[Federal Register Volume 67, Number 19 (Tuesday, January 29, 2002)]
[Proposed Rules]
[Pages 4214-4215]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-2075]


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NUCLEAR REGULATORY COMMISSION

10 CFR Part 50

[Docket No. PRM-50-73A]


Robert H. Leyse; Supplement to a Petition for Rulemaking

AGENCY: Nuclear Regulatory Commission.

ACTION: Supplemental petition for rulemaking; notice of receipt.

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SUMMARY: The Nuclear Regulatory Commission (NRC) has received and 
requests public comment on a supplement to his original petition for 
rulemaking (PRM-50-73) filed with the Commission by Robert H. Leyse. 
The supplemental petition was docketed by the Commission and has been 
assigned Docket No. PRM-50-73A. The petitioner requests, in this 
supplement to his earlier petition, that the NRC amend its regulations 
on the acceptance criteria for emergency core cooling systems for 
light-water nuclear power reactors to address the impact of severe crud 
deposits on fuel bundle coolability during normal operation of a light-
water-reactor (LWR).

DATES: Submit comments by April 15, 2002. Comments received after this 
date will be considered if it is practical to do so, but the Commission 
is able to assure consideration only for comments received on or before 
this date.

ADDRESSES: Submit written comments to the Secretary of the Commission, 
U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, 
Attention: Rulemakings and Adjudications Staff. Deliver comments to: 
11555 Rockville Pike, Rockville, Maryland, between 7:30 a.m. and 4:15 
p.m. Federal workdays.
    For a copy of the petition, write to Michael T. Lesar, Chief, Rules 
and Directives Branch, Division of Administrative Services, Office of 
Administration, U.S. Nuclear Regulatory Commission, Washington, DC 
20555-0001.
    You may also provide comments via the NRC's interactive rulemaking 
Web site at http://ruleforum.llnl.gov. This site provides the 
capability to upload comments as files (any format), if your web 
browser supports that function. For information about the interactive 
rulemaking Web site, contact Ms. Carol Gallagher, 301-415-5905 (e-mail: 
[email protected]).
    The petition and copies of comments received may be inspected and 
copied for a fee at the NRC Public Document Room, 11555 Rockville Pike, 
Public File Area O1F21, Rockville, Maryland. Copies of comments 
received are also available through the NRC's Agencywide Documents 
Access and Management System (ADAMS), which provides text and image 
files of NRC's public documents. These documents may be accessed 
through the NRC's Public Electronic Reading Room on the Internet at 
http://www.nrc.gov/NRC/ADAMS/index.html. If you do not have access to 
ADAMS or if there are problems in accessing the documents located in 
ADAMS contact the NRC Public Document Room (PDR) Reference staff at 1-
800-397-4209, 301-415-4737or by e-mail to [email protected].

FOR FURTHER INFORMATION CONTACT: Michael T. Lesar, Chief, Rules and 
Directives Branch, Division of Administrative Services, Office of 
Administration, U.S. Nuclear Regulatory Commission, Washington, DC 
20555-0001, Telephone: 301-415-7163 or Toll Free: 800-368-5642.

SUPPLEMENTARY INFORMATION:

Background

    The NRC received a petition for rulemaking dated September 4, 2001, 
submitted by Mr. Robert H. Leyse, on his own behalf. The petition was 
docketed as PRM-50-73 on September 6, 2001. The notice of receipt of 
this petition was published on October 12, 2001, (66 FR 52065). On 
November 5, 2001, the NRC received a supplement to PRM-50-73 submitted 
by Mr. Leyse. The supplement to the petition was assigned docket number 
PRM-50-73A.
    In his original petition, the petitioner requested that the NRC 
amend its regulations on the acceptance criteria for emergency core 
cooling systems for light-water nuclear power reactors to address the 
impact of crud on cooling capability during a fast-moving, large-break, 
loss-of-coolant accident (LOCA).
    The petitioner requested that elements in Sec. 50.46 concerning 
comparisons to applicable experimental data, and the following 
paragraphs in Appendix K to part 50, be revised to include the impact 
of crud deposits on fuel pins:

I.B.  Swelling and Rupture of the Cladding and Fuel Rod Thermal 
Parameters;
I.C.2  Frictional Pressure Drops;
I.C.4  Critical Heat Flux;
I.C.5  Post-CHF Heat Transfer Correlations;
I.C.7  Core Flow Distribution During Blowdown;
I.D.3  Calculation of Reflood Rate for Pressurized Water Reactors;
I.D.6  Convective Heat Transfer Coefficients for Boiling Water Reactor 
Fuel Rods Under Spray Cooling; and

[[Page 4215]]

I.D.7  The Boiling-Water Reactor Channel Box Under Spray Cooling.
II.1.a  The documentation requirements in this paragraph should include 
a description of each evaluation model used for estimation of the 
effects of crud deposits on fuel pins.

The Petitioner's Request

    In his supplemental petition (PRM-50-73A), the petitioner requests 
that the NRC revise its regulations on the acceptance criteria for 
emergency core cooling systems for light-water nuclear power reactors 
to address the impact severe crud buildup will have on core coolability 
during normal reactor operations.
    The petitioner states that a certain licensed power reactor has 
operated with unusually heavy crud deposits within several fuel 
bundles. The petitioner states that these deposits were found and at 
least partially classified during a refueling outage. The petitioner 
believes that if these deposits had continued to build during normal 
reactor operation at power, the unusually heavy crud deposits would 
have become severe crud deposits. Blockage of the flow channels within 
the fuel bundles would likely have developed. The petitioner believes 
that severe crud deposits within the fuel bundles can lead to a loss of 
coolability with consequent overheating of zirconium cladding within 
the bundles, autocatalytic zirconium-water reactors of the fuel 
cladding, chemical reactions between the fuel cladding and uranium 
oxide fuel pellets, initiation of zirconium water reactions involving 
zirconium core structures such as fuel bundle spacer grids and channel 
boxes, melting of certain control element materials, melting of braze 
materials in certain fuel bundle spacer grids, metallurgical reactions 
between certain fuel bundle spacer grid springs and the zirconium 
cladding on the fuel pins, and additional sources of structural 
degradation. The petitioner states that these factors can initiate 
substantial and rapid localized core melting while the LWR is at power. 
The petitioner states that if the LWR is then shut down, the core 
meltdown may rapidly propagate among the fuel bundles and core 
structures with sequential and parallel destruction of the barriers 
that constitute defense in depth. Thus, the single entity, unusually 
heavy crud deposits on the fuel pins, might be only one step before 
unusually heavy crud deposits thicken and become severe crud deposits. 
The petitioner states that severe crud deposits then threaten the 
integrity of all of the barriers that in total constitute the defense 
in depth.
    The petitioner states that performance-based experience reveals 
that when unusually heavy crud deposition on fuel bundles occurs during 
normal operation of an LWR, there are likely to be indications of fuel 
element cladding defects by increases in the offgas activity. However, 
the petitioner states that this increase in the offgas activity is not 
regarded as an indicator of a possible heavy crud deposition. The 
petitioner believes that an LWR may be operated within its Licensing 
Basis and the Technical Specifications until the transition from 
unusually heavy crud deposition to severe crud deposition is effected. 
The petitioner believes that at this point it is likely that rapid 
localized core melting will be initiated while the LWR is at power. The 
petitioner also believes that there will likely be delays (several 
seconds) before the LWR is shut down. The petitioner believes that by 
then the rapid propagation of the meltdown will likely be well underway 
and it will likely continue even though the LWR is shut down.
    The petitioner requests that elements in Sec. 50.46 and the 
following paragraphs in Appendix K to part 50, and perhaps other 
regulations, be revised to include the impact of crud deposits on the 
fuel bundles during normal operation:

I.B.  Swelling and Rupture of the Cladding and Fuel Rod Thermal 
Parameters;
I.C.2  Frictional Pressure Drops;
I.C.4  Critical Heat Flux;
I.C.5  Post-CHF Heat Transfer Correlations;
I.C.7  Core Flow Distribution During Blowdown;
I.D.3  Calculation of Reflood Rate for Pressurized Water Reactors;
I.D.6  Convective Heat Transfer Coefficients for Boiling Water Reactor 
Fuel Rods Under Spray Cooling; and
I.D.7  The Boiling-Water Reactor Channel Box Under Spray Cooling.
II.1.a  The documentation requirements in this paragraph should include 
a description of each evaluation model used for estimation of the 
effects of crud deposits on fuel pins.

    Dated at Rockville, Maryland, this 22nd day of January 2002.

    For the Nuclear Regulatory Commission.
Annette L. Vietti-Cook,
Secretary of the Commission.
[FR Doc. 02-2075 Filed 1-28-02; 8:45 am]
BILLING CODE 7590-01-P