clearance practises in germany...clearance paths in germany 6 thomas pöhlsen unconditional...
TRANSCRIPT
CLEARANCE IN THE FRAMEWORK OF
DECOMMISSIONING OF NUCLEAR
POWER PLANTS IN GERMANY
Thomas Pöhlsen
Clearance of Radioactive Material
WHY IS CLEARENCE OF IMPORTANCE IN GERMANY?
– IN THE FRAMEWORK OF DECOMMISSIONING
Thomas Pöhlsen 2
Supervised
area
Control
area
272
.10
0 M
g
127
.54
0 M
g
Masses in a NPP – example:
WHY IS CLEARENCE OF IMPORTANCE IN GERMANY?
– IN THE FRAMEWORK OF DECOMMISSIONING
Thomas Pöhlsen 3
272
.10
0 M
g
127
.54
0 M
g
97,2%
Clearance options:
• unconditional clearance
• clearance for disposal (landfills / incinerators)
• clearance for recycling (melting of metals)
• clearance of buildings for demolition
• clearance of ground area
2,4%
0,4%
rad. waste
further use under a licence
Masses in a NPP – example:
Supervised
area
Control
area
CLEARANCE IN THE REGULATORY FRAMEWORK
4
Radiation Protection Ordinance (StrlSchV), § 29:
radioactive / contaminated material may only be used as non-radioactive
material if clearance is granted by the competent authority
clearence <-> 10 µSv/a criterion for individuals of the population
(in math. models: expectation value ≤ 10 µSv)
nuclide-specific clearance levels for eight different clearing paths
for different materials and different restrictions (in Bq/g, Bq/cm²).
Competent authorities may call in an independent expert (AtG § 20)
TÜV NORD works as an independed expert for several Nuclear
Licencing and Supervisory Authorities in Germany
Internationally TN is a full service provider in the field of nuclear safety.
in preparation: a new ordinance for clearance to transpose the
Council Directive 2013/59/Euratom into national law
Atomic Energy
Act (AtG)
Radiation Protection
Ordinance (StrlSchV) Licences State-of-the-art
technology rules
(ISO, DIN …),
Guidelines, …
CLEARING PATH: CLEARANCE FOR DISPOSAL OF
SOLID MATERIAL ON LANDFILLS
Thomas Pöhlsen 5
Restrictions: Material to be disposed
on a landfill, up to 1000 t/a, …
Higher clearance values than for
unrestriced clearance
(e.g. Co-60: 2 Bq/g instead of 0.1 Bq/g)
CLEARANCE PATHS IN GERMANY
Thomas Pöhlsen 6
Unconditional clearance of
Solid material, oils, coolants
Demolition waste > 1000 t/a
Ground area
Buildings for further use
Clearance for disposal of
Solid material on landfills
Solid and liquid material in incinerators
Clearance of buildings for demolition
Clearance of scrap metal for recycling (melting)
1 Bq/cm²
(1 Bq/cm²)
(1 Bq/cm²)
(1 Bq/cm²)
0.1 Bq/g
0.09 Bq/g
0.03 Bq/g
0.4 Bq/cm²
Clearance values for Co-60
3 Bq/cm²
0.6 Bq/g
6 Bq/g / 2 Bq/g
7 Bq/g / 2 Bq/g
up to
100 t/a / 1000 t/a
Surface contamination:
averaging up to 1000 cm²
Averaging
up to:
300 kg
1000 kg
1000 kg
1 m²
300 kg
300 kg
1 m² (or more)
300 kg
HOW IS COMPLIANCE WITH CLEARANCE LEVELS
DEMONSTRATED? – CLEARANCE PLAN
Thomas Pöhlsen 7
further applicable
documents giving
detailed description
of the step
personnel involved
in treatment or
monitoring
Rules for participation
for independent
experts / supervisory
authority
chronological list
of the treatment
and monitoring
steps
HOW ARE CLEARANCE
MEASUREMENTS PERFORMED
Thomas Pöhlsen 8
Performing measurements in compliance
with state-of-the-art technology rules
(ISO 11929, DIN 25457-1 to -7)
Combined measurements may be
used: e.g. radioactive surface
contamination monitor + gamma-
sensitive measuring system
Key results:
Activity concentration
< clearance levels
with 95 % conf. lev.
Characterization
Dismantling
Decontamination
Screening
Final Measurements
Approval / control by
supervisory authority
typically 100 % of material measured
CURRENT APPLICATIONS, EXAMPLES
Thomas Pöhlsen 9
Buildings for
demolition
Laborious procedures
Every wall area to be
measured
Infiltration of
contamination to be
taken into account
Special structures to
be evaluated
CURRENT APPLICATIONS, EXAMPLES:
CLEARANCE OF A GENERATOR (BWR)
Thomas Pöhlsen 10
Image: Vattenfall Europe Nuclear Energy GmbH
• Approx. 23 m x 5 m
• Approx. 650 Mg
• Stator:
Center & end caps
• Rotor
• Auxiliary units
• Steel body
• Lamination
• Windings
• Cooling systems
(gas & liquid)
• Painted in the control area
• Aim: non-destructive demonstration
of compliance with clearing levels
CURRENT APPLICATIONS, EXAMPLES:
CLEARANCE OF A GENERATOR (BWR)
Thomas Pöhlsen 11
Non-destructive
demonstration of
compliance with clearing
levels considering:
Outer surface
Liquid cooling system
Gas compartments
Combination of
considering the
operational history,
measuring accumulation
points
sampling (paint)
measuring the outer
surface (in-situ)
Image: Vattenfall Europe Nuclear Energy GmbH
Thomas Pöhlsen 12
Clearance for disposal in landfills often causes public interest:
Real conditions
at the location of the
disposal facility
Model parameters for
the conduction of
clearance values
the 10 µSv/a criterium may be checked
for every individual disposal facility
CLEARANCE FOR DISPOSAL
– A TOPIC OF PUBLIC INTEREST
NEEDS FOR FURTHER IMPROVEMENTS, IAEA
ASSISTANCE / TOPICS FOR INT. COOPERATION
Thomas Pöhlsen 13
International guidance on surface contamination values
SR 44 chapter 3.5: „… it has to be recognized that for specific situations such as the
clearance of metal or the reuse of buildings from nuclear installations, additional
criteria relating to the surface contamination may have to be applied that are not
reflected in the derived activity concentration values“.
International guidance on averaging masses (and averaging surfaces) also
taking into account confidence levels to be reached due to measurement
uncertainties for each sample and for larger amounts of material, e.g.:
for clearance it turns out that the consideration of uncertainties
(measurement uncertainties / natural background / initial level of polution)
often contributes significantly to conservatism and can be a challenge
when compliance with clearance values is demonstrated.
especially for H-3 and C-14 with clearance values from SR 44 and required
confidence levels of 95 % for each sample, clearance procedures are more
complex and costly than radiologically necessary.
An international recommendation and clearance values for deposition of
material on landfills.
SUMMARY
Thomas Pöhlsen, [email protected] 14
In Germany clearance is regulated in the Radiation Protection Ordinance,
§29 (StrlSchV).
Radiological basis: eff. dose max. in the order of 10 µSv/a for individuals
Clearance is of importance because about 97 % of the total mass in the
control area is cleared.
Clearance paths exist for
solid and liquid materials
conditional (landfills, incinarators, smelting, buildings for demolishion) and
unconditional clearance (material, buildings, ground, rubble)
International guidance for surface contamination values, averaging
masses / surfaces and confidence levels to be reached would be helpful.
TÜV NORD has a wide experience in clearance in Germany working as
independed experts for several Nuclear Licencing and Supervisory Authorities.
Internationally TN is a full service provider in the field of nuclear safety.