[Federal Register Volume 63, Number 37 (Wednesday, February 25, 1998)]
[Notices]
[Pages 9581-9589]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-4761]
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NUCLEAR REGULATORY COMMISSION
Proposed Generic Communication; Laboratory Testing of Nuclear-
Grade Activated Charcoal (M97978)
AGENCY: Nuclear Regulatory Commission.
ACTION: Notice of opportunity for public comment.
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SUMMARY: The Nuclear Regulatory Commission (NRC) is proposing to issue
a generic letter concerning the laboratory testing of nuclear-grade
activated charcoal that is used in the safety-related air-cleaning
units of engineered safety feature ventilation systems of nuclear power
plants to reduce the potential onsite and offsite consequences of a
radiological accident by adsorbing iodine. The purpose of the proposed
generic letter is to: (1) Alert addressees that the NRC has determined
that testing nuclear-grade activated charcoal to standards other than
American Society for Testing and Materials (ASTM) D3803-1989,
``Standard Test Method for Nuclear-Grade Activated Carbon,'' does not
provide assurance for complying with their current licensing basis as
it relates to the dose limits of General Design Criterion (GDC) 19 of
Appendix A to 10 CFR Part 50 and Subpart A of 10 CFR Part 100, and that
ASTM D3803-1989 should be used for both new and used charcoal because
it allows for accurately monitoring the degradation of the charcoal
over time; (2) request that addressees determine whether their
technical specifications (TS) reference ASTM D3803-1989 for charcoal
filter laboratory testing and if not, either amend their TS to
reference ASTM D3803-1989 or propose an alternative test protocol and
provide the requested information; (3) alert addressees of NRC intent
to exercise enforcement discretion under certain conditions; and (4)
require that addressees submit written responses to this generic
letter.
[[Page 9582]]
The NRC is seeking comment from interested parties regarding both the
technical and regulatory aspects of the proposed generic letter
presented under the Supplementary Information heading.
The proposed generic letter has been endorsed by the Committee to
Review Generic Requirements (CRGR). Relevant information that was sent
to the CRGR will be placed in the NRC Public Document Room. The NRC
will consider comments received from interested parties in the final
evaluation of the proposed generic letter. The NRC's final evaluation
will include a review of the technical position and, as appropriate, an
analysis of the value/impact on licensees. Should this generic letter
be issued by the NRC, it will become available for public inspection in
the NRC Public Document Room.
DATES: Comment period expires March 27, 1998. Comments submitted after
this date will be considered if it is practical to do so, but assurance
of consideration cannot be given except for comments received on or
before this date.
ADDRESSES: Submit written comments to Chief, Rules and Directives
Branch, Division of Administrative Services, U.S. Nuclear Regulatory
Commission, Mail Stop T6-D69, Washington, DC 20555-0001. Written
comments may also be delivered to 11545 Rockville Pike, Rockville,
Maryland, between 7:45 a.m. to 4:15 p.m., Federal workdays. Copies of
written comments received may be examined at the NRC Public Document
Room, 2120 L Street, N.W. (Lower Level), Washington, D.C.
FOR FURTHER INFORMATION CONTACT: John P. Segala, (301) 415-1858.
SUPPLEMENTARY INFORMATION:
NRC Generic Letter 97-XX: Laboratory Testing of Nuclear-Grade
Activated Charcoal
Addressees
All holders of operating licenses for nuclear power reactors,
except those who have permanently ceased operations and have certified
that fuel has been permanently removed from the reactor vessel.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this
generic letter to:
(1) Alert addressees that the NRC has determined that testing
nuclear-grade activated charcoal to standards other than American
Society for Testing and Materials (ASTM) D3803-1989, ``Standard Test
Method for Nuclear-Grade Activated Carbon,'' does not provide assurance
for complying with their current licensing basis as it relates to the
dose limits of General Design Criterion (GDC) 19 of Appendix A to 10
CFR Part 50 and Subpart A of 10 CFR Part 100. In addition, the staff
has determined that ASTM D3803-1989 should be used for both new and
used charcoal because it allows for accurately monitoring the
degradation of the charcoal over time.
(2) Request that all addressees determine whether their technical
specifications (TS) reference ASTM D3803-1989 for charcoal filter
laboratory testing. Addressees whose TS do not reference ASTM D3803-
1989 should either amend their TS to reference ASTM D3803-1989 or
propose an alternative test protocol and provide the information
discussed in the requested actions.
(3) Alert addressees of the staff's intent to exercise enforcement
discretion under certain conditions.
(4) Require that all addressees send the NRC written responses to
this generic letter, relating to implementation of the requested
actions.
Background
Safety-related air-cleaning units used in the engineered safety
feature (ESF) ventilation systems of nuclear power plants reduce the
potential onsite and offsite consequences of a radiological accident by
adsorbing radioiodine. To ensure that the charcoal filters used in
these systems will perform in a manner that is consistent with the
licensing basis of a facility, most licensees have requirements in
their facility TS to periodically test (in a laboratory) samples of
charcoal taken from the air-cleaning units.
The NRC's and the nuclear industry's understandings of the
appropriate laboratory tests for nuclear-grade charcoal have evolved
over the years since the issuance of Regulatory Guide (RG) 1.52,
``Design, Testing, and Maintenance Criteria for Postaccident
Engineered-Safety-Feature Atmosphere Cleanup System Air Filtration and
Adsorption Units of Light-Water-Cooled Nuclear Power Plants,'' which is
referenced in many plant TS. It was initially assumed that high-
temperature/high-relative humidity (RH) conditions were the most
severe. Later, with more testing experience, it became clear that the
most conservative test is at low temperature/high humidity. The use of
outdated test protocols or inappropriate test conditions can lead to an
overestimation of the charcoal's ability to adsorb radioiodine
following an accident.
Problems associated with the performance of the laboratory test of
charcoal under inappropriate test conditions were discussed in
Attachment 1 of Information Notice (IN) 86-76. Attachment 1, ``Summary
of Control Room Habitability Reviews,'' noted that charcoal was being
tested at much higher temperatures than any expected during the course
of an accident, and that the performance of the laboratory test at that
temperature can result in erroneously high efficiency measurements.
In 1982, the American Society of Mechanical Engineers (ASME)
Committee on Nuclear Air and Gas Treatment (CONAGT) conducted an inter-
laboratory comparison test using ASTM D3803-1979 and found that seven
U.S. laboratories and eight foreign laboratories obtained vastly
different results when testing samples of the same charcoal. After
efforts to resolve the differences failed, the NRC contracted with EG&G
at Idaho National Engineering Laboratory (INEL) to assess the problem.
As a result of this assessment, the NRC issued IN 87-32. Through IN 87-
32, the NRC informed licensees of deficiencies in the testing of
nuclear-grade charcoal, specifically noting serious problems with the
capabilities of the testing laboratories and with the testing standard
(ASTM D3803-1979). The NRC contractor detailed the specific problems in
its technical evaluation report, EGG-CS-7653, ``Final Technical
Evaluation Report for the NRC/INEL Activated Carbon Testing Program.''
Specifically, EG&G reported that ASTM D3803-1979 had unacceptable test
parameter tolerances and instrument calibration requirements, and that
ASTM D3803-1979 was nonconservative in not requiring humidity pre-
equilibration of used charcoal. The information notice indicated that
the protocol developed by EG&G could be utilized for performing the
laboratory test until the D-28 committee responsible for ASTM D3803
revised the standard. The committee completed the revision and issued
it in December 1989. The problems associated with the testing
laboratories were resolved after the number of U.S. firms performing
such tests dropped from seven to the current two.
On April 29, 1993, representatives from ASME and CONAGT met with
the NRC staff to express their concerns about laboratory testing of
charcoal. CONAGT discussed the variation in laboratory test results
obtained (methyl iodide penetration) when temperature, RH, face
velocity, bed depth, test protocol, and impregnate were varied. CONAGT
stated that the 1989 version of
[[Page 9583]]
ASTM D3803 is the only acceptable test method for TS applications and
compared the results of laboratory tests performed using the 1986
version of ASTM D3803 (which is the 1979 version with editorial
changes) to results using the 1989 version. The results from the 1986
protocol showed significantly higher iodine-removal capabilities than
the results from the 1989 version.
In addition, CONAGT indicated that testing charcoal at temperatures
greater than 30 deg.C [86 deg.F] almost always results in the
charcoal meeting the TS acceptance criteria, even when the charcoal is
deficient. To support this premise, CONAGT presented the results of
laboratory tests conducted at temperatures of 30 deg.C [86 deg.F], 80
deg.C [176 deg.F], and 130 deg.C [266 deg.F]. The data show
significant increases in iodine-removal capabilities as the test
temperature increases. CONAGT indicated that all systems located
outside of containment should be tested at 30 deg.C [86 deg.F], which
is more representative of the limiting accident conditions. Tests
conducted at 80 deg.C [176 deg.F] or 130 deg.C [266 deg.F] are
inappropriate because tests at these temperatures result in the
regeneration of the charcoal. At elevated temperatures, the charcoal
contains less moisture than at 25 deg.C [77 deg.F] and 30 deg.C [86
deg.F] which results in the charcoal having more surface area available
for adsorption of iodine. Therefore, testing at the elevated
temperatures results in an overestimation of the actual iodine-removal
capability of the charcoal, and testing at 25 deg.C [77 deg.F] or 30
deg.C [86 deg.F] gives results that represent a more realistic
assessment of the capability of the charcoal. CONAGT concluded its
presentation by stating that the major problems associated with the
laboratory test of charcoal are the designation of the test protocol
and the TS that designate the test to be performed.
On November 6, 1996, the staff visited the two remaining
laboratories that test nuclear-grade activated charcoal, NCS
Corporation and NUCON International, Inc. Both laboratories have
resolved the poor reproducibility problem identified in the EG&G report
by performing all tests with calibrated equipment that is capable of
maintaining the tight tolerances of the test parameters as specified in
ASTM D3803-1989. Tight tolerances are very important when tests are
performed at high RH, because slight variations in RH result in
unacceptably large differences in the tested efficiency of the
charcoal.
Discussion
Although some licensees have changed their TS to reference the
latest testing standard (ASTM D3803-1989), many still use outdated
standards and/or test conditions that may overestimate the capability
of the charcoal in their ESF systems. As a result, the ability of the
charcoal filters in these systems to perform in a manner consistent
with the licensing basis for the facility may be in question.
The licensees of three plants (V.C. Summer, Davis-Besse and Oconee)
determined that the tests they performed were not in compliance with
their TS and submitted emergency TS amendments (see Enclosure 1 for
details). As a result of the emergency TS changes, the staff has
performed an internal survey of the TS of operating plants to determine
whether other plants have the potential for similar compliance
problems. The survey indicated that at least one-third of operating
reactor licensees may be out of compliance with their TS because,
although the plant TS reference RG 1.52 or American National Standards
Institute (ANSI) N509-1976, ``Nuclear Power Plant Air-Cleaning Units
and Components,'' the licensees may have used later versions of the
standards for the laboratory tests of their nuclear-grade charcoal. On
the basis of this survey, the staff established the following four
groups of plants:
(1) Plants in compliance with their TS that test in accordance with
ASTM D3803-1989.
(2) Plants in compliance with their TS that test in accordance with
a test protocol other than ASTM D3803-1989.
(3) Plants not in compliance with their TS that test in accordance
with ASTM D3803-1989.
(4) Plants not in compliance with their TS that test in accordance
with a test protocol other than ASTM D3803-1989.
Licensees in Group 1 have TS that require charcoal to be tested in
accordance with ASTM D3803-1989, which adequately demonstrates the
capability of the charcoal. As discussed in Enclosure 1, the staff
considers ASTM D3803-1989 to be the most accurate and most realistic
protocol for testing charcoal in ESF ventilation systems because it
offers the greatest assurance of accurately and consistently
determining the capability of the charcoal. For example, it requires
the test to be performed at a constant low temperature of 30 deg.C
[86 deg.F]; it provides for smaller tolerances in temperature,
humidity, and air flow; and it has a humidity pre-equilibration.
Licensees in Group 2 have TS that require charcoal to be tested in
accordance with test standards other than ASTM D3803-1989. On the basis
of available laboratory test results for more than 50 charcoal samples,
there were significant differences in filter efficiencies for about 15
to 20-percent of the tested samples when comparing the test results
from ASTM D3803-1979 and ASTM D3803-1989. When the charcoal samples
were tested in accordance with ASTM D3803-1979, they always appeared to
have very high efficiencies. However, when the same charcoal samples
were tested in accordance with ASTM D3803-1989, significant reduction
in efficiency was noted. Depending on the system arrangement, this
reduction in filter efficiency can result in calculated doses to the
control room operators exceeding the GDC 19 limits by as much as a
factor of 1.5 to 2. For pressurized-water reactors (PWRs) with
secondary containments and for all boiling-water reactors (BWRs), this
reduction in filter efficiency can result in offsite doses from a
filtered pathway increasing by as much as a factor of 10 to 15. As a
result, the testing of nuclear-grade activated charcoal to standards
other than ASTM D3803-1989 does not provide assurance for complying
with the plant's licensing basis as it relates to the dose limits of
GDC 19 and Part 100.
In addition, the staff has determined that ASTM D3803-1989 should
be used for both new and used charcoal because it allows for accurately
monitoring the degradation of the charcoal over time. The original
rationale for testing used and new charcoal differently was the belief
that a long equilibration period would regenerate the used charcoal by
removing contaminants adsorbed by the charcoal during normal plant use.
However, an EG&G technical evaluation report, described in Enclosure 1,
demonstrated that this is not true. As a result, ASTM D3803-1989
specifies testing both used and new charcoal in the same manner.
Currently, before shipping, suppliers test most new charcoal with
the ASTM D3803-1989 protocol at 30 deg.C [86 deg.F] and 95-percent RH
in addition to the test protocol and test conditions the addressee
records on the purchase order. The results from the new charcoal tested
via ASTM D3803-1989 present a solid baseline for the initial capability
of the charcoal. Using ASTM D3803-1989 to test used charcoal is a very
accurate and reproducible method for determining the capability of the
charcoal. By comparing the results of the used charcoal tests with the
new charcoal test baseline, the addressee can be certain of the
charcoal's level of degradation.
Analyses of design-basis accidents assume a particular engineered
safety features (ESF) charcoal filter adsorption
[[Page 9584]]
efficiency when calculating offsite and control room operator doses.
Licensees then test charcoal filter samples to determine whether the
filter adsorber efficiency is greater than that assumed in the design-
basis accident analysis. The laboratory test acceptance criteria
contain a safety factor to ensure that the efficiency assumed in the
accident analysis is still valid at the end of the operating cycle.
Because ASTM D3803-1989 is a more accurate and demanding test than
older tests, addressees that upgrade their TS to this new protocol will
be able to use a safety factor as low as 2 for determining the
acceptance criteria for charcoal filter efficiency. This safety factor
can be used for systems with or without humidity control because the
lack of humidity control is already accounted for in the test
conditions (systems without humidity control test at 95-percent RH and
systems with humidity control can test at 70-percent RH). The staff has
previously approved reductions in the safety factor for plants adopting
the ASTM D3803-1989 standard on a case-by-case basis. (The staff plans
to make conforming changes to RG 1.52.)
The licensees that received emergency TS changes were in Groups 3
and 4. Licensees in Groups 3 and 4 have TS that require charcoal to be
tested in accordance with RG 1.52 or ANSI N509-1976, and are not in
compliance with their TS because the specified test protocol can not be
successfully completed as discussed in Enclosure 1. These licensees are
either (1) testing in accordance with the desired ASTM D3803-1989
(Group 3) or (2) using earlier revisions of ASTM D3803 or an older
standard which they believe are acceptable (Group 4). The staff does
not have confidence that the results from RG 1.52 or ANSI N509-1976
meet the intent of the TS which is to ensure that the doses are within
the required limits. Therefore, licensees in these groups have not
adequately demonstrated compliance with their licensing basis as it
relates to the dose limits of GDC 19 and Part 100.
The staff believes that (1) conflicting guidance, (2) complex and
ambiguous standards, and (3) licensee belief that using later versions
of the standard would satisfy their TS requirements, contributed to
confusion regarding charcoal testing. These factors may explain why
licensees did not adopt ASTM D3803-1989 (See Enclosure, for further
discussion). In addition, based on the available laboratory test
results, the staff believes that most charcoal in use is not degraded
to an extent that would adversely affect control room habitability or
public health and safety. This confidence in charcoal performance and
given the low probability of a design basis accident, justify the time
frames for the resolution of this matter. Therefore, the staff intends
to exercise enforcement discretion, consistent with Section VII.B.6 of
the Enforcement Policy, for all addressees in Groups 3 and 4, provided:
Within 60 days of the date of this generic letter, either
charcoal samples are tested in accordance with ASTM D3803-1989 and the
results meet the current TS acceptance criteria or all of the charcoal
is replaced with new charcoal that has been tested in accordance with
ASTM D3803-1989;
Acceptable charcoal sample test results discussed in the
first condition are submitted to the NRC within 60 days of the date of
this generic letter;
A TS amendment request is submitted to the NRC within 60
days of the date of this letter; and
The charcoal samples continue to be tested in accordance
with ASTM D3803-1989 until the TS amendment is approved by the NRC.
In cases in which the charcoal samples have been previously tested
in accordance with ASTM D3803-1989 for the last scheduled laboratory
test and the results met the current TS acceptance criteria (Group 3),
the results can be used to satisfy the first condition above.
Licensees in Group 2 have been complying with their TS by testing
their charcoal in accordance with their TS. Therefore, enforcement
discretion is not required.
Requested Actions
Addressees are requested to take the following actions:
1. If your current TS require the laboratory testing of charcoal
samples for each ESF ventilation system to be conducted in accordance
with ASTM D3803-1989, then no TS amendment is required.
2. If your current TS do not require the laboratory testing of
charcoal samples to be conducted in accordance with ASTM D3803-1989,
then:
(i) Your charcoal samples should be tested in accordance with ASTM
D3803-1989 and the results should be submitted to the NRC within 60
days of the date of this generic letter. If your charcoal samples were
already tested in accordance with ASTM D3803-1989 for the last
scheduled laboratory test and the results met the current TS acceptance
criteria, then the results should be submitted to the NRC within 60
days of the date of this generic letter. In either case, the charcoal
samples should continue to be tested in accordance with ASTM D3803-1989
until the TS amendment is approved by the NRC, and
(ii) Your TS should be amended to require the laboratory testing of
charcoal samples to be conducted in accordance with:
(a) ASTM D3803-1989, or
(b) An alternate test protocol should be proposed for the
laboratory testing of charcoal and the following information should be
submitted for staff review to determine the acceptability of the
alternate protocol:
1. Summary of the test method
2. Precision of the method
3. Description of the test apparatus along with tolerances
4. Parameter specifications
5. Material requirements
6. Hazards
7. Preparation of the apparatus before initiation of the test
8. Calibration requirements of the test equipment
9. Test procedure
10. Manner of calculating penetration and error
11. Repeatability and reproducibility of the results for 1-percent and
10-percent penetration and the penetration at a 95-percent confidence
interval for charcoal tested at 70-percent RH and at 95-percent RH
12. Bias associated with the method
13. Results from an independent laboratory which demonstrate that the
alternate test protocol gets results that are consistent with, or more
conservative than, that associated with ASTM D3803-1989
The demonstration identified in Item 13 above should be based upon
a series of tests comparing the alternate test protocol and ASTM D3803-
1989, and it should apply to both new and used charcoal tested at 70-
percent RH and at 95-percent RH. The independent laboratory should be
able to demonstrate that the alternate protocol is at least as
conservative as ASTM D3803-1989, and should be able to perform the ASTM
D3803-1989 test and achieve repeatable and reproducible results. The
laboratory should not be engaged in the measurement of iodine
penetration of charcoal as a business either for TS compliance purposes
or for the sale and/or production of activated charcoal for nuclear
power plant applications.
Requested Information
Within 60 days of the date of this generic letter, addressees are
requested to provide to the NRC the following information:
1. Identify the current TS requirements for the laboratory testing
[[Page 9585]]
of charcoal samples for each ESF ventilation system including the
specific test protocol, temperature, RH, and penetration at which the
TS require the test to be performed. If your current TS specifically
require testing in accordance with the ASTM D3803-1989 protocol, and
you have been testing in accordance with this standard, then no
additional information is required.
2. If you choose to adopt the ASTM D3803-1989 protocol, then submit
a TS amendment request to require testing to this protocol. The request
should contain the test temperature, RH, and penetration at which the
proposed TS will require the test to be performed and the basis for
these values. If the system has a face velocity greater than 10 percent
of 0.203 m/s [40 ft/min], then the revised TS should specify the face
velocity. Also, indicate when the next laboratory test is scheduled to
be performed. (Enclosure 2 is a sample TS that the NRC considers
acceptable.)
3. If you are proposing an alternate test protocol, then address
the attributes discussed in Section 2(ii) of the Requested Actions and
submit a TS amendment request to require testing to this alternate
protocol. The request should contain the test temperature, RH, and
penetration at which the proposed TS will require the test to be
performed and the basis for these values. If the system has a face
velocity greater than 10 percent of 0.203 m/s [40 ft/min], then the
revised TS should specify the face velocity. Also, indicate when the
next laboratory test is scheduled to be performed.
Required Response
Within 30 days of the date of this generic letter, addressees are
required to submit a written response indicating: (1) Whether the
requested actions will be completed, (2) whether the requested
information will be submitted and (3) whether the requested information
will be submitted within the requested time period. Addressees who
choose not to complete the requested actions, or choose not to submit
the requested information, or are unable to satisfy the requested
completion date, must describe in their response any alternative course
of action that is proposed to be taken, including the basis for
establishing the acceptability of the proposed alternative course of
action and the basis for continued operability of affected systems and
components as applicable.
Address the required written response to the U.S. Nuclear
Regulatory Commission, ATTN: Document Control Desk, Washington, D.C.
20555-0001, under oath or affirmation, under the provisions of Section
182a, Atomic Energy Act of 1954, as amended, and 10 CFR 50.54(f). In
addition, send a copy to the appropriate regional administrator.
Backfit Discussion
Appendix A to 10 CFR Part 50, General Design Criteria (GDC) for
Nuclear Power Plants, and the plant safety analyses require and/or
commit that licensees design and test safety-related structures,
systems and components to offer adequate assurance that they can
perform their safety functions. Specifically, GDC 19 of Appendix A to
10 CFR Part 50 specifies dose limits to ensure that control room
operators are provided with adequate radiation protection under
accident conditions. Following the accident at Three Mile Island (TMI),
TMI Action Plan Item III.D.3.4, ``Control Room Habitability
Requirements,'' as specified in NUREG-0737, ``Clarification of TMI
Action Plan Requirements,'' required all licensees to perform
evaluations and identify appropriate modifications to ensure that
control room operators are adequately protected from the release of
radioactive gases and that the nuclear power plant can be safely
operated or shut down under design-basis accident conditions (GDC 19).
When modifications were proposed by licensees, the NRC issued Orders
confirming licensee commitments. As a result, all licensees are
required to meet the dose limits of GDC 19. In addition, Subpart A of
10 CFR Part 100 specifies reference dose values which can be used in
the evaluation of the suitability of proposed sites for nuclear power
plants with respect to potential reactor accidents that could result in
the release of significant quantities of radioactive fission products.
The expectation is that the site location and the engineered safety
features included as safeguards against the hazardous consequences of
an accident, should one occur, should ensure a low risk of public
exposure. In this regard, licensees commit to dose limits that can be
used as the basis for assessing the performance of safety-related
structures, systems and components. Accordingly, licensees are required
to test the nuclear-grade activated charcoal of their engineered safety
feature ventilation systems in accordance with a suitable testing
standard to ensure that the charcoal filters are capable of performing
their required safety function and that the licensing bases of their
respective facilities regarding onsite and offsite dose consequences
continue to be satisfied.
The actions requested in this generic letter are considered
compliance backfits under the provisions of 10 CFR 50.109. If some
licensees test their charcoal in accordance with their TS which
reference an outdated test standard, the staff does not have confidence
that the results of those tests will demonstrate compliance with the
plant's licensing basis as it relates to the dose requirements of GDC
19 and Part 100, including commitment to the resolution of TMI Action
Plan Item III.D.3.4. Therefore, the staff has endorsed the testing
standard ASTM D3803-1989 for referencing in plant TS. In accordance
with the provisions of 10 CFR 50.109(a)(4)(i), regarding compliance
backfits, a full backfit analysis was not performed. However, an
evaluation was performed in accordance with NRC procedures, including a
statement of the objectives of and reasons for the requested actions
and the basis for invoking the compliance exception and is reflected in
this backfit discussion.
Federal Register Notification
(To be completed after the public comment period.)
Paperwork Reduction Act Statement
This Generic Letter contains information collections that are
subject to the Paperwork Reduction Act of 1995 (44 U.S.C. 3501 et
seq.). These information collections were approved by the Office of
Management and Budget, approval number 3150-0011, which expires
September 30, 2000.
The public reporting burden for this mandatory information
collection is estimated to average 40 hours per response, including the
time for reviewing instructions, searching existing data sources,
gathering and maintaining the data needed, and completing and reviewing
the information collection. The U.S. Nuclear Regulatory Commission is
seeking public comment on the potential impact of the information
collections contained in the generic letter and on the following
issues:
1. Is the proposed information collection necessary for the proper
performance of the functions of the NRC, including whether the
information will have practical utility?
2. Is the estimate of burden accurate?
3. Is there a way to enhance the quality, utility, and clarity of
the information to be collected?
4. How can the burden of the information collection be minimized,
including the use of automated collection techniques?
[[Page 9586]]
Send comments on any aspect of this information collection,
including suggestions for reducing the burden, to the Information and
Records Management Branch (T-6 F33), U.S. Nuclear Regulatory
Commission, Washington, DC 20555-0001, or by Internet electronic mail
at [email protected]; and to the Desk Officer, Office of Information and
Regulatory Affairs, NEOB-10202, (3150-0011), Office of Management and
Budget, Washington, DC 20503.
Public Protection Notification
If an information collection does not display a currently valid OMB
control number, the NRC may not conduct or sponsor, and a person is not
required to respond to, the information collection.
Enclosures:
(1) Background Information on the Laboratory Testing of Nuclear-
Grade Activated Charcoal.
(2) Sample Technical Specifications.
Enclosure 1
Background Information on the Laboratory Testing of Nuclear-Grade
Activated Charcoal
Charcoal Testing Requirements
Analyses of design-basis accidents assume a particular engineered
safety features (ESF) charcoal filter adsorption efficiency when
calculating offsite and control room operator doses. Licensees then
test charcoal filter samples to determine whether the filter adsorber
efficiency is greater than that assumed in the design-basis accident
analysis. The laboratory test acceptance criteria contain a safety
factor to ensure that the efficiency assumed in the accident analysis
is still valid at the end of the operating cycle.
Guidance on the frequency of, and the test method for, the
laboratory testing of charcoal appears in various documents, including
all revisions of Regulatory Guide (RG) 1.52, ``Design, Testing, and
Maintenance Criteria for Postaccident Engineered-Safety-Feature
Atmosphere Cleanup System Air Filtration and Adsorption Units of Light-
Water-Cooled Nuclear Power Plants,'' and other NRC documents on plant
technical specifications (TS). Guidance on the laboratory test protocol
appears in such standards as American National Standards Institute
(ANSI) N509, ``Nuclear Power Plant Air-Cleaning Units and Components;''
ANSI N510, ``Testing of Nuclear Air-Cleaning Systems;'' Military
Specification RDT M 16-1T, ``Gas Phase Adsorbents for Trapping
Radioactive Iodine and Iodine Components;'' and American Society for
Testing and Materials (ASTM) Standard D3803, ``Standard Test Method for
Nuclear-Grade Activated Carbon.''
All of the standards describe a pre-equilibration period, a
challenge period, and an elution period. During the pre-equilibration
(pre-sweep) period, the charcoal is exposed to a flow of air controlled
at the test temperature and relative humidity (RH) before the challenge
gas is fed through the charcoal. The pre-equilibration period ensures
that the charcoal has stabilized at the specified test temperature and
RH for a period of time, which results in the charcoal adsorbing all
available moisture before the charcoal is challenged with methyl
iodide. During the challenge period, air at the test temperature and RH
with radio-labeled methyl iodide is injected through the charcoal beds
to challenge the capability of the charcoal. During the elution (post-
sweep) period, air at the test temperature and RH is passed through the
charcoal beds to evaluate the ability of the charcoal to hold the
methyl iodide once it is captured.
The ASTM D3803-1989 standard has two additional testing periods
that are not required by other standards: the stabilization period and
the equilibration period. During the stabilization period, air at the
test temperature is passed through the charcoal beds to bring the
system up to the operating temperature before the start of pre-
equilibration. During the equilibration period, air at the test
temperature and RH is passed through the charcoal beds to ensure the
charcoal adsorbs all the available moisture before the feed period.
During this period, the system is more closely monitored than in the
pre-equilibration period to ensure that all parameters are maintained
within their limits.
Depending upon the plant's TS, typical test temperatures are
usually one of the following: 25 deg.C [77 deg.F], 30 deg.C [86 deg.F],
80 deg.C [176 deg.F], or 130 deg.C [266 deg.F]. In addition, the TS
usually require that the test be conducted at 70-percent RH if the ESF
system controls the RH to 70-percent or less, or at 95-percent if the
RH is not controlled to 70-percent.
The standard technical specifications (STS) and many plant-specific
TS specify Regulatory Position C.6.a of RG 1.52, Revision 2, as the
requirement for the laboratory testing of the charcoal. Regulatory
Position C.6.a refers to Table 2 of RG 1.52. Table 2 references Test
5.b of Table 5-1 of ANSI N509-1976, ``Nuclear Power Plant Air-Cleaning
Units and Components.'' Test 5.b references the test method from
paragraph 4.5.3 of Military Specification RDT M 16-1T, ``Gas Phase
Adsorbents for Trapping Radioactive Iodine and Iodine Components''
(date not indicated), but specifies that the test is to be conducted at
80 deg.C [176 deg.F] and 95-percent RH with preloading and postloading
sweep at 25 deg.C [77 deg.F]. This test is referred to as the ``25-80-
25 test.'' The essential elements of this test are as follows:
70-percent or 95-percent RH.
5-hour pre-equilibration (pre-sweep) time, with air at
25 deg.C [77 deg.F] and plant-specific RH.
2-hour challenge, with gas at 80 deg.C [176 deg.F] and
plant-specific RH.
A 2-hour elution (post-sweep) time, with air at 25 deg.C
[77 deg.F] and plant-specific RH.
The latest acceptable methodology for the laboratory testing of the
charcoal is ASTM Standard D3803-1989, ``Standard Test Method for
Nuclear-Grade Activated Carbon.'' ASTM D3803-1989 is updated guidance
based on an NRC verification and validation effort on ASTM D3803-1979,
which is updated guidance based on RDT M 16-1T. The essential elements
of the ASTM D3803-1989 test are as follows:
70-percent or 95-percent RH.
2-hour thermal stabilization, with air at 30 deg.C
[86 deg.F].
16-hour pre-equilibration (pre-sweep) time, with air at
30 deg.C [86 deg.F] and plant-specific RH.
2-hour equilibration time, with air at 30 deg.C [86 deg.F]
and plant-specific RH.
1-hour challenge, with gas at 30 deg.C [86 deg.F] and
plant-specific RH.
1-hour elution (post-sweep) time, with air at 30 deg.C
[86 deg.F] and plant-specific RH.
The major differences between the ANSI N509-1976 and ASTM D3803-
1989 standards for charcoal testing are as follows:
----------------------------------------------------------------------------------------------------------------
Major differences ASTM D3803-1989 ANSI N509-1976
----------------------------------------------------------------------------------------------------------------
Pre-Equilibration (Pre-Sweep) 30 deg.C [86 deg.F] 25 deg.C [77 deg.F].
Temperature.
Challenge Temperature................. 30 deg.C [86 deg.F] 80 deg.C [176 deg.F].
Elution (Post-Sweep) Temperature...... 30 deg.C [86 deg.F] 25 deg.C [77 deg.F].
Total Pre-Test Equilibration.......... 18 hours 5 hours.
[[Page 9587]]
Tolerances of Test Parameters......... Smaller Larger.
----------------------------------------------------------------------------------------------------------------
As stated above, ASTM D3803-1989 challenges the representative
charcoal samples at 30 deg.C [86 deg.F] rather than at 80 deg.C
[176 deg.F]. The quantity of water retained by charcoal is dependent on
temperature, and less water is retained as the temperature rises. The
water retained by the charcoal decreases its efficiency in adsorbing
other contaminants. At 30 deg.C [86 deg.F] and 95-percent RH, charcoal
will retain about 40 weight-percent water. At 80 deg.C [176 deg.F] and
95-percent RH, charcoal retains only about 2 to 3 weight-percent water.
Because most charcoal is anticipated to be challenged at a temperature
closer to 30 deg.C [86 deg.F] rather than 80 deg.C [176 deg.F], the
lower temperature test condition of ASTM D3803-1989 will yield more
realistic results than would a test performed at 80 deg.C [176 deg.F].
ASTM D3803-1989 specifies a test temperature of 30 deg.C [86 deg.F]
for both the pre- and post-test sweep rather than 25 deg.C [77 deg.F].
There is little difference in the adsorption behavior of charcoal
between these two temperatures. A temperature of 25 deg.C [77 deg.F] is
more conservative; however, the increase from 25 deg.C [77 deg.F] to
30 deg.C [86 deg.F] does not represent a significant variation in the
test results.
ASTM D3803-1989 provides results that are reproducible compared to
RDT M 16-1T because it has smaller tolerances on various test
parameters, and it requires that the charcoal sample be pre-
equilibrated for a much longer period. The longer pre-equilibration
time is more conservative because it will completely saturate the
representative charcoal sample until it is in the condition to which
the subject charcoal adsorbers are expected to be exposed during
design-basis conditions. Therefore, testing in accordance with ASTM
D3803-1989 will result in a more realistic prediction of the capability
of the charcoal.
TS Testing Reference
Laboratory tests of the charcoal are typically required (1) once
every refueling outage, (2) when certain events occur that could
adversely affect the ability of the charcoal to perform its intended
function, and (3) following a defined period of ESF system operation.
The TS require demonstration by laboratory testing that the charcoal is
capable of performing at a level greater than that assumed in the NRC
staff's safety evaluation report. If it fails to perform at that level,
the charcoal must be replaced.
The determination of the appropriate test conditions, test
protocol, and acceptance criteria for laboratory testing of nuclear-
grade activated charcoal is frequently not a straightforward process.
It sometimes requires a complex journey through a number of documents
to ascertain the appropriate test conditions, test protocol, and
acceptance criteria. As described earlier, if the plant has STS, the
STS reference Regulatory Position C.6.a of RG 1.52 for the requirements
for the laboratory testing of charcoal. Regulatory Position C.6.a
refers to Table 2 of the regulatory guide. Table 2 references Test 5.b
of Table 5-1 of ANSI N509-1976. Test 5.b from Table 5-1 references the
test method from paragraph 4.5.3 of RDT M 16-1T (date not indicated),
but specifies that the test is to be conducted at 80 deg.C [176 deg.F]
and 95-percent RH with pre-loading and postloading sweep at 25 deg.C
[77 deg.F]. This test is referred to as the ``25-80-25 test.''
Also contributing to the potential confusion are the various ways
in which TS are written, and conflicting NRC guidance on testing,
particularly NRC letters to the nuclear industry and NRC papers
presented at national conferences. This problem arose from the evolving
understanding of what constituted an appropriate test. At various
times, the NRC has stated that the newest version of a standard can be
used and the test can be conducted at a temperature of 30 deg.C [86
deg.F]. At other times, the NRC indicated that the TS are requirements
and that the tests must be performed at the 25-80-25 conditions. In
various forums, the NRC has also stated that a technical argument may
be made for using the newer standard. However, in some instances when
newer standards were utilized to demonstrate conformance with the TS,
the NRC required licensees to submit TS amendment requests because the
newer standards were not referenced in the TS. Therefore, it is
understandable that licensees may be confused about laboratory testing
protocols, testing conditions, and acceptance criteria. As a result,
many licensees are not testing charcoal in accordance with their TS,
although the tests they conduct may be more conservative than the tests
required by the TS.
Additionally, the 25-80-25 test has difficulties in that none of
the protocols in any version of RDT M 16-1T or ASTM D3803 addresses
performing the laboratory test at multiple temperatures as required by
ANSI N509-1976. If the test protocol described in paragraph 4.5.3 of
RDT M 16-1T (1973) is followed verbatim, a thermal step change must be
made after the 5-hour pre-equilibration period to increase the
temperature from 25 deg.C [77 deg.F] to 80 deg.C [176 deg.F] for
the challenge period. The problem with such thermal step changes is
that they result in condensation forming on the charcoal. The
condensation of free water in the sample bed is cause for aborting the
test, according to the 1977 version of RDT M 16-1T and subsequent
versions of ASTM D3803. Therefore, the 25-80-25 test cannot be
performed pursuant to any existing test protocol.
Because paragraph 4.5.3 cannot be followed verbatim, a few
licensees have changed the 25-80-25 test to thermally equilibrate the
charcoal before introducing the challenge gas. Following the pre-sweep
conditioning at 25 deg.C [77 deg.F], the bed temperature is raised to
80 deg.C [176 deg.F] before introducing the challenge gas. Although
such testing does not cause condensation in the test rig, it is not
acceptable because the results are not easily reproducible, and even
when the test is successfully completed, the results may not be
conservative.
Section 2 of ANSI N509-1976 states for the various documents that
supplement ANSI N509 that the issuance of a document in effect at the
time of the purchase order shall apply unless otherwise specified. In
the case of charcoal, the purchase order date could be considered the
date that the charcoal is procured. Therefore, TS that have the STS
wording may allow the licensee the flexibility to use a more recent
laboratory protocol than the 1973 version of RDT M 16-1T, depending on
the procurement date for the charcoal, without a TS change. However,
although the flexibility of protocol selection exists, the requirement
to perform a 25-80-25 test for those plants that have TS that reference
either Revision 1 or Revision 2 of RG 1.52, Table 5-1 of ANSI N509-
1976, or ANSI N510-1975 can only be relieved by license amendment.
[[Page 9588]]
Categorization of Plants
Since February 1996, the staff has issued three emergency TS
changes to licensees that had determined that the tests they performed
were not in compliance with their TS, because the required testing
standards and test protocols did not support a test in which the
temperature is changed as required by the TS. If the temperature in the
test apparatus is changed from 25 deg.C [77 deg.F] to 80 deg.C [176
deg.F] during the test without modifying the test protocol, water
condenses on the charcoal, thereby causing the test to be aborted (to
fail). The emergency TS changes were issued for the V.C. Summer, Davis-
Besse, and Oconee facilities. The details of these TS changes are
discussed below.
On February 10, 1996, the licensee for the V.C. Summer Nuclear
Station, South Carolina Electric & Gas Company (SCE&G), requested an
emergency TS change. The systems involved were the control room
emergency ventilation system and the fuel handling building exhaust
system. On February 10, 1996, the NRC granted the emergency TS change.
The emergency TS change was requested because SCE&G had determined that
laboratory tests of the charcoal of the control room ventilation system
and the fuel-handling building system had not been performed in
compliance with the V.C. Summer TS. The laboratory test performed for
V.C. Summer was a 25-25-25 test in lieu of the 25-80-25 required by its
TS. The licensee had been performing the 25-25-25 test because, in
consultation with its testing laboratory, it concluded that performance
of the 25-80-25 test would result in condensation on the charcoal and,
thus, an invalid test.
On March 29, 1996, the Toledo Edison Company requested an emergency
TS change for the Davis-Besse plant. The systems involved were the
hydrogen purge, the shield building emergency ventilation, and the
control room. The TS for Davis-Besse required the laboratory test to be
performed in accordance with RG 1.52, Revision 2. In this case, the
licensee was performing a 30-30-30 test using the testing protocol of
ASTM D3803-1979 in lieu of the 25-80-25 test. On March 29, 1996, the
NRC granted the emergency TS change to allow the 30-30-30 test.
On April 2, 1996, Duke Power Company requested an emergency TS
change for the Oconee Nuclear Station. The systems involved were the
reactor building purge, the spent fuel pool ventilation, and the
penetration room ventilation. The TS for Oconee required the laboratory
test of charcoal to be performed in accordance with ANSI N510-1975,
which requires the performance of the 25-80-25 test. However, the
licensee was actually performing a 30-30-30 test using the test
protocol of ASTM D3803-1989. The NRC granted an emergency TS change on
April 2, 1996, to permit the 30-30-30 test.
In each of these cases, the test performed to demonstrate
compliance with TS provided results that the staff considered closer to
reflecting the capability of the charcoal than the test required by the
TS. In addition, the licensees believed that using the newer standard
would satisfy their TS requirement. Their bases for this belief were
the limitations of the test referenced in RG 1.52, their interpretation
of ANSI N509 as allowing the use of later versions of the test
protocol, and some of the guidance provided by the NRC. In the case of
Oconee, the test actually performed is the test that the staff believes
is the appropriate one, ASTM D3803-1989. However, because these tests
had not been conducted in compliance with the plant's TS, each licensee
would have had to shut down its plant or remain in a cold-shutdown mode
until the test required by the TS could be successfully performed, or
until the TS were amended.
On March 21, 1996, Carolina Power & Light Company flew a charcoal
sample from the Brunswick standby gas treatment system (SGTS) to its
testing laboratory in Ohio for the performance of the 25-80-25 test to
comply with the Brunswick TS before restart of an idle unit. The
Brunswick TS required that the laboratory tests be performed in
accordance with Revision 1 of RG 1.52. Previously, the licensee
directed its testing laboratory to perform an 80-80-80 test. To perform
the 25-80-25 test, the laboratory equilibrated the charcoal to 80
deg.C [176 deg.F] before introducing the challenge gas. The licensee
has not requested a TS change for Brunswick to correct the problem and
is awaiting guidance from the NRC.
As a result of the emergency TS changes, the staff has performed an
internal survey of operating plant TS to determine whether other plants
have the potential for similar problems with compliance. The survey
indicated that at least one-third of operating reactor licensees may
not be in compliance with their TS because they reference the flawed
25-80-25 testing protocol and may have used later versions of the
standards for the laboratory tests of their nuclear-grade charcoal. On
the basis of this survey, the staff established the following four
categories of plants:
(1) Plants in compliance with their TS that test in accordance with
ASTM D3803-1989.
(2) Plants in compliance with their TS that test in accordance with
a test protocol other than ASTM D3803-1989.
(3) Plants not in compliance with their TS that test in accordance
with ASTM D3803-1989.
(4) Plants not in compliance with their TS that test in accordance
with a test protocol other than ASTM D3803-1989.
The licensees in Category 1 have TS that require charcoal to be
tested in accordance with ASTM D3803-1989, which adequately
demonstrates the capability of the charcoal. The licensees in Category
2 have TS that require charcoal to be tested in accordance with test
standards other than ASTM D3803-1989. The licensees that received
emergency TS changes were in Categories 3 and 4. Licensees in
Categories 3 and 4 have TS that require charcoal to be tested in
accordance with the 25-80-25 test.
Enclosure 2
Sample Technical Specifications
For Plants With Improved Standard Technical Specifications
C. Demonstrate for each of the ESF systems that a laboratory test
of a sample of the charcoal adsorber, when obtained as described in
[Regulatory Guide 1.52, Revision 2], shows the methyl iodide
penetration less than the value specified below when tested in
accordance with ASTM D3803-1989 at a temperature of
30 deg.C [86 deg.F] and greater than or equal to the relative humidity
specified below.
[[Page 9589]]
[GRAPHIC] [TIFF OMITTED] TN25FE98.003
Note: The use of any standard other than ASTM D3803-1989 to test
the charcoal sample may result in an overestimation of the
capability of the charcoal to adsorb radioiodine. As a result, the
ability of the charcoal filters to perform in a manner consistent
with the licensing basis for the facility is indeterminate.
ASTM D3803-1989 is a more stringent testing standard because it
does not differentiate between used and new charcoal, it has a
longer equilibration period performed at a temperature of 30 deg.C
[86 deg.F] and a relative humidity (RH) of 95% (or 70% RH with
humidity control), and it has more stringent tolerances that improve
repeatability of the test
[GRAPHIC] [TIFF OMITTED] TN25FE98.004
When ASTM D3803-1989 is used with 30 deg.C [86 deg.F] and 95% RH
(or 70% RH with humidity control) is used, the staff will accept the
following:
Safety factor 2 for systems with or without humidity
control.]
For Plants With Older Technical Specifications
Each engineered safety feature (ESF) ventilation system shall be
demonstrated OPERABLE:
a. At least once per 18 months or (1) after any structural
maintenance on the HEPA filter or charcoal adsorber housings, or (2)
following painting, fire, or chemical release in any ventilation zone
communicating with the system by:
(1) Verifying, within 31 days after removal, that a laboratory test
of a sample of the charcoal adsorber, when obtained in accordance with
Regulatory Position C.6.b of Regulatory Guide 1.52, Revision 2, March
1978, shows the methyl iodide penetration less than [see note in
preceding section titled ``For Plants With Improved Standard Technical
Specifications'']% when tested in accordance with ASTM D3803-1989 at a
temperature of 30 deg.C [86 deg.F] and greater than or
equal to a relative humidity of [see note in preceding section titled
``For Plants With Improved Standard Technical Specifications'']%.
b. After every 720 hours of charcoal adsorber operation, by
verifying, within 31 days after removal, that a laboratory test of a
sample of the charcoal adsorber, when obtained in accordance with
Regulatory Position C.6.b of Regulatory Guide 1.52, Revision 2, March
1978, shows the methyl iodide penetration less than [see note in
preceding section titled ``For Plants With Improved Standard Technical
Specifications'']% when tested in accordance with ASTM D3803-1989 at a
temperature of 30 deg.C [86 deg.F] and greater than or
equal to a relative humidity of [see note in preceding section titled
``For Plants With Improved Standard Technical Specifications'']%.
Dated at Rockville, Maryland, this 19th day of February 1998.
For the Nuclear Regulatory Commission.
Jack W. Roe,
Acting Director, Division of Reactor Program Management, Office of
Nuclear Reactor Regulation.
[FR Doc. 98-4761 Filed 2-24-98; 8:45 am]
BILLING CODE 7590-01-P