Transcript 슬라이드 1

Topical Aspects on Monitoring
Airborne Radioactive Effluents
from NPPs
Wan-tae KIM
Contents
• Concepts of Monitoring
• Guidelines of Monitoring
• Status of Monitoring
I. Concepts of Monitoring
WHAT
WHY
HOW
WHEN
MONITORING
WHERE
Monitoring What
• All radioactive effluents to the environment
• Two broad source types at NPPs
• Point source : stacks and ducts
• Nonpoint source : all other sources
• Focus on aerosol effluents from point source
Monitoring Why
• For evaluation
• the environmental impact
• the potential annual radiation doses to the public
• adequacy and performance of containment, waste
treatment methods, and effluent controls
• To ascertain
• regulatory requirements and LCO have been met
• concentrations have been kept ALARA
Monitoring When
• Continuously or periodically
• At all conditions of reactor operation
• Normal
• Off-normal
• Anticipated operational occurrences
• Post-accident
• Off-normal case should consider leakage of
particles through filter media, filter seals, and
cracks in filter frames
Monitoring Where (1)
• All major and potentially significant paths
• In 40 CFR Part 61.93 (4)(i) : continuous monitor
at release points that have the potential
effective dose equivalent (EDE) ≥ 0.1 mrem/yr
• NUREG-0800, SRP 11.5, table 1 lists all paths
Monitoring Where (2)
NUREG-0800
11.5
Table 1
Monitoring How
• Combination of direct measurement, sample
extraction, and analysis
• Sample extraction is performed with sampling
system
• Sampling system is very useful, but there are a
lot of complexities for getting representative
samples
Sampling System
Generic Sampling System (from ANSI N13.1-1999)
Continuous Air Monitor
P&ID of a CAM Sampler
II. Guidelines of Monitoring
1977 CAAA : EPA limit emission to air
1983 EPA : propose NESHAP – DOE &NRC
1987EPA:Case of VCD-reconsider NESHAP
ANSI N13.1-1969
1981 NRC : SRP 11.5 ver.3 - ANSI N13.1(1969)
1989 EPA:promulgate-40 CFR 61, Subpart I & H
Decision-making : VCD & benzene policy
No member of public exceeds 0.1 mSv/yr
1989 NRC : petition for regulation duplicate
1990 EPA: publish Rad NESHAP - 0.1 mSv/yr
EPA(1993a) : ANSI N13.1-1969
EPA(1993b) : “8-2 rule” or “duct diameter”
1990 DOE : follow Rad NESHAP-ANSI N13.1(1969)
1993, propose
ANSI N13.1-199X
1996 NRC : announce new Constraint Rule transfer 0.1 mSv/yr to 10 CFR 20
1996 NRC : SRP11.5 Draft ver.4-ANSI N13.1(1993)
1997 EPA : rescind - 40 CFR 61, Subpart I
1997 KINS : SRP 11.5 ver.0 - ANSI N13.1(1969)
ANSI N13.1-1999
2002 EPA : update - Rad NESHAP
ANSI N13.1-1999 use for new & modified
Impose additional inspection on existing
2000 DOE : present DOE Position to EPA No supporting complete retrofitting &replacement
of all existing monitoring devices
2007 NRC : SRP 11.5 ver.4 - ANSI N13.1(1999)
Rad NESHAP (40 CFR 61, Subpart H)
• Rad NESHAP standard for public dose limit
• from 1 mSv/yr to 0.1 mSv /yr
• from all pathway to just only air pathway
• The technical requirements for determining
dose to the public became more rigidly defined
• So, called out the ANSI N13.1-1969 as in
USEPA(1993a)
• In addition, sampling sites are required to be
selected following procedures in USEPA(1993b)
Deficiency in USEPA(1993b)
• USEPA(1993b) require that sampling should be
done at least 5 - 8 diameters downstream from
a disturbance and at least 2 diameters
upstream flow disturbances
• Techniques is clear, but no criteria
• Assumption : the degree of flow development
and mixing are directly related to the distance
from disturbance
• This, unfortunately, is not necessarily true
Deficiency in USEPA(1993a) - 1
• USEPA(1993a) assumes nothing about flow
development and mixing and calls out ANSI
recommendations for probe design
• However, other characteristics of the bulk
effluent (i.e., the degree of flow development
and particulate mixing) are also critical to
determine the design requirements of the probe
• ANSI N13.1(1969) provides guidance for
particulate sampling probes that utilize a
multinozzle array to accomodate any
deficiencies in the flow development or mixing
Deficiency in USEPA(1993a) – 2
• This scheme has a
significant drawback
• As additional nozzles
are added, the loss of
particles increase due
to impaction in the
small nozzle inlet and
tube bends
• Depending upon the
density of the
particulates at a ratio
2.0, particulates are
underestimated by 10
to 50%
from ANSI N13.1-1969
ANSI N13.1-1999
• ANSI N13.1-1999 compensate the deficiencies
in USEPA(1993a) and USEPA(1993b)
• ANSI N13.1-1999 is a performance-based
standard rather than the prescriptive 1969
version
• To assure a representative sample is collected,
the standard established required sampling
system performance criteria
Performance Criteria (1)
• Total transport of 10 μm AD particles and
vaporous contaminants shall be 〉50% from the
free stream to the collector/analyzer
• Sampler nozzle inlet shall have a transmission
ratio between 80% and 130% for 10 μm AD
particles
• Sampler nozzle shall have an aspiration ratio
that does not exceed 150% for 10 μm AD
particles
Performance Criteria (2)
• Characteristics of a suitable sampling location
are :
• coefficients of variation over the central 2/3 area
of the cross section within ±20% for 10 μm AD
particles, gaseous tracer, and gas velocity
• flow angle 〈 20° relative to the long axis of the
stack and nozzle inlet
• the tracer gas concentration shall not vary from
the mean 〉30% at any point on a 40 CFR 60,
Appendix A, Method 1 velocity mapping grid
Performance Criteria (3)
• Effluent flowrate continuous measurement
required if flow variation is 〉± 20% in a year
• Effluent and sample flow rate shall be
measured within ±10%
• Continuous sample flowrate measurement and
control required if flow varies 〉±20% during a
sample interval
• flow control shall be within ±15%
III. Status of Monitoring
12
10
8
6
4
2
0
P HW R
P W R -W H
P W R -C E
P R A MA TO M O P R -1000
O P R -1400
• 20 units under operation
• 6 units under construction
• All NPPs under operation use stacks (and ducts)
sampling system with isokinetic multiple smalldiameter nozzles
• Besides, the APR-1000 and APR-1400 have much
more number of stacks and ducts
Design Differences
• Status of sampling system at 4 units has been
surveyed during regular inspection in 2007
• Considerable matters are listed :
• the ratio of effluent/sample flow rate ranges from
10000 to 100000
• unbalance seems to exist among the components
• transport line seems too long, lots of bends
• information related sampling location, nozzle,
and transport line for old system is absent
• no total procedures to maintain sampling system
• no method to inspect the inner sampling site
Data Comparability
• Uniform method can provide a uniform basis for
data comparison from the different facilities
• Uniform method can be maintained with
• Periodic inspections of nozzle, transport lines,
sample and effluent flowmeters shall be
conducted
• Periodic calibrations of effluent and sample
flowmeters, CAMs, and sample analysis
instrumentation shall be conducted
Under Tasks
• New plants under
construction in Korea
are planning to use
ANSI N13.1-1999
• The performance
criteria of ANSI N13.11999 have been studied
to impose on the
existing facilities