrations in mica and quartz are also reported. The properties of mica and quartz SSTR subjected to high-fluence (3 X 10 2 1 neutrons (n)/cm 2 ), high-temperature [427°C (800°F)] irradiations have been investigated. Recommendations regarding suitable types of mica and quartz are made.

APPLICATIONS OF SOLID STATE TRACK RECORDERS IN UNITED STATES NUCLEAR REACTOR ENERGY PROGRAMS

The domain of Solid State Track Recorder (SSTR) applications in United States nuclear reactor energy programs extends from the harsh high temperature environments found in high power reactor cores to very low flux environments arising in out-of-core locations, critical assemblies, or away from reactors (AFR) experiments. The neutron energy region arising in these applications is very broad, covering more than eight decades from thermal up to fusion energies. The range of neutron flux/fluence intensity is even greater, extending over more than thirteen decades. As a consequence, use of a variety of SSTR is entailed in U.S. Fast Breeder Reactor (FBR), Light Water Reactor (LWR), and Magnetic Fusion Energy Reactor (MFER) programs. A summary status is presented of selected SSTR experiments undertaken in these programs at the Hanford Engineering Development Laboratory (HEDL).

Buffon needle method of track counting

A new technique of quantitative track counting, the Buffon needle method, is advanced. It is based on random sampling of the solid state track recorder (SSTR) surface. This new method extends quantitative track scanning to track densities well up into the track pile-up regime. It is shown that the Buffon needle method possesses a reduced dependence upon both track density nonuniformity and track size distribution. Sources of experimental error arising in the Buffon needle method are assessed. The validity of the Buffon needle method is demonstrated down to at least the 10% uncertainty level (1sigma) by manual sampling of high fission track density mica SSTR observed with scanning electron microscopy.

Light water reactor pressure vessel surveillance dosimetry using solid state track recorders

Abstract The accumulation of neutron dose by the pressure vessel of an operating nuclear power plant results in damage in the form of steel embrittlement. For example, the ductile to brittle transition temperature increases with increasing damage. To ascertain the safe operating lifetime of the reactor pressure vessel, dosimetric measurements must be made to evaluate the neutron dose to the pressure vessel which is then used to estimate cumulative radiation damage. Advanced dosimetry techniques, including solid state track recorder (SSTR) techniques, are being evaluated for surveillance of operating reactors. Low neutron fluence calibration and standardization measurements using SSTRs in pressure vessel mockup benchmark neutron fields in the U.S.A., Belgium, and England are described. In addition, high fluence SSTR dosimetry capsules have been irradiated with metallurgical specimens in a pressure vessel mockup facility. The design and deployment of advanced SSTR dosimetry capsules in operating power reactors are also described.

Selected etching and annealing properties of Brazilian quartz crystals for solid state track recorder applications

The etching and annealing properties of Brazilian quartz crystals are under investigation to determine their suitability for use as solid state track recorders (SSTR) and damage monitors in nuclear reactor environments, where temperatures and neutron fluences are high. Observer objectivity in counting fission tracks has been established at the 1 to 2% level, and a method of standardizing chemical etching from one sample of quartz to another has been found. A method has also been found to make corrections for track loss due to thermal annealing in terms of the effect of the annealing on the track size in the direction of maximum bulk etch rate parallel to the 100 plane, provided the fractional track loss does not exceed approx. 40%.

OPTICAL EFFICIENCY AND OBSERVER OBJECTIVITY FOR FISSION TRACK COUNTING IN MUSCOVITE SOLID STATE TRACK RECORDERS

ABSTRACT The optical efficiency of Muscovite mica for manual fission track counting is being redetermined to form a data base for comparison with automatic counting systems. Exposures in contact with a 252Cf source prepared at Harwell have been carried out. Whereas the absolute fission rate of the source is still being evaluated, the current results indicate that observer objectivity is at the 0.4% uncertainty level.

Thermal annealing studies in muscovite and in quartz

In order to use Solid State Track Recorders (SSTR) in environments at elevated temperatures, it is necessary to know the thermal annealing characteristics of various types of SSTR. For applications in the nuclear energy program, the principal interest is focused upon the annealing of fission tracks in muscovite mica and in quartz. Data showing correlations between changes in track diameters and track densities as a function of annealing time and temperature will be presented for Amersil quartz glass. Similar data showing changes in track lengths and in track densities will be presented for mica. Time-temperature regions will be defined where muscovite mica can be accurately applied with negligible correction for thermal annealing.