Proposed Generic Communication and Draft Regulatory Guide; Issuance, Availability

NUCLEAR REGULATORY COMMISSION

Proposed Generic Communication and Draft Regulatory Guide;

Issuance, Availability

AGENCY: Nuclear Regulatory Commission.

ACTION: Notice of opportunity for public comment on the proposed

bulletin and draft guide.

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SUMMARY: The Nuclear Regulatory Commission (NRC) is proposing to issue

a bulletin titled ``Potential Plugging of Emergency Core Cooling

Suction Strainers for Debris in Boiling Water Reactors''; the text of

the bulletin is included in this notice under the Supplementary

Information heading. The proposed bulletin would request boiling water

reactor (BWR) licensees to implement appropriate procedural measures

and plant modifications to minimize the potential for clogging of

suppression pool suction strainers of emergency core cooling systems

(ECCS) by debris generated during a loss-of-coolant accident (LOCA).

The NRC has also issued a related Draft Regulatory Guide, DG-1038,

``Water Sources for Long-Term Recirculation Cooling Following a Loss-

of-Coolant Accident,'' which is a proposed Revision 2 to Regulatory

Guide 1.82. The draft guide provides additional technical guidance to

BWR licensees. The draft guide has not received complete staff review

and does not represent an official NRC staff position.

The proposed bulletin and draft guide are being issued to involve

the public in the development of a regulatory position in this area.

The NRC is seeking comment from interested parties regarding both the

technical and regulatory aspects of the proposed bulletin and draft

guide. The titles of the proposed bulletin and draft guide should be

mentioned in all correspondence.

[[Page 39022]]

The staff is also seeking specific technical comments from

interested parties on the following questions:

1. Does reflective metallic insulation contribute to the potential

clogging of the ECCS suction strainers? Provide any available

supporting data with the response.

2. How effective are alternative strainer designs (e.g., the

``star'' strainer or the ``stacked disk'' strainer) at preventing or

reducing the potential for strainer clogging? Provide any available

supporting test data with the response.

3. How effective are active features (e.g., self-cleaning strainer

designs or backflushing of strainers) at mitigating or preventing

strainer clogging? Provide any available supporting test data with the

response.

4. What criteria should be used for determining adequate sizing of

passive ECCS suction strainers? The staff is seeking specific comments

and supporting technical justification regarding what assumptions

should be used in estimating the strainer head loss including types and

amounts of debris generated, debris characteristics (e.g., size and

shape), amounts of debris transported from the drywell to the

suppression pool, calculation of debris quantities entrained on the

strainer surfaces, and head loss correlations. Where possible,

supporting data should be provided along with recommended assumptions.

5. What actions would be required by licensees to ensure

operability of active features (e.g., backflush and self-cleaning

strainers) installed in response to the proposed bulletin's requested

actions? The staff is also seeking suggestions on ways to incorporate

appropriate actions and surveillance requirements into the Technical

Specifications (TS) which are consistent with the form of the improved

standard TS for the associated safety systems.

The proposed bulletin, draft guide, and supporting documentation

were discussed in meeting number 275 of the Committee to Review Generic

Requirements (CRGR) on June 27, 1995. The relevant information that was

sent to the CRGR to support its review of the proposed bulletin is

available in the NRC Public Document Room under accession number

9507200223. The NRC will consider comments received from interested

parties before issuing the final version of the proposed bulletin and

draft guide. The NRC's evaluation will include a review of the

technical position and, as appropriate, an analysis of the value/impact

on licensees.

Public Meeting: During the public comment period, the staff will

hold a public meeting with the Boiling Water Reactor Owners Group to

discuss the above questions as well as any other comments on the

proposed bulletin and draft guide. The meeting will be held on August

24 and 25, 1995. The meeting will run from 8:00 a.m. to 5:00 p.m. on

August 24th and from 8:00 a.m. to 12:00 p.m. on August 25th. The public

meeting will be held at the Two White Flint North Auditorium, U.S.

Nuclear Regulatory Commission, 11545 Rockville Pike, Rockville,

Maryland. A meeting notice will be issued approximately two weeks prior

that will provide the agenda for the meeting. Interested parties, who

have questions about the proposed bulletin or draft guide and plan to

attend this meeting, are requested to submit their questions in writing

to the staff at least a week before the meeting, so that the staff may

be better prepared to respond to the questions at the meeting. Written

questions for the meeting should be sent to M. David Lynch, U.S.

Nuclear Regulatory Commission, Mail Stop 0-13 D1, Washington, DC 20555-

0001.

Visitor parking is very limited around the NRC office in Rockville,

Maryland. No visitor parking is available in the NRC buildings. It is

recommended that people attending the meeting commute to the meeting

via the Metro. The NRC is located immediately across the street from

the White Flint Metro stop.

DATES: Comment period expires October 2, 1995. Comments submitted after

this date will be considered if it is practical to do so, but assurance

of consideration cannot be given except for comments received on or

before this date.

ADDRESSES: The proposed bulletin and the draft guide are available for

inspection at the NRC Public Document Room, 2120 L Street NW (Lower

Level), Washington, DC. Single copies of the proposed bulletin or the

draft guide may be obtained free of charge by writing to the U.S.

Nuclear Regulatory Commission, Washington, DC 20555-0001, Attention:

Distribution and Mail Services Section. Requests for single copies of

the proposed bulletin or draft guide may also be faxed to (301) 415-

2260. Telephone requests cannot be accommodated. Regulatory guides and

bulletins are not copyrighted, and NRC approval is not required to

reproduce them. Both the proposed bulletin and draft guide can be

accessed electronically; instructions for doing this are provided

below.

Written comments on the proposed bulletin and draft guide may be

submitted to the Rules Review and Directives Branch, U.S. Nuclear

Regulatory Commission, Washington, DC 20555-0001. Written comments may

also be delivered to 11545 Rockville Pike, Rockville, Maryland, from

7:30 a.m. to 4:15 p.m., Federal workdays. Copies of written comments

received may be examined at the NRC Public Document Room, 2120 L Street

NW (Lower Level), Washington, DC.

Electronic Access: The proposed bulletin and draft guide may be viewed

electronically, and comments may be submitted electronically, in either

ASCII text or WordPerfect format (version 5.1 or later), by calling the

NRC Electronic Bulletin Board Service (BBS) on FedWorld. The bulletin

board may be accessed using a personal computer, a modem, and one of

the commonly available communications software packages, or directly

via Internet.

By using a personal computer and modem, the NRC subsystem on

FedWorld can be accessed directly by dialing the toll free number: 1-

800-303-9672. Communication software parameters should be set as

follows: parity to none, data bits to 8, and stop bits to 1 (N,8,1).

Using ANSI or VT-100 terminal emulation, the NRC NUREGs and RegGuides

for Comment subsystem can then be accessed by selecting the ``Rules

Menu'' option from the ``NRC Main Menu.'' For further information about

options available for NRC at FedWorld, consult the ``Help/Information

Center'' from the ``NRC Main Menu.'' Users will find that the

``FedWorld Online User's Guides'' are particularly helpful. Many NRC

subsystems and databases also have a ``Help/Information Center'' option

that is tailored to the particular subsystem.

The NRC subsystem on FedWorld can also be accessed by a direct dial

phone number for the main FedWorld BBS, 703-321-3339, or by using

Telnet via Internet, fedworld.gov. If using 703-321-3339 to contact

FedWorld, the NRC subsystem may be accessed from the main FedWorld menu

by selecting the ``Regulatory, Government Administration and State

Systems,'' then selecting ``Regulatory Information Mall.'' At that

point, a menu will be displayed that has an option ``U.S. Nuclear

Regulatory Commission'' that will take the user to the NRC Online main

menu. The NRC Online area also can be accessed directly by typing ``/go

nrc'' at a FedWorld command line. If the user accesses NRC from

FedWorld's main menu, the user may return to FedWorld by selecting the

``Return to FedWorld'' option from the NRC Online Main Menu. However,

if the user accesses NRC at FedWorld by using the NRC's toll-free

number, the user will have full access to all NRC systems, but

[[Page 39023]]

will not have access to the main FedWorld system.

If the user contacts FedWorld using Telnet, the user will see the

NRC area and menus, including the Rules menu. The user will be able to

download documents and leave messages, but will not be able to write

comments or upload files (comments). If the user contacts FedWorld

using file transfer protocol (FTP), all files can be accessed and

downloaded but uploads are not allowed; the user will only see a list

of files without descriptions (normal Gopher look). An index file

listing all files within a subdirectory, with descriptions, is

included. There is a 15-minute time limit for FTP access.

Accessing FedWorld through the World Wide Web, like FTP, only

provides access for downloading files and does not display the NRC

Rules menu.

For more information on NRC bulletin boards call Mr. Arthur Davis,

Systems Integration and Development Branch, U.S. Nuclear Regulatory

Commission, Washington, DC 20555, telephone (301) 415-5780, e-mail

[email protected].

FOR FURTHER INFORMATION CONTACT: M. David Lynch at (301) 415-3023, e-

mail [email protected] or Robert Elliott at (301) 415-1397, e-mail

[email protected].

SUPPLEMENTARY INFORMATION:

United States Nuclear Regulatory Commission, Office of Nuclear Reactor

Regulation, Washington, DC 20555

NRC Bulletin 95-XX: Potential Plugging of Emergency Core Cooling

Suction Strainers by Debris in Boiling Water Reactors

Addressees

All holders of operating licenses or construction permits for

boiling-water reactors (BWRs).

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this

bulletin to: (1) Request addressees to implement appropriate procedural

measures and plant modifications to minimize the potential for clogging

of emergency core cooling system (ECCS) suppression pool suction

strainers by debris generated during a loss-of-coolant accident (LOCA),

and

(2) Require that addressees report to the NRC whether and to what

extent the requested actions will be taken and notify the NRC when

actions associated with this bulletin are complete.

Background

On July 28, 1992, an event occurred at Barseback Unit 2, a Swedish

BWR, which involved the plugging of two ECCS suction strainers. The

strainers were plugged by mineral wool insulation that had been

dislodged by steam from a pilot-operated relief valve that spuriously

opened while the reactor was at 3,100 kPa [435 psig]. Two of the five

strainers on the suction side of the containment spray pumps were in

service and became partially plugged with mineral wool. Following an

indication of high differential pressure across both suction strainers

70 minutes into the event, the operators shut down the containment

spray pumps and backflushed the strainers. The Barseback event

demonstrated that the potential exists for a pipe break to generate

insulation debris and transport a sufficient amount of the debris to

the suppression pool to clog the ECCS strainers.

On January 16 and April 14, 1993, two events involving the clogging

of ECCS strainers also occurred at the Perry Nuclear Power Plant, a

domestic BWR. The first Perry event involved clogging of the suction

strainers for the residual heat removal (RHR) pumps by debris in the

suppression pool. The second Perry event involved the deposition of

filter fibers on these strainers. The debris consisted of glass fibers

from temporary drywell cooling unit filters that had been inadvertently

dropped into the suppression pool, and corrosion products that had been

filtered from the pool by the glass fibers which accumulated on the

surface of the strainer. The Perry events demonstrated the deleterious

effects on strainer pressure drop caused by the filtering of

suppression pool particulates (corrosion products or ``sludge'') by

fibrous glass materials entrained on the ECCS strainer surfaces. These

corrosion products are typically present in large quantities in

domestic BWRs. Separate test programs have been conducted by the

Boiling Water Reactor Owners Group (BWROG) and the staff to quantify

this filtering effect.

Based on these events, the NRC issued Bulletin 93-02, ``Debris

Plugging of Emergency Core Cooling Suction Strainers,'' on May 11,

1993. The bulletin requested licensees to remove fibrous air filters

and other temporary sources of fibrous material, not designed to

withstand a LOCA, from the containment. In addition, licensees were

requested to take any immediate compensatory measures necessary to

ensure the functional capability of the ECCS.

Following these events, the staff performed calculations to assess

the vulnerability of each domestic BWR. The results of these

calculations showed that the potential existed for the ECCS pumps to

lose net positive suction head (NPSH) margin due to clogging of the

suction strainers by LOCA-generated debris. The staff then conducted a

detailed study of a reference BWR 4 plant with a Mark I containment.

The preliminary results of the staff study are contained in a draft

report, ``Parametric Study of the Potential for BWR ECCS Strainer

Blockage Due to LOCA Generated Debris,'' which was published in August

1994. The preliminary study results reaffirmed the results of the

earlier staff calculations.

Members of the NRC staff also attended an Organization for Economic

Cooperation and Development/Nuclear Energy Agency (OECD/NEA) workshop

on the Barseback incident held in Stockholm, Sweden, on January 26 and

27, 1994. Representatives from other countries at this conference

discussed actions taken or planned which would prevent or mitigate the

consequences of BWR strainer blockage. Based on the preliminary results

of the staff's study, as reinforced by information learned at the OECD/

NEA workshop, the staff issued NRC Bulletin 93-02, Supplement 1,

``Debris Plugging of Emergency Core Cooling Suction Strainers,'' on

February 18, 1994. The purpose of the bulletin supplement was to

request that BWR licensees take the appropriate interim actions to

ensure reliability of the ECCS so that the staff and industry would

have sufficient time to develop a permanent resolution. In addition,

the bulletin supplement informed licensees of pressurized water

reactors (PWRs) and BWRs of new information on the vulnerability of

ECCS suction strainers in BWRs and containment sumps in PWRs to

clogging during the recirculation phase of a LOCA.

Licensee responses to NRC Bulletin 93-02 and its supplement have

demonstrated that appropriate interim measures have been implemented by

licensees to ensure adequate protection of public health and safety,

and to allow continued operation until the final actions requested in

this bulletin are implemented.

In responding to these bulletins, licensees ensured: (1) the

availability of alternate water sources (both safety and non-safety

related sources) to mitigate a strainer clogging event, (2) that

emergency operating procedures (EOPs) provided adequate guidance on

mitigating a strainer clogging event, (3) that operators were

adequately trained to mitigate a strainer clogging event, and (4) that

loose and temporary fibrous materials stored in containment were

removed. In addition, a generic safety assessment conducted by the

Boiling Water Reactor Owners Group (BWROG)

[[Page 39024]]

concluded that operators would have adequate time to make use of

alternate water sources (25-35 minutes). The staff also notes that the

probability of the initiating event is low. The actions requested in

this bulletin will ensure that the ECCS can perform its safety function

and minimize the need for operator action to mitigate a LOCA.

Discussion

The results of the staff study, initially documented in the draft

NUREG/CR-6224, demonstrate that for the reference plant, there is a

high probability that the available NPSH margin for the ECCS pumps will

be inadequate following dislodging of insulation caused by a LOCA and

transport of insulation debris to the suction strainers. In addition,

the study calculated that the loss of NPSH could occur quickly (less

than 10 minutes into the event). The study also demonstrated that

determining the adequacy of NPSH margin for an ECCS system is highly

plant-specific because of the large variations in such plant

characteristics as containment type, ECCS flow rates, insulation types,

plant layout, and available NPSH margin. The final version of NUREG/CR-

6224 is scheduled for issuance in September 1995.

The Barseback event demonstrated that a pipe break can generate and

transport large quantities of insulation debris to the suppression pool

where they can be deposited onto strainer surfaces and potentially

cause the ECCS to lose NPSH. The Perry events further demonstrated that

fibrous insulation debris combined with corrosion products present in

the suppression pool (sludge) can exacerbate the problem. This

phenomenon was confirmed in the staff study which showed that the

calculated loss of NPSH could occur soon (less than 10 minutes) after

ECCS initiation. The effect of filtering sludge from the suppression

pool water by fibrous debris deposited on the strainer surface was

further confirmed in NRC-sponsored testing conducted at the Alden

Research Laboratory which demonstrated that the pressure drop across

the strainer was greatly increased by this filtering effect. Additional

testing sponsored by the NRC at Alden Research Laboratory demonstrated

that the energy conveyed to the suppression pool during the

``chugging'' phase of a LOCA is sufficient to ensure that the fibrous

debris and sludge are well-mixed and evenly distributed in the

suppression pool, and can remain suspended for a sufficiently long

period of time to allow large quantities to be deposited onto the

strainer surfaces. The staff has concluded that this problem is

applicable to all domestic BWRs. The basis for the staff's conclusion

is as follows: (1) there does not appear to be any features specific to

a particular plant, class of plants, or containment type which would

mitigate or prevent the generation, transport to the suppression pool,

or deposition on the ECCS strainers of sufficient material to clog the

strainers, and (2) parametric analyses performed in support of the

NUREG/CR-6224 study using parameter ranges which bound most domestic

BWRs failed to find parameter ranges which would prevent BWRs with

other containment types from being susceptible to this problem. In

addition, the staff study was conducted on a Mark I; Barseback had a

strainer clogging event and is similar in design to a Mark II; and

Perry, a Mark III, also had a strainer clogging event.

Section 50.46 of Title 10 of the Code of Federal Regulations (10

CFR 50.46) requires that licensees design their ECCS systems to meet

five criteria, one of which is to provide long-term cooling capability

of sufficient duration following a successful system initiation so that

the core temperature shall be maintained at an acceptably low value and

decay heat shall be removed for the extended period of time required by

the long-lived radioactivity remaining in the core. The ECCS is

designed to meet this criterion, assuming the worst single failure.

Experience gained from operating events and detailed analysis, as

previously discussed, demonstrate that excessive buildup of debris from

thermal insulation, corrosion products, and other particulates on ECCS

pump strainers is highly likely to occur, creating the potential for a

common-cause failure of the ECCS, which could prevent the ECCS from

providing long-term cooling following a LOCA. The staff concludes;

therefore, that this issue must be resolved by licensees in order to

ensure compliance with the regulations; specifically, to ensure that

long-term cooling can be provided in accordance with 10 CFR 50.46.

Plant-specific analyses to resolve this issue are difficult to

perform because a substantial number of uncertainties are involved.

Examples of these uncertainties include the amount of debris that would

be generated by a pipe break for various insulation types; the amount

of the debris that would be transported to the suppression pool; the

characteristics of debris reaching the suppression pool (e.g., size and

shape); and head loss correlations for various insulation types

combined with suppression pool corrosion products, paint chips, dirt,

and other particulates. Many of these uncertainties would be plant-

specific because of the differences in plant characteristics, such as

plant layout, insulation types, ECCS flow rates, containment types, and

NPSH margin. Testing may be required to quantify these uncertainties

for licensees to demonstrate compliance with 10 CFR 50.46.

The staff has also closely followed the work of the BWROG to

resolve this issue. The BWROG has evaluated several potential

solutions, and is currently testing three new strainer designs: two

passive strainer designs and one self-cleaning design. The ongoing

BWROG effort is consistent with the options proposed in this bulletin

for resolution of the the ECCS potential strainer clogging issue. These

options are discussed in the next section under Requested Actions. The

BWROG is also developing a utility resolution guidance (URG) document

for providing the utilities with: 1) guidance on evaluation of the ECCS

potential strainer clogging issue for their plant, 2) a standard

industry approach to resolution of the issue which is technically

sound, and 3) guidance which is consistent with the requested actions

in this bulletin for demonstrating compliance with 10 CFR 50.46. The

staff considers this document to be an important part of the

implementation of the final resolution of this issue, and will closely

monitor the development and application of the URG.

Requested Actions

All BWR licensees are requested to implement appropriate measures

to ensure the capability of the ECCS to perform its safety function

following a LOCA. The staff has identified three potential resolution

options; however, licensees may propose others which provide an

equivalent level of assurance that the ECCS will be able to perform its

safety function following a LOCA. The three options identified by the

staff are as follows:

Option 1: Installation of a large capacity passive strainer design.

Draft Regulatory Guide DG-1038, proposed Revision 2 of Regulatory Guide

1.82 (RG 1.82), ``Water Sources for Long-Term Recirculation Cooling

Following a Loss-of-Coolant Accident,'' has been revised to provide

additional technical guidance to BWR licensees on the conduct of

evaluations to ensure compliance with 10 CFR 50.46. If this option is

selected by a licensee, the strainer design used should have sufficient

capacity to ensure that debris loadings equivalent to a scenario

calculated in accordance with Section C.2.2 of DG-1038 do not cause

[[Page 39025]]

a loss of net positive suction head (NPSH) for the ECCS. This option

has two main advantages. First, it is completely passive and,

therefore, requires no operator intervention. Second, it does not

require an interruption of ECCS flow. While this is the most

advantageous of the options identified, the staff recognizes that it

may be difficult for most licensees to implement this option due to the

difficulty in providing sufficient structural support for the strainers

to handle LOCA-induced hydrodynamic loads. However, the staff notes

that licensees may take appropriate measures in combination with this

option to reduce the potential debris sources in containment and the

suppression pool, which would, in turn, reduce the required capacity

and physical size of the strainer, and therefore, assist in reducing

the structural burden of the strainer installation. Licensees choosing

this option for resolution should establish programs, as necessary, to

ensure that the potential for debris to be generated and transported to

the strainer surface does not at any time exceed the assumptions used

in estimating the amounts of debris for sizing of the strainers in

accordance with DG-1038.

Option 2: Installation of a self-cleaning strainer.

This option automatically prevents strainer clogging by providing

continuous cleaning of the strainer surface with a scraper blade or

brush. Like Option 1, the self-cleaning strainer design would not rely

on operator action or interrupt ECCS flow. However, this option does

rely on an active component which is fully exposed to the LOCA effects

in the suppression pool to keep the strainer surface clean. Therefore,

appropriate measures should be taken to ensure the operability of the

strainer. Installation of this type of strainer should be combined with

the following measures to protect the strainer and ensure its

operability: (1) implementation of reasonable measures to eliminate

debris sources which could potentially damage or overload the strainer

during a LOCA, including, as a minimum, removal of all debris from the

suppression pool every refueling outage, and (2) implementation of

surveillances to ensure periodic cleaning of the suppression pool and

the operability of the strainer.

Option 3: Installation of a backflush system.

The backflush system is a reactive system that relies on operator

action to remove debris from the surface of the strainer to prevent it

from clogging. In order to ensure that operators can adequately deal

with a strainer clogging event, installation of this type of system

should be combined with the following measures: (1) reasonable measures

to maximize the amount of time before clogging could occur; (2)

instrumentation and alarms to indicate when strainer differential

pressure increases; (3) operator training on recognition and mitigation

of a strainer clogging event, and (4) implementation of surveillances

to ensure the operability of the strainer instrumentation and backflush

system. A supporting analysis for installation of a backflush system

which is consistent with Section C.2.2 of DG-1038 should be performed

to demonstrate that operators have sufficient time to recognize the

onset of clogging and to take appropriate action, taking into

consideration their other responsibilities after a LOCA. In addition,

this analysis should ensure that operators have the capability and

sufficient time to cycle backflushing at the expected frequency and for

the required total number of actuations anticipated in providing long-

term core cooling following a LOCA.

Compliance with 10 CFR 50.46 requires the use of safety grade

equipment. Any request to deviate from this position would require an

exemption with a supporting technical analysis, and must meet the

specific requirements of 10 CFR 50.12. Active features such as

backflush and the self-cleaning strainer must be supported by test data

that demonstrate the design effectiveness for removal of debris

entrained on the surface of the strainer. Strainers installed for

Option 1 must be supported by test data that demonstrate their

performance characteristics, and their ability to handle the worst case

scenario for debris deposition on the strainer surface.

On July 22, 1993, the Commission published its final policy

statement on Technical Specifications (TS) improvements for nuclear

power reactors in the Federal Register (58 FR 39132). Part of that

policy statement stated that the purpose of TS is to impose those

conditions or limitations upon reactor operation necessary to obviate

the possibility of an abnormal situation or event giving rise to an

immediate threat to the public health and safety by identifying those

features that are of controlling importance to safety and establishing

on them certain conditions of operation which cannot be changed without

prior Commission approval. Based on this purpose and 10 CFR 50.36, the

Commission also provided four criteria that delineate those constraints

on design and operation of nuclear power plants that belong in TS.

Criterion 3 of the policy statement states that a structure, system or

component which is part of the primary success path and which functions

or actuates to mitigate a Design Basis Accident or Transient that

either assumes the failure of or presents a challenge to the integrity

of a fission product barrier should be captured in the TS. The staff

believes that self-cleaning strainers, backflush systems, and

instrumentation installed to support backflush systems meet Criterion 3

of the Commission's policy and should be captured in the TS because

these components are necessary for the primary success path (i.e., the

ECCS) to mitigate design basis LOCA. TS should be proposed to support

the above actions and should include, where appropriate for the option

selected: (1) appropriate limiting conditions for operation (LCOs); (2)

channel checks, channel functional tests, and calibrations of strainer

instrumentation at an interval commensurate with other ECCS

instrumentation, and (3) testing of active features at the same

interval as functional tests of the low-pressure coolant injection

(LPCI) system. The final version of this bulletin will include sample

TS for Options 2 and 3.

Plant procedures and other actions implemented in response to NRC

Bulletin 93-02 and its supplement, should remain in place until the

final corrective actions requested in this bulletin have been

implemented.

All licensees are requested to implement these actions by December

31, 1997. This timeframe for implementation of the final resolution is

considered appropriate by the staff due to the interim actions already

taken by licensees and the low probability of the initiating event.

Required Response

All addressees are required to submit the following written

reports:

(1) Within 180 days of the date of this bulletin, a report

indicating whether the addressee intends to comply with these requested

actions, including a detailed description of planned actions and

mitigative strategies to be used, the schedule for implementation, and

proposed TS; or, if the licensee does not intend to comply with these

actions, a detailed description of the safety basis for the decision.

The report must contain a detailed description of any proposed

alternative course of action, the schedule for completing this

alternative course of action, the safety basis for determining the

acceptability of the planned alternative course of action, and proposed

TSs, if

[[Page 39026]]

appropriate, that support the proposed alternative course of action and

are consistent with the Commission's Policy Statement on TS. The staff

considers the 180-day response period to be appropriate given the

amount of engineering that licensees may wish to perform before they

provide their formal response to the staff.

(2) Within 30 days of completion of all requested actions, a report

confirming completion and summarizing any actions taken.

Address the required written reports to the U.S. Nuclear Regulatory

Commission, ATTN: Document Control Desk, Washington, D.C. 20555-0001,

under oath or affirmation under the provisions of Section 182a, the

Atomic Energy Act of 1954, as amended, and 10 CFR 50.54(f). In

addition, submit a copy of the reports to the appropriate regional

administrator.

Related Generic Communications

NRC Bulletin 93-02, ``Debris Plugging of Emergency Core Cooling

Suction Strainers,'' dated May 11, 1993 and its supplement dated

February 18, 1994.

Backfit Discussion

The actions requested by this bulletin are considered backfits in

accordance with NRC procedures and are necessary to ensure that

licensees are in compliance with existing NRC rules and regulations.

Specifically, 10 CFR 50.46 requires that adequate ECCS flow be provided

to maintain the core temperature at an acceptably low value and to

remove decay heat for the extended period of time required by the long-

lived radioactivity remaining in the core following a design-basis

accident. Therefore, this bulletin is being issued as a compliance

backfit under the terms of 10 CFR 50.109(a)(4)(i), and a full backfit

analysis was not performed. An evaluation was performed in accordance

with NRC procedures, including a statement of the objectives of and the

reasons for the requested actions and the basis for invoking the

compliance exception. A copy of this evaluation will be made available

in the NRC Public Document Room.

Paperwork Reduction Act Statement

The information collections contained in this request are covered

by the Office of Management and Budget clearance number 3150-0011,

which expires July 31, 1997. The public reporting burden for this

collection of information is estimated to average 160 hours per

response, including the time for reviewing instructions, searching

existing data sources, gathering and maintaining the data needed, and

completing and reviewing the collection of information. Send comments

regarding this burden estimate or any other aspect of this collection

of information, including suggestions for reducing this burden, to the

Information and Records Management Branch (T-6 F33), U.S. Nuclear

Regulatory Commission, Washington, D.C. 20555-0001, and to the Desk

Officer, Office of Information and Regulatory Affairs, NEOB-10202,

(3150-0011), Office of Management and Budget, Washington, D.C. 20503.

Compliance with the following request for information is purely

voluntary. The information would assist NRC in evaluating the cost of

complying with this bulletin:

(1) The licensee staff time and costs to perform requested

inspections, corrective actions, and associated testing;

(2) The licensee staff time and costs to prepare the requested

reports and documentation;

(3) The additional short-term costs incurred as a result of the

inspection findings, such as the costs of the corrective actions or the

costs of down time;

(4) An estimate of the additional long-term costs that will be

incurred in the future as a result of implementing commitments such as

the estimated costs of conducting future inspections or increased

maintenance.

Dated at Rockville, Maryland, this 19th day of July 1995.

For the Nuclear Regulatory Commission.

Brian K. Grimes,

Director Division of Project Support Office of Nuclear Reactor

Regulation.

John W. Craig,

Deputy Director Division of Engineering Technology Office of Nuclear

Regulatory Research.

[FR Doc. 95-18686 Filed 7-28-95; 8:45 am]

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