A. INTRODUCTION 

Paragraph 50.34c) of 10 CFR Part 50, "Licensing 

of* Production and Utilization Facilities," requires each 

application for a liccn 'se to operate a production or 

utilization facility and paragraph 70.22(b).of* 10 CIFR 

Part '70. "Special Nuclear Material," requires. certain 

applications for a license to possess or use special nuclear 

material (SNM) to include a physical security plan to 

demonstrate how thc applicant plans to meet' the 

physical protection requirements of 10 CFR Part 73, 

"~Physical Protection of Plants and Materials." 

Paragraphs 50.54(p) and 70.32(e) require existing 

licensees licensed under Part 50 and certain licensees 

licensed under Part 70 who have noit submitted a 

physical security plan to submit such a plan to the 

C~ommnission for approval. Section 73.40 of 10CFR Part 

73 requires that certain licensees provide. physical 

protectioni against industrial sabotage and against theft 

of SNM at the fixed sites where licensed activities 'are 

conducted. 

Locks are acceptable devices to be used in adhering 

to the physical protection requirements identified above 

to assist in controlling access to areas, facilities, and 

nmaterials through doors, gates, container lids, and similar 

material or personnel access points, and are Iconsidered 

essential components Of a physical barrier. This guide 

provides criteria acceptable to the Regulatory Staff for 

the selection and use of commercially available locks in 

the protection of facilities and SNM. 

B. DISCUSSION 

Loicks are very important components of a physical 

barrier. Their effectiveness, however, lies in their use in 

conjunction with other security measures su6h as 

intrusion alarm systems and seals. Although some locks

November 1973 

IDE

are diffieult to pick or manipulate, no lock can claim to 

Gmearnaiipuation proof." Because of the large variety of' 

Iocks' ivailable, it is necessary to subdivide the discussion 

"`on locks into the following types:.(1) combinat~ion, (2) 

kcy, (3) electrical, and (4) pushbutton mechanical locks. 

The discussion of each type includes a general section on 

advantages and disadvantages, a section on control over 

the locks, and a section on the applicable standards and 

specifications. 

I.: Combinatlon Locks 

a. General. It ~is desirable that a combination 

,lock be designed to afford a choice of a large number of 

combinations. The number of combinations is 

'Ic t.ý miincd by the'number of tumbler wheels in the lock 

mechanism and the number of graduations on the dial. 

High-quality locks 'usually have 100 divisions on the dial 

and -three tumbler wheels; such a lock is capable of 

providing a theoretical 10'- combina13tions, which in 

practice .reduces to -tens of thousands. Sonic 

'Combination locks are made with four tumbler wheels, 

but it is considered that the added number of 

combinations. possible does not proportionally impro%0 

the security of the lock and does increase the 

inconvenience~of,dialing the combination. 

It is. desirable for a combination lock to be 

designed'so its, combinatlion can be easily changed but at 

the same time be tamper resistant. The combination of 

,some locks can be changed by disassembly of' the 

tumbler wheel, pack and relocation of screws or pins. In 

,this method the effective number or combinations 

possible is res'trled. Another method involves taking 

apart, the wheet pack and resetting an insert in each 

whiel.'Irhis method requires, substantial skill on the part 

of he operaf r. The most desirable method of changing 

a combination is ty a special key which requires minimal 

training o( the' operator and provides a mn'aximumn 

number of combinations. The special key is inserted in

USAEC REGULATORY GUIDES Copies of publstid iuidt may be ebtseumd by t~etmmsu he dwo.sons ~efsmsd Ill IMw US. Ato= WcEoe -onlsn Wahngton. D.C. 20545. 

Ruaouloory Guides we Issued to deoscrace and make ovallgtle go I.,. pubic Attention: Ol,.ctor 9RmltrySedre C uset and suggestions for. 

smathods, acceptabie to the. AIEC Repulatory staff of implemesstinq Wecit 11a"no .4 spi osen waninthanI mmuade we encouraged amid shoulid be sen to the Sectotars, 

tim Comm111460's rem~lultlom. to 404ae~1 techniques musd by 1w staff on of also Cotonissien, US. Atomic 6u.vCommission, Wedthngton. D.C. 20615, 

esmlueting specific problems or postulated accidmnts. or to provide guiqens. to Attention -Chilef.PublicProceedingsStff. 

applicants. Regulatory Guides wea not substi wita hr mqgulshlons end N No iipnm omth them, is not reclired. Mothoda end soltitons different fom thI wI Saot on The5 guede am issued Im the following tan broad divisions: 

sheil umds will be acceptable if tlmey lpow. a basis #or few findingi reQuisrte to 

11wmiued m onmnen oa erit or lmcene by the Commintsion. I Power Rosctort 0. Products z. Remairds and Test Reactors 7. Transportaitoin 3. Fuels and Matalriela Pacilitres U. Occupat~onal Health 

Publasied gutdot vall be reme~nd pooodscsmly. es aopropo~ts. to accommnodate 4. Environmental end Sitime 9. Antitrust Revew" 

commn"nt and somaelect no5w mnfornmotmn or esperlence. 5. Materials end Plant Protection SO. General

U.S. ATOMIC ENERGY COMMISSION 

r~REGULATORY, GU / DIRECTORATE OF REGULATORY STANDARDS 

REGULATORY GUIDE 5.12 

GENERAL USE OF LOCKS IN THE PROTECTION AND CONTROL OF 

FACILITIES AND SPECIAL NUCLEAR MATERIALS
the hack of lhe lock case ito ,clea- the wheels from: their 

presenlt combinalion while a new combination Is 

imposed by dialing. 

The 'nhiaigi ii1 .•,el hocIti cans he 

'oves Ily de:rllhiilu l hy usig a tadiographic technique. 

Rcsista•ce it' I his is o lallack is designcd into certain 

locks by wi ilhilg nuilcials in Use munechanism that are 

11111 easily aadiogr: pMIed. V.g.. plastcS. 

(Co ihil a lioli locks are vulnerable to 

cemanpromise if the hack of the lock is readily available, 

e.g.. when the lockable access is open. Removing the 

brck cover from the lock usually allows the combination 

to be determined. The combinations of some key-change 

locks can be changed directly when the lock is in the 

open- position, while other must have the existing 

combination redialed to a different index when the 

access is in the open position to permit the combination 

change. The former type permits an intruder to make a 

quick change of the combination to one of his own 

choosing; this would permit him to enter following the 

closing of the lock and would deny entry to the user. 

For these reasons it is desirable to protect the back of 

the lock by back plates or other devices. 

High-quality combiination locks are designed 

for use in two basic forms: (I) in a lock case to be 

mounted on or into a door as a mortise or rim lock and 

(2) as a padlock. 

Protection against forcible attack of a mortise 

elr rin-mounted lock can be increased if the lock is 

provided with hardened steel plates and If the lock is 

designed with relocking triggers or devices that deadlock 

the bolt or bolt-actuating mechanism. 

Combination padlocks are not vulnerable to 

the usual rapping techniques and are usually resistant to 

manipulation. However, common combination padlocks 

made of a •cast aluminum alloy are without great 

strength, have little resistance to forcible attack, and are 

not weather resistant. There are others that are weather 

resistant but offer little protection against attack. 

b. Combimtion Lock Control. The mint 

important aspect of lock control for comnbinatlon locks 

is the protection of the combination. It Is desirable to 

changb the combination of a lock every time that a 

person who knows the combination no longer requires it 

as a result of termination or reassignment of duties. This 

would assure that only those Individuals actually 

required to gain access would know the combination. 

Losing the combination of a manipulation. 

proof, wdl-dsigned lock in a high-rated door is an 

expemive dtlation. This can be prevented by keeping a 

record of the combination in another location which is 

as secure as the place protected by the lock.

Combin;tlion locks can be set t) a single 

number to simplify the daily chore ofopeni.g, but this 

is.a very poor practice since it reduces the se'urity ol the 

lock. Frequently four-wheel locks are set to only three 

different numbers for ease tf opening. This deifcats thw 

purpose of the Iourth wheel but it is not considercd 

serious since the number of remaining combination 

choices is considered adequate. It is not reconinicnded 

thal one select combinations in common sequences and 

multiples of ten. It is also not generally recommended 

that the last number of a combination be set close to 

zero because in some cases the lock can jam. 

c. Standards and Specificatiomn. A standard for 

three. or four-tumbler combination locks issued by 

Underwriters' Laboratories, U,-768, "Combination 

Locks,"' covers "combination locks designed for 

attachment on doors of safes, cheits, vaults, and' the like 

to provide a means of locking the boltwork against unauthorized opening." Quality assurance provisions covering the description, examination, and testing of the 

product am included through the UL Label Service. A 

Federal Specification issued for combination padlocks. FF-P-IIOF, 'Padlock, Changeable Combination 

(Resistant to Opening by Manipulation and Surreptitious 

Attack),' 'Includes quality assurance provisions for 

design, materials, and performance testing. 

2. Key Locks 

a. GeneraL As in the case of combination locks 

It is desirable for a key lock to be capable of being set 

for a larp, number of different kiys. A high-quality six-pin lock with 10 key cutting levels per pin potentially permits 106 different keys to be used. 

However, this large number of key cuts is not as useful 

as a larIp number of combinations because less 

time.consuming techniques for defeating key locks .are 

available. Nevertheless, there Is value In specifying at 

least 10 key cuts because it requires careful 

construction of the lock. 

It is important that the key 'c60 required to 

open a lock (bitting of a lock) be changeable to permit changes whenever keys are lost or an employee having 

access to a key is reassigned to other duties or 

'Copvie nay be obtained from the offie and testing stations of Underwriters' Laboratories, Inc located at the 

following addreses: 207 East Okle Street, Odcag, ill. 60611; 333 Plnpften Road, North1kok., 1IL 60062; 1285 Waft 

Whitman Road, Melille, I, N.Y. 11746; 1655 Scott 

BouevUrd, Santa Clara. Calif. 95050. 

IC6pies may be- obtained from busizess service centers of 

the General Services Adnin, Reglonal Omca located in 

tih follwtg ili: = M iq, lieNew York, N.Y.; Washin0om, D.C.; Ft. WWOmTex birce. Cob.; S&Ps :ranchc, Calif.; Atlanta, Ca. G"C IVI; Kaxua City, Me Los Arspim Calif.; Settile. Wash.

5.I12.2
terminated. ('hanging the hitting of a lock in' be 

accomplished usually by changing pins, wafers, or lcvers. 

To case the task of a bitting change, some locks have 

cores that are removable for replacement by means of a 

special key called a "control key." If all the locks in a 

given facility are keyed to the same.control key, the 

locks are virtually master keyed because, with the core 

removed, the problem of opening the lock is elementary. 

Master keying is undesirable from a security 

point of view because disassembly and inspection of any 

lock In the system by a competent person provides 

access to all the other locks in the master-keyed system, 

and because termination of an employee who had access 

to a master key would require changing the bitting of all 

locks set for his master key. The changing of the bitting 

of a large number of locks can be costly, but the 

convenience of master systems is such that there is 

strong pressure for using them. A compromise in this 

conflict between convenience and security may be to use 

a nonmastered set of locks for protected areas, material 

access areas, vital areas, and access to vital equipment 

and to permit master key sets for other less sensitive 

areas. 

It is necessary for a lock to have some 

resistance to picking and impressioning (a method used 

to prepare a key by the impressions of the bitting of a 

lock on a blank key). In general, this resistance can be 

provided by precision machining of the mechanisms or 

by special design features such as side bars, odd-shaped 

pins or a large number of levers. 

Protection of key locks against forcible attack 

can be enhanced by the use of hardened steel plates in 

front of the pins or side bars. 

It is essential for a bolt of a lock to be 

retained in the locked position by positive means (dead 

bolt). In some locks, the bolt is held in a locked position 

by a spring only. This permits. in the case of padlocks, 

the use of appropriate rapping or shimming techniques 

and, in the case of door locks, the opportunity to 

surreptitiously retract the bolt without the use of force. 

b. Lock Control. The security of an access 

control system based on key locks depends on complete 

denial of keys to unauthorized persons. It is essential to 

have a record of each key and the names of individuals 

to whom keys have been issued and to check all keys at 

periodic intervals. 

A common weakness in mastered key systems 

is the lack ot accountability of lock cylinders. To correct 

this situation, it would be necessary to require a control 

system involving the accountability of every mastered 

lock cylinder having the bitting in present use either for 

the master or, in the case of removable cores, the control 

key.

c. Standards and Specifications. A standard t'oi 

key locks has been issued by Underwriters' Laboratories. 

UL-437, "Key Locks."' and lnclud quality assurance 

provisions through the UL. Label Service. Interim 

Federal Specification FF-P-001480 (GSA-FSS), 

"Padlock, Key Operated (Resistant to Opening by 

Force, Pick, and Bypass Techniques)," 2 covers two 

types of key-operated dead-bolt padlocks: the exposed 

shackle and the ..shrouded shackle. (4ility assurance 

provisions concerning the design, materials, and 

qualification testing are included. 

3. Electric Locks 

a. General. In the most popular electric locks, a 

signal generated by magnetized elements in a plastic card 

or by sequential activation of buttons is compared with 

a stored code to activate an electrically operated door 

strike, in some cases the magnetic card, and pushbutton 

systems are used in coincidence. Combined card and 

pushbotton systems provide, in general, higher security 

than card-only systems. 

The advantages of the electric lock are 

isolation of the part containing the code from the 

r "posed part of the lock, versatility of programming, 

afid ease of integration into alarm systems. 

Magnetic card systems have some of the 

problems of common key locks because a lost or stolen 

card can be used by an unauthorized person. Howeve%, 

reproduction of a card is more complicated than 

reproduction of a metal key. 

Pushbutton systems require memorization of 

a few digits, usually four, and require more time to 

operate than the magnetic card system. Although the 

number of possible combinations usually is smaller than 

in the combination lock system, quality electric 

pushbutton systems compensate for this by 

incorporating devices which prevent trial and error 

methods of surreptitious attack by activating an alarm 

after a number of unsuccessful attempts or by 

introducing a delay after each unsuccessful attempt 

which prevents operation of the lock for a short period 

of lime. 

It is desirable for an electric lock to have the 

capability for an easy change of combinations. The part 

of the lock where the combination is set and the housing 

of the card reader (if the contents of the housing can 

reveal the combination) should be protected against 

tampering by tamper switches connected to the alarm 

system. 

Generally, where electric locks are installed, a 

mechanical lock is also installed as a bypass. This lock 

should be of a quality as discussed in the part on key 

locks in this guide.

5.12-3
b. Lock Control. The security ofan clectric lock 

system depends on strict control or combinations and 

cards. The magnetic codes in the cards and the 

combinations need to be changed whenever an employee 

having had access to them terminates or is reassigned. 

Strict accountability of cards Is strongly recommended. 

c. Standards and Specifications. There are 

currently no comprehensive standards or specifications 

covering electric locks. The reputation of the 

manufacturer, the specification 'for his product. and the 

experience of users must be carefully considered in their 

selection and use. 

4. Pushbutton Mechanical Locks 

a. General. This is a type of combination lock 

utilizing mechardcal-pushbutton-activated linkages that 

connect a gate with an external knob topermit opening 

of the lock. In this lock it is difficult to design in 

penalties for punching a wrong combination as is done in 

electric locks. Therefore, it is important to have a large 

number of possible combinations. 

Provisions for easy change of combinations 

are desirable. Some locks permit a new combination to 

be dialed in utilizing an Allen wrench when the lock is 

open, a procedure similar to that for some combination 

locks. Others require the replacement of Internal parts to 

change the combination. 

The mechanical locks appear to be fairly 

resistant to concealed attack: however, more 

information is needed on their resistance to forcible 

attack. 

b. Lock Control. Similar to other combination 

locks, the combinations need to be changed when 

employees having access to the combination terminate 

or arereassigned. 

c. Quality Assurance. There are currently no 

comprehensive standards or specifications for 

mechanical pushbutton locks. 

C. REGULATORY POSITION 

The following guidelines are acceptable to the 

Regulatory staff for the selection and use of locks in the 

protection of facilities and SNM: 

I. Combination locks installed in solid doors such as 

those in vaults or vault-type rooms in protected areas 

should he three. or four-position dial.type changeable. 

combination locks meeting the Underwriters' 

Laboratories Standard UL-768. "Combination Locks," 

for Group I locks.' 

2. Combination padlocks should be used when 

practicable on doors or gates to material access areas, in

protected and vital area perimeters, and for access to 

vital equipment in preference to key padlocks. 

Combination padlocks should be used on dosed vehicles 

or containers holding SNM that are required to be 

locked. Combination padlocks should be three-position. 

dial type changeable-combination padlocks meeting Federal Specification FF-P-I I OF, "Padlock, Changeable 

('ombination (Resistant to Opening by Manipulation and 

Surreptitious Attack)." 2 

3. Key locks used in lieu of combination padlocks on 

doors or gates to material access areas, in protected and 

vital area perimeters, and for access to vital equipment 

should provide a high degree of resistance to opening by 

force and tamper techniques and should meet 

Underwrite' Laboratories UL-437, "Key Locks."' 

4., Key padlocks used in lieu of combination padlocks 

on doch or, ptes to material access areas, In protected 

and vital area perimeters, and for access to vital 

equipment should be of nugged and sturdy construction 

and designed for outdoor use if necessary, and should 

meet Interim Federal Specification FF-P-001480 (GSA FSS), "Padlock, Key Operated (Resistant to Opening by 

Force, Pick, and Bypass Techniques)."'2 

S. -ýtric locks should be used inside the protected 

area a, a means of access control only If a magnetic card 

key syysezn is coupled with a pushbutton system and 

!' i,.d into the alarm system. This lock combination 

should have features that resist tampering with the 

combination-changing mechanism and that alarm after a 

set number of errors in punching the combinations is 

made. 

6. Pushbatton mechanical locks are not recommended 

for use at this time because of the lack of comprehensive 

standards and specifications against which the locks can 

be evaluated. 

7. Mechanical locks used as panic locks on emergency 

exit. doors within protected area perimeters should be 

operable only from the inside. 

8.. Combinations, keys and locks should be controlled, 

protected and changed in accordance with the following requirements: 

a. Combinations of locks or padlocks on 

repositories containing SNM or used to secure gates or 

doors to material access areas, in protected and vital area 

perimeters, and for access to vital equipment should be 

known only to those authorized access to the material or 

to the area. They should be changed when repositories 

or areas are first placed in use, whenever a person 

knowing the combination no longer requires it as a result 

of reassignment of duties or termination, whenever the 

combination may have been compromised, or at least 

twice every year. A record of the combinations of locks 

should be kept in a location that is secured by a 

combination lock.
b. Keys and cards to locks or padlocks on 

containers holding SNM or used to secure ptes or doors 

to material access areas and in protected and vital area 

perimeters should be issued only to persons authorized 

acss to the material or to the area. Keys or cards in use 

should be dcecked in at the end of each shift or 

workday, and a log should be maintained showing keys 

and cards, users, in and out times, and other pertinent 

inflrmation. Keys and cards should be recovered from 

reassigned or terminating personnel. Locks should be 

immediately changed or cores replaced and an inventory 

conducted whenever a core, key, or card is lost or 

r.ussing; the lock, care, key, or card has been 

compromised. or unrecorded keys or cards are found. In

a mastered system, a complete remastering of the system 

should be conducted whenever a core, card, master or 

control key, or a lock is lost or compromised. 

c. A record of all locks, cores, keys, and cards 

should be maintained and kept in a location secured by a 

combination lock. A physical inventory of locks, cores. 

keys, and cards should be conducted semiannually when 

the locks are used for protection of facilities and 

bimonthly when the locks are used for the protection of 

SNM. Unused locks, cores, keys, and cards should be 

stored in a location secured by a combination lock. A 

specific individual at each site should be named aid 

placed In charge of all locks, cores, keys, and cards.

5 12-5