ML20236K816
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ll. E Lu MEMORANDUM FOR: Suzanne C. Black, Project Director Project Directorate IV-2 Division of Reactor Projects III, IV and V FROM:
Conrad E. McCracken, Chief Plant Systems Branch Division of Systems Technology
SUBJECT:
REGION IV's REQUEST FOR NRR ASSISTANCE REGARDING TECHNICAL SPECIFICATION (TS) REQUIREMENTS FOR THE SURVEILLANCE OF FUEL BUILDING INTEGRITY (TAC NO. M82018)
Reference:
Memorandum to M. Virgilio from S. Collins, "TIA Regarding Technical Specification Requirements for the Surveillance of Fuel Building Integrity," dated September 23, 1991.
This memorandum is in response to Region IV's request for NRR assistance (Reference) relating to surveillance requirements to ensure integrity of fuel buildings in PWRs. Specifically, Region IV finds that while stringent (i.e., weekly) surveillance verifications to demonstrate that the fuel buildings are at specified negative pressures with respect to the outside atmosphere are required of BWRs to ensure integrity of the buildings during movement of irradiated fuel in the buildings, similarly stringent verifications are not required of PWRs. The PWR technical specifications (TS) call for such verifications once every 18 months. The region finds this apparent inconsistency hard to understand, particularly because the radiological consequences of a fuel handling accident (FHA) can be more severe for a PWR than for a BWR.
Regarding the above concern of Region IV, we have reviewed the safety analyses reports as well as the TS for a number of operating BWRs and PWRs.
Our survey showed that generally BWRs do not have separate fuel handling and associated safety-related building exhaust filtration systems to mitigate the offsite radiological consequences of a fuel handling accident (FHA) outside the containment. Consequently they do not have any TS in this regard. However, BWRs use a secondary containment (SC) and its associated safety-related filtration system, namely, standby ~ gas treatment system (SGTS) or its equivalent for accident mitigation. The SC, a safety-related, limited leakage
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structure completely enclosing the primary containment (PC), collects the design basis PC leakage of radioactive material during a LOCA. The SC serves as a passive feature that mitigates the consequences of design basis accidents such as LOCA and FHA by controlling and filtering release of radioactive material to the environs. Because of the pivotal role the SC plays in mitigating the consequences of design basis accidents, particularly LOCA, it is maintained at a desired negative pressure with respect to the outside atmosphere. This prevents exfiltration of radioactive material from the SC to the environs during normal plant operation, special operations (movement of irradiated fuel in the SC; core alteration; and operations with a potential l
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i for draining the reactor vessel) and accidents. During normal plant operations and special operations, the negative pressure is generally maintained by operating a nonsafety-related normal ventilation system. During accidents, the l
negative pressure is maintained by the safety-related SGTS or its equivaltnt.
The above procedures ensure controlled and either filtered or unfiltered release of radioactive material from the SC to the environs at all times (filtered during accidents and generally unfiltered at other times). Therefore, the TS for BWRs generally include both a SR to verify the SC negative pressure once every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> during applicable modes of reactor operation (Modes 1, 2 and 3 and special operations identified above) and a SR to verify the capability of SGTS or its equivalent to draw the SC into the TS specified negative pressure (0.25 inch water guage) within a specified time-once every 18 months.
For reactors which do not have their fuel buildings encompassed within the envelope of a SC, but have separate fuel buildings (for example, the Perry BWR and most of the PWRs), there is no specific SR that calls for verifying fuel building negative pressure frequently (like once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or once a week) during movement of irradiated fuel in the building. However, for these reactors, the current practice has been generally to require verification of l
the capability of the associated safety-related building ventilation exhaust j
filtration system to draw the building into the specified negative pressure within the TS specified time once per 18 months (Perry TS do not include any j
SR for verification of its fuel building negative pressure; however, the i
TS ensure fuel building integrity during fuel handling in the fuel building.
j Associated SRs verify that the fuel building doors are closed and hatches are in place once every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />).
Furthermore, the staff notes that PWRs have TS requirements to ensure the integrity of containment during refueling. This requirement establishes containment integrity during refueling to mitigate the offsite radiological consequences of a FHA inside the containment. BWRs with Mark I and Mark II containment designs, on the other hand, do not have a primary containment available during refueling for mitigating the offsite radiological consequences of a FHA but a SC as discussed above. Because of the design differences as mentioned above, the staff considers that it is appropriate to l
have more stringent requirements for BWR SCs.
For the reasons stated above, we find that the inconsistency noted by Region IV i
between PWRs and BWRs as it relates to surveillance frequencies pertaining to fuel building negative pressure verification, understandable.
In this context, we note that the surveillance frequency of once per 18 months is consistent I
l with surveillance frequencies specified for other areas or buildings that are drawn into specified negative pressures or positive pressures by associated safety-related air cleanup systems (e.g., safety-related air cleanup systems for auxiliary building ECCS equipment area, shield building annulus (negative pressure); control room (positive pressure)). The once per 18 months verification of negative or positive pressure of the area or building in question by operating the associated safety-related filtration system is reasonable, given the consideration that frequent operation of the filtration i
systems may degrade the systems. We do not believe that consistency between the PWR TS and BWF TS in this regard, absent any observed safety problem like degradation of the fuel building integrity between two successive surveillance 0
l verifications due to such verifications being conducted less frequently for PWRs, should be a basis for imposing additional TS requirements for PWRs.
Specifically, we consider that absent any observed safety problem, to require PWR licensees to take actions such as more frequent fuel building pressure l
verifications at least during movement of irradiated fuel in the fuel building, performing the once per 18 month pressure verification test near to the time of l
fuel handling or use of a permanently mounted pressure gauge in the fuel building to perform the test, would be an unwarranted backfit.
i OdchsfshQw' i
l Conrad E. McCrackH, Chief i
Plant Systems Branch Division of Systems Technology Enclosures DISTRIBUTION As stated Docket File Plant File cc w/ enclosures:
RArchitzel M. Fields GHubbard R. Giardina JKudrick JLyons CONTACT: T. Chandrasekaran AThadani l
504-2859 GHolahan l
TChandrasekaran
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