INVESTIGATION OF A PULSE PERIODIC NUCLEAR PUMPED LASER SYSTEM

Transcription

1 1 VSTGATO OF A PS PRODC CAR PMPD ASR SYSTM A.P. Barzilov, A.V. Gulevich, P.P. Dyachenko, O.F. Kukharchuk,.A. Pashin, S.S. Satin nstitute for Physics and Power ngineering, Bondarenko Sq.1, Obninsk, Kaluga reg., RSSA Conception of high-power reactor pumped laser system (RPS) is discussed. Described is a system which consist of a thermal subcritical (in neutron physics aspect) laser module controlled with a neutron flux from reactor block (one or more fast burst periodic reactors could be placed inside a laser module) (see Fig.1). The «master oscillator - two round trip amplifier» optical scheme principle is used [1]. )J Reactor pumped laser system: 1 - laser module; 2 - reactor block; 3 - reactor core; 4 - reactivity modulator; 5 - cooling system; 6 - neutron reflector. The laser module (M) (1) is designed as a cylindrical structure with a longitudinal cavity for reactor block (2): one or more cores of the fast burst BR-type reactor (3) with liquid metal cooling system (5) and reactivity modulator (4). M is equipped with an external neutron reflector (6). The basic element of laser module is the laser active element [1] where immediately direct nuclear-to-optical energy conversion carried out. Proc. ntern. Conf. CS 98, nstitute for Physics and Power ngineering, Technical Physics aboratory -mail: kuh@ippe.obninsk.ru

2 2 RPS is a coupled reactor system. The kinetic model to describe the neutron transient processes in such system is as follows: O 1 = ( ( β ) ) 1 + ( β ) 1 + λ & + λ & + 6 = = O 1 = ( ( β ) ) 1 + ( β ) 1 + λ & + & 6 λ + = = & = β 1 λ & = & = β 1 λ & = 1 () = 1 ( τ ) 1 () = 1 ( τ ) & () = & ( τ ) = & () = & ( τ ) =. (1) Here i is the intensity of fissions (index «r» - reactor; «b» - laser module); k ii and l ii are multiplication factor and average lifetime of prompt neutrons, respectively; k ij is a coupling coefficient; β ij, λ ij and C ij are parameters of the delayed neutrons; D i is the number of delayed neutron groups; S i is the neutron intensity of the source. The dependence of the reactor multiplication factor may be approximated by [2]: () W = + H α ( τ ) Y W P f f. Here is value of the reactor multiplication factor between the pulses; f is the reactivity modulator efficiency; τ r is pulses period ( ν = τ - pulse frequency); m=1, integer number. t should be noted that value ε ( )( β ) ( f)( β ) = = + f is the maximum prompt neutron reactivity of the modulator. Proc. ntern. Conf. CS 98, nstitute for Physics and Power ngineering, Technical Physics aboratory -mail: kuh@ippe.obninsk.ru

3 3 Parameters of model (1) and main neutron-physical characteristics of RPS were calculated using Monte Carlo method. As a result calculated kinetic parameters are: k b-r =0.4; k b =0.9; l r = s; l b = s; β r =0.002; β b =0.007; f V -1 f V k r-b Fig.2. «Criticality condition» for f = k r-b Fig.3. «Criticality condition» for f =0.08; ν=5 s -1. αy = /s 2. The calculations were made for various k r-b values. t should be noted that pulse periodic system operates in the static mode (all pulses energy is constant) in the case when the system parameters are complied with the «criticality condition» [2]. The average power of RPS depends on the efficiency of the cooling system for various f and ν. The «criticality condition» of RPS may be obtained only numerically. The calculated values versus the k r-b are shown in Fig.2 and 3. The results of calculations of the system parameters are shown in Tables 1 and 2. t is supposed that the reactor block consists of one reactor. The calculations has been performed using special Proc. ntern. Conf. CS 98, nstitute for Physics and Power ngineering, Technical Physics aboratory -mail: kuh@ippe.obninsk.ru

4 4 computer codes [3]. Here: r and b are the full output energies in reactor block and M per one period, respectively; Q r is the energy release in reactor pulse; Q i and Q b are the output energies in prompt neutron reactor and M pulses, respectively; 1 and 1 are the maximum of reactor and M pulses, respectively; 1 and 1 are reactor and laser module powers between pulses, respectively. Table 1. The kinetic system characteristics for f =0.04. ν r Q r Q i b Q b k r-b s -1 MJ MW t should be noted that full energy released in M during the period may be estimated using the formula: ( = ( The reactor and laser module pulses for various k r-b and f are shown in Fig.4-7. Proc. ntern. Conf. CS 98, nstitute for Physics and Power ngineering, Technical Physics aboratory -mail: kuh@ippe.obninsk.ru

5 5 Table 2. The kinetic system characteristics for f =0.08. ν r Q r Q i b Q b k r-b s -1 MJ MW The pulse characteristics for system with a few reactors may be estimated as follows. «Criticality condition» (k r-b ) (see Fig.2,3) must be decreased on the value : = M M P = M Here m is number of reactors in the system; M is the coupling neutron coefficient between reactors. Full laser module energy released during the period may be calculated using the formula: ( = P( The values of the maximum power and power between pulses in the laser module may be estimated as follows: 1 = P 1 n n 1 = P 1. ; Here 1 and 1 are pulse maximum laser module power and power between pulses for system with one reactor, respectively. Proc. ntern. Conf. CS 98, nstitute for Physics and Power ngineering, Technical Physics aboratory -mail: kuh@ippe.obninsk.ru

6 6,W 1+11,W HDFWR ODVH PRGXOH 1+9 HDFWR ODVH PRGXOH a b Fig.4. Power of reactor and laser module for k r-b =0 (a) and k r-b =0.007 (b): f =0.04; ν=5 s -1.,W 1+10,W f k =0.04 f k = Fig.5. Power of reactor for ν=1 s -1 (1) and ν=5 s -1 (2): Fig.6. Power of reactor for various f values: k r-b =0.007; f =0.04; r =2 MJ. k r-b =0.007; ν=5 s -1 ; r =2 MJ. Proc. ntern. Conf. CS 98, nstitute for Physics and Power ngineering, Technical Physics aboratory -mail: kuh@ippe.obninsk.ru

7 7,W Fig.7. Power of reactor: k r-b =0.007; f =0.04; r =2 MJ; ν=5 s -1. The «nuclear-to-laser energy conversion efficiency» (η) (ratio of the output laser energy to fission fragments energy) for gaseous laser active medium is about The «uranium medium efficiency» (ε) (ratio of the fission fragments energy deposited into laser medium to full fission energy) for geterogenious laser active elements is about 0.1. Thus, the full energy release in laser module may be calculated as follows: ( ( O ηε. Here l is the output laser energy. The full energy of laser module will be b = MJ (η= ) if l =1 MJ. For the case of k b-r =0.4; k b =0.9; k r-b =0.007; l r = s; l b = s; f =0.08; β r =0.002; β b =0.007; m=5; ν=1 s -1 we can estimate the system characteristics using the previous calculated data: Proc. ntern. Conf. CS 98, nstitute for Physics and Power ngineering, Technical Physics aboratory -mail: kuh@ippe.obninsk.ru

8 8 Q r =9.3 MJ; Q i =6 MJ; Q b =175 MJ; 1 = MW; 1 = MW; 1 =0.7 MW; 1 =25 MW. Thus, some conclusions can be made: the «criticality conditions» of RPS has been obtained; the coupling coefficient k r-b must be less 0.007; the reactivity modulator efficiency f must be increasing for coupled reactor-laser module system; pulses frequency ν must be about 1 s -1 for power and cooling system requirements decreasing; the optimized parameters of pulse periodic nuclear pumped laser system with output laser energy about 1 MJ has been calculated. RFRCS 1. Dyachenko P.P. et al. // Fusion Technology, Vol Shabalin.P. Fast burst reactors. Moscow, Atomizdat, Gulevich A.V., Kachanov B.V., Kukharchuk O.F. Mathematical models and computer codes for calculations of the reactor-laser system dynamic: PP #2454, Proc. ntern. Conf. CS 98, nstitute for Physics and Power ngineering, Technical Physics aboratory -mail: kuh@ippe.obninsk.ru