Forschungszentrum Jülich in der Helmholtz-Gemeinschaft
EURISOL Task 5: Safety and Radioprotection & EURONS-SAFERIB
Progress Report Rainer Moormann EURISOL-Safety&Radioprotection + SAFERIB Meeting CEA-Saclay 27/28.10.2005
Institut für Sicherheit sforschung und Reaktortechnik - ISR
Rainer Moormann
1
Forschungszentrum Jülich in der Helmholtz-Gemeinschaft
Content • Radioactive Inventories and Radiotoxicities • Oxidation Behaviour in Targets • Shielding Issues • Disposal • Migration of Activitiy with Groundwater • Deliverables and time scale to the before mentioned items Institut für Sicherheit sforschung und Reaktortechnik - ISR
Rainer Moormann
2
Forschungszentrum Jülich in der Helmholtz-Gemeinschaft
Radioactive Inventories and Toxicities (WP5 A) • For Hg-targets, the inventories of about 1000 nuclides were determined by SNS, JSNS and ESS and most relevant discrepancies were clarified. An updated listing to be used by EURISOL was prepared (including identification of nuclides relevant for safety examinations and for disposal) • Radiologically dominant nuclides in Hg were identified using German dose calculation regulations for DBA. If no specific source terms are assumed, the dominance sequence is (40 y target operation): 1 Hg-194, Hf-172, Gd-148, Hg-203, I-125, Au-195 Taking into account the volatility (source terms of volatiles, Hg-isotopes, low volatiles = 1 : 0.1 : 0.01) the sequence changes to 1 Hg-194, I-125, I-124, Hg-203, Hf-172, Gd-148 Institut für Sicherheit sforschung und Reaktortechnik - ISR
Rainer Moormann
3
Forschungszentrum Jülich in der Helmholtz-Gemeinschaft
…….Radioactive Inventories and Toxicities • Spallation targets (Hg) contain more or less the same amount of activity as fission reactors of corresponding size (safety and disposal items to be considered) • Actinide specific problems are however much smaller in spallation related systems • Minor problems with decay heat in a Hg converter compared to fission systems are partly compensated by the high Hg volatility and by the small retention capabilities of liquids in general
Time 10 y 1000 y 100000 y
Hg target 5 MW 5.E6 1.E5 1.5E2
Research Reactor 20 MW 2.E8 2.E4 1.E3
Time dependent amount of activity [GBq] to be disposed from a Hg-target (40 y operation) and from a Research Reactor Core (100 fuel loadings) Institut für Sicherheit sforschung und Reaktortechnik - ISR
Rainer Moormann
4
Forschungszentrum Jülich in der Helmholtz-Gemeinschaft
……Radioactive Inventories and Toxicities
Comparison of activities in a Hg-target and in a research fission reactor Institut für Sicherheit sforschung und Reaktortechnik - ISR
Rainer Moormann
5
Forschungszentrum Jülich in der Helmholtz-Gemeinschaft
….Radioactive Inventories and Toxicities • Comparison of conventional and radio-toxicity of mercury leads to the following conclusions: - The total radiotoxicity (incorporation pathways) of the total volatile radioactive inventory (mercury isotopes and lower volatile nuclides) and the conventional toxicity of 10 t Hg are in terms of LD50 in the same order (2*107 – 108 times of LD50) - A relevant impact of radiotoxicity results from groundshine (Hg-194, Hf-172), which cannot be directly compared to conventional toxicity - Altogether, conventional mercury toxicity may not be neglected in relation to the radiotoxicity - The report in preparation contains an overview on legal aspects concerning conventional toxicity of mercury; the corresponding contribution will be ready in time (end of 2005) Institut für Sicherheit sforschung und Reaktortechnik - ISR
Rainer Moormann
6
Forschungszentrum Jülich in der Helmholtz-Gemeinschaft
Oxidation of target materials (WP5 A) • Relevant in EURISOL for 2 reasons: - Mobilization of activity enclosed in the oxidizing target materials (accidents with ingress of air/steam) - Heat generation by oxidation may enhance the vaporization of mercury: Fire in the target area was found by PRA to be the most relevant driving force for activity release in SNS accidents
• Examinations performed so far and planned ones: - Data on oxidation kinetics for several low oxidation resistant target materials were collected and compared - Relevant lack of data will be identified - The corresponding report is planned for the 16th month of EURISOL Institut für Sicherheit sforschung und Reaktortechnik - ISR
Rainer Moormann
7
Forschungszentrum Jülich in der Helmholtz-Gemeinschaft
Institut für Sicherheit sforschung und Reaktortechnik - ISR
Rainer Moormann
8
Forschungszentrum Jülich in der Helmholtz-Gemeinschaft
Shielding issues (WP5 A) Goal: Make available and apply ESS experience on EURISOL shielding General output from ESS shielding work: • High power target shielding requires special attention due to complex geometries (penetrations); Monte Carlo methods to be applied • (Driver) accelerator shielding nevertheless requires most effort despite of easier calculation methods because – also considering decommissioning - it is the more costly issue
Institut für Sicherheit sforschung und Reaktortechnik - ISR
Rainer Moormann
9
Forschungszentrum Jülich in der Helmholtz-Gemeinschaft
Driver accelerator shielding Comparison of EURISOL and ESS accelerator: - Alltogether similar (5 MW, 1 (2) GeV, SC Linac in EURISOL, 10 MW, 1.334 GeV, SC Linac in ESS) except of 1 CW H+ (EURISOL)
1 pulsed H- (ESS)
- CW makes shielding easier (less local beam losses), but creates no principle differences in shielding treatment
Institut für Sicherheit sforschung und Reaktortechnik - ISR
Rainer Moormann
10
Forschungszentrum Jülich in der Helmholtz-Gemeinschaft
………Driver accelerator shielding Recommendations to EURISOL from ESS shielding work: Normal losses – standard operation - In addition to EURISOL feasibility study, report App. B, an average normal loss of 2 W/m (instead of 1 W/m) should be taken into account in order to consider beam tuning periods implications on shielding thickness are however small (some 10 cm of soil) - In transition ranges of different LINAC sections continuous beam losses of 20 W/m should be assumed, as higher losses are expected to occur here
Institut für Sicherheit sforschung und Reaktortechnik - ISR
Rainer Moormann
11
Forschungszentrum Jülich in der Helmholtz-Gemeinschaft
………Driver accelerator shielding Local (accidental) losses – standard operation -
In contrast to the EURISOL feasibility study, App. B (1 beam loss/y of 1 s hits a worker behind shielding), a probabilistic method for dose estimation was assumed in ESS, leading to 5 beam losses/y for the reference worker; despite of the lower beam loss frequency due to CW, this method should be applied to EURISOL, too.
Local (accidental) losses – start-up operation -
During start-up high losses have to be expected, which cannot be quantified in detail. Following ESS examinations it is advisable to allow radiation controlled areas around the accelerator during start-up periods.
Institut für Sicherheit sforschung und Reaktortechnik - ISR
Rainer Moormann
12
Forschungszentrum Jülich in der Helmholtz-Gemeinschaft
………Driver accelerator shielding Radiation burden to the public (skyshine, direct radiation) -
For start-up operation of ESS with conservative assumptions on beam losses, simplified dose calculations (point source) led to a slight transgression of the 1 mSv limit in a distance of 300 m (fence). More sophisticated calculations are advisable for EURISOL.
Shielding material and its disposal -
Shielding by soil is cheaper during construction than concrete, but more problematic in disposal: Following German regulations, parts of soil (CERN) may be activated even in presence of 0.6 m of concrete for about 50 y after shut down to a ‚nuclear waste‘ level. An optimum concrete thickness for the EURISOL driver accelerator, leading to soil within the free handling limits already 10 y after shut down, was estimated to about 1.5 – 2 m.
A report will be ready some month before of the overall shielding report date Institut für Sicherheit sforschung und Reaktortechnik - ISR
Rainer Moormann
13
Forschungszentrum Jülich in der Helmholtz-Gemeinschaft
Disposal items (WP 5 D) 1 Objectives: Development of disposal stratefies mainly for spent targets. Mercury is a particular problem, because it has to be solidified before of disposal; removal of radioactivity is impossible because of the long lived Hg-194. 1 The disposal work is mainly foreseen from 2007. However, the experimental (hot cell) work foreseen requires more time. Accordingly, in order to prepare that work in an adequate manner, a PhD student (Suresh Chiriki, MSc Chemical Engineering) started on 1st of October 2005 by FZJ funding with the theme ‚Disposal strategy for proton irradiated mercury‘, including Hg solidification. - Experimental work will start the 2nd halve of 2006. - SINQ mercury will probably be available in 2007. - The intended work will be explained more detailed on the EURISOL town meeting, Caen. Institut für Sicherheit sforschung und Reaktortechnik - ISR
Rainer Moormann
14
Forschungszentrum Jülich in der Helmholtz-Gemeinschaft
Activity migration in ground water (SAFERIB and EURISOL Task B) • Background: Accelerator shielding requirements to the bottom resp. activity retention measures strongly depend on activation of soil and groundwater and on the migration velocity of the activity with ground water to the site boundary (where tap water quality is required) • Work performed so far: 2An overview on sorption coefficients (which determine the effective migration velocities in soil by a ‚chromatography effect‘) was collected 2 Most relevant nuclides (considering activation yields by thermal and by fast neutrons in ground water and in soil, sorption coefficients, life times and radiotoxicities) were identified: Institut für Sicherheit sforschung und Reaktortechnik - ISR
Rainer Moormann
15
Forschungszentrum Jülich in der Helmholtz-Gemeinschaft
……….Activity migration in ground water
Most relevant nuclides in soil/ground water 1234567
H-3
Be-7
Na-22
P-32
Cl-36
Fe-55
Co-60
6
Eu-152 (CERN)
12.3 y
53 d
2.6 y
14.3 d
3.1E5 y
2.6 y
5.3 y
13.3 y
< 10
>100
< 10
10-100
< 10
> 100
> 100
> 100
+
+
+
(+)
-
(+)
(+)
+
(-)
-
-
(+)
+
(-)
(+)
(-)
(-)
(+)
(+)
+
(+)
(+)
+
(+)
8
12345
6
12345 67389 4 52 6226
rs = retention by sorption on soil
Institut für Sicherheit sforschung und Reaktortechnik - ISR
Rainer Moormann
16
Forschungszentrum Jülich in der Helmholtz-Gemeinschaft
……….Activity migration in ground water 2 Activation calculations/data collections for soil and ground water were performed on example of CERN and Jülich site conditions; the basis for an efficient computer modelling of activation was developed 2 The influence of the proton energy (1 or 2 GeV options in discussion for EURISOL) on the relative activation level in soil was studied 2 Preliminary activity transport calculations were started with TRACE/PARTRACE on example of the Jülich site
Institut für Sicherheit sforschung und Reaktortechnik - ISR
Rainer Moormann
17
Forschungszentrum Jülich in der Helmholtz-Gemeinschaft
……….Activity migration in ground water
Specific activity in CERN type soil surrounding an accelerator (1.3 GeV) behind a 60 cm concrete layer (beam loss 1 W/m, 30 y operation time) Institut für Sicherheit sforschung und Reaktortechnik - ISR
Rainer Moormann
18
Forschungszentrum Jülich in der Helmholtz-Gemeinschaft
……….Activity migration in ground water
Dependence of maximum soil activation on proton energy for different thickness of concrete: No difference between 1 or 2 GeV options Institut für Sicherheit sforschung und Reaktortechnik - ISR
Rainer Moormann
19
Forschungszentrum Jülich in der Helmholtz-Gemeinschaft
……….Activity migration in ground water • Work foreseen for 2006:
2 Integration of an activation module in TRACE/PARTRACE (Collaboration with FI) 2 Calculations on activation/nuclide migration behaviour on example of Jülich site conditions
Institut für Sicherheit sforschung und Reaktortechnik - ISR
Rainer Moormann
20
Forschungszentrum Jülich in der Helmholtz-Gemeinschaft
Time Scale + Deliverables 2005 + 2006 1 Report on radioactive inventories, radiotoxicities and conventional toxicities in the EURISOL Hg-target: 2 Finished December, 31st 2005 1 Report on oxidation of target materials: 2 To be finished May, 31st 2006
1 Report on shielding recommendations for EURISOL: 2To be finished June, 30th 2006
1 Report on sorption coefficients for relevant migrating nuclides 2 To be finished January, 31st 2006 (EURONS-SAFERIB)
1 Report on TRACE model and its upgrading for nuclide migration 2 To be finished June, 30th 2006 (EURISOL)
1 Report on nuclide migration in ground water 2 To be finished December, 31st 2006 (EURONS-SAFERIB) 1 Preliminary report on selection of a Hg-form for disposal 2 To be finished May, 31st 2006
Institut für Sicherheit sforschung und Reaktortechnik - ISR
Rainer Moormann
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