the impact of the fukushimadaiichi accident on nrc’sregulation of research and testreactors

7/31/2019 The Impact of the FukushimaDaiichi Accident on NRCsRegulation of Research and TestReactors

1/24

The Impact of the Fukushima-Daiichi Accident on NRCs

Regulation of Research and Test

ReactorsAlexander Adams Jr., Senior Project Manager

Research and Test Reactor Licensing Branch

March 15, 20121


2/24


3/24

NRCs regulation of RTRs NRC is not taking any actions at this time related to

RTRs because of the accident.

RTRs will be evaluated in an integrated manner withfuel cycle facilities, decommissioning power reactorswith spent fuel pools and independent spent fuelstorage installations.

This evaluation will subject to steering committeedirection.

3


4/24

NRCs regulation of RTRs

The mission of the NRC is to license andregulate the United States civilian use of

byproduct, source, and special nuclearmaterials in order to protect public health andsafety, promote the common defense andsecurity, and protect the environment.

NRC normally does not regulate Department ofEnergy or Defense reactors.

4


5/24

NRCs Regulation of RTRs 31 RTRs operate across the U.S. in support of

research, service and education.

11 RTRs are in the process of decommissioning.

Reactor Type Number Power Level Operating Schedule

Low Power Research

Reactors

26 5 W to 1.25 MW Day shift or as needed

High Power ResearchReactors

4 2 MW to 10 MW Day shift or continuous

Test Reactor 1 20 MW Continuous

5


6/24

NRCs Regulation of RTRs

The Atomic Energy Act requires minimum regulation. The Commission is directed to impose only such minimum amount of regulation

of the licensee as the Commission finds will permit the Commission to fulfill its

obligations under this Act to promote the common defense and security and toprotect the health and safety of the public and will permit the conduct of

widespread and diverse research and development.

NRCs regulation of RTRs applies a graded approachthe licensing process and technical requirementsbecome more rigorous as facilities progress from low-power research reactors to high-power researchreactors to test reactors.

6


7/24


Significant fission product releases are generally notcredible for RTR designs.

RTR safety analyses analyze a maximum hypotheticalaccident (MHA) fission product release to bound dosesto staff and public.

All RTRs maintain NRC-approved emergency plansand procedures.

7


8/24


Compensatory measures put in place afterSeptember 11 attacks that contribute to event

mitigation and emergency response.

NRC conducted detailed analyses after the

attacks of September 11 that involved fissionproduct releases significantly beyond the MHA.

8


9/24

NRC Lessons Learned Review Commission directed a methodical and

systematic review of the safety of U.S.

power reactors in light of events in Japan.

Near-Term Task Force

review complete.(www.nrc.gov)

9
http://www.nrc.gov/http://www.nrc.gov/


10/24

Current U.S. Power Reactor PlantSafety

Similar sequence of events in the U.S. isunlikely.

Existing mitigation measures could reducethe likelihood of core damage andradiological releases.

No imminent risk from continued operationand licensing activities.

10


11/24

Power Reactor Recommendations theNRC Intends to Pursue Without Delay

Reevaluate all external hazards includingseismic and flooding hazards.

Perform seismic and flooding hazardwalkdowns.

Modify station backout (SBO) rule torequire enhanced capability to mitigateprolonged SBO.

11


12/24


Mitigation Strategies for Beyond DesignBasis Events.

Require reliable hardened vent designs in

BWRs with Mark I and II containments.

Enhancement of spent fuel poolinstrumentation.

12


13/24


Strengthen and integrate onsiteemergency response capabilities.

Require EP staffing and communicationsequipment to respond to multiunit eventsand prolonged SBO.

13


14/24

Path Forward on Near Term PowerReactor Recommendations

NRC Staff directed by the Commission to

implement specific recommendations Staff will issue orders, requests for

information (50.54(f) letters), and new

regulations Staff is seeking stakeholder input in

determining action on each

recommendation 14


15/24

Issues Considered for RTRs

Station black out

Natural events Spent fuel pools

Shutdown cooling

Hydrogen generation Reactor confinement or containment

15


16/24

Station Black Out

Most RTRs have emergency power.

No RTR needs electric power to safelyshut down.

No RTR needs electric power for short-

term (up to several hours) fuel cooling. Only one RTR needs electric power for

long term core fuel cooling.

16


17/24

Natural Events

All RTRs are evaluated for natural events.

Meteorology, seismic and flooding eventsare considered.

No RTR sites are near the Pacific Ocean

coast. Higher-powered RTRs are designed to

specific seismic accelerations.

17


18/24

Spent Fuel Pools Most RTRs do not generate significant quantities of

spent fuel due to low power and limited operation.

The Department of Energy accepts return of spent fuelfrom most RTRs to minimize on-site inventory.

Most RTRs do not have spent fuel pools. Fuel is storedin reactor pool except for two facilities.

Spent fuel pools do not need active cooling systemsbecause natural convection cooling can remove decayheat.

Fuel storage locations are designed to preventcriticality.

18


19/24

Shutdown Cooling Natural convection cooling is sufficient for shutdown

cooling at all but one facility.

For loss of coolant, air cooling is generally sufficient to

remove decay heat a few seconds after shutdown forlow -power RTRs.

For loss of coolant in high- power RTRs there is acombination of-

Design features keep the core partially covered in the case of alarge loss of coolant.

Core spray (ECCS) from diverse coolant supplies includinggravity feed tanks, municipal water and sump pumps. Systemsare passive.

Facilities have backup batteries or generators. 19


20/24

Hydrogen Generation

Low-power RTRs do not generate significant quantitiesof hydrogen during operation or after shutdown.

Most RTR cores are in open pools or tanks vented tothe atmosphere, so any hydrogen readily disperses.

Some high-power RTRs operate hydrogen controlsystems during reactor operation, but hydrogen

generation after shutdown is insufficient to causeexplosive concentrations.

Only one low-power RTR has zirconium cladding.

20


21/24

Reactor Confinement or Containment

Most RTRs have confinement buildings designed toconfine radioactive releases to a known pathway, such

as an elevated filtered stack. Confinementconfiguration during accidents is determined byanalyses.

Containment buildings mitigate the consequences of a

fission product release by filtering the building air anddispersing it to the atmosphere. Containment buildingshave requirements on leakage rates.

Containment buildings are protected against over andunder pressure.

21


22/24

Next Steps

The applicability of lessons learned from powerreactor evaluations will be considered.

Any significant new findings will be evaluated.

Work with the NEA on the assessment ofFukushima lessons learned and research

reactor stress test results and their possibleimplications to research reactors.

NRC is interested in other regulators RTRstress tests.

22


23/24

NRC is Seeking Fuel EvaluationExpertise

NRC is conducting market research by

seeking information on known individualsand organizations to assist NRC in theconduct of LEU fuel reviews.

Please see me if you can suggest someone.

23


24/24

Thank you

Questions

24

the impact of the fukushimadaiichi accident on nrc’sregulation of research and testreactors

Documents