# Presentation: 476759

## Dose Quantities:Operational (ICRU) v. Protection (ICRP) Quantities

- Daniel J. Strom
- Pacific Northwest National Laboratory
- Richland, Washington USA
- strom@pnl.gov        +1 (509) 375-2626
- Battelle operates Pacific Northwest National Laboratory for
- the U.S. Department of Energy under Contract No. DE-AC05-76RLO 1830

**Notes:**
Applied health physics often involves measurements of radiation or radioactivity, and radiation protection decisions are based on inferences made from such measurements. Because measurements can be imprecise, often to the point that one is not even certain that radiation or radioactive material is present, statistical tools are needed. Since the Health Physics Society Summer School in 2000 was devoted entirely to applications of probability and statistics in health physics (Borak 2000a), this chapter will focus only on a few aspects of the problem, with many references to the earlier proceedings. In addition, so much excellent material is available for free over the internet that links are provided wherever possible.
This chapter consists of a review of general statistical concepts, including meanings of probability; statistical distributions; population versus sample statistics; variability, uncertainty, bias, error, and blunder; correlation and “shared” uncertainty; the source of uncertainty; and expressions of uncertainty. Next is a discussion of the various notions of numerical thresholds for decisions, such as whether radioactive material is present above background levels, concepts from MARSSIM and MARLAP, frisking, missed dose, and unmonitored dose. Finally, case studies are presented on reconstructing x-ray doses, reconstructing worker doses, and uncertainty in internal dosimetry. 
*Pacific Northwest National Laboratory is operated for the U.S. Department of Energy by Battelle under Contract DE-AC05-76RLO 1830. 

## Relationships among Physical, Operational, and Protection Quantities (ICRP 74, 1996)

- ICRU & ICRP are at odds over some quantities and values.

## ICRP and ICRU are working together to build a coherent set of quantities and units for radiation protection 

**Notes:**
Cover from The Economist, July 22-28, 2000 Vol. 336 No. 8180

## Average ionizing energy per unit mass m deposited in matter or tissue

For x and  radiation, 1 R  1 rad = 0.01 Gy = 10 mGy
The rad was originally defined as 100 ergs/gram

- For x and  radiation, 1 R  1 rad = 0.01 Gy = 10 mGy
*The rad was originally defined as 100 ergs/gram*

- Absorbed Dose, *D*

| System | Unit Name | Unit Symbol | Definition |
| --- | --- | --- | --- |
| SI | gray | Gy | 1 J kg1 |
| Old | rad | rad | 102 J kg1 |

## Mean Absorbed Dose

- The mean absorbed dose in a specified tissue or organ *T* is
- 	where *m**T* is the mass of the tissue or organ, and *D* is the absorbed dose in the mass element d*m*
- a.k.a. “organ dose”
- Can be specified for various types of radiation, *R: D**T,R*

## For Limitation Purposes: 2007Equivalent Dose

- The equivalent dose in a tissue or organ is

## Equivalent Dose = (Absorbed Dose) × (Radiation Weighting Factor)

	Thus 1 R of x or  1 rad =  1 rem
	for neutrons, 1 rad = 10 rem
	for , 1 rad = 20 rem

- 	Thus 1 R of x or  1 rad =  1 rem
- 	for neutrons, 1 rad = 10 rem
- 	for , 1 rad = 20 rem

- Tissue Equivalent Dose, *H**T*

| System | Unit Name | Unit Symbol | Definition |
| --- | --- | --- | --- |
| SI | sievert | Sv | 1 J kg1 |
| Old | rem | rem | 102 J kg1 |

## Quality Factors, Q or Radiation Weighting Factors, wR

| Radiation |  Old NRC* | 1991 ICRP**
1993 NCRP** | 1989 ICRU | 1993 DOE, 1993 NRC |
| --- | --- | --- | --- | --- |
| gamma, x ray | 1 | 1 | 1 | 1 |
| beta, electron | 1 | 1 | 1 | 1 |
| thermal neutron | 2.3 | 5 | - | 3 (DOE)
2 (NRC) |
| fast neutron | 10 | 20 | 25 | 10 |
| alpha | 10 | 20 | 25 | 20 |
| proton | 10 | 20 | 25 | 10 |
| *10 CFR 20 "Standards for Protection Against Radiation" until 1993 |  |  |  |  |
| ** Strictly speaking, these are “radiation weighting factors,” wR |  |  |  |  |

*Q:* replaced by *w**R* in recommendations and international regulations.

**Notes:**
There is considerable disagreement about Q values.  Some have changed by a factor of 2 since they were first used for neutrons in the 1940s.  Both the U.S. Nuclear Regulatory Commission (NRC) and the U.S. Department of Energy (DOE) specify quality factors in their regulations  (U.S. Nuclear Regulatory Commission (NRC) 1993, U.S. Department of Energy (DOE) 1993).  Other recommendations come from the ICRU  (International Commission on Radiation Units and Measurements (ICRU) 1986), the ICRP  (International Commission on Radiological Protection (ICRP) 1977, International Commission on Radiological Protection (ICRP) 1991), and the NCRP  (National Council on Radiation Protection and Measurements (NCRP) 1993).

## ICRP 2007 Recommendations: wR

## ICRP Quality Factors versus Unrestricted LET

*ICRP 26 & 60*

## Quality Factor versus Lineal Energy (1 m)

*ICRU 40 (1986)*

## Calculated values of Q vs. photon energy under conditions of charged-particle equilibrium

*ICRU 40 (1986)*

## Calculated values of Q for the entire range of alpha particles of given initial energy

*ICRU 40 (1986)*

## Calculated values of Q vs. neutron energy under conditions of charged-particle equilibrium

*ICRU 40 (1986)*

## Neutron wR versus Energy

*ICRP 60 (1991)*

## ICRP 2007 Recommendations: wR=neutron

## Fluence

- The number of particles that pass through a sphere of unit cross-sectional area
-  = *number/area*, m2
- The number of particles that pass through a sphere of unit cross-sectional area per unit time
-  = *number/area*, m2 s1

- Fluence Rate

## Neutron Dose Equivalent per Unit Fluence

*McDonald et al. 1998*

## Combining Doses to All Tissues from Different Kinds of Radiation

## For Limitation Purposes: 2007Effective Dose

- The effective dose is
- 	where *w**T* is the tissue weighting factor
- Accounts for non-uniform irradiation

## Tissue Weighting Factors, wT

- a1977: each of 5 highest dose organs included in remainder with 0.06 weighting factors; stomach, liver, small intestine, upper and lower large intestine each count as 0.06 if receiving high doses.
- b1985: skin was added; total no longer 1.00.
- c1990: remainder included adrenals, brain, upper large intestine, small intestine, kidney, muscle, pancreas, spleen, thymus, and uterus.
- d1977: not listed.
- e2005: Adipose tissue, adrenals, connective tissue, extrathoracic airways, gall bladder, heart wall, lymphatic nodes, muscle, pancreas, prostate, si wall, spleen, thymus, and uterus/cervix.
- f2007: Adrenals, extrathoracic (ET) region, gall bladder, heart, kidneys, lymphatic nodes, muscle, oral mucosa, pancreas, prostate (♂), small intestine, spleen, thymus, uterus/cervix (♀).

| Tissue or Organ | 2007 | 2005 | 1990 | 1977 |
| --- | --- | --- | --- | --- |
| Gonads | 0.08 | 0.05 | 0.20 | 0.25 |
| Bone marrow | 0.12 | 0.12 | 0.12 | 0.12 |
| Colon | 0.12 | 0.12 | 0.12 | 0.06a |
| Lung | 0.12 | 0.12 | 0.12 | 0.12 |
| Stomach | 0.12 | 0.12 | 0.12 | 0.06a |
| Bladder | 0.04 | 0.05 | 0.05 | 0.06a |
| Breast | 0.12 | 0.12 | 0.05 | 0.15 |
| Liver | 0.04 | 0.05 | 0.05 | 0.06a |
| Esophagus | 0.04 | 0.05 | 0.05 | 0.06a |
| Thyroid | 0.04 | 0.05 | 0.05 | 0.03 |
| Remainder | 0.12f | 0.10e | [0.05]c | [0.30]a |
| Skin | 0.01 | 0.01 | 0.01 | 0.01b |
| Bone surface | 0.01 | 0.01 | 0.01 | 0.03 |
| Brain | 0.01 | 0.01 | 0.005c | d |
| Kidneys | 0.00923f | 0.01 | 0.005c | d |
| Salivary Glands | 0.01 | 0.01 | 0.005c | d |
| Total | 1.00 | 1.00 | 1.00 | 1.01 |

## Total Effective Dose

*TED* emphasizes the summation of doses from internal and external irradiation
- Suppose a worker receives
- an equivalent dose of 1.00 mSv to the whole body
- a committed equivalent dose (*CED*) of 10.00 mSv to his thyroid
- a *CED* of 3.00 mSv to his bone marrow
- 	What is his *TED*?
*	**Answer:*	*TED **	**= *1(1.00)  +  10(0.04)  +  3 (0.12)
- 						= 1.76 mSv

## A “Quantity” That Never Occurred to the ICRP: Total Effective Dose (Equivalent)

- USA regulators explicitly *named* the sum of doses from external sources and committed doses from intakes of radionuclides *TEDE*
- USA regulators also explicitly *named* the implicit whole body tissue weighting factor (*w*(*T *= whole body) = 1)
- also have cumulative or lifetime *TEDE*

## IAEA’s Total Effective Dose, ET

- IAEA SS 115 (1996): for verification of compliance with dose limits, use
- 	where the sums are over radionuclides *j*, ing means ingestion, and inh means inhalation
- intakes *I* and personal dose equivalent *H*p, are within a specified time period, e.g., 1 y
- looks like an *operational* quantity

## Groupings of Radiation Quantities

**Indirectly Ionizing Radiation**

**Directly Ionizing Radiation**

- kerma [rate]

- cema [rate]

**Photons**

- exposure [rate]

***/****, ***tr/**, **en/*** *

**Radioactive Material**

- decay constant 

- activity*

- number of transitions

**Radon & Progeny**

- potential  energy concentration

- potential  energy exposure

- equilibrium factor

- equilibrium equivalent concentration

- potential  energy

- equilibrium equivalent exposure

- absorbed dose [rate]

**Neutrons**

- air kerma rate constant

- equivalent dose [rate]

- effective dose [equivalent] [rate]

*S*/***,*      *S*col/***,* *S*rad/**

- specific activity

- specific energy

- energy deposit, energy imparted

- energy
- dose-like quantity
- dose-rate-like quantity
- interaction of radiation with material
- biology or risk
- other

- cross section

- *“intake” is implicitly “dose-like” due to retention

- radiation chemical yield

- fluence, energy fluence [rate]

- linear energy transfer, lineal energy

*h**T**(****)*

*w**T*

**Biology or Risk**

- energy per ion pair

*f**1*

*SEE*

*AF*

*Q, w**R*

- activity concentration

*{F, M, S}*

- unattached fraction

- retained quantity

- fraction deposited

- particle size

*e(****)*

*IRF*

****** ****recoils**