Source Term Study on Tritium in HTR-PM: Theoretical Calculations and Experimental Design

Abstract

The high temperature gas-cooled reactor pebble-bed module (HTR-PM) in China received much attention for its inherent safety performance and high thermal efficiency. The generation mechanism, distribution, reduction route, and release type of tritium (H-3) in HTR-PM are presented with a complete theoretical model. The calculation results indicate the majority of H-3 in the core is generated by the activation reaction of B-10. The activity concentration of H-3 in the primary loop and the specific activity of H-3 in the secondary loop at the operating equilibrium are computed as 3.69 × 10 6 Bq/m 3 STP of helium and 4.22 × 10 4 Bq/kg of water, respectively. The H-3 sampling measurement in HTR-PM has been designed to collect data from the primary coolant, from the liquid waste storage tank, from the secondary coolant, and from the liquid and gaseous effluents, separately. In this paper, the design of H-3 sampling positions in the helium purification system is discussed. The H-3 sampling measurement from the primary helium in HTR-PM has been improved, which can provide reliable activity concentration data of H-3 in the primary loop and supply accurate evaluation for the efficiency of the helium purification system.

Functional Requirements for the Modeling and Simulation of Advanced (Non-LWR) Reactor Mechanistic Source Term

“…While fissions inside the fuel kernel are the main production of radionuclides, care must be taken to estimate radionuclides produced via neutron activation of the core materials. These core materials are including but not limited to a graphite fuel matrix, graphite reflectors, carbon bricks, helium coolant, and control rods and absorber balls containing boron and lithium [9]. Recent studies have been performed focusing on the tritium source in HTGR designs [10], including source term analyses specific to irradiated graphite [11].…”

Design of the Online Gross γ Monitoring Instrument at the Exit of the Helium Purification System in HTR-PM

“…The process and effluent radiation monitoring system in HTR-PM was designed based on the source term research of HTR-10, including the experimental measurement of the activity concentration of H-3 and C-14 in the primary loop [11], radioactive dust concentration in the primary loop [12][13][14], and types and distributions of typical nuclides in the irradiated graphite spheres from the core [15][16][17]. The source terms in the primary loop of HTR-PM, which contains fission and activation products, radioactive dust, H-3, and C-14, have been designed to be monitored using the online monitoring instrument and/or the sampling measurement [10,18,19].…”