Controllability of MSR-FUJI

Transcription

1 Controllability of MSR-FUJI Ritsuo Yoshioka(*), Koshi Mitachi International Thorium Molten-Salt Forum (*): 1

2 Table of contents (1) Molten Salt Reactor "FUJI" (2) Control Design of MSR (3) Conclusion 2

3 (1) Molten-Salt Reactor "FUJI" R. Yoshioka, et.al, Molten-Salt Reactor FUJI and Related Thorium Cycles, TEA Spring conference

4 (small-sized) FUJI-U3 Design Electric output 200 MWe Thermal output 450 MW(th) Core 1 Core 2 Core 3 Thermal efficiency 44.4% r or Δr (m) h or Δh (m) Conversion ratio (average) 1.01 Graphite volume fraction Keff and Conversion Ratio 1.05 keff, CR Effective Full Power Days [days]

5 Super-FUJI design Thermal output 2,272 MWt Electric output 1,000 MWe Thermal efficiency 44.0% Reactor vesse1 Diameter / Height 9.9 m / 6.7 m Power density 7.2 MWt/m 3 5

6 FUJI-Pu design Fissile inventry vs. Time *: Initial condition (Time behaviour for 900 Effective Full Power Days) 6

7 Summary of FUJI designs 1 Small sized FUJI and 1GWe superfuji have been studied. The 233 U requirement for FUJI-U3 is 32% of BWR, Pu production is only 0.1% of BWR, and Minor Actinides production is only 4% of BWR. 2 FUJI can achieve self-sustaining (CR=1.0) with U233 fuel. 3 MSR can start with Pu, from LWR reprocessed fuels, as shown in FUJI-Pu. 4 Huge number of MSR can start by U233 produced in AMSB. 5 MSR can operate with U235, as is shown in Mr. Sakuraba s presentation in this conference. 7

8 (2) Control Design of MSR 8

9 Control Rod Design of MSBR ORNL proposed 2 types of control rods for MSBR. 1 2 Shut-down control rods, using strong neutron absorber such as B 4 C. Power control rod, which is made of graphite. Insertion of graphite rod increases the reactivity, and vice versa. Control Rod Primary Pump Secondary Pump Graphite Heat Exchanger Steam Generator Chemical processing plant Freeze Valve Drain Tank Turbine & Generator 9

10 Reactor Control System Current reactor licensing requires 2 types of shut-down systems. LWR MSBR MSR-FUJI 1 Control rod system 1)Shut-down control rod (B 4 C rod ) 1)Shut-down control rod (B 4 C rod ) 2)Graphite rod 2)Graphite rod Fuel salt flow control system 2 Boric acid injection system Fuel salt drain system Same as left 3 Fuel salt concentration adjusting system Same as left 10

11 Shut-down Control Rod Shut-down control rod using Gadolinia(Gd 2 O 3 ) was applied in MSRE. But there was no actual design in MSBR. For FUJI, this has to be studied in future. Shut-down rods may be as shown in the right X-Y geometry. Shut-down control rod 11

12 Reactivity of Graphite Rod in FUJI Control rod cell model (R=10cm) Graphite rod Fuel salt %ΔK Parameter :Graphite fraction 0.1 RZ core model Core Reflector Graphite fraction Maximum reactivity of one graphite rod is about 0.2%dK.

13 Flow Control Technology MSR is equipped with fuel salt pumps, and the fuel salt flow rate can be easily changed by the pump speed. This method is established in BWR as a Flow-control technology, utilizing its negative reactivity coefficient as shown below. 100% Core Power Typical flow control line in BWR For lower core flow, fuel salt temperature increases, and negative reactivity coefficient causes negative reactivity, and then core power decreases. 0% 0% Core flow 100% 13

14 Flow Control for FUJI Flow control technology was studied using 2-group diffusion equations, 6-group kinetic equations, and core thermal hydraulic equation for the following FUJI reactor. Core thermal power Electric power Fuel salt composition (LiF-BeF 2 -ThF 4 -UF 4 ) Rated core flow Reactivity Coefficient (Temp.Co. for salt&gr) 450MWt 200MWE mol% 0.711m 3 /s dk/k/deg.k K. Mitachi et.al, A Study for Power Control of Three-Core Molten Salt Reactor by Fuel Salt Flow Control, Transaction of JAES Spring conference in

15 Flow Control Result Steady state power and flow were studied for 6 cases. It is shown that FUJI is stable at any power with consistent flow. 15

16 Control Stability After the stepwise decrease of core flow from 100% to 75%, Keff decreases and then increases after 15sec. Core power decreases and stabilizes to 345MWt (77% of rated power)±5%, within 100 sec. 16

17 Alternative Technology Flow-control technology is a simple method as established in BWR. On the other hand, PWR is applying temperature control of the reactor by its turbine power, and this method can be also applied to MSR. This will be investigated in future. 17

18 (3) Conclusion 18

19 Conclusion 1) Summary of several FUJI designs are shown. 2) Control rod design of FUJI is discussed, and we proposed alternative method of Flow control by changing fuel salt pump speed. 3) The results are very satisfactory, same as graphite control rod. 19

20 Thank you for the attention! Any questions/comments? 20