INR Pitesti, D. Dobrea, L. Aioanei Task 4.3. Instrumentation Specifications 4. Core C& I devices 5. Primary coolant C&I devices Based on [1], [2] and [3], there are identified: - Parameters related to core and coolant measurements - Techniques and devices for measuring parameters Literature regarding similar facilities was used as hint for preliminary choices of techniques and devices

General Here we focus on main parameters: - neutron flux - temperature - coolant flow Were not depending of other inputs (WPs), choices of devices/techniques were presented

Neutron Measurements Devices presented in Task 4.2, [1], [2]). In-core neutron detectors are divided for safety and control For safety external gamma does not affect the function at power. At low power or start-up gamma from accumulated fission products affects linearity of some detector types Local power effects are not expected (the core is strongly coupled, Xe effects are not important).

Self-Powered Detectors (SPND) Prompt (or small delayed delayed fraction) SPNDs could be used for protection signals at power Delayed SPNDs respond to local neutron flux and could be used for more accurate fission power computation, responding well to core configuration long-term modifications. They could be used in automated regulating systems through weighted sums of their signals. Weights, position, influence of their assemblies on the core balances and flux distribution: may be assessed by detailed neutronic design.

Neutron Instrumentation Range Intermediate range out-of core detectors could be boron lined ion chamber or high-sensitivity FCs. Start-up detectors: in-core (to be used after long-term shutdowns) and out-of core (until intermediate range is reached). They could be He or BF3 detectors (sensitivity to be assessed) or high sensitivity FCs. The FCs could be used for all power ranges working in impulse, fluctuations and current regimes Requirements for in-core: high temperature (min 500 C)

Neutron Instrumentation Preliminary Choice Wide-range FCs could be used for all ranges High sensitivity FCs could be used out-of-core and for start-up (source) range SPNDs extend the temperature range; they could be used for protection together FCs, ensuring diversity Number and position of in-core detectors: to be established in connection with advanced neutronic design Redundancy, independence, separation, diversity for protection: to be analyzed in the next stage of the T4.3.

Lead Temperature At core outlet, core inlet, SG outlet and significant points in pool (high/low values). At each assembly outlet (for pump failure, DBC4 fuel assembly partial blockage) [1](DEL014)  T for power calculation (as close as possible to channels inlet and outlet) Type: Chromel-Allumel thermocouples (usual in existing fast reactors), J-type (mentioned in Task 4.2, as having small time constant - ms) Range: min 700 C

Lead Temperature (contd.) Response Time for thermocouples: milliseconds, to allow fast response for protection and temperature fluctuations measurements, as indicative for onset of fuel assembly blockage (increased temperature power spectrum density is more sensitive than flow measurements, although the effect could be masked by neighbour assemblies).

Lead Temperature Discussion Whether is possible to instrument each assembly for inlet/outlet temperature measurements How to establish the critical points inside the pool where temperatures are measured

Lead Flow DEL014: Lead flow rate at pump outlet (for pump failure detection and DBC4 pump shaft break/seizure) Flow measurements could be used to assess flow blockage, complementary to temperature measurements close to fuel assemblies outlet Flow-meters: -  P flow-meters (Venturi – large, heavy, accurate at high flow, but with small range ~ 25%FP, Sharp-edge orifice)

Lead Flow (contd.) Magnetic flow-meters (Permanent magnet, DC electromagnetic, AC electromagnetic – large range, good linearity, need recalibration in pool, temperature-dependent response) Ultrasonic flow-meters, Time-of-Flight flow-meters (correlation of magnetic-flow-meter noise) NOTE. It is difficult to use flow measurement in pool- type reactors in order to compute reactor power, due to complicated flow pattern. Phenix reactor use pump speed to compute power.

Lead Flow Discussion EM flowmeters seem most suited to use How does the actual design allow attaching flow- metters to piping

Other Measurements Lead level in pool (for main vessel break) [1] (DEL06) Oxygen concentration. Ytria Stabilized Sensors - YSZ solid-electrolyte oxygen sensor is suited for high temperatures and low oxygen partial pressures. The gas dynamic equilibrium method the most promising method for control of large, full-scale LBE systems [4] Cover gas pressure (Pressure devices in DEL06) Loose parts (acoustic monitors; they are also used in other facilities used as backups for temperature measurements detecting onset of fuel assembly blockage)

References [1] F. Rivero, State of the art Instrumentation and Control Survey, DEL006/2011 [2] L. Vermeeren, Task 4.2 Presentation, May 2011 [3] A. Campedrer, Normal, transient and accidental operational modes: control and protection functions identification, DEL014/2011 [4] A. Bolind, Control of the Oxygen Content of the Cover Gas in a Molten Lead-Bismuth Euthectic System, Master Thesis, Urbana, Illinois