ML20043F027

Carr Response to Bevill Subcommittee on Energy & Water Development Question 29 for 900327 Hearing

ML20043F027
Person / Time
Issue date:	03/27/1990
From:	Carr NRC COMMISSION (OCM)
To:	Bevill HOUSE OF REP., APPROPRIATIONS
References
BEVILL-900327, CCS, NUDOCS 9006140104
Download: ML20043F027 (3)

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$do/ok MR. BEVILL:

What.is the relationship between research projects ano the development of rules and regulations? What are some examples of how research has directly supported the rulemaking process?

CHAIRMAN CARR:

The work carried out by the Office of Nuclear Regulatory Research (RES) provides the quantitative bases and evaluation methods needed to confirm the

' adequacy of existing regulatory requirments and to identify where and to what L

extent nodifications to these requirements, including the establishment of new rules, are needed to maintain adequate protection of the public.

Specific research programs are undertaken for the expressed purpose of ceveloping new information or evaluation methods or for confirming existing data that the staff has determined-to be necessary to resolve an identified safety issue.

Examples of the type of data developed in this program are the characteri-zation of radiation damage to reactor piping and structural material, the-determination of corrosion and wear rates of piping and equipment, the behavior of plant and safety related components to earthquake = forces, and the behavior of fission products released to the environment.' RES also develops specialized, validated computer codes and models which allow predictions to be made of, among other things, the performance of safety related equipment, fuel,-cladding and containment systems under abnormal plant operating conditions and accidents.

In addition, and equally important, the Research program provides the

-licensing and inspection staff with independent and unbiased technical irformation and validated evaluation methods needed to assess licensee generated data submitted in support of new license applications, on omendments to the licenses of operating plants and to facilitate staff evaluations of plant performance including assessing the safety significance of abnormal operating events and the effectiveness of related remedial actions.

Some notable examples of where research results have directly supported the development or modification of Commission requirements are:

Ouestion 29/Bevill/RES 9006140104 900327 03/27/90 CONG *****

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l The Station Blackout Rule revision of 10 CFR 50.63. This rule _ specifies requirements that all reactor licensees rmst meet to provide assurance that these stations can cope with loss of off-site electrical power. The extensive work that has been done in reactur risk analyses have provided the quantita--

tive bases upon which the requirements set forth in this rule have been formulated.

The revision of 10 CFR 50 Appendix K.

This rule, based on 14 years of thormal hydraulic and related research, sets forth requirements for evaluating the performance of emergency core cooling systems. This revision permits increased utilization of nuclear fuel and flexibility in plant operations which could result in ratepayer savings of several million dollars per plant with no reduction in safety.

The revision cf General Cesign Criterion 4,10 CFR 50, Appendix A. -This.

change. permitted the removal of certain hardware, e.g., pipe whip restraints, jet -impingement shields, and hydraulic snubbers in nuclear power plants.

This modification reflects tha results of research on materials, accident, and earthquake phenomenology which indicated that therirally caused pipe expansion ond associated stresses and cracking in power plant piping, and

-the unforeseen impacting between piping and pipe restraints, can be worsened by their use, thus increasing, rather than decreasing, the probability of failures under severe conditions.

In ac;dition, removal'of hardware greatly facilitates inspection of critical plant piping, thus, increasing our ability

.to. detect leaks in piping before serious breaks develop.

The ATWS Rule - revision to 10 CFR 50. This rule, based on extensive research analysis of the behaviur of reactor coolant, equipment and fuels under severe transients, identified changes in plant equipment and operating procedures that would be required to ensure power plants would be able to cope with a

. situation in which the reactor would not be automatically shut down in response to a transient. This type of event has, for certain plants, been shown to be a source of the risk of a severe accident.

Quest'on 29/Bevill/RES 03/27/90

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The pressurized-Thermal Shock Rule - Revision to 10 CFR 50 - Based on research results'in our materials research program,. a rule was issued which set forth the limitation on embrittlement of reactor vessels for operatingEplants'to avoid pressure vessel failure due to pressurized overcooling.

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