[Federal Register Volume 68, Number 136 (Wednesday, July 16, 2003)]
[Proposed Rules]
[Pages 41963-41967]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-17963]



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NUCLEAR REGULATORY COMMISSION

10 CFR Part 50

[Docket Nos. PRM-50-73 and PRM-50-73A]


Mr. Robert H. Leyse; Denial of Petition for Rulemaking

AGENCY: Nuclear Regulatory Commission.

ACTION: Denial of petition for rulemaking.

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SUMMARY: The Nuclear Regulatory Commission (NRC) is denying two related 
petitions for rulemaking submitted by Mr. Robert H. Leyse (PRM-50-73 
and PRM-50-73A). The petitioner requested that the NRC revise its 
regulations to address the effect of crud on the cooling of the reactor 
core under the turbulent coolant flow conditions of a loss-of-coolant-
accident (LOCA), and during normal operations. Crud is a colloquial 
term for corrosion and wear products (rust particles, etc.) that become 
radioactive (i.e., activated) when exposed to neutron irradiation. The 
petitioner states that crud buildup during normal operations and its 
detachment and resuspension during a LOCA could obstruct flow of 
coolant, resulting in inadequate cooling and ultimately leading to 
melting of the nuclear fuel. In addition, the petitioner requested that 
the NRC amend its regulations to include comparisons to applicable 
experimental data that address the impact of crud deposits on the 
ability to cool fuel rods.

ADDRESSES: Copies of the petitions for rulemaking, the public comments 
received, and the NRC's letter of denial to the petitioner may be 
examined, and/or copied for a fee, at the NRC's Public Document Room, 
located at One White Flint North, 11555 Rockville Pike, Public File 
Area 01 F21, Rockville, Maryland. These documents are also available 
electronically at the NRC's Public Electronic Reading Room on the 
Internet at http://www.nrc.gov/reading-rm/adams.html. From this site, 
the public can gain entry into the NRC's Agencywide Document Access and 
Management System (ADAMS), which provides text and image files of NRC's 
public documents. For further information contact the PDR reference 
staff at 1-800-387-4209, (301) 415-4737 or by e-mail to [email protected].

FOR FURTHER INFORMATION CONTACT: Alan K. Roecklein, Office of Nuclear 
Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, DC 
20555-0001, telephone (301) 415-3883, e-mail [email protected].

SUPPLEMENTARY INFORMATION:

Background

    Section 50.46 specifies the performance criteria against which the 
emergency core cooling system (ECCS) must be evaluated. Appendix K to 
part 50 provides the required and acceptable features of ECCS 
evaluation models. The criteria are: (1) Peak cladding temperature that 
cannot be exceeded, (2) the maximum cladding oxidation thickness, (3) 
the maximum total hydrogen generation, (4) assurance of a core geometry 
that can be cooled, and (5) assurance of abundant long term cooling. 
The regulations also state that assessments of cooling performance 
following postulated LOCAs must be calculated in accordance with an 
acceptable evaluation model and that in applying the model, comparisons 
to applicable experimental data must be made.
    The petitioner identified numerous elements of the specified ECCS 
evaluation procedures and the evaluation model that he believed need to 
include additional comparisons to applicable experimental data.

The Petitions

    The petition for rulemaking designated PRM-50-73 addressing 
potential crud interference with coolant flow during a fast-moving 
(large-break) LOCA, was sent to the NRC September 4, 2001, and the 
notice of receipt of the petition and request for public comment was 
published in the Federal Register (FR) on October 12, 2001 (66 FR 
52065). The public comment period ended on December 26, 2001. On 
November 5, 2001, the supplemental petition, designated PRM-50-73A, was 
sent by the same petitioner alleging crud interference with coolant 
flow during normal operations. The notice of receipt of the second 
petition was published on January 29, 2002 (67 FR 4214). The public 
comment period ended on April 15, 2002. Five letters of public comment 
were received on PRM-50-73 and seven letters were received on PRM-50-
73A. The NRC staff determined that the two petitions should be 
addressed as one action.

PRM-50-73

    The petitioner stated that Sec.  50.46 and Appendix K to part 50 do 
not address the impact of crud on core cooling during a fast-moving 
(large-break) LOCA. The petitioner noted that a licensed power reactor 
had operated with heavy crud deposits on many of the fuel rods. The 
petitioner stated that had a fast-moving (large-break) LOCA occurred 
before shutdown for refueling, extensive blockage of flow channels 
within the fuel bundles would have developed, leading to a degradation 
of core cooling and compromising defense-in-depth. The petitioner 
further stated that significant crud deposits could lead to an 
extensive fuel failure during full-power operation and that the amount 
of failed fuel would then lead to a decision to shut down the reactor 
as the inventory of radioactive material in the reactor coolant reached 
the limits allowed by the technical specifications.

PRM-50-73A

    The petitioner stated that Sec.  50.46 and Appendix K to part 50 do 
not address the impact of severe crud deposits on fuel bundle cooling 
during normal power operations. The petitioner stated that a licensed 
power reactor had operated with unusually heavy crud deposits which, 
had they been allowed to build, would likely have blocked flow 
channels, interfered with core cooling and led to significant damage to 
structural components of the core. The petitioner requested that Sec.  
50.46 and Appendix K be revised to include consideration of the impact 
of crud deposits on fuel bundles during normal operations.

Public Comments on the Petitions

PRM-50-73

    The five letters of public comment received were opposed to this 
petition. Framatome ANP, a nuclear vendor, did not agree that crud 
would collect within the core as the petitioner suggested, nor that it 
would pose blockage problems. Framatome discussed the effects of crud 
for the sections of the regulations addressed by the petition, and 
stated that for each section, the effects of crud are adequately 
addressed. In Framatome's experience, typical crud formed on the 
surface of fuel cladding does not have the consistency to create 
coolant flow blockage during either normal operation or blowdown (i.e., 
a LOCA). Framatome ANP stated that thermal transients in the cladding 
and movement resulting from strain might promote crud breakoff from the 
cladding but would produce small pieces that would be further broken 
down by the turbulence and velocity of the blowdown flow rates.
    Exelon Nuclear, a power reactor licensee, stated that the 
petitioner's requested action was not necessary because 10 CFR 50.46 
already requires that the cooling performance of the ECCS following 
postulated LOCAs meet certain acceptance criteria. Exelon stated that 
NRC regulatory guidance and approved ECCS evaluation models

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already address crud and other phenomena that could potentially impact 
performance relative to the acceptance criteria. Furthermore, Exelon 
Nuclear stated that it and its predecessors have over 30 years of 
experience in monitoring fuel performance in numerous nuclear power 
plants (NPPs) and that they have identified only one cycle, in one 
unit, with crud induced failures. Exelon further stated that corrective 
actions taken after those observed failures have resulted in no further 
failures due to crud at this or any other Exelon unit. In Exelon's 
experience, crud is powdery, and its characteristics, in terms of size 
or strength, indicate that it would not block the coolant flow channels 
and lead to fuel failures.
    In general, Exelon asserted, industry experience related to 
significant crud deposits has been that they are isolated cases, and 
that after extensive root cause evaluations, effective corrective 
actions have prevented recurrence. Exelon also stated that crud 
deposits are effectively controlled through the use of the Electric 
Power Research Institute (EPRI) Chemistry Guidelines.
    Westinghouse Electric Company, LLC, a nuclear vendor, opposed the 
petition based on its extensive poolside and laboratory examinations of 
crud deposits on fuel rods used in pressurized-water reactors (PWRs), 
including cases in which abnormally high levels of crud could be 
detected during normal operation. Its results showed that it would be 
virtually impossible for any significant amount of the crud to 
contribute to flow blockage in the event of a large-break LOCA. 
Westinghouse also stated that most of any crud released would become 
suspended particles that would not affect core coolant flow. In one 
cited case, a water chemistry change resulted in a sudden release of 
all the accumulated crud in the core. A very small change in reactor 
coolant flow was observed as a result of this release.
    GE Nuclear Energy, a nuclear vendor, opposed the proposed change on 
the basis that the event described in the petition was a unique event, 
not typical of crud buildup in boiling water reactors (BWRs). Even with 
that unusual buildup the core remained in a configuration that could be 
cooled throughout the cycle and would have remained in a configuration 
that could be cooled in the event of a LOCA. GE also stated that the 
safety evaluation concerning this event showed that, even with crud 
deposition, there would be substantial margin to the 2200[deg] F peak 
cladding temperature acceptance criterion specified by 10 CFR 50.46.
    The Nuclear Energy Institute (NEI), an industry group representing 
all U.S. commercial nuclear power plants, plant designers, architect/
engineering firms, and fuel cycle facilities, opposed the petition. NEI 
stated that existing NRC regulations establish performance criteria for 
maintaining core cooling and specify realistic ECCS evaluation models 
that address potential impacts on these performance measures. NEI 
stated that numerous thermal-hydraulic phenomena are addressed in the 
technical evaluation models. However, the regulations are not overly 
prescriptive in terms of phenomena to be addressed, which allows for 
advances in the technical database and updating of the evaluation 
procedures without the need for rulemaking. Fuel performance and other 
performance measures are monitored routinely to ensure that core 
evaluation models accurately reflect real conditions.
    NEI stated that considerable data has been accumulated on crud 
deposits and their impact on coolant flow properties. The data do not 
support the postulated existence of characteristics that might lead to 
a substantial blockage of flow. NEI believes that the provisions of 10 
CFR 50.46 and Appendix K provide an adequate mechanism for ensuring 
that coolant flow and fuel performance are thoroughly monitored and 
maintained.

PRM 50-73A

    Of the seven letters of public comment received in response to PRM-
50-73A, two were submitted by the petitioner, and provided additional 
information and related technical support for his assertions in PRM-50-
73 and PRM-50-73A. The other five letters opposed the request for 
rulemaking contained in PRM-50-73A.
    NEI noted that it had commented on the initial PRM-50-73 and 
provided a copy of the initial NEI comment letter. With respect to the 
changes to the regulations for normal operating conditions requested in 
this supplemental petition, NEI stated that the changes are not needed. 
In NEI's view the NRC Standard Review Plan (SRP) specifies a 
comprehensive set of acceptance criteria that specifically address the 
impact of fuel crud deposits and ensure that fuel design limits are not 
exceeded during any conditions of normal operation, including the 
effects of anticipated operational occurrences. NEI stated that any 
accumulation of crud that interfered with coolant flow would be 
detected quickly by pressure drop monitoring throughout the reactor 
cooling system.
    A consortium of nuclear power plants, Strategic Teaming and 
Resource Sharing (STARS), supported the arguments against the petition 
presented by NEI and stated that STARS opposed the subject petition. 
STARS stated that chemistry controls and core design constraints are in 
place to reduce susceptibility to heavy crud deposition and that during 
operation, chemistry indicators and core power measurements are 
evaluated continuously for evidence of heavy crud deposition or 
movement. STARS also stated that visual inspections of fuel assemblies 
during refueling have found no evidence of heavy crud deposits. STARS 
stated that it does not believe that nuclear safety would be enhanced 
by adopting the requested rulemaking.
    GE Nuclear Energy stated that the supplemental petition for 
rulemaking held no technical merit. GE stated that the requested 
revision of the ECCS evaluation basis and criteria is based on a single 
event that occurred at one plant during one cycle of operation; that 
the unique condition of heavy crud buildup has occurred only once in 
over 1,000 reactor years of BWR operation, and the postulated scenario 
(rapid and uncontrollable fuel and core melt) is not a credible 
scenario as shown by the damage characteristics observed for the cited 
event; and that the postulated inability to effectively detect and 
mitigate the occurrence of a heavy-crud-induced fuel damage condition 
during normal operation is invalid, as was adequately shown by the 
responsible and effective actions taken by the affected plant.
    Tennessee Valley Authority (TVA), a nuclear power plant licensee, 
stated that the requested revisions in the supplemental petition are 
unnecessary because current regulations adequately address the impact 
of fuel crud deposits on the cooling of nuclear fuel during normal 
reactor operations. In addition, TVA supported the comments submitted 
by NEI.
    Westinghouse Electric Company opposed the action requested in PRM-
50-73, stating that the postulated scenario leading to rapid core 
melting is completely speculative and is not supported by technical or 
scientific data. Westinghouse also noted that the regulations 
recommended for modification in PRM-50-73A are not related to normal 
operating conditions, but rather apply to LOCAs.

NRC Technical Evaluation

    The NRC reviewed each of the petitioner's claims and provides the 
following analysis.
    1. The petitioner stated that a licensed power reactor operated 
with unusually heavy crud deposits on many of the fuel

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rods, which could lead to restricted coolant flow and ultimate core 
meltdown.
    The event referred to by the petitioner occurred at the River Bend 
Station in 1999. A coolant chemistry excursion occurred with relatively 
high iron and copper levels, leading to unusually heavy crud 
deposition. As the licensee event report (LER 50-458/99-016-00) 
indicated, the occurrence of this event was unusual and only happened 
once. The NRC staff has not found any other nuclear power plants that 
experienced this unusually heavy crud formation. Although a thin 
oxidation layer appears in almost every operating reactor, the staff 
considers heavy crud build up to be extremely rare. Therefore, the 
probability of a large break LOCA occurring while some of the high 
power fuel bundles have severe crud deposition is significantly lower 
than that of the LOCA alone and thus reduces the estimated risk of this 
scenario.
    2. The petitioner contended that if a fast moving LOCA had occurred 
with severe crud deposited on some high power fuel bundles, extensive 
blockage of the flow channels within the fuel bundles would likely have 
developed. In addition, he stated that during a blowdown, the 
redistribution of crud into any or all of several restricted channels 
would result in substantial flow blockage. The petitioner postulated 
that the crud would break off during a LOCA to form a blockage at the 
down stream fuel grid locations.
    The operating experience relative to significant crud deposits has 
been that the observed crud is powdery or fluffy. During a large-break 
LOCA, even if crud broke off, only small solid particles are expected 
to be carried downstream. No data was provided in the petition to 
support the petitioner's rationale for crud blockage. The NRC also 
reviewed records of licensee event reports and found no test data or 
documents supporting the assumption that the crud might break off and 
form a flow blockage. Therefore, the NRC believes that the petitioner's 
concerns about the flow blockage due to crud are not supported by 
technical or scientific data.
    3. The petitioner stated that if severe crud existed within the 
fuel bundles, the crud could lead to a loss of cooling with consequent 
overheating of zirconium and rapid autocatalytic zirconium-water 
reactions of the fuel cladding.
    The NRC agrees that heavy crud could cause higher-than-normal fuel 
cladding temperatures due to the additional heat transfer resistance 
during normal operation and postulated accidents. In particular, the 
porous form of crud could function as an insulator between the 
zirconium cladding and the coolant. If the metal-water reaction is 
assumed to occur, this additional layer of material would also form a 
shield between the coolant and the cladding material that would reduce 
the metal-water reaction rate. Should the metal-water reaction occur, 
the steam from the coolant stream would need to penetrate inward 
through the crud layer in order to reach the cladding, and the 
resulting hydrogen generated at the cladding surface would need to 
penetrate outward through the crud. Therefore, compared to a bare metal 
surface at the same temperature, a fuel rod with a layer of crud would 
be expected to have a reduced metal-water reaction rate, thus reducing 
the additional heat generated by the metal-water reaction. It would be 
inappropriate to consider only the additional heat transfer resistance 
and assume zero reduction of the metal-water reaction rate. Some 
locations where the crud has cracks would not see the reduction of the 
metal-water reaction. However, at these locations, it is expected that 
the steam would directly cool the bare metal surface and form a colder 
surface region before the temperature rose high enough to trigger the 
metal-water reaction. Therefore, the NRC has concluded that the 
petitioner's concern about autocatalytic zirconium-water reactions is 
not valid.
    4. The petitioner asserted that 10 CFR 50.46 does not address the 
impact of crud on core cooling during the large-break LOCA.
    Section 50.46 (b)(4) provides a requirement regarding the cooling 
of the core. This section states: ``Calculated changes in core geometry 
shall be such that the core remains amenable to cooling''. In addition, 
Section I.C.3 of Appendix K to part 50 states: ``The following effects 
shall be taken into account in the conservation of momentum equation: * 
* * (3) area change momentum flux * * * (6) pressure loss resulting 
from area change * * *''. Many phenomena and mechanisms may cause a 
change in core geometry (e.g., the rod ballooning effect, thermal 
expansion, crud buildup). It is not necessary for the regulation to 
explicitly include all the possible mechanisms causing a change in core 
geometry.
    Although the scenario of a large break LOCA coinciding with heavy 
crud formation is considered a low probability event, NRC's Standard 
Review Plan (SRP) for ECCS has already defined detailed requirements to 
monitor the effect of crud deposits. The SRP outlines a comprehensive 
set of acceptance criteria that serve to demonstrate compliance with 
regulatory requirements. Three acceptance criteria that specifically 
address the impact of fuel crud deposits are provided below:

SRP Section 4.2 Fuel System Design, Acceptance Criterion II.A.1.(d)

    ``Oxidation, hydriding, and the buildup of corrosion products 
(crud) should be limited. Allowable oxidation, hydriding, and crud 
levels should be discussed in the Safety Analysis Report and shown to 
be acceptable.''

SRP Section 4.4 Thermal and Hydraulic Design (II. Acceptance Criteria)

    ``8. The effects of crud should be accounted for in the thermal-
hydraulic design by including it in the CHF [critical heat flux] 
calculations in the core or in the pressure drop throughout the RCS 
[reactor coolant system]. Process monitoring provisions should assure 
the capability for detection of a three percent drop in the reactor 
coolant flow. The flow should be monitored every 24 hours.''

SRP Section 4.4 Thermal and Hydraulic Design (III. Review Procedures)

    ``The reviewer ensures that adequate account is taken of the effect 
of crud in the primary coolant system, such as in the calculation of 
CHF in the core, heat transfer in the steam generators, and pressure 
drop throughout the RCS.''
    The NRC staff believes that these guidelines adequately address the 
impacts of fuel crud on normal reactor operation and ECCS performance 
during a large break LOCA.
    In addition, strong incentives exist for the nuclear industry to 
control crud buildup. Excessive crud formation could lead to operation 
at reduced power levels or even shutdown if coolant activity levels 
(suspended activated corrosion products) were to exceed technical 
specifications. Activated crud deposition throughout plant systems 
increases dose-rates that result in costly increases in worker doses. 
Because the industry is required to demonstrate efforts to maintain 
occupational doses as low as is reasonably achievable (ALARA), the NRC 
believes that incentives for optimizing power output and minimizing 
occupational doses are strong. EPRI water chemistry guidelines that the 
industry follows provide effective methods to control crud formation 
and buildup. Occupational doses over the past fifteen years have 
declined, and sustained power output levels have increased, suggesting 
that

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crud control incentives and methods are effective.
    5. In PRM-50-73A, the petitioner contended that if the deposits 
continued to build during normal reactor operation, a severe crud 
buildup might form. Blockage of the flow within the fuel bundles would 
likely develop and overheating of the cladding would trigger an 
autocatalytic [i.e., self-propagative] zirconium-water reaction. 
Subsequently, the petitioner stated that buildup could initiate 
substantial and rapid localized core melting while the reactor is at 
(full) power. Further, the petitioner contended that a reactor may be 
operated within its licensing basis and the technical specifications 
during the transition from unusually heavy crud to severe crud. The 
petitioner made a hypothesis that the increase of the off-gas system 
activity would not be regarded as an indicator of a possible heavy crud 
deposition and, therefore, the plant would continue to operate until 
the transition from heavy crud deposition to a severe level occurs.
    Crud build-up is generally a very slow process. With water 
chemistry control, the transition time from heavy crud to severe crud 
deposition will be on the order of weeks. Even before the formation of 
a heavy crud layer, the elevated cladding temperature due to crud can 
cause crud-assisted corrosion which usually results in pin-hole type 
fuel cladding damage. The longer the rod experiences the elevated 
temperature caused by the crud, the more damage to the fuel rod 
cladding would occur. With only a few fuel rods damaged, the off-gas 
activity would increase. Abnormally high activity readings in the off-
gas system require operators to take action to mitigate fuel cladding 
damage. In several cases at different operating reactors, the operators 
were able to adjust the control rod pattern to lower the local power 
peaking factor around the damaged fuel bundles after the high off-gas 
system activity reading was observed even though the activity levels 
were below the technical specifications limit. Therefore, observed 
practice shows that fuel cladding damage due to excess crud formation 
is readily detectable during normal operation, and effective mitigation 
measures have been taken by operators.
    Under conditions where heavy crud deposition occurs, fuel damage 
could eventually lead to cladding cracks or ballooning effects. The 
crud layer may then break off and fuel pellets will be cooled directly 
by the water, thus lowering the cladding temperature. Although the 
elevated cladding temperature could theoretically trigger a metal-water 
reaction in a very limited area of the fuel cladding, the crud also 
shields the cladding from the water and causes significant resistance 
to the metal-water reaction. Therefore, the NRC has concluded that the 
petitioner's concern about autocatalytic zirconium-water reactions is 
not valid.
    Furthermore, the NRC has not found any evidence to support the 
petitioner's view that the off-gas activity would stay below the 
technical specification limit while the heavy crud deposition 
continues. Operating experience has shown that if a reactor operates 
continuously under heavy crud conditions, the cladding damage will 
result in higher off-gas activity readings that are quickly noted by 
the plant operators. It is highly unlikely that the off-gas activity 
would remain undetected by plant operators. Recent operating experience 
at plants with leaking fuel demonstrates that plant operators quickly 
take action to suppress fuel leaks, and in many cases, shut down the 
reactor to inspect and replace leaking fuel.
    Finally, crud formation is one of many items which are required to 
be considered for both LOCA and transient safety analyses, and existing 
regulations and the NRC Standard Review Plan already provide adequate 
guidance on addressing the impact of crud on plant safety.

NRC Strategic Performance Goals

    The NRC has evaluated the advantages and disadvantages of the 
rulemaking requested by the petitioner with respect to the four NRC 
Strategic Performance Goals as follows:
    1. Maintaining Safety: The NRC believes that the requested 
rulemaking would not make a significant contribution to maintaining 
safety because current regulations and regulatory guidance already 
address the effect of crud-related parameters on core cooling, because 
no existing data suggests that the amount of crud normally deposited on 
reactor fuel can significantly interfere with coolant flow, and because 
the probable cause of the single event at River Bend Station noted by 
the petitioner, namely a transient coolant chemistry excursion with 
high iron and copper levels, is known and has been corrected. The NRC 
believes that existing regulations, guidance and practices provide for 
monitoring, detecting and correcting any possible crud effects on core 
cooling before any significant safety problems could occur.
    2. Enhancing Public Confidence: The NRC believes that the proposed 
revisions would not enhance public confidence. First, the NRC has 
concluded that the petitioner's contentions lack an adequate technical 
basis. Second, current regulations and guidance already address the 
effects of normal crud accumulation on core cooling. The petitioner's 
request in effect would require that substantial, additional 
consideration be given to abnormally heavy accumulations of crud as a 
potential source of coolant flow obstruction, which is a condition that 
has never been observed. Taking such an unnecessary action may actually 
detract from public confidence in the NRC as an effective regulator.
    3. Improving Efficiency, Effectiveness, and Realism: The proposed 
revisions would not improve efficiency, effectiveness, and realism 
because licensees would be required to generate unnecessary additional 
information as part of the development of their ECCS evaluation models 
and the NRC would need to evaluate the licensee's data and analysis. 
The NRC staff believes that this additional consideration is 
unnecessary because the petitioner's scenarios are not supported by a 
technical basis. The additional NRC staff and licensee effort would not 
improve efficiency or effectiveness. In addition, the NRC resources 
expended to promulgate the rule and supporting regulatory guidance 
would be significant and is unnecessary.
    4. Reducing Unnecessary Regulatory Burden: The requested rule would 
increase licensee burden by unnecessarily requiring significant 
additional testing and analysis of ECCS effectiveness.

Reasons for Denial

    The Commission is denying the petitions for rulemaking. Section 
50.46 currently requires a nuclear power plant applicant/licensee to 
address the impacts of the core geometry change on cooling in ECCS 
analyses. An acceptable implementation of this requirement has been 
documented in the Commission's Standard Review Plan, which specifically 
addresses the potential buildup of crud and its effects for ECCS 
analyses and transient analyses. The petitioner's hypothetical 
discussion of fuel clad performance with severe levels of crud buildup 
was not supported by modeling, experimental results or operational data 
sufficient to demonstrate that fuel with high crud levels will actually 
behave in the manner postulated by the petitioner. The NRC believes 
that there are other phenomena the petitioner failed to consider that 
would tend to reduce metal-water reactions and counteract autocatalytic 
reactions even if the extreme conditions postulated by the

[[Page 41967]]

petitioner could be reached. The operating experience at several 
nuclear power plants that have experienced fuel failures shows that 
fuel degradation has progressed in a manner which is controllable. The 
event (River Bend) identified by the petitioner as evidence of the 
likelihood of high crud levels occurred only once at that plant and has 
not been repeated there, or at any other plant in the United States. 
Finally, technical specifications for monitoring of reactor coolant 
activity and the requirements in 10 CFR Part 20 to maintain 
occupational exposures as low as reasonably achievable have resulted in 
licensee operational practices for early identification of coolant 
activity increase due to crud deposits before they build to the levels 
postulated by the petitioner. The Commission considers that the 
petitioner's hypothetical discussion of a mechanism preventing early 
detection of abnormal activity levels is not credible. For these 
reasons, the Commission has determined that the petitioner's bases for 
requesting rulemaking have not been substantiated.
    For these reasons, the Commission denies PRM-50-73 and PRM-50-73A.

    Dated at Rockville, Maryland, this 9th day of July, 2003.

    For the Nuclear Regulatory Commission
Annette Vietti-Cook,
Secretary of the Commission.
[FR Doc. 03-17963 Filed 7-15-03; 8:45 am]
BILLING CODE 7590-01-P