Status Report on the Water-Based NSTF RCCS Capability: Preparations and Design for the Transformation of the Natural Convection Shutdown Heat Removal Test Facility (NSTF) From Air to Water-based Cooling

Abstract

The following report provides an overview of the current status of the water-based transformation, including details of the design, geometry, and fabrication of the test section and network piping, for the ½ scale water-based NSTF program at Argonne National Laboratory.In early FY2015, efforts towards a water-based design began in parallel with on-going airbased work, and began by identifying top level objectives of the transformation. Scaling studies and preparation tasks with computational modeling were carried out to guide the design decisions, minimize distortions, and ensure relevant data among scales. This entailed close collaboration with AREVA, whose water-based RCCS (included as part of their 625 MWt SC-HTGR) served as the primary design basis for incorporation into the NSTF. A literature review of previous works was made, with an emphasis placed on similar facilities, relevance to passive decay heat removal, and details pertaining to two-phase flow and measurement techniques.The study focused on input from key designers and a thermal analysis of existing cooling panels (e.g. at TAMU and UW-Madison) and two proposed AREVA cooling panels. A base case was used as a reference point for parametric studies of effects from varying tube spacing (pitch), tube diameter, fin thickness, and materials. Then, a structural analysis was performed to ensure safe material stresses during high temperature operation. Details of the pipe network geometry and guidelines for design of the water storage tank are finally presented, followed by engineering drawings in the appendix.

FY23 Report on Water NSTF Testing at Two-Phase Conditions: Off-normal Scenarios

“…As the intention of the NSTF throttling parametric testing is to provide generalizable data on blockages, K is the more meaningful value to report. In the case that CV is preferred by a user, Eq [4] provides a ready translation for any size valve.…”

“…These mean values over time of the raw coefficients are listed in Table 9. Through Eq [4] we can translate each value into the other and compare the calculations. The two values are consistent, as expected given that they rely on the same two data inputs of flow rate and DP.…”

“…From here there are two options to translating to CV. We can either use Eq [4], as before, or modify Eq [1] with the determined valve K:…”

“…After this, the inlet header valve position was varied according to Table 14. CV and K are calculated using Eqs [13] and [4]. (The assumed values for K = 0.048 at 0° are substituted for the fitted values, which overshoot this by roughly 1%.)…”