Patent Number: 043080995
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing wherein the showings are for purposes of illustrating a detailed description of a preferred embodiment and are not intended to limit the invention thereto, FIG. 1 shows a nuclear reactor safety system 10 which develops a control signal S indicative of the percentage of reactor full power limit. This signal S is compared in a comparing amplifier 12 to a reference signal R indicative of a reactor full power. The comparing amplifier 12 establishes an alarm or shut down signal to the reactor (not shown) whenever the control signal S is equal to or less than the power signal R. The control signal S may be represented as the sum of functions of various measured reactor parameters as follows: EQU S=f(P)+f(T)+f(.phi..sub.B)+f(W) Where: EQU f(P)=A.sub.0 +A.sub.1 P+A.sub.2 P.sup.2 +--A.sub.x P.sup.x EQU f(T)=B.sub.0 +B.sub.1 T+B.sub.2 T.sup.2 +--B.sub.y T.sup.y EQU f(.phi..sub.T)=C.sub.0 +C.sub.1 .phi..sub.T +C.sub.2 .phi..sub.T.sup.2 +--C.sub.z .phi..sub.T.sup.z EQU f(.phi..sub.B)=D.sub.0 +D.sub.1 .phi..sub.B +D.sub.2 .phi..sub.B.sup.2 +--D.sub.k .phi..sub.B.sup.k EQU f(W)+E.sub.0 +E.sub.1 W+E.sub.2 W.sup.2 +--E.sub.m W.sup.m where the A's, B's, C's, D's, and E's are constants selected to fit a pre-calculated safety function by some criteria (such as least square) and where P=reactor pressure, T=reactor temperature, .phi..sub.T =neutron flux escaping from the upper portion of the reactor, .phi..sub.B =the neutron flux escaping from the lower portion of the reactor, and W=flow of cooling fluid in the reactor. The pre-calculated function for each of the sensed reactor parameters, P, T, .phi..sub.T, .phi..sub.B, W is determined from thermal hydraulic experiments which determine the maximum amount of heat which can be removed from a specific volume of an operating nuclear reactor. By way of example, the pressure parameter P contribution has been experimentally found to be EQU f(P)=A.sub.1 P+A.sub.2 /P.sup.2 This experimentally-derived expression can be fit, for all usuable values of P, by an polynomial expression of the form shown on page 7, line 6. The values for A.sub.0, A.sub.1, A.sub.2, . . . A.sub.x are set by the required accuracy of the fit. In practice, no polynominal has been found to adequately represent the expression less than third degree terms of P. Similarly, the functions of T, .phi..sub.T, .phi..sub.B, and W have been experimentally derived and adequately fit with polynomials of third degree or less. Such experimentally-derived expressions and their polymonial fit are known to those skilled in the art and will not be detailed herein for the sake of conciseness. In the safety system 10 the reactor parameters are sensed by transducers appropriately placed on and in the reactor in a manner known to those skilled in the art. These measured parameter signals, P, T, .phi..sub.T, .phi..sub.B, W are individually amplified by their respective amplifiers 20a, 20b, 20c, 20d, and 20e and the respective amplified signals are converted to digital values analog to digital converters 22a, 22b, 22c, 22d, and 22e series connected to the amplifiers 20a, 20b, 20c, 20d, and 20e. Each of the forementioned functions f(P), f(T), f(.phi..sub.T), f(.phi..sub.B), f(W) forming the control signal S are respectively calculated in parallel-connected microprocessors 14a, 14b, 14c, 14d, and 14e. The microprocessors 14a, 14b, 14c, 14d, 14e have respective memory sections 16a, 16b, 16c, 16d, 16e and respective program sections 18a, 18b, 18c, 18d, 18e. The operation of the system 10 can be best described as simultaneously conducting similar operations on each sensed reactor parameter P, T, .phi..sub.T, .phi..sub.B, W as will be described occurring to the parameter P. The then current value of the parameter P (pressure) is sensed by a transducer properly located in or on the nuclear reactor to provide such a measurement. This measured pressure P analog value is then transmitted to the amplifier 20a which amplifies and filters the analog pressure P signal before transmitting it to an analog to digital converter 22a which forms the digital counterpart of the analog amplified signal for pressure P. The digital counterpart of the measured pressure P signal is then transmitted along line 24a to be inputed simultaneously along parallel terminals of the line 24a to the programming section 18a of the microprocessor 14a into each of the polynomial elements indicating the measured pressure signal P. The programming section 18a of the microprocessor 14a then calls for the input of the various precalculated constants A.sub.0, A.sub.1, A.sub.2, . . . A.sub.x stored in the memory section 16aof the microprocessor 14a to be fed into the programming section 18a. The programming section 18a then calculates the digital value for the polynomial expressions stored in the programming section 18a. The digital value of the polynomial or f(P) is then transmitted along line 26a to a digital to analog converter 28a which then produces an analog value for the calculated expression of the function f(T). Calculations of the recited type which form the function f(P) can be done on single chip microprocessors commercially available. Such a microprocessor is Model Number 8085 manufactured by The Intel Corporation. These types of microprocessors are acceptable for all the microprocessors 14a, 14b, 14c, 14d, and 14e. As was mentioned, all of the microprocessors 14a, 14b, 14c, 14d, and 14e simultaneously act in a similar manner on their respective parameter to calculate their respective functional parameter expressions from their respectively programmed functional polynomial calculations. All of these simultaneously calculated functional expressions f(P), f(T), f(.phi..sub.T), f(.phi..sub.B), f(W) are then added together at an adding station 30 to provide the previously mentioned control signal which when compared to the reference signal R establishes the safety alarm signal A. Clearly, various improvements and modifications will occur to those skilled in the art upon the reading of this specification. All such improvements and modifications have been deleted herein for the sake of conciseness and readability but are intended to be within the scope of the following claims.