Background

Released in 1993, NCRP 116 is an update to the NCRP 91 (released 1987). NCRP 91 was largely based on study of atomic bomb survivors completed by the Radiaton Effects Research Foundation (RERF). Three important factors were recognized as result of RERF’s work. First, excess cancers continued to be observed in atomic bomb survivors into the latest study period, at time of writing. Second, cancer incidence appeared at a rate consistent with a multiplicative projection model. Third, revised risk-dose estimates became available. However, because the risk assessment was incomplete, the limits set by NCRP 91 were considered upper limits rather than radiation safety design goals.  NCRP 116 was created upon completion of risk assessments from several national and international bodies and generally increases the reported risks of radiation exposure.

Definitions

• Deterministic vs Stochastic Effects
  • Deterministic Effect: a somatic effect which increases in severity with increasing radiation dose above a threshold dose.
  • Stochastic Effects: health effects which occur randomly and for which the probability of the effect, rather than the effect’s severity, is related to dose.
    • “For radiation-protection purposes, the risk of a stochastic effect is proportional to dose without threshold, throughout the range of dose and dose rates of importance in routine radiation protection.”
• As Low As Reasonably Achievable (ALARA): making every reasonable effort to maintain exposures to radiation as far below the dose limits as is practical

Tables

Group	Risk Factor	NCRP Report 91	ICRP Publication 60	NCRP Report 116
Workers	Fatal cancer	1.25% per Sv	4% per Sv	4% per Sv
Workers	Non-fatal cancer	–	0.8% per Sv	0.8% per Sv
Worker	Severe genetic effects	0.4% per Sv	0.8% per Sv	0.8% per Sv
Members of the Public	Fatal cancer	–	5% per Sv	5% per Sv
Members of the Public	Non-fatal cancer	–	1% per Sv	1% per Sv
Members of the Public	Severe genetic effects	–	1.3% per Sv	1.3% per Sv
Embryo/fetus	–	20% per Sv	–	~10% per Sv

	NCRP Report 91	ICRP Puclication 60	NCRP Report 116
Based on Stochastic Effects	50 mSv annual effective dose limit 10 mSv × age (y) cumulative effective dose limit for workplace	50 mSv annual effective dose limit 100 mSv in 5 year cumulative effective dose limit	50 mSv annual effective dose limit 10 mSv × age (y) cumulative effective dose limit for workplace
Based on Deterministic Effects	150 mSv annual dose equivalent limit to lens 500 mSv annual dose equivalent limit to all other organs (e.g. red bone marrow, breast, lung, gonads, skin, extremities)	150 mSv equivalent dose limit to lens 500 mSv annual equivalent dose limit to skin, hands, and feet	150 mSv annual equivalent dose limit to lens 500 mSv annual equivalent dose limit to skin, hands, and feet
Annual Limits of Intake (ALI)	[50 mSv]/[HE (50)  Bq-1]	[20 mSv]/[HE (50)  Bq-1]	–
Annual Reference Levels of Intake	–	–	[20 mSv]/[HE (50)  Bq-1]

	NCRP Report 91	ICRP Publication 60	NCRP Report 116
Based on Stochastic Effects	1 mSv annual for continuous exposure 5 mSv annual for infrequent exposure	1 mSv annual A higher value may be acceptable if average annual over 5 years is less than 1 mSv	1 mSv annual for continuous exposure 5 mSv annual for infrequent exposure
Based on Deterministic Effects	50 mSv annual limit to lens, skin, and extremities	15 mSv annual limit to lens 50 mSv annual limit to skin, hands, and feet	50 mSv annual limit to lens, skin, and extremities
Embryo/fetus	5 mSv annual limit 0.5 mSv per month once pregnancy is known	2 mSv limit to woman’s abdomen once pregnancy is declared Limit intake of radionuclides to 1/20 of ALI	0.5 mSv limit per month once pregnancy is known
Negligible Individual Dose (NID)	0.01 mSv annual per source or practice	–	0.01 mSv annual per source or practice

Organ	NCRP Report 91	ICRP Publication 60	NCRP 116
Gonads	0.25	0.20	0.20
Red bone marrow	0.12	0.12	0.12
Colon	–	0.12	0.12
Lung	0.12	0.12	0.12
Stomach	–	0.12	0.12
Bladder	–	0.05	0.05
Breast	0.15	0.05	0.05
Liver	–	0.05	0.05
Esophagus	–	0.05	0.05
Thyroid	0.03	0.05	0.05
Skin	0.01	0.01	0.01
Bone surface	0.03	0.01	0.01
Remainder	0.30	0.05	0.05
SUM	1.01	1.0	1.0

Radiation Type	NCRP Report 91 (Q)	ICRP Publication 60 (wR)	NCRP Report 116 (wR)
X and γ-ray, electrons, positrons, and muons	1	1	1
Neutrons	Thermal: 5 Other than thermal: 20	<10 keV: 5 10 keV – 100 keV: 10 100keV – 2 MeV: 20 2MeV – 20 MeV: 10 > 20 MeV: 5	<10 keV: 5 10 keV – 100 keV: 10 100keV – 2 MeV: 20 2MeV – 20 MeV: 10 > 20 MeV: 5
Protons > 2 MeV	–	5	2
Alpha particles, fission fragments, nonrelativistic heavy nuclei	20	20	20

Related Pages

Click here to download NCRP 116: Limitations of Exposure to Ionizing Radiation.

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