ML19011A419

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Background - Slides
ML19011A419
Person / Time
Issue date: 01/16/2019
From:
Office of Nuclear Regulatory Research
To:
Nathan Siu 415-0744
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ML19011A416 List:
References
Download: ML19011A419 (23)
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Text

References and

Background

1

References See separate handouts

  • List of references

Continuous Probability Distributions

Background

3

Continuous Distributions - General Definitions and Useful Relationships

  • Probability density functions (pdfs)

< + D q q q q = =

D0 D

  • Cumulative distribution functions q q q = q 2

1 < 2 q = q = 2 q 1 q 1

4

Continuous Distributions - General Definitions and Useful Relationships

  • Complementary cumulative distribution functions q > q q = q
  • Hazard functions

< + Dl >

q D0 D q

q = q = 1 q 1 q 5

Continuous Distributions - General Definitions and Useful Relationships

  • Moments
  • Percentiles

- General - General: xa is the value that satisfies

- Mean Value

- Median x0.50 0.50 0.50 =

- Variance 2 = 2 2 6

Some Continuous Univariate Distributions Distribution Domain Density Function Cumulative Hazard Exponential X0 l l 1 l l 1

Gamma X0 Numerical Numerical G

1 1 Weibull X0 1

1 1 2 Lognormal X0 2 Numerical Numerical 2

1 ,

Gumbel Type I - < X < + exp 1 ,

1 1 Uniform aXb G + 1 1 Beta 0X1 1 Numerical Numerical G G B-7

Some Continuous Univariate Distributions Distribution Domain Mean Variance Notes 1 1 Exponential X0 2 Reverse J-shaped (mode at x = 0) l l Reverse J-shaped (mode at x = 0) if Gamma X0 2 a1 1 2 G 1 + 2 G 1 + 2 Reverse J-shaped (mode at x = 0) if Weibull X0 a1 Mode:

1 2 2 2 1 Median:

Lognormal X0 +2 Range Factor (X.95/X.05): 1.645 2 2 Mode: m Gumbel Type I - < X < + 0.5772 Median: m - bln(ln(2))

6

+ 2 Uniform aXb 2 12 Uniform if a = b = 1; reverse J-shaped (mode at x = 0) if a

< 1 and b 1; Beta 0X1 J-shaped (mode at x = 1) if a 1 and

+ + 2 ++1 b < 1; unimodal with mode between a and b otherwise.

B-8

U.S. Nuclear Regulatory Commission

Background

9

NRC Mission The U.S. Nuclear Regulatory Commission licenses and regulates the Nations civilian use of radioactive materials to protect public health and safety, promote the common defense and security, and protect the environment.

- NUREG-1614 (NRC Strategic Plan) 10

NRC Organization

  • Headquarters + 4 Regional Offices
  • 5 Commissioners
  • Staff and budget (FY 2018)

- ~3200 staff

- Total budget ~$940M

- Research budget ~$43M

  • Website: www.nrc.gov

Regulatory Approach Standard Principles

  • Independence Reasonable assurance
  • Openness of adequate protection
  • Efficiency
  • Clarity
  • Reliability 12

How We Regulate 13

U.S. Nuclear Power Plants NUREG-1350, v30, 2018

  • 99 plants (61 sites)
  • ~99 GWe, ~805 GW-hr (2017) = 20% U.S. total
  • Worldwide: 450 plants, 394 GWe capacity 14

Regulatory Documents

  • Standard Review Plan (SRP) -

http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr0800/

15

Backup Regulatory Documents - Examples

  • Structures, systems, and components important to safety shall be designed to withstand the effects of natural phenomena such as Regulation earthquakes, tornadoes, hurricanes, floods, tsunami, and seiches without loss of capability to perform their safety functions.
  • NUREG/CR-4461, Tornado Climatology of the Contiguous United States,
  • RG1.221, Design-Basis Hurricane and Hurricane Missiles for Nuclear Power Plants
  • NUREG/CR-7004 Technical Basis for Regulatory Guidance on Design-Basis RG Hurricane-Borne Missile Speeds for Nuclear Power Plants
  • NUREG/CR-7005 Technical Basis for Regulatory Guidance on Design-Basis Hurricane Wind Speeds for Nuclear Power Plants
  • Standard Review Plan Chapter 3.3.1, Wind Loading
  • Standard Review Plan Chapter 3.5.1.4, Missiles Generated By SRP Tornadoes And Extreme Winds 16

General Design Criterion 35 Emergency core cooling. A system to provide abundant emergency core cooling shall be provided. The system safety function shall be to transfer heat from the reactor core following any loss of reactor coolant at a rate such that (1) fuel and clad damage that could interfere with continued effective core cooling is prevented and (2) clad metal-water reaction is limited to negligible amounts.

Suitable redundancy in components and features, and suitable interconnections, leak detection, isolation, and containment capabilities shall be provided to assure that for onsite electric power system operation (assuming offsite power is not available) and for offsite electric power system operation (assuming onsite power is not available) the system safety function can be accomplished, assuming a single failure.

17

Safety Goal Policy Statement (51 FR 30028; August 21, 1986)

  • Commission view on how safe is safe enough?
  • Two quantitative health objectives (QHO) for the current generation of light water reactors

- The risk to an average individual in the vicinity of a nuclear power plant of prompt fatalities that might result from reactor accidents should not exceed 0.1% of the sum of prompt fatality risks resulting from other accident to which members of the U.S.

population are generally exposed

- The risk to the population in the area of nuclear power plant of cancer fatalities that might result from nuclear power plant operation should not exceed 0.1% of the sum of cancer fatality risks resulting from all other causes.

18

Safety Goal Policy Statement (cont.)

Based on CDC data,* the QHOs translate to:

  • Accidents: 41.3 per 100,000 per year 41.3/100,000
  • 0.001 = ~5E-07/yr
  • Cancers: 185 per 100,000 per yr 185/100,000
  • 0.001 = ~2E-06/yr
  • Note: these are population-averaged risks to an individual

Safety Goal Policy Statement (cont.)

Surrogate safety goals*

- Worst case conditional probability of individual prompt early fatality (CPEF) for large early release = 3E-2**

- 3E-2 fatality risk/large early release

  • CDF <10-4 per year => surrogate for latent cancer QHO

- Worst case conditional probability of latent cancer fatality (CPLF) from large release = 4E-03

- 4E-3 latent fatality/large release

  • 1E-4 core damage/year
  • 1 large release/core damage = 4E-07 individual latent cancer fatality risk/yr.

PRA Policy Statement (60 FR 42622; August 16, 1995)

1) The use of PRA technology should be increased in all regulatory matters to the extent supported by the state-of-the-art in PRA methods and data and in a manner that complements the NRCs deterministic approach and supports the NRCs traditional defense-in-depth philosophy.
2) PRA and associated analyses should be used in regulatory matters, where practical within the bounds of the state-of-the-art, to reduce unnecessary conservatism associated with current regulatory requirements, regulatory guides, license commitments, and staff practices. Where appropriate, PRA should be used to support the proposal for additional regulatory requirements in accordance with 10 CFR 50.109 (Backfit Rule).
3) PRA evaluations in support of regulatory decisions should be as realistic as practicable and appropriate supporting data should be publicly available for review.
4) The Commissions safety goals for nuclear power plants and subsidiary numerical objectives are to be used with appropriate consideration of uncertainties in making regulatory judgments on the need for proposing and backfitting new generic requirements on nuclear power plant licensees.

21

NRC R&D in the System PROCESSING SYSTEM RECEIVING NRC/RES SYSTEM THE WORLD Nuclear:

Activities NRC Tests/experiments U.S. Industry Licensed Surveys/reviews International Orgs Facilities INPUT OUTPUT RESPONSES &

OUTCOMES Technical analyses R&D needs Development Facts/Knowledge Other: Policies Activities Safety U.S. Congress Resources Recommendations Decisions Security OGAs Other

- People Methods Technical Community Actions Environment

- Funds Models General Public Information

- Infrastructure Tools

- Information MEASUREMENT Data AND FEEDBACK Guidance MEASUREMENT AND FEEDBACK MEASUREMENT AND FEEDBACK MEASUREMENT AND FEEDBACK Adapted from National Research Council, World-Class Research and Development Characteristics for an Army Research, Development and Engineering Organization, National Academy Press, Washington, DC, 1996, ISBN 0-309-05589-X. 22

Backup NRC Information

  • Website: www.nrc.gov
  • Status of Risk-Informed Activities:

https://www.nrc.gov/about-nrc/regulatory/risk-informed/rpp.html 23

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