13534 Federal Register / Vol. 72, No. 55 / Thursday, March 22, 2007 / Notices 

that document the information that was 

reviewed and NRC’s conclusions. In 

accordance with 10 CFR 2.390 of the 

NRC’s ‘‘Rules of Practice,’’ details with 

respect to this action, including the 

SER, EIS, and accompanying 

documentation included in the early 

site permit package, are available 

electronically at the NRC’s Electronic 

Reading Room at http://www.nrc.gov/ 

reading-rm/adams.html. From this site, 

members of the public can access the 

NRC’s Agencywide Document Access 

and Management System (ADAMS), 

which provides text and image files of 

NRC’s public documents. The ADAMS 

accession numbers for the documents 

related to this notice are: 

ML070670140 ...................... Issuance of Early Site Permit for Exelon Generation Company, LLC (ESP–001). 

ML061210203 ...................... NUREG–1844—‘‘Safety Evaluation Report for an Early Site Permit (ESP) at the Exelon Generation Company, 

LLC (EGC) ESP Site’’. 

ML061930264 ...................... NUREG–1815 Vol 1—‘‘Environmental Impact Statement for an Early Site Permit (ESP) at the Exelon ESP 

Site’’ Main Report. 

ML061930275 ...................... NUREG–1815 Vol 2—‘‘Environmental Impact Statement for an Early Site Permit (ESP) at the Exelon ESP 

Site’’ Appendices A–K. 

ML061100260 ...................... Exelon Early Site Permit Application—Revision 4. 

Persons who do not have access to 

ADAMS or who encounter problems in 

accessing the documents located in 

ADAMS should contact the NRC Public 

Document Room (PDR) Reference staff 

at 1–800–397–4209, 301–415–4737, or 

by e-mail to pdr@nrc.gov. 

These documents may also be viewed 

electronically on the public computers 

located at the NRC’s Public Document 

Room (PDR), O 1 F21, One White Flint 

North, 11555 Rockville Pike, Rockville, 

MD 20852. The PDR reproduction 

contractor will copy documents for a 

fee. 

Dated at Rockville, Maryland, this 15th day 

of March, 2007. 

For the Nuclear Regulatory Commission. 

Stephanie M. Coffin, 

Chief, AP1000 Projects Branch, Division of 

New Reactor Licensing, Office of New 

Reactors. 

[FR Doc. E7–5247 Filed 3–21–07; 8:45 am] 

BILLING CODE 7590–01–P 

NUCLEAR REGULATORY 

COMMISSION 

Florida Power Corporation; Notice of 

Consideration of Issuance of 

Amendment to Facility Operating 

License, Proposed No Significant 

Hazards Consideration Determination, 

and Opportunity for a Hearing; 

Correction 

AGENCY: Nuclear Regulatory 

Commission. 

ACTION: Notice of Issuance; Correction. 

SUMMARY: This document corrects a 

notice published in the Federal Register 

on March 13, 2007 (72 FR 11381), which 

informs the public that the NRC is 

considering issuance of an amendment 

to Renewed Facility Operating License 

No. DPR–72. This action is necessary to 

correct the name of the licensee. 

FOR FURTHER INFORMATION CONTACT: 

Beverly A. Clayton, Office of Nuclear 

Reactor Regulation, Nuclear Regulatory 

Commission, Washington, DC 20555–

0001, telephone: 301–415–3475, e-mail: 

bac2@nrc.gov. 

SUPPLEMENTARY INFORMATION: On page 

11381, appearing near the bottom of the 

second column, the heading is corrected 

to read as above, and in the last line of 

the second column and the first line of 

the third column, ‘‘Florida Power and 

Light’’ is corrected to read ‘‘Florida 

Power Corporation.’’

Dated in Rockville, Maryland, this 16th 

day of March 2007. 

For the U.S. Nuclear Regulatory 

Commission. 

Stewart N. Bailey, 

Senior Project Manager, Plant Licensing 

Branch II–2, Division of Operating Reactor 

Licensing, Office of Nuclear Reactor 

Regulation. 

[FR Doc. E7–5249 Filed 3–21–07; 8:45 am] 

BILLING CODE 7590–01–P 

NUCLEAR REGULATORY 

COMMISSION 

[HLWRS–ISG–02] 

Preclosure Safety Analysis—Level of 

Information and Reliability Estimation; 

Availability of Final Interim Staff 

Guidance Document 

AGENCY: Nuclear Regulatory 

Commission. 

ACTION: Notice of availability. 

SUMMARY: The U.S. Nuclear Regulatory 

Commission (NRC) is announcing the 

availability of the final interim staff 

guidance (ISG) document HLWRS–ISG–

02, ‘‘Preclosure Safety Analysis—Level 

of Information and Reliability 

Estimation,’’ and NRC responses to the 

public comments received on that 

document. The ISG clarifies or refines 

the guidance provided in the Yucca 

Mountain Review Plan (YMRP) 

(NUREG–1804, Revision 2, July 2003). 

The YMRP provides guidance to NRC 

staff to evaluate a potential license 

application for a high-level radioactive 

waste at a geologic repository 

constructed or operated at Yucca 

Mountain (YM), Nevada. 

ADDRESSES: The document HLWRS–

ISG–02 is available electronically at 

NRC’s Electronic Reading Room, at 

http://www.nrc.gov/reading-rm.html. 

From this site, a member of the public 

can access NRC’s Agencywide 

Documents Access and Management 

System (ADAMS), which provides text 

and image files of NRC’s public 

documents. The ADAMS accession 

number for ISG–02 is ML070260204. If 

an individual does 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, or (301) 415–4737, 

or (by e-mail) at pdr@nrc.gov. 

This document may also be viewed 

electronically on the public computers 

located at NRC’s PDR, Mail Stop: O–

1F21, One White Flint North, 11555 

Rockville Pike, Rockville, MD 20852. 

The PDR reproduction contractor will 

copy documents, for a fee. 

NRC Responses to Public Comments 

on HLWRS–ISG–02: In preparing final 

HLWRS–ISG–02, ‘‘Preclosure Safety 

Analysis—Level of Information and 

Reliability Estimation,’’ ADAMS 

ML070260204, the NRC staff reviewed 

and considered 23 comments, including 

two editorial comments, received from 

two organizations during the public 

comment period. Two of the comments 

were identical; three comments were 

related to the ISG process; one comment 

endorsed NRC’s recognition of the use 

of the published reliability values for 

structures, systems, and components 

(SSCs); and the remaining comments 

included recommendations on specific 

clarifying changes to the ISG. Three 

comments on the ISG process were 

consistent with the comments made 

earlier on HLWRS–ISG–01, and were 

addressed in responses to public 

comment on HLWRS–ISG–01 [see 71 FR 

57582, Comments 13(a) and (b)]. 


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Federal Register / Vol. 72, No. 55 / Thursday, March 22, 2007 / Notices 13535 

The following discussion indicates 

how the comments were addressed, and 

the changes, if any, made to ISG–02 as 

a result of the comments. Line numbers 

in the following comments refer to the 

draft HLWRS–ISG–02, ADAMS 

ML062360241, which was made 

available for public comment on 

September 29, 2006 (71 FR 57584). 

Comment 1. One commenter was 

concerned that the changes in the 

YMRP, recommended in ISG lines 59–

66, 222–224, and 271–273, appear to 

suggest that information regarding 

‘‘design bases and design criteria’’ for 

non-important to safety (non-ITS) SSCs 

be similar to those for ITS SSCs. Since 

non-ITS SSCs have been determined not 

to be necessary to assure compliance 

with 10 CFR Part 63 preclosure 

performance objectives, the commenter 

states that subsection 63.21(c)(3) does 

not appear to support inclusion of 

information related to design bases and 

design criteria for non-ITS SSCs. The 

commenter recommends specific 

changes to ISG lines 62, 222, 239, 254, 

258, 263, 266, and 272, to clarify its 

position. 

Response. NRC agrees that 

information required for non-ITS SSCs 

would be less than for ITS SSCs. 

Subsection 63.21(c)(3) requires a 

description and discussion of the design 

of the YM geologic repository operations 

area, that is sufficient to permit an 

evaluation of the preclosure safety 

analysis (PCSA). DOE will have to 

provide sufficient information to 

discuss how the proposed design would 

function. This also includes the general 

arrangements of SSCs, capacities of 

SSCs, and levels at which the SSCs are 

operated. Staff agrees with the 

commenter that 10 CRF Part 63 requires 

the design bases and design criteria for 

ITS SSCs, and not for non-ITS SSCs. 

ISG lines 62, 222, 254, and 272 have 

been revised to state that design bases 

and design criteria refer to SSCs that 

have been designated as ITS. ISG lines 

239, 258, 263, and 266 have not been 

revised, because these lines refer to 

estimating the reliability of SSCs 

sufficient for performing the PCSA and 

identifying ITS SSCs, as per 63.112. 

Comment 2. The commenter stated 

that, in lines 57–259, it would be more 

appropriate to use ‘‘accept,’’ instead of 

‘‘recognize,’’ because it is unclear. The 

same commenter also noted that lines 

276–284 do not include an acceptance 

criterion element related to 

‘‘acceptability of codes and standards,’’

as proposed in lines 258–259, and 

supplemented in lines 121–124. 

Response. NRC disagrees that the 

word ‘‘recognize’’ is unclear in the 

context of the sentence in lines 257–

259. Staff believes that the use of the 

word ‘‘accept’’ would be inappropriate 

here, because the codes and standards 

do not provide explicit reliability values 

requiring acceptance. Staff also 

disagrees with the commenter’s 

recommendation on the addition of a 

new acceptance criterion item (7), 

regarding the use of codes and standards 

to obtain a probability of unacceptable 

performance. Staff believes that, as 

stated in ISG lines 121–124, the 

application of the codes and standards, 

to the design and operation of an ITS 

SSC, is an accepted engineering 

practice, and is addressed as new item 

(2), of ‘‘Acceptance Criterion 2,’’ in ISG 

lines 276–277. 

No changes to the ISG were made as 

a result of this comment. 

Comment 3. The commenter states 

that the phrases ‘‘risk-significant’’ or 

‘‘risk-significance’’ have a multiplicity 

of meanings. For example, in nuclear 

power plant probabilistic risk 

assessment applications, the terms refer 

to a metric of risk that is a function of 

both probability (or frequency) of 

occurrence, and consequences. 

However, in the context of Part 63, 

event sequence categorization is 

performed on the basis of probability, 

only. The consequences of interest 

(public and worker doses) are 

deterministic in nature. The commenter 

recommended that the terms ‘‘risksignificant’’ or ‘‘risk-significance’’ be 

avoided or defined specifically in the 

context of this ISG. 

Response. NRC agrees that use of the 

terms ‘‘risk-significant’’ or ‘‘risksignificance’’ in the ISG requires 

clarification where reference is to the 

consequences only and not to the 

‘‘risk,’’ which includes both the 

probability and the consequences. 

Changes to lines 41 and 162 were made 

to either clarify or remove redundancy 

of the ‘‘risk’’ term. Specific changes to 

the ISG, suggested by the commenter on 

lines 210, 268, 289, 382, and 574, are 

not made, because these lines refer to 

the ‘‘risk’’ consistent with the 

traditional definition (U.S. Nuclear 

Regulatory Commission, White Paper on 

Risk-informed and Performance-based 

Regulation, SECY–98–144, June 22, 

1998, as revised by the Staff 

Requirements Memorandum, March 1, 

1998). 

The ISG has been revised as follows: 

Line 41: Change ‘‘risk-significant’’ to 

‘‘significant.’’

Line 162: Delete ‘‘risk-significance or 

***’’

Comment 4. The commenter 

suggested that the lines 86 and 240 of 

the ISG be revised to state that ‘‘Explicit 

quantitative reliability estimates of 

software failure modes during event 

sequences are beyond the state-of-the-art 

and are not expected for the PCSA. It is 

acceptable to use reliability estimates of 

digital control units, which would 

implicitly include hardware and 

software effects.’’

Response. NRC disagrees that 

revisions to lines 86 and 240 are 

needed. For SSCs where the reliability 

estimates include hardware and 

software effects, it is acceptable to use 

the reliability estimates, without 

explicit consideration of software 

failures. However, for SSCs where such 

data are not available, an estimate for 

reliability needs to include 

consideration of hardware and software 

failures. NRC believes that ISG lines 86 

and 240 do not need to be revised 

because these statements allow the U.S. 

Department of Energy (DOE) the 

flexibility to consider hardware and 

software failures with appropriate 

technical bases. 

No changes to the ISG were made as 

a result of this comment. 

Comment 5. The commenter states 

that the sentence starting at line 89 be 

revised by replacing ‘‘event’’ with 

‘‘event sequences.’’

Response. NRC agrees with the 

suggested change. 

ISG line 89 has been revised to change 

‘‘events’’ to ‘‘event sequences.’’

Comment 6. The commenter 

recommends that a definition of the 

mean value of a probability distribution 

be included after line 90 of the ISG. 

Response. NRC disagrees that the 

mean value of a probability distribution 

needs to be defined in the ISG. The 

mean of a distribution is a clear and 

unambiguous statistical term. 

No changes to the ISG were made as 

a result of this comment. 

Comment 7. The commenter states 

that items 2 and 3, in lines 129–132 of 

the ISG, ‘‘* * * appear to contradict the 

indication that a quantitative reliability 

estimate is needed,’’ and recommends 

revising the ISG to clarify that 

quantitative reliability estimates are 

needed. 

Response. NRC disagrees that the 

changes recommended by the 

commenter are necessary. As stated in 

the ISG, items 1, 2, and 3 are given as 

examples of methods that may be used, 

in combination with a code and 

standard, to obtain quantitative 

reliability estimates, and do not 

contradict the need for the quantitative 

reliability estimates. 

No changes to the ISG were made as 

a result of this comment. 

Comment 8. The commenter states 

that the use of the term ‘‘procedure,’’ in 

ISG line 229, does not recognize that 


rwilkins on PROD1PC63 with NOTICES
13536 Federal Register / Vol. 72, No. 55 / Thursday, March 22, 2007 / Notices 

many of the actions associated with 

repository operations, such as crane and 

trolley operations, will also be skillbased. The commenter recommends that 

the ISG line 229 be revised to clarify 

that the review will be of ‘‘procedures 

and activities,’’ related to the controls 

and the human interactions associated 

with each SSC. 

Response. NRC agrees with the 

commenter. 

ISG line 229 has been revised to add 

‘‘and activities’’ after ‘‘procedures.’’

Comment 9. The commenter states 

that, in Appendix A of the ISG, the 

probability of dropping a heavy load is 

estimated with empirical data, then 

multiplied by the number of times that 

heavy loads are lifted, to arrive at a 

number that is characterized as the 

‘‘expected number of drops.’’ The use of 

the word ‘‘expected’’ is misleading, 

because it implies expected value, 

which is often used as a synonym for 

the mean value. The product of these 

two point estimates cannot be construed 

as a mean or expected value of the 

number of drops, because the 

underlying probability distributions 

were not developed for them. The 

commenter recommends that the phrase 

‘‘expected number of drops’’ in ISG line 

451 should be changed to ‘‘point 

estimate number of drops.’’

Response. NRC disagrees with the 

change recommended by the 

commenter. However, the ISG has been 

revised to clarify the staff’s approach. 

Whereas the staff agrees that the use of 

the phrase ‘‘expected number of drops’’

may be misleading, the staff disagrees 

with the reason given in the comment. 

The ISG calculation uses a classical 

statistical approach. With this approach, 

the number of drops in L lifts has a 

binomial distribution which is typically 

approximated by a Poisson distribution. 

The expected value of the Poisson 

distribution is the product of the drop 

probability and the presumed number of 

lifts that may occur in the preclosure 

facility. Since the drop probability is 

estimated in this case, the expected 

number of drops is also estimated. 

The ISG has been revised to add the 

above approach after line 449. ISG line 

451 has been revised to change 

‘‘expected’’ to ‘‘estimated.’’ Also, ISG 

lines 432 and 489 have been similarly 

changed. 

Comment 10. Two commenters stated 

that scientific and technical precedent 

point to the use of the mean value of a 

frequency distribution as the 

appropriate metric for event sequence 

categorization. One commenter adds 

that, contrary to this, ISG lines 465–472 

appear to point to the use of a fraction 

of a confidence interval, on which to 

base a conclusion about categorization 

of an event sequence. The commenter 

recommends deleting the sentence, 

beginning on line 467, and changing 

lines 470–472 to read as, ‘‘The number 

of expected drops, in this example, 

would be the mean value of a joint 

probability distribution of both the 

conditional drop probability and the 

number of lifts.’’

Response. In Appendix A of ISG–02, 

empirical data were used to derive a 

point estimate for the probability of 

dropping a cask. To address uncertainty 

in this point estimate, staff chose a 

standard statistical approach of the 

confidence interval method, to 

determine the confidence level in 

categorization of the event sequence for 

the example. 

NRC does not agree that the sentence 

beginning on line 467 should be 

deleted, because it provides an example 

of a method to illustrate consideration 

of uncertainty. The 48-percent level of 

confidence is analogous to reporting the 

descriptive level of significance, which 

is often used in reporting the results of 

a test of a hypothesis. 

According to the ‘‘Statement of 

Considerations’’ for Part 63, November 

2, 2001 (66 FR 55742), the approach in 

the rule is to provide DOE with the 

flexibility to select the type of analysis 

it believes most appropriate for the 

license application. Whatever approach 

DOE uses will need to be supported, 

taking into account uncertainties. 

Therefore, analyses relying on point 

values (e.g., best-estimate values) will 

need to discuss how uncertainties are 

taken into account. 

NRC agrees that DOE can use the 

mean value of an event sequence 

frequency distribution to categorize an 

event sequence. However, DOE should 

to consider the uncertainty in any mean 

value used to categorize event 

sequences. In particular, DOE should to 

provide the technical bases for 

developing the event sequence 

frequency distribution, including 

consideration of uncertainties in 

performance of individual SSCs, the 

choice of distribution type, and the 

values of the parameters. 

ISG lines 470–472 have been deleted, 

because these lines refer to the 

estimated conditional drop probability 

for a specific confidence level, which is 

not discussed in the ISG. 

Comment 11. The commenter states 

that ISG line 592 be revised to clarify 

that the design bases are associated with 

SSCs and not with an event sequence 

category, as stated in the ISG. 

Response. NRC agrees with the 

comment. 

ISG line 592 has been revised to read 

as follows: ‘‘Design bases (e.g., loadings 

on SSCs associated with Category 1 and 

Category 2 event sequences, such as a 

canister drop event); and * * *.’’

Comment 12. The commenter states 

that the definition of ‘‘S = C/D,’’ in line 

617, appears to be inconsistent with the 

definition in Figure B–2 of the ISG. The 

commenter recommends that either the 

definition of ‘‘S,’’ in line 617, be 

revised, or that Figure B–2 be revised. 

Response. NRC disagrees with the 

commenter that definition of ‘‘S’’ in ISG 

line 617, and Figure B–2 are 

inconsistent. Figure B–2 is consistent 

with the commonly used definition of 

the limit state function in the form of S 

= C/D, as shown in line 617, where C 

and D are the capacity and demand, 

respectively. Staff, however, recognizes 

that Y-axis labeling in Figure B–2, and 

description of the ISG lines 680–681, 

may have resulted in an appearance of 

inconsistency. As stated in ISG line 676, 

Figure B–2 shows the cumulative 

distribution function of S, with the 

probability of failure defined as the 

probability that S is less than or equal 

to 1. The curve, shown in Figure B–2, 

is for the constant demand D = 497 

mega pascals (MPa) [72 kips per square 

inch (ksi)]. Similar curves are derived 

for two other values of demand values, 

listed in Appendix B, using a lognormal distribution of the capacity, C, 

divided by a constant demand, D (see 

Ref. B.3), and are included in the 

revised Figure B–2 in the ISG. 

Probability of failure values for three 

different demand values, along with 

their corresponding ratios of American 

Society of Mechanical Engineers 

(ASME) code allowable stress to 

demand, are shown in Table B–3. The 

results show, as expected, that the 

probability of failure decreases as the 

demand decreases. The ISG has been 

revised as follows: 

• Figure B–2 has been revised to 

include plots for all three demand 

values shown in Table B–3, and the 

caption has been revised to include ‘‘for 

three demand values’’; 

• Label for the ordinate axis has been 

changed from ‘‘Probability of Failure (x 

10¥5)’’ to ‘‘Cumulative Probability,’’ and 

is replotted in the log-scale; 

• Line 622: The phrase, ‘‘ * * * 

which is traditionally defined as the 

limit state function’’ is added at the end 

of the sentence. 

• Line 680: A new sentence, ‘‘Failure 

probabilities for various values of 

demand are shown in Figure B–2.’’ has 

been added; 

• Lines 680–681: sentence has been 

revised to ‘‘Failure probabilities for 

various values of ratios of ASME 


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Federal Register / Vol. 72, No. 55 / Thursday, March 22, 2007 / Notices 13537 

allowable stress to these corresponding 

demand values are given in Table B–3.’’

Comment 13. The commenter stated 

that the paragraph beginning with line 

156 of the ISG specifies that the NRC 

staff will verify that uncertainty is 

addressed in the PCSA. The commenter 

is concerned that this may be 

interpreted as requiring excessive 

conservatism in the analysis, and that 

such an approach would be the opposite 

of the intent of risk-informed regulation. 

The commenter recommends that text of 

the discussion on uncertainty be revised 

to explicitly recognize this intent. 

Response. NRC agrees that excessive 

conservatism should be avoided in 

considering uncertainty. DOE has the 

flexibility to choose the method to 

demonstrate that the performance 

objectives are met. For example, DOE 

could perform a bounding calculation. 

As stated in the ‘‘Statement of 

Considerations,’’ for Part 63, ‘‘* * * 

whatever approach DOE uses will need 

to be supported, taking into account 

uncertainties.’’ For example, if DOE is to 

portray its PCSA results as best 

estimates, this term will need to be 

defined because it has no statistical 

meaning (see ‘‘A Review of Staff Uses of 

Probabilistic Risk Assessment,’’

NUREG–1489, March 1994). Staff 

believes that the paragraph on 

uncertainty, beginning with ISG line 

156, is sufficiently clear, and that no 

changes are required. 

No changes to the ISG were made as 

a result of this comment. 

Comment 14. The commenter stated 

that the screening criteria in ISG lines 

127–128 presume a preclosure period of 

100 years by specifying that the lower 

bound of Category 2 event sequence 

frequency is 10¥6 failures/yr. Instead, 

the staff should be consistent with Part 

63 in referring to the lower bound of 

Category 2 event sequence frequency as 

the one chance in 10,000 during the 

period of operation. 

Response. NRC agrees with the 

comment. Unless there is a reason to 

state otherwise, the staff will refer to the 

terminology, used in Part 63, for 

Category 2 event sequence frequency as 

having at least one chance in 10,000 of 

occurring during the preclosure period. 

The quantitative frequency limit of a 

Category 2 event sequence is 

determined by the duration of the 

preclosure period. 

ISG line 127 has been revised to 

change ‘‘(e.g., ≤10¥6 failures/year)’’ to 

‘‘(e.g., ≤ one chance in 10,000 of 

occurring during the preclosure 

period).’’

ISG line 128 has been revised to 

delete ‘‘(e.g., ≤10¥6 failures/year).’’

Comment 15. The commenter stated 

that, in ISG line 136, the NRC staff 

recognizes various sources of reasonable 

input to the PCSA. It is important that 

such information does not have to be 

created under an NRC-licensed quality 

assurance program. The sources cited in 

the ISG [e.g., ‘‘Generic Data Base, 

developed by Savannah River Site,’’ and 

the Equipment Performance and 

Information Exchange (EPIX) System], 

for reliability input, are reasonable, 

based on actual operating data, and not 

skewed by conservatism. Even though 

applying conservatism is acceptable for 

safety analysis purposes (e.g., for 

analytical simplification or bounding 

uncertainties), doing so distorts the 

foundation of risk-informed regulation 

by implying higher risks than actually 

exist. 

Response. NRC agrees that DOE can 

use reliability information from 

published references. However, DOE 

must provide the technical basis to 

demonstrate that any reliability 

information is applicable to the 

proposed design of the GROA. 

No changes to the ISG were made as 

a result of this comment. 

Comment 16. The commenter stated 

that, in ISG lines 157–168, the staff 

should apply additional scrutiny or 

focus in its review, in cases where a 

reliability estimate is close to a Category 

1 or 2 limit. The ISG should not be 

taken to imply that DOE is required to 

submit any additional analysis with its 

license application. The guidance 

should be clarified to explicitly 

recognize that it is incumbent on DOE 

to determine both if and when a 

reliability estimate is sufficiently close 

to a Category 1 or 2 limit to warrant 

additional consideration, in the license 

application, as well as the specific 

nature and extent of any such 

consideration in the application. 

Response. NRC has not specified 

criteria for determining when a 

sequence frequency is close enough to a 

category limit to warrant additional 

scrutiny. DOE is expected to provide 

NRC with enough information to 

demonstrate that sequences have been 

correctly categorized. 

No changes to the ISG were made as 

a result of this comment. 

Comment 17. The commenter stated 

that the demand in ISG lines 636–638 is 

a function of several parameters (e.g., 

modulus of elasticity, dimension, 

thermal expansion). The commenter 

adds that these parameters would affect 

the material capacity, not the demands 

placed on the material, and 

recommends that this sentence be 

revised by deleting the words ‘‘modulus 

of elasticity, dimensions, thermal 

expansion.’’

Response. NRC agrees with the 

comment. Demand on an SSC because 

of an event, such as a drop or a natural 

event, would not depend on the 

modulus of elasticity, dimension, and 

thermal expansion. 

ISG lines 636–637 have been revised 

to delete ‘‘modulus of elasticity, 

dimensions, thermal expansion.’’

Comment 18. One commenter 

suggested the following editorial 

changes: Lines 587–588: Revise ‘‘* * * 

including major components of canister 

structure, internals’’ to read ‘‘* * * 

including major components of canister 

structure, and its internals’’; Line 622: 

Revise ‘‘function can developed’’ to read 

‘‘function can be developed.’’

Response. NRC agrees with the 

comment. The ISG has been revised to 

reflect the suggested changes. 

In addition to the changes described 

above, the ISG has also been revised, as 

follows, for clarification: 

Line 91: The sentence ‘‘DOE should 

identify the key SSCs in an event 

sequence.’’ was deleted because ‘‘key’’

SSCs is not formally defined; a new 

sentence to replace the deleted sentence 

has been added; 

Line 446: The definition of λ (now pˆ

was reworded for clarity; 

Lines 445: Though 453: λ was 

changed to, to distinguish this quantity 

from λ, which often is used to indicate 

a rate in the Poisson distribution, and 

that the quantity is an estimate; 

Line 622: Clarifying words were 

added. 

FOR FURTHER INFORMATION CONTACT: Jon 

Chen, Project Manager, Division of 

High-Level Waste Repository Safety, 

Office of Nuclear Material Safety and 

Safeguards, U.S. Nuclear Regulatory 

Commission, Washington, DC 20555–

0001 [Telephone: (301) 415–5526; fax 

number: (301) 415–5399; e-mail: 

jcc2@nrc.gov]; 

Robert Johnson, Senior Project 

Manager, Division of High-Level Waste 

Repository Safety, Office of Nuclear 

Material Safety and Safeguards, U.S. 

Nuclear Regulatory Commission, 

Washington, DC 20555–0001 

[Telephone: (301) 415–6900; fax 

number: (301) 415–5399; e-mail: 

rkj@nrc.gov]. 

Dated at Rockville, Maryland this 8th day 

of March, 2007. 

For the Nuclear Regulatory Commission., 

N. King Stablein, 

Chief, Project Management Branch B, Division 

of High-Level Waste Repository Safety, Office 

of Nuclear Material Safety and Safeguards. 

[FR Doc. 07–1404 Filed 3–21–07; 8:45 am] 

BILLING CODE 7590–01–P 


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