atw - International Journal for Nuclear Power | 2.2024
Internationale Entwicklungen und Trends
Internationale Entwicklungen und Trends
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Environment and Safety<br />
63<br />
dosimetry(EVND) and the upper part of the sur veillance<br />
capsule monitor bias factors(BE/C) are 1.06 and<br />
0.97. Combined bias factor (BE/C) is 1.01. In the case of<br />
the OPR-1000 results, the upper part of the Ex-vessel<br />
neutron dosimetry(EVND) and the upper part of<br />
the surveillance capsule monitor bias factors(BE/C)<br />
are 1.11 and 1.02. Combined bias factor (BE/C) is 1.06.<br />
Both Westinghouse 3-loop and OPR-1000 results<br />
meet within the range of ±20% of the acceptance<br />
criteria applied when comparing the measured and<br />
calculated values specified in Regulatory Guide 1.190 [6] .<br />
As a result, the reliability of the neutron fluence<br />
evaluation at reactor pressure vessel nozzle using<br />
upper part of surveillance capsule monitor and Exvessel<br />
neutron dosimetry (EVND) is confirmed. Both<br />
Westinghouse 3-loop and OPR-1000 results using<br />
upper part of surveillance capsule monitor and Exvessel<br />
neutron dosimetry(EVND) are higher than<br />
mid- plane data. As a result, the nozzle neutron fluence<br />
when nozzle region bias factor is evaluated<br />
conservatively.<br />
3.2 Neutron fluence of reactor pressure vessel<br />
nozzle<br />
The nozzle neutron fluence was evaluated at the lowest<br />
weld region of the reactor pressure vessel nozzle.<br />
(Figure 6) shows the neutron fluence evaluated with<br />
the different bias factors at the nozzle with respect to<br />
the effective full power years of the Westinghouse<br />
3-loop. The projected neutron fluence <strong>for</strong> Westinghouse<br />
3-loop nozzle will be greater than 1×10 17 n/cm² (1 > MeV)<br />
at the time of 36EFPY. (Figure 7) shows the projected<br />
neutron fluence of the nozzle with respect to the<br />
effective full power years of the OPR-1000. And the<br />
projected neutron fluence will be greater than<br />
1×10 17 n/cm² (1 > MeV) at the time of 41EFPY.<br />
(Figure 8) is a graph comparing the neutron fluence<br />
of the core region and the nozzle of the Westinghouse<br />
3-loop. (Figure 9) is a graph comparing the neutron<br />
Parameter<br />
Midplane of<br />
EVND<br />
Midplane of SC<br />
Monitor<br />
EVND and SC<br />
Combined<br />
Average<br />
BE/C<br />
Average<br />
BE/C<br />
Average<br />
BE/C<br />
Flux<br />
(E > 1.0 MeV)<br />
0.92 0.93 0.93<br />
Tab. 2.<br />
Westinghouse 3-loop BE/C using Mid-plane Data<br />
Parameter<br />
Upper part of<br />
EVND<br />
Upper part of<br />
SC Monitor<br />
EVND and SC<br />
Combined<br />
Average<br />
BE/C<br />
Average<br />
BE/C<br />
Average<br />
BE/C<br />
Flux<br />
(E > 1.0 MeV)<br />
1.06 0.97 1.01<br />
Tab. 3.<br />
Westinghouse 3-loop RPV BE/C using Upper Part Data<br />
Fig. 6.<br />
Westinghouse 3-loop RPV nozzle neutron fluence<br />
Parameter<br />
Upper part of<br />
EVND<br />
Upper part of<br />
SC Monitor<br />
EVND and SC<br />
Combined<br />
Average<br />
BE/C<br />
Average<br />
BE/C<br />
Average<br />
BE/C<br />
Flux<br />
(E > 1.0 MeV)<br />
1.04 1.03 1.04<br />
Tab. 4.<br />
OPR-1000 RPV BE/C using Mid-plane Data<br />
Parameter<br />
Upper part of<br />
EVND<br />
Upper part of<br />
Monitor<br />
EVND and SC<br />
Combined<br />
Average<br />
BE/C<br />
Average<br />
BE/C<br />
Average<br />
BE/C<br />
Flux<br />
(E > 1.0 MeV)<br />
1.11 1.02 1.06<br />
Tab. 5.<br />
OPR-1000 RPV BE/C using Upper Part Data<br />
Fig. 7.<br />
OPR-1000 RPV nozzle neutron fluence<br />
Vol. 69 (2024)
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