Krypton-85 Monitoring at BfS in Germany and Possible Applications for Safeguards

Transcription

1 Krypton- Monitoring at BfS in Germany and Possible Applications for Safeguards Symposium on International Safeguards Linking Strategy, Implementation and People CN-220 IAEA, Vienna, Austria October 2014 Clemens Schlosser(a) and Franziska Klingberg(b) (a) Bundesamt für Strahlenschutz, Freiburg, Germany (b) The University of Texas at Austin, USA

2 Outline Introduction and Background Kr Monitoring at BfS, Germany Suggested Technical Solutions for Safeguards Summary and Conclusions

3 Possible Applications of the Noble Gas Kr Kr: T 1/2 = a Noble gas Production of Kr during nuclear power production and Pu breeding: Main Source: Nuclear Reprocessing Plants (16*10 12 Bq Kr/kg weapons-grade Pu, 10-35*10 12 Bq Kr/kg reactorgrade Pu) Verification of (military/undeclared) nuclear reprocessing activities (Pu-production) Significant Quantity (IAEA, NPT): 8 kg Pu Tracer in environmental studies and validation of ATM models Radiation protection

4 Nuclear Weapon Tests: PBq Global Kr Sources Natural: 0,0009 PBq Chernobyl (1986): 35 PBq Kr in the Atmosphere 5000 PBq (2014) β decay: 6,4 %/a (T 1/2 : 10,76 a) Rb (stable) Ocean < 0,1% Fukushima (2011) ~ 45 PBq Nuclear Reprocessing: ~ 300 PBq/a

5 Noble Gas Laboratory and Sampling Network (BfS) Manual system (1973): Measurement of atmospheric activity concentrations of Kr and 133 Xe Cryogenic sampling (LN 2 temperature, 1 week, 10 m³ air) Gas Chromatography for processing and purification Noble Gas Laboratory at BfS in Freiburg World wide network and central lab in Freiburg Sampling stations operated in co-operation with institutions on-site Detector: 7 proportional gas counters Pb-shielding and anticoincidence counters Darwin August MDA for Kr: 0,03 Bq (1 m³ air) for 133 Xe: 0,01 Bq (2 m³ air) Approx analyses per year

6 Global Atmospheric Kr Activity Concentration Peaks from Nuclear Reprocessing Kr Activity Concentration in Bq/m³ (Weekly Samples) + 0,03 Bq/m³ *year Year Kr Activity Concentration in Ground Level Air in Bq/m³ in the Southern and in the Northern Hemisphere Schauinsland Baseline NH Southern Hemisphere Stations (Antartica, Australia, South Africa) BfS Measurements

7 Modelling the Global Atmospheric Kr Distribution Nuclear Reprocessing: Distribution of known NRPs and reported Kr releases Kr- Release in Bq/Year Year BfS data base Ref: J.O. Ross, PhD University Hamburg, 2010

8 Case Study Around Karlsruhe Pilot Reprocessing Plant Kr monitoring in the vicinity of the WAK Karlsruhe ( km) and conclusion on Pu separation ( ) Detection probability for 4 kg Pu per week: 90% 50% Detection Prob. In % False alarms Distances up to 40 km: < 3.5% Sensitivity Minimum detectable weapon grade (wg) Pu production rate in weekly samples: 2 g/week at 1 km distance Ref: Kalinowski et al, JER 73 (2004), g/week at 130 km distance

9 Case Study MRI Tsukuba NRP Tokai Mura (d= 55 km) 8 kg/day Kr releases from NRP Tokai Mura 8 kg in 6 months Kr activity concentrations in ground level air measured in weekly samples at MRI intsukuba Minimum detectable release: 45 g wg Pu/day (90 GBq Kr/day) Meteorological conditions important - ATM improves detectability Ref: Kemp and Schlosser, JER 99 (2008)

10 Daily Sampling Kr Activity Concentration in Bq/m³ Kr Freiburg: Daily Sampling in Weeks11 and12/ / weekly samples Backround level Higher time resolution improves: - signal/background ratio - source localization by ATM daily samples Date

11 Atmospheric Transport Model Backwards Mode NRP Sellafield NRP La Hague Freiburg (Sampling Location)

12 Suggested Technical Solutions for IAEA Needs 1 Safeguards Verification Scenarios To verify operational status of shut-down reprocessing plant of operational reprocessing plant To detect unreported Pu production at known facilities at unknown locations To support Safeguards implementation at geological repositories To deter unreported Pu production Inspection Implementation Needs High reliability Minimal maintenance Minimum Detection Limit For atmospheric samples at locations which are unaffected by presence of other sources of Kr: 1 Bq/m 3 For on-site (stack) samples: 1kBq/m 3 Technologies for Noble Gas Detection Whole Air grab sampling Air sampling (cryogenic adsorption) Automated air sampling Off-gas monitoring 1: All needs and Technical Solutions described in detail in SG-EQ-GNRL-RP-0001 (including cost estimates)

13 Whole Air and Grab Sampling under INFCIRC/540, Art. 5C for location specific environmental sample Adjustable sampling durations/volumes Analysis at laboratory, e.g. with IGU system or Atom Trap Trace Analysis (requires only 1-3L of whole air) Technical Solutions (1) On-site OR Location Specific Possible unattended: Inspector only needs to transfer containers to lab Easy and cost effective IGU (BfS)Sampling and Analysis System Two component system (sampling and analysis) Similar to BfS system Activated charcoal Gas enrichment Gas chromatography Proportional counter Front view of Kr system with U-tube for 2 nd enrichment 1: Institute for applied isotopes, gas and environmental research

14 Off-gas monitoring Technical Solutions (2) Automated Sampling & Analysis Has been implemented at Tokai Reprocessing Plant Release behavior consistent with steps in fuel reprocessing Miniaturize Kr off-gas monitor to make it transportable (e.g. for Complimentary Access inspections) Manual or half-automated for NG sampling exists benefit from CTBTO experience Under FRA 1707 development of SPARK (SPALAX derived) Sampling, trapping at ambient temperature, 6-hour operating cycle, proportional counter Requires min. 0.5 cm 3 for detection capability of 0.1 Bq/m 3 above background ARIX was adapted and tested for Kr Kr gas releasing behavior during fuel reprocessing (JAEA, 2011) Ref: SG-EQ-GNRL-RP-0001

15 Summary and Conclusions (1) Since the early1950 s Kr was identified as a strong signature for reprocessing activities. At present, civil nuclear reprocessing is the major source of the Kr activity in the atmosphere. BfS long term time series of Kr concentrations give an invaluable overview about the global background with significant timely and geographical variations and are very useful to investigate the influence of nuclear reprocessing plants on the measured concentrations. Case studies proved the applicability of Kr sampling for Safeguards under INFCIRC/540, Art. 5C for location specific environmental sample Atmosperic Transport Modelling improves the application for the detection of unreported reprocessing activities.

16 Summary and Conclusions (2) IAEA needs regarding Kr detection were specified: Sampling and Analysis Technologies for different applications were identified. Besides the measurements, the release data of nuclear reprocessing plants would be very helpful for discriminating reported from unreported releases. Such data sets could be used for optimizing source localisation and identification as well as for the validation of models and assumptions. There are many common tasks between Kr applications for Safequards and existing Noble Gas Technologies in the CTBT verification system (e.g. On-Site Inspection). Exchange of knowledge and Joint Projects would enhance the effectiveness of IAEA Safeguards Noble Gas Monitoring.

17 Thanks for your attention! Any questions or remarks?