U.S. NUCLEAR REGULATORY COMMISSION July 2015

OFFICE OF NUCLEAR REGULATORY RESEARCH Revision 1

REGULATORY GUIDE Technical Lead

A. Tardiff

Written suggestions regarding this guide or development of new guides may be submitted through the NRC’s public Web site under the 

Regulatory Guides document collection of the NRC Library at http://www.nrc.gov/reading-rm/doc-collections/reg-guides/contactus.html.

 

Electronic copies of this regulatory guide, previous versions of this guide, and other recently issued guides are available through the NRC’s 

public Web site under the Regulatory Guides document collection of the NRC Library at http://www.nrc.gov/reading-rm/doc-collections/. The 

regulatory guide is also available through the NRC’s Agencywide Documents Access and Management System (ADAMS) at 

http://www.nrc.gov/reading-rm/adams.html, under ADAMS Accession No. ML14290A268. The regulatory analysis may be found in ADAMS 

under Accession No. ML12237A124 and the staff responses to the public comments on DG-5038 may be found under ADAMS Accession No. 

ML14288A653. 

REGULATORY GUIDE 5.27 

(Draft was issued as DG-5038, dated March 2014)

SPECIAL NUCLEAR MATERIAL DOORWAY MONITORS

A. INTRODUCTION

Purpose 

The U.S. Nuclear Regulatory Commission (NRC) developed this regulatory guide (RG) to 

describe a method that the NRC staff considers acceptable to implement the search requirement for 

concealed special nuclear material (SNM) applied to personnel, vehicles, packages and all other materials 

exiting a material access area (MAA). 

For holders of a reactor license under Title 10 of the Code of Federal Regulations (10 CFR)

Part 50, “Domestic Licensing of Production and Utilization Facilities” (Ref. 1), a combined license under 

10 CFR Part 52, “Licenses, Certifications, and Approvals for Nuclear Power Plants” (Ref. 2), or a fuel 

cycle facility license under 10 CFR Part 76, “Certification of Gaseous Diffusion Plants” (Ref. 3), having 

the need to possess or use SNM within their facility, the NRC typically has included in their license a 

condition granting a general license to use SNM under 10 CFR Part 70, “Domestic Licensing of Special 

Nuclear Material.”

Applicable Rules and Regulations

The requirements for physical protection found within 10 CFR Parts 50, 52, 70, and 76 refer to 

the physical protection requirements of 10 CFR Part 73, “Physical Protection of Plants and Materials.” 

Part 73 (Ref. 4) requires, in part, in 10 CFR 73.46(d)(9) and 10 CFR 73.60(b), that each individual, 

package, materials and vehicle exiting an MAA is searched for concealed SNM. Specific testing and 

maintenance requirements, as stated in 10 CFR 73.20(b)(4), 10 CFR 73.46(g), and 10 CFR 73.60(d)(1) 

also apply. 

Related Guidance

• Regulatory Guide 5.7, “Entry/Exit Control of Personnel Access to Protected Areas, Vital Areas, 

and Material Access Areas” (Ref. 5)

• NUREG 1964, “Access Control Systems: Technical Information for NRC Licensees” (Ref. 6)
RG 5.27, Rev. 1, Page 2

Purpose of Regulatory Guides 

The NRC issues RGs to describe to the public methods that the staff considers acceptable for use 

in implementing specific parts of the agency’s regulations, to explain techniques that the staff uses in 

evaluating specific problems or postulated accidents, and to provide guidance to applicants. Regulatory 

guides are not substitutes for regulations and compliance with them is not required. Methods and 

solutions that differ from those set forth in RGs will be deemed acceptable if they provide a basis for the 

findings required for the issuance or continuance of a permit or license by the Commission.

Information Collection Requirements

This RG contains information collection requirements covered by 10 CFR Part 73, “Physical 

Protection of Plants and Materials,” that the Office of Management and Budget (OMB) approved under 

OMB control number 3150-0002. The NRC may neither conduct nor sponsor, and a person is not 

required to respond to, an information collection request or requirement unless the requesting document 

displays a currently valid OMB control number. 

B. DISCUSSION

Reason for Revision 

This RG is being revised because it was out-of-date with current related guidance and references 

in the CFR. Related specifications and standards for SNM monitors and metal detectors have been 

updated or developed since the previous revision was issued in 1974. This revision has been developed to 

provide detection practices and criteria that licensees may use to demonstrate compliance with NRC 

regulations in 10 CFR Part 73 and to augment programmatic information within the general reference, 

NUREG-1964, “Access Control Systems: Technical Information for NRC Licensees,” (Ref. 6) issued in 

April of 2011.

Background 

Special nuclear material doorway monitors provide an efficient, sensitive, and reasonably 

unobtrusive way of searching individuals for concealed SNM upon exit from an MAA. With proper 

installation and operation, gram quantities or less of SNM can be detected with a high level of reliability 

while maintaining a low false alarm rate. Portal type walk-through metal detectors are often used in 

conjunction with radiation detection to assure that personnel entering or leaving MAAs are screened for 

metallic nuclear shielding materials.

Theory of Operation

The doorway monitor comprises one or more detector unit(s), associated electronics, and alarm 

logic. The detector units are sensitive to the SNM radiation and responds to the emitted radiation (gamma 

rays and neutrons) by generating electronic current pulses. These pulses are amplified, filtered, and fed to 

alarm logic circuits that interpret the number (or rate) of pulses during a sampling. The alarm logic may 

be either a digital or analog system. In either case, if the rate of pulses exceed a set level, the alarm is 

triggered. Additional information pertaining to detector theory can be found in Knoll’s, “Radiation 

Detection and Measurement.” (Ref.7) 
RG 5.27, Rev. 1, Page 3

General Characteristics

Doorway Monitors

Doorway monitors detect gamma-ray radiation using scintillation or semiconductor detectors. To 

detect neutrons, plastic scintillators or gas-filled proportional counters are used. Geiger-Mueller counters 

have been used in this application; however, their lower intrinsic efficiency renders them less suitable 

than scintillation detectors. Scintillation detectors are often used for discriminating pulses based on 

imparted energy. Plastic scintillation detectors have the advantage of responding well to gamma-ray and 

energetic neutrons whereas the sodium iodide thallium-activated NaI(Tl) scintillation detectors have good 

gamma-ray sensitivity but poor neutron response. Helium-3 (He-3) gas is used in tubes as a proportional 

counter for neutron detection. The trend in industry is to use both scintillation detectors and He-3

detectors for doorway monitor systems.

Detectors are arranged so that a detection area is defined by a plane perpendicular to the line of 

passage of individuals through the doorway monitor. Various arrangements of the detectors are possible. 

However, specific placement of detectors should be based on the need to eliminate areas of no detection.

Commercially available doorway monitors are equipped with an automatic radiation background 

updating system that periodically monitors and averages the background count rate. A doorway monitor 

equipped with an automatic radiation background updating system is also provided with a treadle pad or 

beam break system to indicate that the zone of detection is occupied. When the zone of detection is 

occupied, the radiation level detected by the doorway monitor is compared to the mean background. If 

the level is greater than the mean background by a predetermined trigger level, an alarm is actuated. 

Alarm actuation point is usually determined by comparing the radiation levels within the zone of 

detection while occupied to the sum of the mean background while unoccupied and a factor to account for 

predetermined statistical accuracy.

1

Thus, the condition for an alarm can be written as:

G>B+n(B) 1⁄2

Where B is the mean background, G is the radiation level within the zone of detection while 

occupied and n is a multiplier, usually between 4 and 10.2

Although the automatic background updating system allows unattended use of the doorway 

monitor, for technical reasons, the system may be less effective in certain situations. Techniques to 

prevent this are provided in the regulatory position.

Whether or not a doorway monitor is equipped with an automatic background updating system, 

high background activity will decrease sensitivity. Measuring activity in the zone of detection for longer 

 1 The square root of the mean of a Poisson-distributed quantity is the unbiased estimate of the standard deviation of that 

quantity.

2 Note that, in general, for a count rate system, the condition for alarm should be modified to account for the response

time of the instrument as follows:

G>B+n(B)1/2 (1-e-t/r)

Where t is the counting time and r is the time constant of the instrument. If, as should be the case, t/r>5, the added 

factor is essentially unity.
RG 5.27, Rev. 1, Page 4

periods of time will compensate somewhat for a high radiation background. However, longer 

measurement periods can make the use of the doorway monitor less convenient. Because of the adequate 

radiation detection sensitivity and high-throughput capability associated with processing many personnel 

through the detection system on a daily basis, walk-through pedestrian monitors are the primary SNM 

detection system used in personnel portals at MAAs.

Hand-Held Monitors

Hand-held monitors can use detectors made of NaI(Tl), plastic scintillators, semiconductors, or 

He-3 gas-filled tubes. Commercially available systems have rechargeable batteries that assist in ensuring 

continuous availability. Training the operator of a hand-held monitor is essential. The operator must scan 

an individual in the correct way for a hand-held monitor to be fully effective. In addition, the operator 

must understand the capabilities of the equipment, when the equipment is working within acceptable 

parameters and when it is not.

Radioisotope identification systems that detect radiation with high purity germanium (HPGe) 

detectors can be hand-held. These monitors are commercially available and may have a special cooling 

device, instead of a cryogenic bath, to cool the semiconductor HPGe crystal. Special cooling devices 

(e.g., Stirling cooler) allow a light-weight design useful as a hand held detection system. 

Hand-held monitors complement SNM search operations by enabling a more thorough search of 

an individual to locate the radiation source after a doorway monitor has alarmed, enabling pedestrian 

searches to continue when a doorway monitor is inoperative and, if technically outfitted to do so, identify 

specific radionuclide(s) causing a doorway alarm.

Because of the time required to scan an individual with a hand-held monitor, it is used as a 

secondary SNM detection system at an MAA personnel portal.

Vehicle Monitors

Two types of automatic vehicle monitors presently in use are the vehicle monitoring station and 

the drive-through vehicle monitor. Commercially available vehicle drive-through SNM portals generally 

consist of two vertical cabinets containing both large plastic scintillators and decision -making 

electronics. These scintillators continuously measure the gamma ray background intensity and adjust the 

alarm threshold to maintain a constant nuisance alarm rate. The sensitivity of SNM vehicle monitors vary

for different types of vehicles and depends on the size, spacing, and number of detectors. For an 

individual detector configuration and vehicle, two of the dominate sensitivity factors are the occupancy 

background suppression and shielding provided by the components of the vehicle.3

 

Standards Associated with Monitoring

Selection of equipment, setup, operation calibration, testing and performance evaluation of portal 

monitoring systems should be performed using procedures designed for the specific facility and 

configuration. Guidance that pertains to the use of radiation detection and metal detection 

instrumentation is available from several standards organizations. The NRC staff finds that the following 

guidance, which has been successfully used by SNM licensees and is available from the American 

Society for Testing and Materials (ASTM), Conshohocken, Pennsylvania, acceptable for use: 

 3 LA-UR-96-4505: “An Optimized International Vehicle Monitor,” (Ref. 8) 
RG 5.27, Rev. 1, Page 5

• ASTM C1189-11, “Standard Guide to Procedures for Calibrating Automatic Pedestrian 

SNM Monitors.” (Ref. 9) 

• ASTM C1112-99 (2005), “Standard Guide for Application of Radiation Monitors to the 

Control and Physical Security of Special Nuclear Material.” (Ref. 10) 

• ASTM C1237-99 (2005), “Standard Guide to In-Plant Performance Evaluation of HandHeld SNM Monitors.” (Ref. 11) 

• ASTM C993-97 (2012), “Standard Guide for In-Plant Performance Evaluation of 

Automatic Pedestrian SNM Monitors.” (Ref. 12) 

• ASTM C1270-97 (2012), “Standard Practice for Detection Sensitivity Mapping of InPlant Walk Through Metal Detectors.” (Ref. 13) 

• ASTM C1269-97 (2012), “Standard Practice for Adjusting the Operational Sensitivity 

Setting of In-Plant Walk-Through Metal Detectors.” (Ref. 14) 

• ASTM C1309-97 (2012), “Standard Practice for Performance Evaluation of In-Plant 

Walk-Through Metal Detectors.” (Ref. 15) 

In addition, ASTM C1236-99 (2005), Standard Guide for In-Plant Performance Evaluation of 

Automatic Vehicle SNM Monitors (Ref. 16) was withdrawn in 2014, but can be used by licensees as a 

development tool.

Harmonization with International Standards

The International Atomic Energy Agency (IAEA) has established a series of safety guides and 

standards constituting a high level of safety for protecting people and the environment. IAEA safety 

guides present international good practices and increasingly reflects best practices to help users striving to 

achieve high levels of safety. Pertinent to this RG, “IAEA Nuclear Security Series No. 13, Nuclear 

Security Recommendations on Physical Protection of Nuclear Material and Nuclear Facilities,” issued 

January 2011, (Ref. 17) et. al., addresses considerations necessary for a nuclear material security program. 

While the NRC has an interest in facilitating the harmonization of standards used domestically and 

internationally, the NRC does not specifically endorse the IAEA document, and is only acknowledging 

that it may be useful as a reference for general information.
RG 5.27, Rev. 1, Page 6

Documents Discussed in Staff Regulatory Guidance

This RG endorses the use of one or more codes or standards developed by external organizations, 

and other third party guidance documents. These codes, standards and third party guidance documents 

may contain references to other codes, standards or third party guidance documents (“secondary 

references”). If a secondary reference has itself been incorporated by reference into NRC regulations as a 

requirement, then licensees and applicants must comply with that standard as set forth in the 

regulation. If the secondary reference has been endorsed in a RG as an acceptable approach for meeting 

an NRC requirement, then the standard constitutes a method acceptable to the NRC staff for meeting that 

regulatory requirement as described in the specific RG. If the secondary reference has neither been 

incorporated by reference into NRC regulations nor endorsed in a RG, then the secondary reference is 

neither a legally-binding requirement nor a “generic” NRC approval as an acceptable approach for 

meeting an NRC requirement. However, licensees and applicants may consider and use the information 

in the secondary reference, if appropriately justified and consistent with current regulatory practice, 

consistent with applicable NRC requirements such as 10 CFR 50.59.

C. STAFF REGULATORY GUIDANCE

1. Considerations for SNM Doorway Monitors

a. General

(1) Metal detectors should be used in conjunction with an SNM doorway monitor as an SNM 

detection system and can be one of the two required separate searches for concealed 

SNM (10 CFR 73.46(d)(9)). The metal detector unit should be installed in the pedestrian 

passageway as described in RG 5.7, “Entry/Exit Control of Personnel Access to Protected 

Areas, Vital Areas, and Material Access Areas” with the SNM monitor in such a way that 

objects cannot be passed over, around, or under the detection area without being 

appropriately searched. The entire process begins when the individual, package, or other 

item approaches the monitoring area and ends when the individual, package or other item 

is exiting the monitoring area after the completion of a monitoring event. 

(2) Alarm actuation for detectable metal mass should be the amount necessary to shield SNM 

that would allow a protracted theft of a formula quantity of strategic SNM to occur before 

the inventory process identifies it as missing.

(3) The detector elements should be designed and positioned so that detection sensitivity is 

as uniform as possible over the zone of detection; in no case should any area within the 

zone of detection not be able to detect SNM.

(4) Power, sensitivity, and other controls of the doorway monitor and metal detector should 

be tamper-safe when unattended. Doorway monitors and metal detectors that are secured 

behind locked and alarmed doors when unattended is an acceptable alternative measure to 

implementing tamper- safe devices on the SNM monitoring system. 

(5) Metal and SNM detection equipment should be provided with uninterruptible power 

sources and/or emergency generator power.

(6) Signal lines connecting alarm relays to the alarm monitors for both metal and SNM 

detectors should be supervised electronically or by direct surveillance to detect 

tampering.
RG 5.27, Rev. 1, Page 7

(7) Some doorway monitors may require an individual to occupy the detection area for a 

specified time (e.g., longer than what a normal walking pace would provide). In this 

case, the doorway monitor should be provided with a treadle pad and a timer to ensure 

that the zone of detection is occupied for the requisite time. Audible and visual alarms

should actuate if the individual being searched does not occupy the detection area for the 

entire count period.

(8) The doorway monitor should be equipped with a high-background radiation alarm, which 

will announce if the measurement of the radiation background exceeds the appropriate 

maximum permissible background. The doorway monitor should not be used during 

periods of high background radiation. Calibration and determination of allowable 

background thresholds should be done in accordance with ASTM C1189-11, (Ref. 9)

 

(9) System specifications guidance for specific radioisotopes are identified below. See 

ASTM C1112-99(2005), (Ref. 10) for supporting information. 

(a) Plutonium-239. A doorway monitor used to detect plutonium (Pu) should be 

capable of detecting 0.5grams of plutonium with an isotopic content of at least 

93 percent Pu-239 and less than 6.5 percent Pu-240. The Pu should contain less 

than 0.5 percent impurities. The form of the material should be a metallic sphere 

or cube. The impact of Am-241, a Pu decay product that will build up over time 

and emit increasing amounts of 60-keV gamma radiation, must be minimized by 

including a cadmium filter 0.04 cm to 0.08 cm thick as part of the source 

encapsulation. Protective encapsulation should be in as many layers as local 

rules require of a material such as aluminum (≤0.32 cm thickness) or thin (≤0.16 

cm thickness) stainless steel or nickel that minimize unnecessary radiation 

absorption. The source should be encased in a minimum of 3 mm brass and 

detected at a 50 percent probability of detection with a 95 percent confidence 

limit. The false alarm rate should be less than 0.1 percent.

(b) Uranium-235. A doorway monitor used to detect uranium-235 (U-235) should 

be capable of detecting highly enriched (i.e., 20 percent or more) uranium 

containing at least 93 percent U-235 and less than 0.25 percent impurities. The 

form of the material should be a metallic sphere or cube. Encapsulation should 

be applied in such manner that it minimizes unnecessary radiation absorption in 

the encapsulation. The source should be encased in a minimum of 3 mm brass 

and detected at a 50 percent probability of detection with a 95 percent confidence 

limit. The false alarm rate should be less than 0.1 percent.

(c) Uranium-233. Adequate sensitivity for uranium-233 (U-233) may be 

demonstrated by meeting the detection requirements for U-235. 
RG 5.27, Rev. 1, Page 8

2. Operations with Doorway and Hand-Held Monitors

In general, doorway monitors are the primary method used to search for concealed SNM, 

hand-held monitors are secondary, and a physical search is tertiary. Doorway monitors should be 

used in locations with minimum background radiation and minimum background radiation 

fluctuation. If circumstances dictate the use of a doorway monitor in an area of high background 

radiation, sufficient shielding should be provided to maintain necessary sensitivity.

a. The procedures, or changes to procedures developed to implement requirements of 10 CFR 73.46 

should be prepared sufficiently in advance of intended implementation to provide verification of 

satisfactory performance. 

b. The plan for metal detection equipment functionality and performance testing periodicity, 

procedures, and test sources should be submitted to the NRC for approval within 360 days for 

licensed operating facilities, 180 days before revising existing licensee SNM search programs, 

and 180 days before initial start of operations for newly licensed facilities. 

c. During use, the doorway monitor system should check the radiation background and adjust the 

measurement offset at least every 15 minutes.

d. Doorway monitors shall be attended by two armed guards at an MAA (10 CFR 73.46 (d)(9)) 

within a facility containing a formula quantity of strategic SNM. The two armed guards may 

consist of a guard manning the SNM monitoring system and the other providing oversight of the 

SNM monitoring system activities by residing in an adjacent protective enclosure. Doorway 

monitors should be attended at non-power reactors.

e. Each individual to be checked should, in turn, enter the doorway monitor detection area and be 

required to remain still long enough for the device to operate properly. 

f. With the individual in the doorway monitor detection area, an alarm should audibly and visually 

announce in the vicinity of the monitor if the activity in the detection area exceeds the set alarm 

threshold for radiation, possibly indicating the presence of SNM. 

g. When a doorway monitor signals an alarm, the individual generating the alarm should pass 

through the monitor a second time to confirm the signal. If the second pass through the SNM 

monitor does not result in a detection, then a third pass through the monitor should be conducted 

to verify no detection. If the second pass through the monitor also generates an alarm, the 

individual should be retained and subjected to a body search, typically with a hand-held monitor, 

as described in ASTM C1237-99 (2005), (Ref. 11) to locate and identify the source of the signal. 

If the hand-held monitor does not confirm the alarm signals generated by the doorway monitor, 

the hand-held monitor should be tested against a known source to confirm it is working properly. 

If it responds to the source in the anticipated manner, it should be concluded that the doorway 

monitor should be tested, repaired if necessary, and retested before returning to service. The 

individual generating the alarm should be released after confirmation that no SNM was detected. 

If detection is suspected to be from SNM contamination, health physics personnel should verify 

this finding. A monitoring flow diagram is provided in Figure 1. 

h. A hand-held SNM monitor should be used when the doorway monitor is not functioning as 

intended. Search personnel should be trained on the correct use of the hand-held monitoring. A 

hand-held monitor should have the capability to identify specific radioisotopes.
RG 5.27, Rev. 1, Page 9

3. Physical Searches and Training

a. A physical search for concealed SNM should be conducted as necessary.

b. To enhance the probability of detection, random searches for concealed SNM at the protected 

area boundary may be conducted, including searches of hand-carried items.

c. At facilities with formula quantities of strategic SNM, personnel having search duties and 

responsibilities must be trained and qualified.(10 CFR 73.45(g)(1)(i)).

Pedestrian in 

Monitoring Zone 

Sets Off Alarm at 

First and Second 

Pass

Hand-Held 

Detector Search 

for Source

Nuclide?

SNM?

Tactical Response 

by Security

Release 

Pedestrian

Release 

Pedestrian

Document False 

Alarm for Later 

Investigation 

Yes

No

Yes

No

Document Type of 

Nuclide Detected 

Figure 1 Flow diagram for SNM searches
RG 5.27, Rev. 1, Page 10

4. Calibration, Testing, Maintenance, and Operating Instructions

a. Calibration

Doorway and hand-held monitors should be calibrated with a source of the amount, 

configuration, and variety of SNM to be detected. Doorway and hand-held monitor calibration 

should be conducted in accordance with Reference 7 or as recommended by the manufacturer. 

Calibration should be conducted before initial use and after monitor repair or maintenance. 

Calibration should be conducted at least every three months. As a quality assurance measure, 

consideration should be given to having SNM calibration standards traceable to certified 

reference standards or materials.

b. Testing

(1) Doorway, Hand-Held and Vehicle SNM Monitors

Methods of performance testing doorway and hand-held monitors are found within 

ASTM C993-97(2012), (Ref. 12) and Reference 9 (as well as reference 13). These

references may be used to develop instructions for testing SNM monitors to assure 

system specifications are met. Daily testing should be a simple functional test (i.e. 

operational test) to assure the detector is working. Daily testing should be performed 

during each shift, or once per day if there is only one shift. Reference 9 describes an 

acceptable approach for daily testing. As described in reference 9 and reference 11, 

testing sources may be different than those used during calibration. 

(2) Metal Detectors

Sensitivity mapping and operational sensitivity testing methods are described within 

ASTM C1270-97 (2012), (Ref. 13), ASTM C1269-97 (2012), (Ref 14) and ASTM 

C1309-97 (2012), (Ref 15). The references may be used to develop instructions for 

performance testing the metal detection system used to search for concealed, shielded 

strategic SNM. The metal detection system should be capable of detecting the minimum 

metal shielding concealed anywhere on an individual three times out of three trials. 

Performance testing should be conducted at least once every three months. The 

performance testing should include passing the minimum metal test source through a 

honeycomb configuration test apparatus that covers the entire detection area as described 

in references 13, 14 and 15. The honeycomb channels should be a maximum of 6 inches 

by 6 inches in dimension. The test source should be passed through the detection area as 

close as possible to the same rate (speed) as a pedestrian walking through the metal 

detector unit. Attaching the metal test source to a wooden dowel rod to conduct this test 

can facilitate the effective rate of passage of the metal source through the honeycomb test 

apparatus. A detection of the metal test source in each of the honeycomb test channels 

constitutes an acceptable performance test. Daily operability testing should be conducted 

once per shift, or at least daily.

c. Maintenance

Metal detection and SNM monitoring equipment shall be maintained to be operable and effective 

as intended (10 CFR 73.20(4), 10 CFR 73.46(g), and 10 CFR 73.60(d)(1)).
RG 5.27, Rev. 1, Page 11

d. Operating Instructions

Operating instructions should be available near the search activity. The procedural elements 

listed below should be included in the procedures for the search activity. A management system 

shall provide for the development, revision, implementation, and enforcement of security 

procedures (10 CFR 73.46 (b)(3)). Written procedures detailing the duties of search personnel for 

operation of SNM monitors and metal detection equipment shall be developed 

(10 CFR 73.46 (b)(3)(i)). Procedures should address the following: 

• metal detection threshold criteria,

• test sources and their use,

• monitor background reduction and sensitivity,

• searching pedestrians with doorway and hand-held monitors,

• recording, retention, and analysis of monitor performance data,

• recording and resolution of alarm events, 

• quarterly performance testing, 

• daily operational testing,

• environmental operating constraints (e.g., temperature and humidity),

• search operations during an emergency or loss of power,

• maintenance of monitors and metal detection equipment,

• security for the system equipment, communications, software, and data,

• training for operating personnel, and

• documentation requirements for authorized removals of SNM.

D. IMPLEMENTATION

The purpose of this section is to provide information on how applicants and licensees4 may use 

this guide and information regarding the NRC’s plans for using this RG. In addition, it describes how the 

NRC staff complies with the Backfit Rule found in 10 CFR 50.109(a)(1), 10 CFR 70.76(a)(1), and 

10 CFR 76.76(a)(1) or any applicable finality provisions in 10 CFR Part 52.

Use by Applicants and Licensees

Applicants and licensees may voluntarily5 use the guidance in this document to demonstrate 

compliance with the underlying NRC regulations. Methods or solutions that differ from those described 

in this RG may be deemed acceptable if they provide sufficient basis and information for the NRC staff to 

verify that the proposed alternative demonstrates compliance with the appropriate NRC regulations. 

Current licensees may continue to use guidance the NRC found acceptable for complying with the 

identified regulations as long as their current licensing basis remains unchanged. The acceptable 

guidance may be a previous version of this RG. 

Licensees may use the information in this RG for actions which do not require NRC review and 

approval. However, voluntarily using the subject matter in the guidance may change the facilities 

 4 In this section, “licensees” refers to holders of, and the term “applicants” refers to applicants for, the following: (1) 

special nuclear material licenses under 10 CFR Part 70; (2) operating licenses under 10 CFR Part 50; (3) combined 

licenses under 10 CFR Part 52; and (4) certificates of compliance or approvals of a compliance plan for gaseous 

diffusion plants under 10 CFR Part 76.

5 In this section, “voluntary” and “voluntarily” means that the licensee is seeking the action of its own accord, without 

the force of a legally binding requirement or an NRC representation of further licensing or enforcement action. 
RG 5.27, Rev. 1, Page 12

security plan such that NRC review may be required under the provisions of 10 CFR Part 50.54, 

10 CFR Part 70.32 or 10 CFR Part 76.68, and should be evaluated prior to incorporating the methods into 

the security plans. Licensees may use the information in this RG or applicable parts to resolve regulatory 

or inspection issues. 

Use by NRC Staff 

The NRC staff does not intend or approve any imposition or backfitting of the guidance in this 

RG. The NRC staff does not expect any existing licensee to use or commit to using the guidance in this 

RG, unless the licensee makes a change to its licensing basis. The NRC staff does not expect or plan to 

request licensees to voluntarily adopt this RG to resolve a generic regulatory issue. The NRC staff does 

not expect or plan to initiate NRC regulatory action which would require the use of this RG. Examples of 

such unplanned NRC regulatory actions include issuance of an order requiring the use of the RG, generic 

communication, or promulgation of a rule requiring the use of this RG without further backfit 

consideration.

During regulatory discussions on plant specific operational issues, the staff may discuss with 

licensees various actions consistent with staff positions in this RG, as one acceptable means of meeting 

the underlying NRC regulatory requirement. Such discussions would not ordinarily be considered 

backfitting even if prior versions of this RG are part of the licensing basis of the facility. However, unless 

this RG is part of the licensing basis for a facility, the staff may not represent to the licensee that the 

licensee’s failure to comply with the positions in this RG constitutes a violation. 

If an existing licensee voluntarily seeks a license amendment or change and (1) the NRC staff’s 

consideration of the request involves a regulatory issue directly relevant to this revised RG and (2) the 

specific subject matter of this RG is an essential consideration in the staff’s determination of the 

acceptability of the licensee’s request, then the staff may request that the licensee either follow the 

guidance in this RG or provide an equivalent alternative process that demonstrates compliance with the 

underlying NRC regulatory requirements. This is not considered backfitting as defined in 

10 CFR 50.109(a)(1), 10 CFR 70.76(a)(1), or 10 CFR 76.76(a)(1) or any applicable finality provisions in 

10 CFR Part 52.

If a licensee believes that the NRC is either using this RG or requesting or requiring the licensee 

to implement the methods or processes in this RG in a manner inconsistent with the discussion in this 

Implementation section, then the licensee may file a backfit appeal with the NRC in accordance with the 

guidance in NUREG-1409, “Backfitting Guidelines,” (Ref. 18) and the NRC Management Directive 8.4, 

“Management of Facility-Specific Backfitting and Information Collection” (Ref 19). 
RG 5.27, Rev. 1, Page 13

REFERENCES6

1. U.S. Code of Federal Regulations, “Domestic Licensing of Production and Utilization Facilities,” 

Part 50 (10 CFR 50), Title 10, “Energy.”

2. 10 CFR 52, “Licenses, Certifications, and Approvals for Nuclear Power Plants,” Title 10, 

“Energy” 

3. 10 CFR 76, “Physical Protection of Plants and Materials,” Title 10, “Energy” 

4. 10 CFR 73, “Certification of Gaseous Diffusion Plants,” Title 10, “Energy” 

5. U.S. Nuclear Regulatory Commission (NRC), “Entry/Exit Control of Personnel Access to 

Protected Areas, Vital Areas, and Material Access Areas,” Regulatory Guide (RG) 5.7, 

Washington, DC, Agencywide Document Access and Management System (ADAMS) 

Accession No. ML003739976.

6. NRC, “Access Control Systems: Technical Information for NRC Licensees,” NUREG-1964, 

Washington, DC. (ML1115A078)

7. Knoll, Glenn F., “Radiation Detection and Measurement,” 4th ed., John Wiley and Sons7, 2010.

8. LA-UR-96-4505, “An Optimized International Vehicle Monitor,” R. L. York, D. A. Close, and P. 

E. Fehlau, Los Alamos National Labs, Los Alamos, NM (1997).8

9. American Society for Testing and Materials (ASTM) C1189-11, “Standard Guide to Procedures 

for Calibrating Automatic Pedestrian SNM Monitors,” West Conshohocken, PA. 9

10. ASTM, C1112-99(2005), “Standard Guide for Application of Radiation Monitors to the Control 

and Physical Security of Special Nuclear Material,” West Conshohocken, PA.

11. ASTM C1237-99(2005), “Standard Guide to In-Plant Performance Evaluation of Hand-Held 

SNM Monitors,” West Conshohocken, PA.

12. ASTM C993-97(2012), “Standard Guide for In-Plant Performance Evaluation of Automatic 

Pedestrian SNM Monitors,” West Conshohocken, PA.

 6 Publicly available NRC published documents are available electronically through the NRC Library on the NRC’s 

public Web site at http://www.nrc.gov/reading-rm/doc-collections/ and through the NRC’s Agencywide Documents 

Access and Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html The documents can also be 

viewed online or printed for a fee in the NRC’s Public Document Room (PDR) at 11555 Rockville Pike, Rockville, 

MD. For problems with ADAMS, contact the PDR staff at 301-415-4737 or (800) 397-4209; fax (301) 415-3548; or 

e-mail pdr.resource@nrc.gov.

7 Copies of this publication and, or current edition are available thru the Wiley website at: http://www.wiley.com/

8 Copies of this publication are available thru the US Department of Energy, Office of Scientific and Technical 

Information (OSTI) website at: http://www.osti.gov/scitech/servlets/purl/444040

9 Copies of American Society for Testing and Materials (ASTM) standards may be purchased from ASTM, 100 Barr 

Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959; telephone 610-832-9585. Purchase information 

is available through the ASTM Web site at http://www.astm.org.
RG 5.27, Rev. 1, Page 14

13. ASTM C1270-97(2012), “Standard Practice for Detection Sensitivity Mapping of In-Plant Walk 

Through Metal Detectors,” West Conshohocken, PA.

14. ASTM C1270-97(2012), “Standard Practice for Detection Sensitivity Mapping of In-Plant Walk 

Through Metal Detectors,” West Conshohocken, PA.

15. ASTM C1269-97(2012), “Standard Practice for Adjusting the Operational Sensitivity Setting of 

In-Plant Walk-Through Metal Detectors,” West Conshohocken, PA

16. ASTM C1309-97(2012), “Standard Practice for Performance Evaluation of In-Plant 

Walk-Through Metal Detectors,” West Conshohocken, PA

17. ASTM C1236-99(2005), “Standard Guide for In-Plant Performance Evaluation of Automatic 

Vehicle SNM Monitors,” (Withdrawn 2014) West Conshohocken, PA

18. International Atomic Energy Agency (IAEA), “IAEA Nuclear Security Series No. 13, Nuclear 

Security Recommendations on Physical Protection of Nuclear Material and Nuclear Facilities,” 

Vienna, Austria, January 2011.10

19. NRC, “Backfitting Guidelines,” NUREG-1409, Washington, DC. (ML032230247)

20. NRC, “Management of Facility-specific Backfitting and Information Collection,” Management 

Directive 8.4, Washington, DC. (ML12059A460)

 10 Copies of International Atomic Energy Agency (IAEA) documents may be obtained through their Web site: 

WWW.IAEA.Org/ or by writing the International Atomic Energy Agency P.O. Box 100 Wagramer Strasse 5, A-1400 

Vienna, Austria. Telephone (+431) 2600-0, Fax (+431) 2600-7, or E-Mail at Official.Mail@IAEA.Org 
RG 5.27, Rev. 1, Page 15