[Federal Register Volume 60, Number 146 (Monday, July 31, 1995)]
[Notices]
[Pages 39021-39026]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-18686]



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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]
BILLING CODE 7590-01-P