Topical report: Natural convection shutdown heat removal test facility (NSTF) evaluation for generating additional reactor cavity cooling system (RCCS) data.

Prioritization of VHTR system modeling needs based on phenomena identification, ranking and sensitivity studies.

“…142 -block interface coolant momentum balance @ level k, Eqs. (15) and (16) 1 -channel coolant axial momentum balance @ level k, Eq. 17w gap-ax l,k-1 , w chan l,k-1 w leak-in l,k , w leak-out l,k , w gap-lat l,k w gap-ax l,k , w chan l,k , boundary condition variables unit networks 7*n col *n lev (i.e.…”

Topical report : NSTF facilities plan for water-cooled VHTR RCCS : normal operational tests.

“…Since the facility has not been actively utilized since the early 1990's, the next step was to assess the current facility status; and this step was completed as part of last year's workscope. 1 (The assessment indicated that the facility is in sound mechanical shape; refer to Reference 1 for details.) With this background material in place, the data needs and requirements for the water-based RCCS facility are then defined on the basis of the supporting scaling analysis.…”

“…Work last year addressed the air-based system, 1 while the work documented in this report addresses the water-based system. Supporting scaling and scoping cavity analysis activities 2 for the RCCS carried out in parallel with this experiment planning task, in addition to results available in the open literature, indicate that: (a) strong 3-D effects result in large heat flux, temperature, and heat transfer variations around the standpipe wall; (b) there are large differences in the heat transfer coefficients predicted by turbulence models and heat transfer correlations, and this underscores the need of experimental work to validate the thermal performance of the RCCS; (c) there are complicated two phase flow issues (i.e., steam flashing in the upper regions of the test section, and the possibility of nucleate boiling in the heated section) that complicate the system analysis; and (d) scaled tests at the NSTF would embody all important fluid flow and heat transfer phenomena in the RCCS, in addition to covering the entire parameter ranges that characterize these phenomena.…”

Feasibility study for use of the natural convection shutdown heat removal test facility (NSTF) for VHTR water-cooled RCCS shutdown.

“…The Natural Convection Shutdown Heat Removal Test Facility (NSTF) at ANL was built to provide a full scale simulation of the air-side of the PRISM RVACS system, and to provide experimental support for the design and analysis of this system. In FY05, work was performed to demonstrate that the NSTF facility can be used to generate experimental data to validate CFD and systems codes for the analysis of an air-cooled RCCS for the VHTR and to support the design and safety analysis of this RCCS type [1][2][3]. More specifically, the objectives were to: (a) develop the scaling relations to be used in modifying the existing NSTF facility into a scaled model of the VHTR air-cooled RCCS; and (b) provide a summary of the NSTF modifications needed to conduct scaled simulations of the RCCS.…”