Core Inventory Research Articles

The inventories of anthropogenic Ph, Zn, As, Cd, and the radionuclides 137Cs and excess 210Pb in lake sediments of the Adirondack region, USA

We determined the inventories of four anthropogenic trace elements, Pb, Zn, As, and Cd, and two radionuclides, 137Cs and excess 210Pb, in sediment cores collected from eight remote lakes in the Adirondack region of the northeastern United States. The inventories of all six substances vary considerably among the sediment cores, although the lakes and their associated catchments must have received similar cumulative per unit area atmospheric inputs of these substances. These variations are highly correlated, indicating that the trace elements and radionuclides are affected in a coherent way by the processes controlling their deposition to the sediments of these lakes. Assuming that the anthropogenic trace element inventories in each sediment core are enhanced or depleted relative to cumulative atmospheric deposition to the extent indicated by the sediment core inventories of either 137Cs or excess 210Pb, we produced estimates of the cumulative atmospheric inputs of the four anthropogenic trace elements to this region. Comparison of the excess 210Pb normalized anthropogenic Pb, Zn, Cd inventories of the Adirondack sediment cores with excess 210Pb normalized inventories of the same substances in a group of South Central Ontario lakes suggests that the Adirondack region has received greater cumulative anthropogenic inputs of Pb, Zn and Cd by a factor of 1.6, 4.5, and 2.9, respectively.

Fission Product Release Pathways in Three Mile Island Unit 2

AbstractThe release of fission products from the Three Mile Island Unit 2 plant during and following the accident was low and consisted almost entirely of noble gases and an estimated 15 Ci of 131 I. Such a small iodine release is surprising considering that 52% of the core inventory of radiocesium and 40% of the radioiodine were released from the reactor core. Significant releases of fission products to the plant systems commenced at 138 min following failure of the fuel rods. The primary pathway to the environment was through the letdown/makeup purification system to the auxiliary building plant stack. The large releases (40 to 50%) of noble gases, cesium, and iodine to the reactor building were contained within the building for 1 yr until the noble gases were released under controlled conditions.

The Current Status of ARAC and Its Application to the Chernobyl Event

The Atmospheric Release Advisory Capability (ARAC) project, developed by the Lawrence Livermore National Laboratory (LLNL), provides real-time dose assessments and estimates of the extent of surface contamination that may result from an atmospheric release of radioactivity. It utilizes advanced computer-based data communication and processing systems to acquire the meteorological and source term information needed by the three-dimensional atmospheric dispersion models to derive the consequence assessments. The ARAC responded to the recent Chernobyl reactor accident in the Soviet Union by estimating the source term and the radiation dose distribution due to exposure to the radioactive cloud over Europe and the Northern Hemisphere. This analysis revealed that approximately 50% of the estimated core inventories of 1-131 and Cs-137 were released. The estimated committed effective dose equivalent due to inhalation of radioactivity during cloud passage is of the order of 10 mrem within parts of Scandinavia and eastern Europe, while most of the populations within central Europe were exposed to levels ranging from 1-10 mrem. The amount of Cs-137 released by the Chernobyl accident far exceeds that released by previous reactor accidents, but is only about 6% o of the Cs-137 produced by the atmospheric weapon testing programs.

An initial assessment of the Chernobyl-4 reactor accident release source

The long-range atmospheric dispersion model MESOS has been used to provide a preliminary evaluation of the distribution over Western Europe of radioactivity released during the accident which occurred at the Chernobyl-4 reactor in the USSR in April 1986. The results of this analysis have been compared with observations during the first week or so following the accident of airborne contamination levels at a range of locations across Europe in order to obtain an estimate of the accident release source. The work presented here was performed during the 6-8 weeks following the accident and the results obtained will be subject to refinement as more detailed data become available. However, at this early stage they indicate a release source for the Chernobyl accident, expressed as a fraction of the estimated reactor core inventory, of approximately 15-20% of the iodine, tellurium and caesium isotopes, approximately 1% of the ruthenium and lesser amounts of the other fission products and actinides, together with an implied major fraction of the krypton and xenon noble gases.

The Filtered Venting System Under Construction at Barsebäck

A filter venting containment system, bearing the acronym FILTRA, will be installed at the Swedish nuclear power plant Barsebäck. The Barsebäck Power Plant is owned by the Southern Sweden Power Supply (Sydkraft AB) and has two 1700-MW boiling water reactors. The reactors are of ASEA-ATOM design with pressure suppression containments (Mark II-type).The installation of the filter venting system is a condition set by the Swedish government for a continued operating license after September 1, 1986. The construction work for the FILTRA plant, the first of its kind ever planned, will be completed at the end of 1985.The FILTRA is designed so that 99.9% of the core inventory of radioactivity, excluding inert gases, is retained in the reactor containment and filter system in the event of containment venting. Another design guideline is to achieve passive functioning of the FILTRA plant during the first 24 h of an accident.The FILTRA plant is common to the two reactors on the site and consists mainly of two systems, a venting system (pressure relief system) and a filtering system. The total cost is approximately U.S. $15 million.

U.S. chemical exporters face EEC rule deadline

The primary tool in the U.S. for regulating new and existing chemicals is the Toxic Substances Control Act. In the European Economic Community, the comparable tool is the directive commonly referred to as the sixth amendment. The purposes of the regulations are fundamentally the same, as are their requirements for premarket notification. But there are many differences in the way these two work, and these differences are becoming more and more apparent as the sixth amendment is implemented. The sixth amendment, passed on Sept. 18, 1979, recently has entered an important phase, one that is particularly important to U.S. companies that market chemicals in Europe. EEC published its European Core Inventory (ECOIN) March 31, signaling the beginning of a nine-month open period during which companies can add to the inventory compounds that are being marketed in Europe. A time frame, however, is specified for these entries. The substance must have been sold between January 1979 ...

On the failure modes of alternative containment designs following postulated core meltdown

The containment response to a postulated core meltdown accident in a PWR ice condenser containment, a BWR Mark III containment and a BWR non-inerted Mark I containment has been examined to see if the WASH-1400 containment failure mode judgement for the Surry large, dry containment and the Peach Bottom Mark I inerted-containment are likely to be appropriate for these alternative containment plant designs. For the PWR, the representative accident chosen for the analysis is a large cold leg break accompanied by a loss of all electric power while the BWR representative event chosen is a recirculation line break without adequate core cooling function. Two containment event paths are studied for each of these two cases, depending on whether or not containment vapor suppression function is assumed to be available. Both the core and the containment pressure and temperature response to the accident events are computed for the four time intervals which characterize (a) blowdown of the pipe break, (b) core melt, (c) vessel melt-through, and (d) containment foundation penetration. The calculations are based on a best estimate of the most probable sequence, but certain phenomena and events were followed down multiple tracks. These include the temperature of the non-condensibles escaping the ice condenser into the upper compartment, the performance of the pressure suppression system, the distribution of non-condensibles between compartments, and the degree and rate of combustion of hydrogen generated from metal-water reactions. For the PWR ice condenser case, results indicate that the containment would be breached by (i) steam overpressurization during the blowdown period (time less than 20 sec) if the ice condenser fails to perform its function, (ii) by overpressurization and thermal stress during the core melt period if 25% or more of the core zirconium reacts with water followed by hydrogen burning and, and (iii) by the overpressurization due to non-condensibles before containment floor penetration is completed. For the BWR Mark III case, similar conclusions can be drawn for the loss of vapor suppression, and for the hydrogen burning if the extent of zirconium-water reaction is more than 35% of the core inventory. If the hydrogen burning fails to materialize, the containment can retain its integrity until containment meltthrough provided the melting is confined to the reactor pedestal area. It appears that the non-inerted Mark I containment is not so vulnerable to overpressurization from hydrogen burning as the Mark III; however, acceptable temperatures may be exceeded.

Gas-cooled fast breeder reactor designs with advanced fuel and cladding

This paper examines the potential impact of some alternative cladding and fuel materials being considered for the liquid metal fast breeder reactor (LMFBR) on the performance and design of large commercial gas-cooled fast breeder reactors (GCFRs). Mixed carbide fuel and Inconel 718 cladding material were examined. Another cladding alternative considered was silicon carbide (SiC), which presents some interesting possibilities in high-temperature performance. Design concepts based on the above fuel and claddings were examined and compared with a reference oxide/316 stainless steel design based on a commercial 4000 MW(th) [∼1500 MW(e)] system. Substantial benefits can be derived from a high-temperature cladding material such as Inconel 718 or 16Pe; core volume and steam generator heat transfer area could be reduced by 20% or more, and significant reductions in core inventory and doubling time are possible. Carbide fuels would reduce the number of fuel rods by 50% because of higher linear power, and doubling time would be lowered.

Civil Defense Implications of an LMFBR in a Thermonuclear Target Area

A pot-type Liquid-Metal-Cooled Fast Breeder Reactor was analyzed as a civil defense problem in a nuclear atiack. In order for the core inventory of fission products to add significantly to casualties, they must be promptly released from the reactor structure due to blast from the weapon, and added to the fallout. The analysis of the interaction of weapon effects with the significant elements of the structure surrounding the reactors was checked by high explosive tests on scale models. It is concluded that for prompt ejection of the core, a megaton-range weapon must be detonated close enough so that the reactor is in the crater, or that an air shock greater than 170 atm impacts at near normal incidence the fueling cell wall crossing the sodium tank. For megaton weapons, delivery accuracy substantially exceeding that ascribed to deployed strategic delivery systems would be required. 16 references. (auth)