Peter S. Winokur, Chairman 

Jessie H. Roberson, Vice Chairman 

John E. Mansfield 

DEFENSE NUCLEAR FACILITIES 

SAFETY BOARD 

Joseph F. Bader 

Sean Sullivan 

The Honorable Ernest J. Moniz 

Secretary of Energy 

U.S. Department of Energy 

1000 Independence Avenue, SW 

Washington, DC 20585-1000 

Dear Secretary Moniz: 

Washington, DC 20004-2901 

July 15, 2013 

The staff of the Defense Nuclear Facilities Safety Board (Board) performed a review of 

the Criticality Safety Program at Los Alamos National Laboratory in May 2013. This review 

identified significant non-compliances with applicable Department of Energy requirements and 

industry standards in the implementation of the Criticality Safety Program. In addition, this 

review identified criticality safety concerns stemming from weaknesses in conduct of operations 

at the Plutonium Facility. The Board notes that some of these deficiencies are long standing and 

indicate flaws in the federal oversight and contractor assurance systems. 

The Board is aware that the Laboratory Director paused programmatic activities in the 

Plutonium Facility on June 27, 2013. The Board provides the attached report to aid in the 

ongoing assessment and development of corrective actions. Pursuant to 42 U.S.C. § 2286b(d), 

the Board requests a report and briefing by the National Nuclear Security Administration 

(NNSA) within 30 days of receipt of this letter that details (a) any corrective actions NNSA is 

taking to incorporate criticality safety controls into procedures, and to improve procedures, 

procedure use, criticality safety postings, and criticality safety support of operations, (b) any root 

causes NNSA has identified for recent criticality safety infractions, and (c) any improvements 

NNSA has determined are needed to the federal oversight and contractor assurance systems 

relative to criticality safety, conduct of operations, and effectiveness of corrective actions. 

Enclosure 

c: Mr. Bruce Held 

Mr. Geoffrey L. Beausoleil 

Mrs. Mari-Jo Campagnone 

Sincerely, 

Q~lf,.n_ 

Peter S. Winokur, Ph.D. 

Chairnrnn 
DEFENSE NUCLEAR FACILITIES SAFETY BOARD

Staff Issue Report

July 2, 2013 

 

MEMORANDUM FOR: S. Stokes, Acting Technical Director 

COPIES: Board Members 

FROM: D. Kupferer and J. McComb 

 

SUBJECT: Criticality Safety at Los Alamos National Laboratory 

This report documents a review performed by the staff of the Defense Nuclear Facilities 

Safety Board (Board) of the Los Alamos National Laboratory (LANL) Criticality Safety 

Program (CSP) during May 21–23, 2013. The staff’s review included discussions with 

personnel representing the Los Alamos Field Office (LAFO) and the contractor, Los Alamos 

National Security, LLC (LANS), as well as walk-downs of various fissile material workstations 

and operations in the Plutonium Facility (PF-4). The staff conducted a follow-up teleconference 

with LAFO and LANS personnel on June 19, 2013, to obtain additional information. 

Summary. National Nuclear Security Administration (NNSA) Headquarters, LAFO, and 

LANS have acknowledged that the LANL CSP is not compliant1

 with applicable requirements. 

The significant shortage of LANS criticality safety staff has hindered the ability of LANS to 

address these deficiencies, and the backlog of unresolved criticality safety issues continues to 

grow. In addition, the Board’s staff identified the following non-compliances during its review: 

 Most criticality safety controls are not incorporated into operating procedures. 

 Operators typically do not utilize written procedures when performing work. 

 Fissile material labels do not list parameters relevant to criticality safety (e.g., mass). 

 Some fissile material operations lack Criticality Safety Evaluations (CSEs). 

 Some CSEs do not analyze all credible abnormal conditions. 

On June 27, 2013, the LANL Laboratory Director paused programmatic activities in 

PF-4. LANS has committed to develop a comprehensive “get-well” plan to bring the LANL 

CSP into compliance with applicable requirements. Given the deficiencies associated with 

criticality safety and conduct of operations, the staff believes the following actions should be 

considered during resumption of fissile material operations in PF-4: 

 

1

 Throughout this report, the terms compliance and non-compliance refer specifically to alignment of the LANL 

CSP with Department of Energy directives and the American National Standards Institute (ANSI)/American Nuclear 

Society (ANS)-8 standards. 
2 

(1) incorporate criticality controls and limits into procedures; (2) improve conduct of operations 

including utilization of procedures; (3) evaluate procedures that contain criticality safety controls 

for designation as Use Every Time procedures; (4) review and approve criticality safety postings 

to ensure they are accurate and of high quality; and (5) enhance criticality safety support for 

ongoing operations. 

Background. Prior to 2005, LANL’s CSP was expert-based and highly dependent on the 

knowledge and experience of its criticality safety staff. In 2005, NNSA performed an 

assessment and determined that LANL’s expert-based CSP was not compliant with applicable 

Department of Energy (DOE) requirements and industry standards [1]. In 2006, in response to 

NNSA’s review, LANS developed a Nuclear Criticality Safety Program Improvement Plan 

(PIP), which was intended to align LANL’s CSP with applicable requirements. The PIP’s 

primary objective was to establish compliant CSEs for all operations [2]. 

In 2007, in response to concerns raised by the Board’s staff, LANS determined that the 

authorized loading of vault storage rooms in PF-4 could lead to a critical configuration. As a 

result, LANS performed an Augmented Limit Review of all fissile material operations (FMOs) 

to confirm the adequacy of existing criticality safety limits. Due to a variety of issues, including 

staffing shortages, LANS did not complete execution of the PIP and, to date, has not developed 

updated CSEs for more than 100 FMOs. 

In 2011, an event occurred at PF-4 in which fissile material handlers violated procedural 

requirements and criticality safety controls while moving and photographing eight plutonium 

rods. These violations included the following: failure to properly plan and obtain authorization 

for the activity, failure to adhere to posted requirements, and improper response to the infraction 

[3]. Following this event, LANS executed several corrective actions including improvements to 

the training, qualification, and certification processes for fissile material handlers. 

In 2012, DOE’s Criticality Safety Support Group (CSSG) performed a review of the 

LANL CSP and identified several deficiencies, including the operational impact of the 

contractor’s declining criticality safety staff [4]. In response to the CSSG’s review, LANS 

developed a Corrective Action Plan to improve several aspects of the CSP [5]. Beginning in 

2012, LANS experienced an 18-month exodus of criticality safety professionals from its 

criticality safety group. LANS currently employs 2 full-time and 2 part-time qualified criticality 

safety analysts, in addition to 3 part-time subcontractors—far fewer than the 17 criticality safety 

analysts it has determined to be necessary to support operations, meet mission goals, and 

maintain the CSP. 

DOE Requirements and Guidance. Title 10, Code of Federal Regulations, Part 830, 

Nuclear Safety Management (10 CFR Part 830), requires all Documented Safety Analyses 

(DSAs) to define a CSP that meets applicable nuclear criticality safety standards. In addition, 

Appendix A to Subpart B of 10 CFR Part 830 states that DOE Order 420.1, Facility Safety, 

provides DOE’s expectations with respect to criticality safety. DOE Order 420.1B requires the 

development of a CSE for each FMO in accordance with DOE Standard 3007, Guidelines for 

Preparing Criticality Safety Evaluations at Department of Energy Non-Reactor Nuclear 
3 

Facilities. Each CSE provides the basis for subcritical operations under all normal and credible 

abnormal conditions. DOE Order 420.1B states that CSPs must satisfy the requirements of the 

criticality safety standards of American National Standards Institute (ANSI)/American Nuclear 

Society (ANS)-8, which include ANSI/ANS-8.1, Nuclear Criticality Safety in Operations With 

Fissionable Materials Outside Reactors, and ANSI/ANS-8.19, Administrative Practices for 

Nuclear Criticality Safety. 

Staff Observations. During its review, the staff identified the following noncompliances and weaknesses associated with LANL’s CSP and conduct of operations in PF-4. 

Collectively, the staff’s observations call into question whether controls have been properly 

identified and implemented. Additional areas for improvement are discussed in the Attachment. 

Procedures—The staff reviewed operating procedures for more than a dozen PF-4 FMOs 

during the onsite review. The Board’s site representatives subsequently observed LANS 

evaluations of the workability of procedures in PF-4. The staff identified the following 

deficiencies regarding content and execution of procedures at PF-4. 

 Incorporation of Criticality Safety Requirements—Procedures fail to incorporate 

many of the criticality safety controls and limits relevant to the operations in PF-4. 

This practice is not compliant with ANSI/ANS-8.1, Section 4.1.3, which states, 

“[p]rocedures shall specify all parameters that they are intended to control,” and 

ANSI/ANS-8.19, Section 7.2, which states “[p]rocedures shall include those controls 

and limits significant to the nuclear criticality safety of the operation.” Although the 

reviewed procedures typically cited the applicable Criticality Safety Limit Approval 

(CSLA)2

, CSLA documents were not readily available at some workstations. 

 Procedure Use—ANSI/ANS-8.19, Section 1, states, “An effective nuclear criticality 

safety program ... relies upon conformance with operating procedures.” During 

discussions with operators and walk-downs in PF-4, the staff observed that operators 

rely on postings rather than written procedures when performing work. Criticality 

safety postings are considered by the ANSI/ANS-8 Standards, the site-wide CSP, and 

the TA-55 CSP to be only supplements to procedures. During the LANS workability 

evaluations, the Board’s site representatives observed several instances in which 

either (a) operating procedures could not be executed as written or (b) procedural 

steps were inconsistent with how operators actually performed work. These 

observations further indicate that operators typically do not rely on procedures when 

performing work. 

All operating procedures reviewed by the staff are designated as Reference 

procedures rather than Use Every Time procedures. LANL’s Conduct of Operations 

Manual states that a Use Every Time procedure must be considered if a procedural 

error could result in significant consequences [6]. Conversely, the Conduct of 

Operations Manual states that a Reference procedure describes activities for which 

 

2 The CSLA is a complete listing of all the criticality safety controls that establish the required safety margin. 
4 

training and expertise may be relied upon. The manual also states that Use Every 

Time procedures are to be present and in use during operations, while Reference 

procedures are not required to be located at the immediate workstation. 

According to LANS, approximately 70% of procedures associated with FMOs in PF4 are designated as Reference procedures. A June 13, 2013, memorandum from the 

LANS Associate Director for Plutonium Science and Manufacturing to his workforce 

notes that, “Two of the most critical elements of safe operations are that written 

technical procedures define the proper operational parameters and controls and that 

those procedures are followed as intended” [7]. Given these critical elements and the 

nature of many PF-4 operations, the staff believes it would be prudent to evaluate 

designating procedures for appropriate PF-4 operations as Use Every Time, 

particularly when criticality safety controls are required. 

 Posting Quality—As discussed above, PF-4 fissile material handlers rely on the 

content and accuracy of facility postings. ANSI/ANS-8.1, Section 4.1.4 states, “area 

posting shall be maintained specifying material identification and all limits on 

parameters subject to procedural control.” The staff identified several criticality 

safety postings that included unclear or inconsistent requirements, and other postings 

with basic formatting errors. Postings often directly reflect language from their 

parent CSLAs and CSEs, and the deficiencies typically extend to these documents. 

Posting quality was also listed as an opportunity for improvement in the 2012 CSSG 

report [4], yet was not addressed by the Corrective Action Plan developed in response 

to the CSSG’s report. 

LANL criticality safety postings require no formal approval. The lack of a rigorous 

review and approval process for postings, in addition to the posting deficiencies 

observed by the staff, underscores the fault of relying on these postings (rather than 

procedures) to meet criticality limits. The staff believes it would be prudent to 

consider near-term improvements to postings while procedural upgrades are 

completed. 

Fissile Material Tracking and Labeling—During walk-downs, the staff observed that 

fissile material handlers rely on an electronic inventory database (LANMAS), rather than 

material and container labeling, to adhere to applicable criticality safety limits. Typically, 

container labels included only a material tracking number and the material type. This practice is 

not compliant with ANSI/ANS-8.19, Section 9.2, which states, “appropriate material labeling ... 

shall be maintained, specifying material identification and all limits on parameters that are 

subject to procedural nuclear criticality safety control.” Additionally, the LANL CSP states, 

“The ORS [Operations Responsible Supervisor] must require that material/containers be 

unambiguously labeled with specifications consistent with parameters that are under control 

(e.g., mass, material type, and volume)” [8]. The staff believes it would be prudent to consider 

implementing a clear and rigorous method for ensuring compliance with criticality safety limits 

and ANSI/ANS-8 requirements. 
5 

Criticality Safety Evaluation Quality—Starting in 2005, the PIP aimed to develop 

evaluations for FMOs with missing CSEs and update evaluations for FMOs with deficient CSEs. 

This effort attempted to bring these operations into compliance with DOE Standard 3007, and 

LANL Policy 06.06, Criticality Safety Evaluations. A number of issues, including limited staff 

resources, impacted execution of the PIP, and many of the CSEs were never developed. While 

updating CSEs, operations were subjected to an Augmented Limit Review, which took place in 

2007 and 2008. Documentation of this review process is sparse. Currently, 135 of 513 LANL 

FMOs (110 of 419 PF-4 FMOs) lack CSEs [9]. 

In preparation for the review, the staff analyzed updated CSEs associated with twelve 

FMOs in PF-4. Although these updated CSEs were intended to align with DOE and ANSI/ANS 

requirements, numerous deficiencies remain. The staff identified several (a) upset conditions 

that are inadequately analyzed or wholly unanalyzed and (b) assumptions that lack documented 

technical bases. These deficiencies conflict with DOE Standard 3007, which states, “all credible 

contingencies shall be identified, analyzed, and documented,” and “assumptions about the 

process and scope limitations that impact the CSE should be stated and justified.” Examples of 

unanalyzed upset conditions identified by the Board’s staff include: 

 Potential upsets associated with fires and earthquake scenarios are not evaluated in 

the following CSEs: NCS-CSED-12-001, NCS-CSED-09-042, NCS-CSED-07-034, 

and NCS-CSED-08-074. 

 NCS-CSED-12-001 does not evaluate a situation in which a fissile material container 

could become fully moderated and reflected due to a leak in collocated cooling water 

system. 

The staff believes it would be prudent to analyze these upsets to determine whether 

additional controls are warranted. Examples of assumptions that lack documented technical 

bases include: 

 In NCS-CSED-07-034, collocation of more than three containers is assumed to be 

incredible without justification. 

 NCS-CSED-09-002 states that, “moderation is explicitly controlled by exclusion of 

solution/moderated materials.” However, no administrative requirements are 

identified to limit moderating materials. Polyethylene, an effective moderator, is a 

packaging material commonly used in this storage location. 

Similar deficiencies in updated CSEs were noted by a recent extent-of-condition review 

conducted by LANS. The LANS review found that, “CSEDs have consistently lacked (1) 

applicable controls, (2) content accuracy, (3) scenario clarity, and/or (4) upset condition 

completeness” [10]. In addition, LAFO has provided comments to LANS on 150 CSEs that 

indicate non-compliance with requirements [9]. LANS reported three Potential Inadequacies in 

the Safety Analysis to NNSA during the past two years as a result of CSE deficiencies [11-13]. 
6 

Issue Tracking and Compliance with Requirements—NNSA Headquarters, LAFO, and 

LANS have acknowledged that the LANL CSP is not compliant with DOE Order 420.1B and 

applicable ANSI/ANS-8 Standards. Furthermore, LANS relies on several disconnected 

databases and improvement plans to track its corrective actions, including the Corrective Action 

Plan, the PIP, the Performance Feedback and Improvement Tracking System, and a database of 

LAFO comments. However, LANS has not comprehensively identified the gaps between its 

CSP and the applicable requirements, and has no comprehensive, resource-loaded plan to address 

these gaps. On June 20, subsequent to the staff’s review, LANS committed to provide LAFO 

with a comprehensive “get-well” plan for the CSP by October 1, 2013 [14]. 

Staffing—Maintaining a qualified criticality safety staff has challenged LANS for the 

past eight years. The severe staffing shortage in the criticality safety group raises significant 

questions regarding the ability of LANS to support safe operations. This staffing shortage also 

inhibits the ability of LANS to resolve the deficiencies identified in its existing plans and 

databases (e.g., Corrective Action Plan, PIP, Performance Feedback and Improvement Tracking 

System, and LAFO CSE comments). Currently, LANS employs 2 full-time and 2 part-time 

qualified criticality safety analysts, in addition to 3 part-time subcontractors fulfilling some 

analyst roles and responsibilities. A 2013 CSSG review found that LANS will likely require 3 to 

5 years to hire, train, and qualify the targeted number of additional criticality safety analysts [15]. 

This is especially concerning given that the LANS staffing plan does not account for the 

resources necessary to address existing deficiencies. LANS has recently made progress to 

address its staffing shortage. However, the staff believes more aggressive actions and additional 

resources may be necessary to expedite these efforts (e.g., utilizing available DOE and corporate 

resources). 

Fissile Material Handler Training and Certification—The number of infractions 

identified in the first 6 months of 2013 nearly matches the yearly totals from 2012 and 2011 (15 

in the first half of 2013, 15 in all of 2012, and 16 in all of 2011) [16,17]. Of the 15 criticality 

safety infractions identified in PF-4 this year, 9 were identified by LANS personnel, 5 were 

identified by LAFO personnel, and one was identified by the Board’s staff during its review. 

The staff is concerned that the significant proportion of infractions identified by oversight 

personnel may indicate that facility personnel should be more familiar with and sensitive to 

criticality safety requirements. The overall increase in infractions this year may indicate a halflife of the fissile material handler training and certification effort which took place after the 

significant criticality infraction in August 2011. The staff believes that it would be prudent to 

consider criticality safety refresher training for fissile material handlers. 

While performing a walk-down of a glovebox in Room 429 of PF-4, the staff identified a 

container of fissile material in a portion of the glovebox without an assigned mass limit (i.e., the 

CSLA did not allow fissile material to be stored in this location). LANS personnel took 

appropriate actions by evacuating the room and notifying criticality safety staff of the potential 

criticality safety infraction. The following day, LANS conducted a critique to discuss and 

resolve the potential infraction. At the conclusion of the critique, senior LANS management 

appropriately determined the configuration resulted in a criticality safety infraction. Based on 

this infraction and other recent infractions, LANS paused operations in the room until an extent-
7 

of-condition walk-down could be performed. During the critique, several fissile material 

handlers and production managers argued against categorizing the event as an infraction due to 

the current configuration of the glovebox. Specifically, the argument was made that certain 

requirements did not apply at that time because no liquids were present in the glovebox. The 

staff believes this argument may further indicate that facility personnel should be more sensitive 

to criticality safety requirements. 

Conclusion. The LANL CSP states that written procedures, formality of operations, and 

criticality safety controls are essential elements to a properly functioning CSP and that, “the only 

safe course of action, under circumstances in which any one element is inadequate, is not to 

perform operations until appropriate corrective actions are implemented” [8]. Before PF-4 

personnel resume fissile material operations in the Plutonium Facility, the staff believes that it is 

essential to demonstrate the adequacy of these elements. 

The staff believes the following actions should be considered during resumption of fissile 

material operations in the Plutonium Facility: (1) incorporate criticality controls and limits into 

procedures; (2) improve conduct of operations including utilization of procedures; (3) evaluate 

procedures that contain criticality safety controls for designation as Use Every Time; (4) review 

and approve postings to ensure they are accurate and of high quality; and (5) enhance criticality 

safety support for ongoing operations. 

The staff recognizes that achieving compliance with applicable requirements will involve 

significant time and resources. LANS has committed to provide LAFO with a comprehensive 

“get well” plan for criticality safety by October 1, 2013. The staff believes this plan should 

identify the resources and schedule required to achieve compliance milestones. Additionally, the 

staff notes that long-standing issues, such as staffing shortages in the LANS criticality safety 

group and CSE compliance, indicate flaws in the federal oversight and contractor assurance 

systems.
A-1 

Attachment – Additional Staff Observations 

Upper Subcritical Limit—The staff notes that LANS analysts use a non-conservative 

upper subcritical limit (USL) when performing evaluations. The USL is a value of keff against 

which the results of a model may be compared to determine whether the modeled condition is 

subcritical.3

 ANSI/ANS-8.24, Validation of Neutron Transport Methods for Nuclear Criticality 

Safety Calculations, Section 7.3 states, “An upper subcritical limit shall be established based on 

the calculational margin and the margin of subcriticality.” The calculational margin includes 

bias, bias uncertainty, and additional uncertainties associated with extrapolation and 

interpolation. Bias represents the systematic difference between calculated results and 

experimental data. Bias is often determined by modeling well-documented benchmark 

experiments and comparing the modeled result to the experimental result. Effectively, the 

calculational margin represents how accurately (and with what uncertainty) a computer code can 

reproduce the properties (i.e., keff) of a well-known physical system. 

In addition to this calculational margin, as ANSI/ANS-8.24, Section 6.4, states, “a margin 

of subcriticality must be applied that is sufficiently large to ensure that the calculated conditions 

will actually be subcritical. The selection of a margin of subcriticality should take into account 

the sensitivity of the system or process to variations in fissile form, geometry, or other physical 

characteristics.” ANSI/ANS-8.24 further states in Section 8.1.5, “The margin of subcriticality 

and its basis shall be documented.” 

In all 12 of the CSEs reviewed by the staff, LANS compares its modeled keff values 

against an upper subcritical limit of 0.98 to determine whether the evaluated process would 

remain subcritical during all normal and credible abnormal conditions. Effectively, LANS 

derives its USL of 0.98 by assigning a value of 0.02 to the sum of the calculational margin and 

margin of subcriticality. LANS’s calculational margins range between 0.0099 and 0.0186 for 

various subsets of benchmark models [18]. In other words, LANS uses a variable margin of 

subcriticality between 0.0101 and 0.0014. The smallest value is more than an order of 

magnitude smaller than the margin of subcriticality used at other DOE sites. For example, 

Lawrence Livermore National Laboratory and the Y-12 National Security Complex both 

typically use a margin of subcriticality of 0.02 [19, 20]. 

Of the 12 CSEs reviewed by the staff, 8 describe credible abnormal conditions where the 

modeled keff is greater than 0.96. If LANS were to use a margin of subcriticality of 0.02, many 

of these conditions would exceed the USL. The staff believes it would be prudent to reevaluate 

this margin of subcriticality and to determine whether additional controls are necessary. 

Control Evaluation Linkage Document—DOE does not require the incorporation of all 

criticality safety controls into the Documented Safety Analysis (DSA) and associated Technical 

Safety Requirements (TSRs). Rather, DOE Standard 3007 requires all criticality safety controls 

be evaluated for inclusion in the DSA and TSRs. The standard recommends the development of 

 

3

 Theoretically, keff = 1 represents a critical configuration. 
A-2 

a linking document to summarize the results of this evaluation. The staff notes that LANS does 

not document its control evaluation process. 

Annual Walk-down Form—ANSI/ANS-8.19, Section 7.8, states, “operations shall be 

reviewed frequently (at least annually) to ascertain that procedures are being followed and that 

process conditions have not been altered so as to affect the nuclear criticality safety evaluation.” 

The staff notes that the Implementation and Annual Process Review Form currently used in PF-4 

lacks detail and may not prompt the appropriate level of scrutiny during the performance of 

annual walk-downs. The staff believes a more detailed form (e.g., a detailed checklist) could 

improve the rigor of these walk-downs. LANS has created a corrective action in its Performance 

Feedback and Improvement Tracking System to address this deficiency by August 2013.
R-1 

References 

[1] Technical Evaluation of the Los Alamos National Laboratory Nuclear Criticality Safety 

Program, National Nuclear Security Administration, October 2005. 

[2] NCS-MEMO-11-003, Los Alamos National Laboratory Nuclear Criticality Safety 

Program Improvement Plan, Los Alamos National Laboratory, Safety Basis, Criticality 

Safety, March 7, 2011. 

[3] OE-3:2012-07, Importance of Conduct of Operations and Training for Effective 

Criticality Safety Programs, Department of Energy, Office of Health, Safety and 

Security, December 2012. 

[4] CSSG Review of LANL Criticality Safety at PF-4, Criticality Safety Support Group, April 

13, 2012. 

[5] SBCS-CAP-12-265, Corrective Action Plan for Nuclear Criticality Safety Program, Los 

Alamos National Laboratory, Safety Basis, Criticality Safety, February 14, 2013. 

[6] P315, Conduct of Operations Manual, Los Alamos National Laboratory, Operations 

Support, February 20, 2013. 

[7] ADPSM:13-007, Procedure Adherence Requirements for ADPSM Operations, Los 

Alamos National Laboratory, Office of the Associate Director for Plutonium Science & 

Manufacturing, June 13, 2013. 

[8] SD130, Nuclear Criticality Program, Los Alamos National Laboratory, Safety Basis, 

Criticality Safety, August 30, 2009. 

[9] List of FMOs: CSED Level & Status, CSLA Status, DOE Comment Level and PIP 

Designation, Los Alamos National Laboratory, Safety Basis, Criticality Safety, May 17, 

2013. 

[10] NCS-MEMO-13-008, Closure and Extent of Condition Review of Completed Nuclear 

Criticality Safety Actions, Los Alamos National Laboratory, Safety Basis, Criticality 

Safety, April 24, 2013. 

[11] AD-NHHO:11-305, Evaluation of the Safety of the Situation and Unreviewed Safety 

Question Determination for Nitric Acid Backflow Potentially Inadequate Safety Analysis, 

Los Alamos National Laboratory, Associate Directorate, Nuclear & High Hazard 

Operations, December 21, 2011. 

[12] AD-NHHO:12-133, Transmittal of Positive Unreviewed Safety Question Determination 

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Directorate, Nuclear & High Hazard Operations, May 11, 2011. 

[13] AD-NHHO:12-343, Evaluation of the Safety of the Situation: Unclear Criticality Safety 

Evaluations for Two Vault Rooms at TA55 and Related Controls for Approval, Los 

Alamos National Laboratory, Associate Directorate, Nuclear & High Hazard Operations, 

December 7, 2012. 

[14] AD-NHHO:13-165, Expected Submittal Date for LANS Evaluation and Path Forward, 

Los Alamos National Laboratory, Associate Directorate, Nuclear & High Hazard 

Operations, June 20, 2013. 
R-2 

[15] CSSG Assessment of Scope of Operations and Criticality Safety Staff Capacity and 

Review of Los Alamos National Laboratory CAP and Metrics for the Nuclear Criticality 

Safety Program, Criticality Safety Support Group, May 2013. 

[16] SBCS-ASMT-13-002, 2Q FY13 Assessment of the Nuclear Criticality Safety Program 

Metrics, Los Alamos National Laboratory, Safety Basis, Criticality Safety, May 8, 2013. 

[17] SB-CS:13-001, 1Q FY13 Assessment of the Nuclear Criticality Safety Program Metrics, 

Los Alamos National Laboratory, Safety Basis, Criticality Safety, February 22, 2013. 

[18] NCS-TECH-07-002, Validation of MCNP5 on the Ganglion Cyst Computer Cluster with 

Various Cross-Section Libraries, Los Alamos National Laboratory, Nuclear Criticality 

Safety Group, September 18, 2007. 

[19] CSM 1516, Validation of MCNP5 (Version 1.30) on Belenos for General Application to 

Plutonium Systems, Lawrence Livermore National Laboratory, Nuclear Criticality Safety 

Division, April 22, 2008. 

[20] Y/DD-1221, Determination of the Upper Subcritical Limit for Criticality Calculations for 

Criticality Safety Analyses, Y-12 National Security Complex, Nuclear Criticality Safety 

Organization, March 2006.