Issue Date: 08/19/08 C-1 0609 

IMC 0609 

Appendix C 

OCCUPATIONAL RADIATION SAFETY 

SIGNIFICANCE DETERMINATION PROCESS 

I. APPLICABILITY 

The significance determination process (SDP) in this Appendix is designed to provide a 

means by which NRC inspectors and management can assess the significance of 

inspection findings related to worker health and safety from exposure to radiation from 

licensed or unlicensed radioactive materials during routine operations of civilian nuclear 

reactors. 

Background and basis information related to this SDP can be found in Inspection Manual 

Chapter 0308, “Reactor Oversight Process (ROP) Basis Document,” Appendix C, Section 

6, “Occupational Radiation Safety SDP.” 

II. ENTRY CONDITIONS 

Each issue entering the SDP process must first be screened using IMC 0612, Appendix B, 

“Issue Screening.” 

III. DEFINITIONS 

Within this SDP, the following definitions apply: 

A. ALARA. Maintaining radiation dose as low as is reasonably achievable. 

B. Compromised ability to assess dose. Deficient program requirements (i.e., 

inadequate procedures that resulted in program failures), or failures to implement 

adequate program requirements, that resulted in chronic failure to account for 

exposures that exceed, or could have exceeded; 

1. an acute intake of radionuclides greater than 0.02 annual level of intake 

(ALI), per individual, or 

2. 100 mrem whole body from external exposure, per individual. 

A compromised ability to assess dose can result from: 

1. the licensee's failure to use a National Voluntary Laboratory Accreditation 

Program (NVLAP) certified dosimeter processor when required by 10 CFR 

Part 20, or 
Issue Date: 08/19/08 C-2 0609 

2. failure of the electronic dosimeters (EDs) to respond to, or record, radiation 

dose, or 

3. the improper calibration of instruments or monitors which are used as a basis 

for establishing protective controls, or 

 4. the improper analysis of bioassay data that results in missed intakes of 

radioisotopes, or, 

 5. the failure to recognize a radiologic hazard in the work place (i.e., the 

potential for exposure to alpha emitting, radionuclides resulting in the failure 

to appropriately assess intakes of these nuclides). 

C. Substantial potential for overexposure. An event presents a substantial potential 

when it was fortuitous that the resulting exposure did not exceed the limits of 10 

CFR 20. The concern is not the significance of the resulting, or potential, 

exposure, but whether the licensee provided adequate controls over the situation, 

as required, to ensure the Part 20 dose limits are not exceeded. No credit is given 

for luck. When assessing whether a finding constitutes a substantial potential for 

overexposure, consider if it is possible to construct a reasonable scenario in which 

a minor alteration of circumstances (as they actually happened) would have 

resulted in a violation of the Part 20 limits. The following circumstances should be 

considered: 

1. Timing - Could the exposure period have reasonably been longer? 

EXAMPLE: An individual in the proximity of an unknown source of radiation 

receives an unplanned excessive exposure. Because of the duration of the 

exposure, no limits were exceeded; however, the individual could have 

reasonably stayed in the proximity of the source long enough to be 

overexposed. 

2. Source Strength - Could the radiation source have reasonably been 

stronger? 

EXAMPLE: While working in the spent fuel transfer canal a worker picked up 

and handled a piece of activated debris, contrary to the RWP instructions. 

Although this deficiency did not result in an overexposure, similar (but more 

highly activated) debris was in the same area of the transfer canal. Had the 

worker picked up one of the more activated pieces of debris, his actions 

would have resulted in a dose in excess of the Part 20 limits. Nothing 

prevented the worker from picking up the more highly activated debris. 

3. Distance - Could the person have reasonably been closer to the source? 

EXAMPLE: In example (1) above, the individual could have been 

overexposed by standing closer to the source of the radiation. 

4. Shielding - Could some unintended shielding have been reasonably 

removed? 

EXAMPLE: A radioactive source (i.e., activated component) was left in a 

work area such that the only thing preventing the overexposure of an 
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individual worker was the shielding provided by intervening equipment. This 

was not part of the work activity. The presence of the equipment was 

fortuitous and nothing prevented the source from being left in an area that 

would not have provided shielding. 

D. Unplanned, unintended occupational collective dose. The total sum of the 

occupational radiation doses (collective dose) received by individuals for a work 

activity in excess of that collective dose planned or intended (i.e., that dose the 

licensee determined was ALARA) for that work activity. 

1. Planned, or intended, collective dose can be the result of a realistic dose 

estimates (or projection) established during ALARA planning or the dose 

expected by the licensee (i.e., historically achievable) for the reasonable 

exposure control measures specified in ALARA procedures/planning. These 

do not include “stretch goals” set by a licensee to challenge their organization 

to strive for excellence in ALARA performance. 

2. Collective dose associated with reasonably unexpected changes in the scope 

of work, material conditions, or radiological conditions, during a work activity 

(and for which measures are implemented to track, and if necessary, to 

reduce these doses) should also be considered intended dose. 

E. Work activity. One or more closely related tasks that the licensee has (or 

reasonably should have) grouped together as a unit of work for the purpose of 

ALARA planning and work controls. In determining a reasonable grouping of 

radiological work, factors such as historical precedence, industry norms, and 

special circumstances should be considered. 

IV. SIGNIFICANCE DETERMINATION PROCESS FOR OCCUPATIONAL 

RADIATION SAFETY 

Step 1. Identify whether the inspection finding is related to ALARA (e.g., does the 

finding concern unplanned, unintended occupational collective dose resulting 

from a deficiency in the ALARA planning or work control, or exposure 

control?). 

a. If the inspection finding is related to ALARA, then go to Step 2. 

b. If the inspection finding is not related to ALARA, then go to Step 5. 

Step 2. Consider the licensee’s overall ALARA performance. The three-year rolling 

average collective dose is a high level indication of the radiological 

challenges the program faces. This SDP decision is intended to direct NRC 

inspection resources to those programs with the largest challenges. 
Issue Date: 08/19/08 C-4 0609 

a. If the licensee’s current 3-year rolling average collective dose is MORE than 

135 person-rem/unit for a PWR or more than 240 person-rem/unit for a BWR, 

then go to Step 3. 

b. If the licensee’s current 3-year rolling average collective dose is LESS than, 

or equal to, 135 person-rem/unit for a PWR or LESS than, or equal to, 240 

person-rem/unit for a BWR, then the significance of the inspection finding is 

GREEN. 

Step 3. Consider the magnitude of the actual collective dose associated with a work 

activity. The criterion in this step represents a level of actual dose at which it 

is reasonably expected that there will be licensee management review and 

oversight to confirm the adequacy of ALARA measures. 

a. If the actual dose is GREATER than 25 person-rem, then the significance of 

the finding is WHITE. 

b. If the actual does is LESS than, or equal to, 25 person-rem, then go to step 

4. 

Step 4. Consider the overall ALARA program performance and the aggregate impact 

of the licensee’s collective dose. 

a. If the licensee has MORE than 4 occurrences, then the significance of the 

inspection finding is WHITE. 

b. If the licensee has LESS than, or equal to, 4 occurrences, then the 

significance of the inspection finding is GREEN. 

Step 5. Identify if the inspection finding involved an overexposure. 

a. If the finding involves an overexposure, then go to Step 6. 

b. If the finding DOES NOT involve an overexposure, then go to Step11. 

Step 6. Identify if the exposure was a shallow dose equivalent from a discrete 

radioactive particle (SDE/DRP). 

a. If the overexposure was an SDE/DRP exposure, then go to Step 7. 

b. If the overexposure WAS NOT an SDE/DRP exposure, then go to Step 8.

Step 7. Consider the magnitude of the SDE. 

a. If the SDE was MORE than 5 times the limit, then the significance of the 

inspection finding is YELLOW. 
Issue Date: 08/19/08 C-5 0609 

b. If the SDE was LESS than, or equal to, 5 times the limit, then the significance 

of the inspection finding is WHITE. 

Step 8. Consider the dose when the overexposure is NOT an SDE/DRP exposure. 

a. If the dose was LESS than, or equal to, 2 times the limit go to step 9. 

 b. If the dose was MORE than 2 times the limit, go to step 10. 

Step 9. Consider the risk of an overexposure in a Very High Radiation Area 

a. If the dose limit was exceeded from external exposures while IN a Very High 

Radiation Area, then the significance is YELLOW. 

b. If dose limit was exceeded from external exposures while NOT IN a Very 

High Radiation Area, then the significance is WHITE. 

Step 10. Consider the magnitude of the dose received. 

a. If the dose was MORE than 5 times the limit, then the significance of the 

inspection finding is RED. 

b. If the dose was LESS than, or equal to, 5 times the limit, then the significance 

of the inspection finding is YELLOW. 

Step 11. Consider if the performance deficiency constituted a substantial potential for 

overexposure. 

a. If there was a substantial potential for overexposure, then go to Step 12. 

b. If there was no substantial potential for overexposure, then go to Step 14. 

Step 12. Consider the substantial potential associated with a SDE/DRP exposure. 

a. If the exposure WAS a SDE/DRP exposure, then the significance of the 

inspection finding is GREEN. 

b. If the exposure WAS NOT a SDE/DRP exposure, then go to Step 13. 

Step 13. Consider the risk of an external exposure in a Very High Radiation Area that 

resulted in substantial potential for overexposure. 

a. If the substantial potential WAS an external exposure in a Very High 

Radiation Area, then the significance of the inspection finding is YELLOW. 

b. If the substantial potential WAS NOT an external exposure in a Very High 

Radiation Area, then the significance of the inspection finding is WHITE. 
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Step 14. Does the finding involve a situation where the licensee’s ability to assess 

dose was compromised? 

a. If the licensee’s ability to assess dose WAS compromised, then the 

significance of the inspection finding is WHITE. 

b. If the licensee’s ability to assess dose WAS NOT compromised, then the 

significance of the inspection finding is GREEN. 

Note: An individual or isolated failure to survey, or monitor, does not constitute a 

compromised ability to assess dose. However, each should be considered as a failure of a 

radiation safety barrier and should have been evaluated for its potential for an 

overexposure in steps 5 and 11 above. 
Issue Date: 08/19/08 C-7 0609 
Issue Date: 08/19/08 C-8 0609 
Issue Date: 08/19/08 C-9 

Revision History Page 

Commitment Tracking Number 

Issue Date 

Description of Change Training 

Needed 

Training CompletioDate 

n/a 12/16/2003 Added definition and criteria for 

determining when a licensee has a compromised ability to assess dose 

none n/a 

0609C-1192 0609C-1064 

08/19/08 CN 08-024 

Revised definition of a substantial potential for overexposure; revised text to match flow diagram; revised text and flow diagram to bring SDP outcomes more in line with Enforcement Policy Supplements 

none n/a