Transient monitor for nuclear reactor

• US 4,678,622 A
• Filed: 08/20/1985
• Issued: 07/07/1987
• Est. Priority Date: 08/20/1985
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Chao, Fred C., Rowe, William S.
• Primary Examiner(s): Cangialosi, Salvatore
• Application Number:
  US06/767,551
• Time in Patent Office: 686 Days
• Field of Search: 376/254, 376/255, 376/259, 376/216, 376/217
• US Class Current: 376/259
• CPC Class Codes: G21C 17/00 Monitoring; Testing measuring in general G01; Maintaining
• CPC Class Codes: G21C 7/36 Control circuits
• CPC Class Codes: G21D 3/08 Regulation of any parameters in the plant
• CPC Class Codes: Y02E 30/00 Energy generation of nuclear origin
• CPC Class Codes: Y02E 30/30 Nuclear fission reactors

Abstract

A monitored nuclear reactor parameter, such as a startup range neutron monitoring signal, is filtered at a filter having a preselected time constant and amplified with the output being passed to one channel of a two channel comparator. The level of the amplification and the filter time constant are chosen to discriminate between normally increasing startup neutron density including the prompt-jump effect and exponentially increasing neutron density due to the occurrence of reactor casualty in view of the design parameters of the reactor. This same startup range neutron monitoring signal is passed unprocessed to the other channel of the two channel comparator. Comparison of the two signals is made with the binary output of the comparator flagging excess of the unprocessed signal over the filtered and amplified signal. Presence of the appropriate reactor flag is typically used to cause rod withdrawal blockage and/or SCRAM. The time constant of the filter causes the monitored neutron density signal to be delayed in its tracking of reactor startup. The level of amplification of the monitored neutron density signal establishes the reference level in the comparator which when exceeded sets the comparator flag. Consequently, comparator response time varies inversely with the severity of increase in neutron density. Preferably a first amplification level is used for determining rod withdrawal block and a second and higher level of amplification is used for plant SCRAM comparators. A dynamic display to the operator of comparison between monitored neutron density and the dynamically tailored trip levels is provided.

Claims

1. A startup range transient monitor for a reactor comprising in combination:

a comparator having first and second inputs and an output for indicating an exceeded limit;

a monitored reactor parameter signal directly channeled to one input of said comparator;

a filter having a preselected time constant for filtering and an amplifier for amplifying said monitored reactor parameter signal and passing said signal to the other input of said comparator whereby the output of said comparator flags the exceeding of limit when said direct signal in one input exceeds said filtered and amplified signal in the other input.

2. The apparatus of claim 1 and wherein the output of the comparator is binary.

3. The apparatus of claim 1 and wherein said signal is filtered before it is amplified;

or amplified before it is filtered.

4. The apparatus of claim 1 and wherein said monitored signal is neutron density.

5. The invention of claim 1 and wherein said monitored parameter is pressure in said reactor vessel.

6. A process for monitoring a reactor parameter including the steps of providing a comparator having two inputs and an output indicating the state of one input relative to the other input;

inputting a monitored reactor parameter to one input of said comparator;

providing a filter having a time constant;

providing an amplifier;

filtering and amplifying the same monitored parameter to the other input of said comparator;

comparing said inputs to determine the state of one input relative to the other input.

7. The invention of claim 6 and wherein the comparator output is binary and blocks rod withdrawal.

8. The apparatus of claim 6 and wherein said comparator output is binary and initiates SCRAM.

9. The process of claim 6 and wherein said comparator output is displayed to an operator relative to the filtered and amplified parameter.

10. The process of claim 6 and wherein the monitored parameter is neutron density.

11. The process of claim 6 and wherein the monitored parameter is reactor vessel pressure.

12. The apparatus of claim 6 including the step of adjusting the time constant of said filter to produce variable response at said comparator.

13. The process of claim 6 including the step of adjusting the amplification to produce variable time response at said comparator.

14. The apparatus for monitoring neutron density in a nuclear reactor comprising:

a startup range neutron density monitor;

a first comparator having two inputs and a binary output to initiate rod withdrawal blockage;

a second comparator having two inputs and a binary output to initiate plant SCRAM;

the output of said startup neutron monitor being input to each of said comparators at one input thereof;

a filter for having a preselected time constant for processing the monitored neutron range density;

a first amplifier;

said filter passing its output to said first amplifier having an amplification level to the other input of said first comparator to initiate rod block when said directly monitored signal exceeds said filtered signal;

a second amplifier;

said filter having a second output to said second amplifier for initiating plant SCRAM when said directly monitored output exceeds said filtered and amplified input to said comparator.

15. The invention of claim 14 and wherein said rod block amplification is less than said SCRAM input amplification.

16. The invention of claim 14 and including a analog comparator for display to an operator illustrating the comparison of said monitored parameter with respect to the compared parameter level of rod block and the level of SCRAM.

17. The invention of claim 16 and wherein said analog comparator is scaled to display rate of reactor power increase in terms of the standard reactor period.

18. The invention of claim 16 and wherein said analog comparator is scaled to display rate of reactor power increase relative to a rod block level and a SCRAM level.