Failure benign

The primary system level safety requirement which drives risk control is failure tolerance. Failure tolerance embraces many design approaches. These include, but are not limited to functional redundancy functional inhibits safety devices manual back-up to automatic functions benign failure modes and failure effect isolation and containment. Damage tolerance (fracture control) and safety factor requirements are applied to structures as an equivalent to functional failure tolerance, although structural failure tolerance is acceptable where it can be implemented. Common cause and common mode failure mechanisms are taken into account in the implementation of Failure Tolerance. 

Alkaline batteries have a history of benign failure, meaning that they may cease operation or possibly even leak electrolyte, but instances of fire and explosion are rare. They are typically considered one of the safest technologies commercially available. 

MCLCPs are tough materials and a benign failure is experienced on impact, similar to that exhibited by long-fibre-reinforced polymers or natural wood i.e. the failure is neither ductile nor brittle and the mouldings generally do not shatter. 

The nuclear equipment failure rate database has not changed markedly since the RSS and chemical process data contains information for non-chemical process equipment in a more benign environment. Uncertainty in the database results from the statistical sample, heterogeneity, incompleteness, and unrepresentative environment, operation, and maintenance. Some PSA.s use extensive studies of plant-specific data to augment the generic database by Bayesian methods and others do not. No standard guidance is available for when to use which and the improvement in accuracy that is achieved thereby. Improvements in the database and in the treatment of data requires, uhstaiui.il indu.sinal support but it is expensive. 

There are numerous abnormalities of cysteine metabolism. Cystine, lysine, arginine, and ornithine are excreted in cystine-lysinuria (cystinuria), a defect in renal reabsorption. Apart from cystine calculi, cystinuria is benign. The mixed disulfide of L-cysteine and L-homocysteine (Figure 30-9) excreted by cystinuric patients is more soluble than cystine and reduces formation of cystine calculi. Several metabolic defects result in vitamin Bg-responsive or -unresponsive ho-mocystinurias. Defective carrier-mediated transport of cystine results in cystinosis (cystine storage disease) with deposition of cystine crystals in tissues and early mortality from acute renal failure. Despite... 

Surgical intervention should be reserved for patients with severe lower urinary tract symptoms of benign prostatic hyperplasia or those with complications of disease (such as recurrent urinary tract infections, renal failure, and bladder calculi). 

Failure of the gastric acid barrier and URT overgrowth are benign alterations of gut function, as opposed to bacterial overgrowth with Gram-negative bacilli associated... 

Examination of reinforced structures has so far shown the creep strain to be less than predicted, generally because the soil carries more load than is allowed for in design. Tests on materials buried and then exhumed after 10-20 years have so far shown little significant evidence of degradation, although little would be expected in the relatively benign soil conditions experienced. In common with industrial products, early failures have been shown to be due to errors in design or construction any failures due to poor durability will occur later, hopefully very much later. 

Geriatric Considerations - Summary Alpha-adrenergic blockers are modestly effective alone, and in combination with 5-alpha reductase inhibitors (e g, finasteride) in the treatment of urinary obstructive symptoms related to benign prostatic hyperplasia, The main side effect of these agents is orthostatic hypotension, and in hypertensive patients, these agents may increase the risk of congestive heart failure as reported in the ALLHAT study. 

Genitourinary system (nephrologic— glomemlonephritis, chronic renal failure urological— benign prostatic hypertrophy, prostatitis)... 

Some of the surprise effects of chemicals have been due to a failure to predict the scale on which technologies might be used once they were shown to be beneficial when used on a limited scale. For example, DDT has side effects that have increased nonlinearly with the scale of application as a result, the incremental benefits of a seemingly benign technology reversed when it was applied on a larger scale (the problem of MTBE was discussed earlier in this chapter). New technologies have to be constantly reevaluated in anticipation of scale effects. 

A 6-year-old girl, who had taken prednisone for 2.5 years for nephrotic syndrome with seven relapses in 3 years, developed symptoms of benign intracranial hypertension after oral glucocorticoid dosage reduction over 10 months from 30 mg/day to 2.5 mg/every other day (46). Laboratory studies and head CT scan were normal, but there was bilateral papilledema and the cerebrospinal fluid pressure was increased. She was given prednisone 1 mg/kg/day initially, with acetazola-mide, and 25 ml of cerebrospinal fluid was removed. All her symptoms resolved and treatment was gradually withdrawn. She developed no further visual failure. 

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