1. magnetic confinement - ENEA - Fusione

102
3. FUSION TECHNOLOGY
3.12 Safety and Environment, Power
Plant Studies and Socio-Economics
3.12.1 Occupational radiation exposure assessment for ITER-FEAT
The first occupational radiation exposure (ORE) analysis for ITER-FEAT was
completed during 2001 [3.54]. The collective dose results provided in the previous
analysis were reviewed, and the final assessment was completed regarding hands-on
activities for maintaining, inspecting and/or replacing the following items:
blanket/limiter, electron cyclotron heating system, ion cyclotron heating system,
cryopumps, divertor cassettes, three loops of the tokamak cooling water system
(TCWS). Airborne tritium was also considered, together with the other radiological
sources already included in the previous study (neutron activation due to plasma
burning, activated corrosion products on the inner surface of the TCWS pipes and
components).
The collective dose results are: for the hands-on assistance activities at the tokamak
ports, 197 person-mSv/y; for the five loops of the TCWS (first-wall blanket, divertor
and neutron-beam injector), 105 person-mSv/y, about 21 person-mSv/y per loop
[3.55 (Vol VI)].
3.12.2 Validation of computer codes and models (EFDA Task SEA5)
Several simulation codes are used for the ITER safety analyses. The codes for treating
thermal-hydraulic phenomena, aerosol and neutron transport, materials activation
and the generation of activated corrosion products are validated by comparing them
with experimental results and codes already validated, by means of benchmarks.
Thermal-hydraulic phenomena
To validate the thermal-hydraulic computer codes, calculations were performed
[3.56] against a set of five experimental cases of loss of coolant in volumes at subatmospheric
pressure in the Inlet of Coolant Events (ICE) facility at the JAERI
laboratories in Japan. A further check was performed [3.57], [3.58] against a second
set of four test cases, to verify the behaviour of the codes in condensation and
evaporation phases. The codes involved in the campaign were the ISAS system
(linking ATHENA, for thermal-hydraulic transients, and INTRA, for containment
simulations) and the fast running code CONSEN. The comparison between blindtest,
experimental and post-test results was examined in detail to point out the main
differences.
The peak of pressure in the plasma chamber (figs. 3.43 and 3.44) and vacuum vessel,
the most important outcome of the accident analyses, is quite well matched in the
post-test calculations by both ISAS and CONSEN. In all the cases, they showed a
maximum deviation from the experiments within the range of 5%.
The overall results indicate the high accuracy of the ISAS tool in coupling the
different codes for accident analyses. CONSEN proved to be flexible and also
suitable in two-phase flow
conditions. Both the simulation
tools can be considered adequate
for the thermal-hydraulic
applications requested.
CONSEN [3.59] was also
implemented for validation
against the results of the French
EVITA facility (built by CEA,
Cadarache), with the same
satisfactory results.
Pressure (kPa)
700
600
500
400
300
200
100
Exper
Post
Pre
0
0 50 100 150 200
Time (s)
[3.55] ITER Generic Site
Safety Report, ITER
JCT (2001)
[3.56] M.T. Porfiri, P.
Meloni, ISAS post test
calculation for inlet of
coolant experiments,
FUS-TN-SA-SE-R-006
(2001)
[3.54] S. Sandri, EU
Task TW0-SEA2:
Personnel Safety ITER
Task No. G81TD10FE
(D453), FUS-TN-SA-
SE-R-013 (2001)
[3.57] M.T. Porfiri, P.
Meloni ISAS calculations
for inlet of coolant
(ICE) experiments in
2001: pre and post-tests
2a, 2b, 6 and 7, FUS-TN-
SA-SE-R-031 (2001)
[3.58] G. Caruso, M.T.
Porfiri,“CONSEN validation
against ICE –
Experimental campaign
2001 - Post-test calculations
for the cases 2a,
2b, 6 and 7-Post-test
calculations for the
cases 2a, 2b, 6 and 7,
FUS-TN-SA-SE-R-032
(2001)
[3.59] G. Caruso, M.T.
Porfiri, “CONSEN validation
against EVITA -
Experimental campaign
2001 - Post-test calculations”,
FUS-TN-SA-SE-
R-033 (2001)
Fig. 3.43 – Plasma
chamber pressure for ICE
case 6 (CONSEN).