**NRC INSPECTION MANUAL**

SSIB

Temporary Instruction 2515/166

PRESSURIZED WATER REACTOR CONTAINMENT SUMP BLOCKAGE

(NRC GENERIC LETTER 2004-02)

CORNERSTONE: MITIGATING SYSTEMS

APPLICABILITY: This temporary instruction applies to all holders of
operating licenses for pressurized-water reactors.

2515/166-01 OBJECTIVE

01.01 The objective of this Temporary Instruction (TI) is to support the
Nuclear Regulatory Commission (NRC) review of licensees' activities in
response to NRC Generic Letter (GL) 2004-02, "Potential Impact of Debris
Blockage on Emergency Sump Recirculation at Pressurized Water Reactors
(PWRs)." This TI requires NRC inspectors to verify actions implemented
in response to NRC Generic Letter 2004-02 are complete and, where
applicable, are programmatically controlled. It is not the objective of
this TI to determine the adequacy of the licensee actions taken as a
response to GL 2004-02; that is an Office of Nuclear Reactor Regulation
(NRR) function. NRR will be reviewing licensee GL responses and
conducting audits to assess the adequacy of licensee actions.

2515/166-02 BACKGROUND

Generic Safety Issue (GSI) 191 was established to determine whether the
transport and accumulation of debris in PWR containments following a
loss-of-coolant accident (LOCA) (or other high-energy line breaks if
recirculation is credited) will impede the long-term operation of the
emergency core cooling systems (ECCS) or containment spray systems
(CSS). In the event of a LOCA, materials in the vicinity of the break,
such as thermal insulation, coatings, and concrete, would be damaged and
dislodged. A fraction of this material would then be transported to the
recirculation sump and accumulate on its screens. Debris accumulating on
the sump screens has the tendency to form a bed which, much like a
filter, results in an increased head loss across the sump screens. The
additional head loss due to the accumulation of debris is a safety
concern because it has the potential to exceed the net positive suction
head (NPSH) margin required to assure the successful operation of the
ECCS and CSS pumps.

Sump blockage had initially been evaluated in the early 1980s under
unresolved safety issue (USI) A-43. Although the original regulatory
guidance to assume 50% screen blockage was determined to be
non-conservative and revised in 1985, a backfit was not then considered
justified. However, Generic Letter 85-22 advised licensees to consider
the revised (mechanistic) guidance in Regulatory Guide 1.82, Revision 1,
"Water Sources for Long-Term Recirculation Cooling Following a
Loss-of-Coolant Accident," for the conduct of 10 CFR 50.59 reviews
associated with the changeout or modification of thermal insulation.

Subsequent blockage events at BWRs and additional research revealed that
there could be more and finer debris than previously thought,
accumulating uniformly. The effect of filtration of particulates by
fibers, previously not considered, would result in higher than
previously expected head losses. The Office of Nuclear Regulatory
Research (RES) technical review also identified concerns with the
potential deleterious effects that both upstream blockage (reducing
available NPSH due to lower pool levels) and downstream blockage (from
material passing through the screens) could have on ECCS performance.
Based upon the findings of its technical evaluation, RES concluded that
GSI-191 was a valid concern and recommended detailed plant-specific
evaluations to determine the susceptibility of each PWR to
sump-clogging.

NRR concurred with RES's conclusion and developed an action plan to
resolve GSI-191. Public meetings were held with Nuclear Energy Institute
(NEI) and the PWR Owners' Group representatives to discuss development
of industry evaluation guidelines for plant-specific sump-clogging
evaluations. NRC's plans to revise Regulatory Guide (RG) 1.82 and issue
a generic letter to support closure of GSI-191 were also discussed in
the meetings. The staff briefed the Advisory Committee on Reactor
Safeguards (ACRS) on both the draft generic letter and draft revision to
Regulatory Guide 1.82 (DG 1107, Reference 1). Their letter dated
February 20, 2003, endorsed issuance of the draft RG and draft generic
letter to expedite resolution of GSI-191.

During review of the draft generic communications, concerns were
elevated regarding the need for near-term determinations as to whether
the ECCS and CSS recirculation functions are in compliance with
applicable regulatory requirements, in particular the 10 CFR 50.46
requirement for long-term cooling, when a mechanistic evaluation of
debris generation, transport, and accumulation on the sump screens is
performed. These concerns were based on recent events such as
Davis-Besse Licensee Event Report (LER) 50-346/2002-005-01, which showed
the potential for increased failure probability of the ECCS due to
debris accumulation and potential debris passage through the screens.
Also, LER 50-346/2003-002-00, stated that the high pressure injection
(HPI) pumps had been declared inoperable as a result of the potential
for debris to damage the pump internals during the recirculation phase
of certain postulated LOCAs when the HPI pumps are required to take
suction from the containment recirculation sump. Additionally, in
February 2003, Los Alamos National Laboratory published the
NRC-sponsored technical report LA-UR-02-7562 (Reference 2) which
analyzed the potential risk benefit of operator actions to recover from
sump clogging events. The ACRS has recommended expeditious resolution of
this issue.

Therefore, consistent with the risk significance of the PWR
sump-clogging concern, the staff issued NRC Bulletin 2003-01 to request
information on compliance and information on compensatory measures if
compliance cannot be demonstrated. The underlying purpose of
Bulletin 2003-01 was to make sure that the licensees implemented
near-term compensatory measures that reduce the risk associated with
sump failure at plants whose sump screens may be degraded or potentially
challenged in the event of a LOCA.

The NRC recognized that complex evaluations are required to analyze
recirculation performance during design basis accidents if debris
generation, transport and accumulation are analyzed mechanistically. The
NRC staff also recognized that the methodology needed to perform these
evaluations was not then available. As a result, that information was
not requested in the bulletin, but addressees were informed that the
staff was preparing a generic letter that would request this
information. Generic Letter 2004-02 is the follow-on to the bulletin.
Generic Letter 2004-02 requested that addressees perform a mechanistic
evaluation of the potential for the adverse effects of post-accident
debris blockage and operation with debris-laden fluids to impede or
prevent the recirculation functions of the ECCS and CSS following all
postulated accidents for which the recirculation of these systems is
required. The generic letter also requested that addressees implement
any needed plant modifications. In support of the generic letter, the
staff issued a safety evaluation (SE) endorsing acceptable portions of
the generic industry guidance. The SE may be used to assist in
determining the status of regulatory compliance. For areas not addressed
in the industry guidance, the staff provided guidance in the SE
(Accession Number ML043280641) for evaluating those areas. Individual
addressees may also develop an alternative to the approaches mentioned
in this paragraph for responding to this generic letter. However,
additional staff review will be required to assess the adequacy of such
approaches.

For additional background on the technical and safety concerns and
descriptions of selected plant events, see the Discussion and Background
Sections in Generic Letter 2004-02, "Potential Impact of Debris Blockage
on Emergency Sump Recirculation at Pressurized-Water Reactors (Accession
Number ML031600259)" or

[http://www.nrc.gov/reading-rm/doc-collections/gen-comm/gen-letters/2004/gl200402.pdfhttp://www.nrc.gov/reading-rm/doc-collections/gen-comm/gen-letters/2004/gl200402.pdf](http://www.nrc.gov/reading-rm/doc-collections/gen-comm/gen-letters/2004/gl200402.pdf)

2515/166-03 INSPECTION REQUIREMENTS

03.01 Verify the implementation of the plant modifications and procedure
changes committed to by the licensee in their GL 2004-02 responses.

03.02 Verify that changes to the facility or procedures, as described in
the UFSAR, that are identified in the licensee's GL 2004-02 response
were reviewed and documented in accordance with 10 CFR 50.59. Verify
that the licensee has obtained NRC approval prior to implementing those
changes that require such approval as stated in 10 CFR 50.59.

2515/166-04 GUIDANCE

[General Guidance.]{.underline}

In lieu of performing a separate inspection for this TI, the Region can
use the actions performed by the licensee in response to GL 2004-02 as
samples for regularly scheduled baseline inspection activities.

As part of closing out GSI-191, the NRC needs to verify that the plant
modifications and procedure changes identified in the licensee's
September 2005 or subsequent GL 2004-02 responses were properly
implemented. The plant modifications and procedure changes may be
implemented over several refueling outages. The inspector should use the
GL 2004-02 responses to identify the corrective actions that should be
inspected. Note that final responses have not yet been submitted by the
licensees. The complete set of activities to be inspected will not be
known until the final responses are submitted. However, given the
limited time between submittal of final GL responses and expiration of
this TI, it will be necessary for the inspectors to interact with the
licensee before its final GL response is submitted. This will maximize
the opportunity to inspect the modifications that address the GL.

At multi-unit sites, inspectors should verify the installation of all
significant modifications identified in GL 2004-02 responses for each
unit. If common to all units, procedure and programmatic changes need
only to be inspected for one unit.

[Specific Guidance]{.underline}

04.01 The inspector should use Inspection Procedure 71111.17, "Permanent
Plant Modifications," as the basis for verifying the implementation of
licensee modifications. The inspector should verify the installation of
all significant modifications identified in the licensee's GL 2004-02
responses for each unit. The inspector should perform the activities
associated with an "Annual Review" as identified in Section 71111.17-02,
"Inspection Activities," including the activities in Section 02.02.d. If
the inspection is performed as part of a "Biennial Review," inspectors
should perform the activities identified in Section 71111.17-02,
"Inspection Activities," including the activities in Section 02.02.b.
Inspectors are to only verify the implementation of the identified
corrective actions. The determination of the adequacy of the corrective
actions in addressing the concerns in GSI-191 and GL 2004-02 is not
within in the scope of this inspection. NRR will be reviewing licensee
GL responses and conducting audits to assess the adequacy of licensee
actions. If an inspector has an adequacy concern, they should contact
the Branch Chief, Safety Issues Resolution Branch of NRR.

a.  With the exception of Section 02.02.d (Annual Review) and Section
    02.02.b (Biennial Review), no additional specific guidance is
    needed.

b.  As part of the inspection activities for Section 02.02.d., "Updating
    Review," of Inspection Procedure 71111.17, "Permanent
    Modifications," verify that plant procedures have been updated to
    include programmatic controls that as a minimum:

    i.  Control the introduction of materials into containment that
        could impact sump performance. This includes materials such as
        insulation that could affect the chemical composition of the
        water.

    ii. Identify the need to perform an assessment of the introduction
        of new materials into containment or a change in the amount of
        existing materials in containment (e.g., insulation, signs,
        coatings, and foreign materials) for potential adverse effects
        on the ECCS and CSS recirculation functions.

    iii. Control any action, as appropriate, credited by the licensee as
         part of their resolution of GSI-191.

04.02 The inspector should use Inspection Procedure 71111.02,
"Evaluations of Changes, Tests, or Experiments," as the basis for
verifying if licensee facility and procedure changes made as part of the
licensee's resolution of GSI-191 were reviewed and documented in
accordance with 10 CFR 50.59.

2515/166-05 REPORTING REQUIREMENTS

Document inspection results including findings, if applicable, in a
resident inspectors' integrated inspection report (i.e., quarterly
inspection report) and send a copy of the applicable sections via e-mail
to Michael L. Scott (MLS3@NRC.GOV).

The results of an inspection of any modification or change should be
included in the applicable inspectable area of the inspection report
(i.e., 1R02, 1R17). At a minimum, the inspectors should briefly describe
the areas reviewed and results of the inspection, including answers to
the following questions and inspection observations in Section 4OA5,
"Other," of the next integrated inspection report. (This is an interim
deviation from the requirements of IMC 0612).

a\. Did the licensee implement the plant modifications and procedure
changes committed to in their GL 2004-02 responses? List the commitments
and the actions taken to meet each commitment. List when each action to
meet each commitment was completed. State whether additional inspections
are required to ensure all commitments have been met by the plant. (Such
inspections should be conducted at the earliest opportunity in
accordance with standard inspection processes.)

b\. Has the licensee updated its licensing bases to reflect the
corrective actions taken in response to GL 2004-02? Licensing bases may
not be updated until the licensee fully addresses GL 2004-02 (by
December 31, 2007 unless an extension has been granted).

c\. If the licensee or plant has obtained an extension past the
completion date of this TI, document what actions have been completed,
what actions are outstanding, and close the TI for the plant that has
the extension. Items not finished by the TI completion date can be
inspected in the future using the generic RFO inspection procedure.

2515/166-06 COMPLETION SCHEDULE

The installation of modifications committed to in licensees' GL 2004-02
responses will occur during refueling outages identified in the GL
2004-02 response. In most cases the outages will be before December 31,
2007. Some licensees have obtained extensions past this date for
completion of certain corrective actions. Inspectors should be prepared
to perform all or most of the inspection activities in this TI during
the refueling outage in which the changes are completed. More than one
outage may be needed to complete the changes associated with this issue,
so more than one inspection may also be required. In any event, the
inspection activities identified in this TI should be completed by June
30, 2008. By that date, most (but not necessarily all) corrective
actions should be complete.

2515/166-07 EXPIRATION

This TI will expire on June 30, 2008. This TI will be in effect for more
than 24 months because the generic letter for which it was issued for
will not be fully addressed by all licensees by the original due date.
To verify most corrective actions, inspections beyond the original date
will be required.

2515/166-08 CONTACT

For questions regarding the performance of this TI and emergent issues,
contact Steve Smith at (301) 415-3190 or SJS2@NRC.GOV.

2515/166-09 STATISTICAL DATA REPORTING

All direct inspection effort expended on this TI is to be charged
to 2515/166 for reporting by the Regulatory Information Tracking System
(RITS) with an IPE code of TI. All indirect inspection effort on this TI
is to be charged to a specific inspection report number with an IPE code
GIP/GIPD.

2515/166-10 ORIGINATING ORGANIZATION INFORMATION

10.01 [Organizational Responsibility]{.underline}.

This TI was initiated by the Safety Issues Resolution Branch
(NRR/DSS/SSIB).

10.02 [Resource Estimate]{.underline}.

The estimated direct inspection effort to perform this TI is estimated
to be 10-80 hours per PWR unit.

10.03 [Training]{.underline}.

No specialized training is needed to perform inspection requirements in
this TI beyond basic training for inspectors (specified in IMC 1245,
\"Inspector Qualifications\"). However, if technical support is needed
during the inspection of licensee actions, contact Steve Smith at
(301) 415-3190 or SJS2@NRC.GOV

10.04 [References]{.underline}.

Generic Letter 04-02, " Potential Impact of Debris Blockage on Emergency
Recirculation During Design Basis Accidents at Pressurized-water
Reactors," September 2004 (accession number ML042360586)

Safety Evaluation of the NEI report on "Pressurized Water Reactor
Containment Sump Evaluation Methodology (NEI 04-07),dated May 28,
2004,\" December 2004. (Accession number ML043280641)

Regulatory Guide 1.82, Revision 3, "Water Sources for Long-Term
Recirculation Cooling Following a Loss-of-Coolant Accident," November
2003. (accession number ML030420318).

Regulatory Guide 1.187, "Guidance for Implementation of 10 CFR 50.59,
Changes, Tests, and Experiments," April 2000 (accession number
ML003759710)

Los Alamos National Laboratory Technical Report LA-UR-02-7562, \"The
Impact of Recovery From Debris-Induced Loss of ECCS Recirculation on PWR
Core Damage Frequency,\" dated February 2003 (accession number
ML030690174).

NUREG/CR-6808, "Knowledge Base for the Effect of Debris on Pressurized
Water Reactor Emergency Core Cooling Sump Performance," dated
February 2003; available at
<http://www.nrc.gov/reading-rm/doc-collections/nuregs/contract/cr6808/cr6808.pdf>
(or accession numbers ML030780733 and ML030920540).

NEI 02-01, Revision 1, "Condition Assessment Guidelines: Debris Sources
Inside PWR Containments," dated September 2002 (accession number
ML030420318).

Generic Letter 98-04, " Potential for Degradation of the Emergency Core
Cooling System and the Containment Spray System After a Loss-of-Coolant
Accident Because of Construction and Protective Coating Deficiencies and
Foreign Material in Containment."

10 CFR 50.59, "Changes, Tests, and Experiments."

NRC Staff Responses to Industry Pre-Meeting Questions and Comments on
Bulletin 2003-01 Provided in Support of June 30, 2003 NRC Public
Meeting, June 30, 2003 (accession number ML031810371).

Revised NRC Staff Responses to Three Industry Questions on Bulletin
2003-01 Submitted Prior to the June 30, 2003, Public Meeting, August 7,
2003 (accession number ML032180011).

END

ATTACHMENT 1

Revision History For

[Temporary Instruction 2515/166]{.underline}

+--------+--------+-----------------------+-----+-------+-------------+
| Comm   | Issue  | Description of Change | Tr  | Tra   | Comment     |
| itment | Date   |                       | ain | ining | Resolution  |
| Tr     |        |                       | ing | Compl | Accession   |
| acking |        |                       | Nee | etion | Number      |
| Number |        |                       | ded | Date  |             |
+--------+--------+-----------------------+-----+-------+-------------+
| N/A    | 03     | [TI                   | N   | N/A   | ML060520046 |
|        | /16/06 | 2515/166]{.underline} | one |       |             |
|        |        | has been issued to    |     |       |             |
|        |        | support the NRC       |     |       |             |
|        |        | review of licensees\' |     |       |             |
|        |        | activities in         |     |       |             |
|        |        | response to Generic   |     |       |             |
|        |        | Letter 2004-02,       |     |       |             |
|        |        | \"Potential Impact of |     |       |             |
|        |        | Debris Blockage on    |     |       |             |
|        |        | Emergency Sump        |     |       |             |
|        |        | Recirculation at      |     |       |             |
|        |        | Pressurized Water     |     |       |             |
|        |        | Reactors (PWRs).\"    |     |       |             |
|        |        | The verification      |     |       |             |
|        |        | activities explained  |     |       |             |
|        |        | in the TI will also   |     |       |             |
|        |        | support the staff\'s  |     |       |             |
|        |        | closure of Generic    |     |       |             |
|        |        | Safety Issue - 191,   |     |       |             |
|        |        | \"Assessment of       |     |       |             |
|        |        | Debris Accumulation   |     |       |             |
|        |        | on PWR Sump           |     |       |             |
|        |        | Performance."         |     |       |             |
+--------+--------+-----------------------+-----+-------+-------------+
| N/A    | 05     | TI 2515/166 has been  | N   | N/A   | N/A         |
|        | /16/07 | revised to clarify    | one |       |             |
|        |        | verification          |     |       |             |
|        | CN     | activities to be      |     |       |             |
|        | 07-016 | completed during      |     |       |             |
|        |        | plant inspections     |     |       |             |
|        |        | based on feedback     |     |       |             |
|        |        | from the regions. The |     |       |             |
|        |        | responsible contact   |     |       |             |
|        |        | was updated. An       |     |       |             |
|        |        | explanation that the  |     |       |             |
|        |        | issue may require     |     |       |             |
|        |        | more than one         |     |       |             |
|        |        | inspection due to     |     |       |             |
|        |        | extensions granted to |     |       |             |
|        |        | some licensees is     |     |       |             |
|        |        | also included. The    |     |       |             |
|        |        | expiration date was   |     |       |             |
|        |        | extended. Four years  |     |       |             |
|        |        | of commitments were   |     |       |             |
|        |        | researched and none   |     |       |             |
|        |        | were found.           |     |       |             |
+--------+--------+-----------------------+-----+-------+-------------+