N REACTOR

The Hanford N Reactor. The Hanford N reactor was built in 1964 for purposes of plutonium production during the Cold War. It used graphite as moderator, pierced by over 1000 Zircaloy 2 tubes. These pressure tubes contained slightly enriched uranium fuel cooled by high temperature light water. The reactor also provided 800 MWe to the Washington PubHc Power Supply System. This reactor was shut down in 1992 because of age and concern for safety. The similarity to the Chemobyl-type reactors played a role in the decision. 

Woodruff, E.M., Graphite surveillance in N reactor. In Proceedings of the IAEA Specialists meeting on the Status of Graphite Development for Gas Cooled Reactors, IAEA-TECHDOC-690, IAEA, Vienna, 1993. pp. 273 280. 

The DOE N-Reactor is one of the plutonium production reactors located on the Hanford Reservation near Richland, Washington. It is graphite moderated, pressurized water reactors that in addition to production of special nuclear materials also provided steam to turbine generators owned by the Washington Public Power Supply System for electric power production. It began op ition in 1 is put into standby status in 1988 and closed because of similarities to Chernobyl. 

The mean frequencies of events damaging more than 5% of the reactor core per year were found to be Internal Events 6.7E-5, Fire 1.7E-5, Seismic 1.7E-4, and total 2,5E-4. Thus, within the range of U. S. commercial light water reactors The core damage frequency itself, is only part of the story because many N-Reactor accident sequences damage only a small fraction of the core. The... 

N Reactor accidents are expected at lower fuel temperatures than LWR accidents. The large thermal capacity of the graphite moderator stack, the low melting point of the fuel (1,407"K) and the GSCS contribute to lower accident temperatures which retains heavy metals in the fuel. 

Miller, L. A., et al., 1990, Application of Phenomenological Calculations to the N-Reactor Probabilistic Risk Assessment, ANS Topical Meeting, The Safety, Status and Future of Non-Commercial Reactors and Irradiation Facilities, Boise, ID, Sept. 31 - Octobier 4, 1990. 

Wyss, G. D. et al., 1990, Accident Progression Event Tree Analysis for Postulated Severe Accidents at N-Reactor, SNL, SAND89-2100. 

Irradiated Fuel A historically important and continuing mission at the Hanford site is to chemically process irradiated reactor fuel to recover and purify weapons-grade plutonium. Over the last 40 years, or so, several processes and plants— Bismuth Phosphate, REDOX, and PUREX—have been operated to accomplish this mission. Presently, only the Hanford PUREX Plant is operational, and although it has not been operated since the fall of 1972, it is scheduled to start up in the early 1980 s to process stored and currently produced Hanford -Reactor fuel. Of nine plutonium-production reactors built at the Hanford site, only the N-Reactor is still operating. 

Obviously this approach is not easily extended to cascades containing more than three reactors and, in those cases, an alternative trial and error procedure is preferable. One chooses a reactor volume and then determines the overall fraction conversion that would be obtained in a cascade of N reactors. When one s choice of individual reactor size meets the specified overall degree of conversion, the choice may be regarded as the desired solution. This latter approach is readily amenable to iterative programming techniques using a digital computer. 

One may proceed stepwise in this fashion to develop a general recursion formula for the concentration leaving reactor j in an n reactor cascade. 

Handylab, 26 976 Hanford N reactor, 17 572-573 Hanford production reactors, 17 570 Hanksite, 5 785t Hansa yellows, 14 317 Hansch equation, 10 329 Hansenula polymorpha, 12 479 Hantaviruses, 3 137 Hantzsch pyridine synthesis, 16 550 Hantzsch-Widman nomenclature system, 17 399... 

Appendix B. Reordered Occurrence Matrix of the Hanford N-Reactor System 252... 

To illustrate a complete decomposition for a process represented by a large number of equations is not feasible in this review because of the practical difficulties of printing the resulting matrices. Also, the problem statements would probably be longer than the review itself. Consequently, decomposition of two modest-sized processes is illustrated in this section, one a process of sufficient scale to be quite impracticable to decompose by inspection. The first example model has been taken from Analog Simulation of the Hanford N-Reactor Plant (S5), a documentation readily available from the Clearinghouse for Technical and Scientific Information as well as AEC depositories. 

The size and complexity of the N-reactor plant and the limited amount of computing equipment that was available necessitated a judicious use of simplifying assumptions. For instance, primary coolant temperature transport lags were lumped into two groups, one each for the hot and cold loop legs thermodynamic effects in the secondary system condensate headers and surge... 

In order to decompose the system equations successfully, it was necessary to prepare carefully the occurrence matrix (of equations and variables) for introduction into the computer program listed in Appendix A. The major difficulty that faces any analyst is distinguishing between system variables and parameters included in the equations. Actually, several sets of system variables could have been chosen depending upon whether one wished to study the design or simulation of the N-reactor plant. It was found that assigning... 

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